Electrocatalysts, their preparation and use in ammonia synthesis.

Description

1 / 126 Electrocatalysts, their preparation and use in ammonia synthesis. REFERENCE TO RELATED ORDERS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 455,263, filed March 29, 2023, the contents of which are incorporated herein by reference in their entirety. FIELD OF THE INVENTION

[0002] The present invention, in some of its embodiments, relates to metal-based catalysts and their uses for the synthesis of ammonia. BACKGROUND OF THE INVENTION

[0003] Ammonia is widely produced using the Haber-Bosch process, developed in the 19th century, which requires very high pressure and temperature. Industries produce more than 200 million tons of ammonia annually using this method, and most of it is used for fertilizer production. The hydrogen needed for this process is generated from steam reforming, which consumes three to five percent of total natural gas production and releases a huge amount of greenhouse carbon dioxide into the atmosphere.

[0004] Therefore, the alternative synthesis of ammonia that is more environmentally friendly, energy-efficient and under milder conditions is one of the major global challenges. SUMMARY OF THE INVENTION

[0005] According to one aspect of some embodiments of the present invention, an electrocatalyst is provided comprising a transition metal oxide; wherein the transition metal oxide is Petition 870250100702, dated 03 / 11 / 2025, page 5 / 141 2 / 126 characterized by an electrocatalytic activity and wherein the electrocatalytic activity comprises any of the following: (i) reduction of nitrogen to ammonia; (ii) reduction of nitrate or nitrite to ammonia, or both (i) and (ii); and wherein the transition metal oxide is devoid of iron oxide and TiO2, and is further devoid of a metal in the elemental state or a salt thereof.

[0006] In one embodiment, the transition metal oxide is in contact with (i) a conductive material; (ii) a co-catalyst, or both (i) and (ii); and wherein the concentration of the transition metal oxide in the electrocatalyst is between 1 and 90% w / w.

[0007] In one embodiment, the conductive material comprises a carbon material, a metal, a conductive metal oxide, or any combination thereof; and wherein the co-catalyst comprises a metal phthalocyanine dye.

[0008] In one embodiment, the carbon material comprises carbon black, activated carbon, graphite, carbon nanotubes, graphene, and any combination thereof.

[0009] In one embodiment, the transition metal oxide comprises a transition metal selected from (i) Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, W, Re, Os, Ir, Pt, a lanthanide and Au, including any combination thereof; and (ii) a combination of iron oxide and (i).

[0010] In one embodiment, the transition metal in the transition metal oxide is selected from Ru, Fe, Petition 870250100702, dated 03 / 11 / 2025, page 6 / 141 3 / 126 Co, Ni, Cu, Mo, Mn, V, Ag, Pt, Pd and Pt or any combination thereof.

[0011] In one embodiment, the transition metal oxide is selected from RuO2, cerium oxide-iron oxide and PdO.

[0012] In one embodiment, the outer surface of the transition metal oxide comprises a plurality of reactive oxygen species; optionally, wherein the reactive oxygen species are selected from singlet oxygen, a peroxide, a superoxide, a hydroxyl radical, or any combination thereof.

[0013] In another aspect, an electrode is provided comprising a conductive substrate and the electrocatalyst of the invention, wherein the electrocatalyst is deposited on a surface of the conductive substrate; and wherein the electrode is configured to electrochemically induce the synthesis of ammonia from a composition comprising at least one of the following: nitrogen, nitrogen oxide, nitrite and nitrate, including any salt or any combination thereof.

[0014] In one embodiment, the electrocatalyst has the form of a layer.

[0015] In one embodiment, the conductive substrate comprises a carbon substrate, a metallic substrate, a conductive metal oxide substrate, or any combination thereof.

[0016] In one embodiment, the electrode is a cathode.

[0017] In another aspect, an electrochemical cell is provided comprising a working electrode in Petition 870250100702, dated 03 / 11 / 2025, page 7 / 141 4 / 126 operational communication with a chamber configured to contain an aqueous electrolyte comprising a nitrate salt or a nitrite salt; the electrochemical cell further comprises an additional electrode; wherein: the additional electrode and the working electrode are connectable to a power source; the electrochemical cell is configured to generate ammonia under operating conditions; the working electrode is (i) the electrode of the invention; or (ii) comprises an electrocatalyst deposited on a conductive substrate, wherein the electrocatalyst is selected from an iron oxide-TiO2 compound, a noble metal or a noble metal compound.

[0018] In one embodiment, the noble metal compound comprises a first noble metal and a second noble metal, wherein the molar ratio of the first noble metal to the second noble metal is in the range of 1:9 to 9:1.

[0019] In one embodiment, the noble metal is selected from Ru, Rh, Pt, Pd, Ag, Re, Ir and Au.

[0020] In one embodiment, the molar ratio of the first noble metal to the second noble metal is in the range of about 2:1 to about 1:2.

[0021] In one embodiment, the noble metal compound is a multilayered material, in which each of the first noble metals and second noble metals is found in the form of a distinct layer.

[0022] In one embodiment, the iron oxide-TiO2 compound comprises (i) Fe2O3, Fe3O4 and / or Fe2O3FeO and (ii) TiO2.

[0023] In one embodiment, the weight ratio between Fe and Ti in the iron oxide compound TiO2 is between Petition 870250100702, dated 03 / 11 / 2025, p. 8 / 141 5 / 126 approximately 4:1 and 1.5:1, and wherein the iron oxide compound TiO2 is a layered material comprising a first layer in contact with a second layer, wherein the first layer comprises or consists essentially of iron oxide and the second layer comprises or consists essentially of TiO2.

[0024] In one embodiment, the operating conditions comprise a temperature in the range of 5 °C to 150 °C; and the application of a voltage.

[0025] In one mode, the voltage is between 0.3 V and -2 V.

[0026] In one embodiment, the aqueous electrolyte is an alkaline electrolytic solution; and where the concentration of the nitrate ion in the aqueous electrolyte is between 0.01 and 5 M; optionally, where the aqueous electrolyte is a supersaturated solution.

[0027] In one embodiment, the aqueous electrolyte is pressurized with a gas comprising nitrogen.

[0028] In another aspect, an electrochemical cell is provided comprising a working electrode and an additional electrode; wherein the working electrode and the additional electrode are in operational communication with a chamber configured to contain a supersaturated alkaline electrolytic solution pressurized with a gas comprising nitrogen; the working electrode is (i) the electrode of the invention; or (ii) comprises an electrocatalyst deposited on a conductive substrate and, wherein the electrocatalyst is selected from an iron oxide-TiO2 compound and a noble metal compound; the working electrode and the additional electrode are in Petition 870250100702, dated 03 / 11 / 2025, page 9 / 141 6 / 126 electrical communication with a power supply; and wherein the electrochemical cell is configured to generate ammonia under operating conditions comprising the application of a cathodic electrical potential.

[0029] In one embodiment, the cathodic electric potential comprises: (i) a positive electric potential above 0.5 V relative to SHE, sufficient to oxidize nitrogen to a nitrogen oxide; and (ii) a negative electric potential of at least -0.05 V relative to SHE, sufficient to generate ammonia from nitrogen oxide.

[0030] In one embodiment, the positive electric potential is between 1 and 2 V; and where the negative electric potential is between -0.1 and -0.5 V.

[0031] In one embodiment, the operating conditions also include a temperature in the range of 5 °C to 150 °C.

[0032] In one embodiment, the electrochemical cell is characterized by at least one of the following: configured to synthesize ammonia at a rate of at least 1 x 10-11 mol cm-2s-1; and has a faradaic efficiency greater than 30% at an electrical potential between about -0.1 and about -0.3 V.

[0033] In one embodiment, the supersaturated alkaline electrolyte solution comprises a nitrate salt, a nitrite salt, or both.

[0034] In another aspect, a method for synthesizing ammonia is provided, comprising: supplying the aqueous electrolyte comprising a nitrate salt or a nitrite salt to the electrochemical cell of the invention, or supplying the supersaturated alkaline electrolytic solution comprising Petition 870250100702, dated 03 / 11 / 2025, page 10 / 141 7 / 126 optionally a nitrate salt or a nitrite salt and a gas to the electrochemical cell of the invention; and apply a negative electrical potential to the electrochemical cell of the invention, under suitable conditions to generate ammonia; wherein the gas comprises air, nitrogen, a mixture of oxygen and nitrogen or a mixture of hydrogen and nitrogen; and wherein the negative electrical potential is at least -0.05 V.

[0035] In one embodiment, the conditions comprise a temperature between 5 °C and 150 °C; wherein the negative electric potential is between -0.1 V and -0.5 V; and wherein the aqueous electrolyte is a supersaturated solution with a pH between 10 and 14.

[0036] In one embodiment, the method further comprises a preliminary activation step of the working electrode by (i) contacting the working electrode with an oxidizing solution ee; or (ii) applying to the working electrode in contact with a gas comprising oxygen an electrical potential of at least 0.5 V; and wherein the preliminary step is performed before performing step (i) or step (ii).

[0037] In one embodiment, the method is characterized by (i) an ammonia production rate in the range of 1 x 10-11 mol s-1cm-2 to 1 x 10-6 mol s-1cm-2; (ii) faradaic efficiency of at least 5% at an electrical potential of about -0.3 V, or both (i) and (ii).

[0038] In one embodiment, step (i), step (ii) or both comprise the introduction of the gas into the aqueous electrolyte.

[0039] Other embodiments and the full scope of applicability of the present invention will become Petition 870250100702, dated 03 / 11 / 2025, p. 11 / 141 8 / 126 evident from the detailed description presented below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are presented for illustrative purposes only, since various alterations and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

[0040] Unless otherwise indicated, all technical and / or scientific terms used herein have the same meaning as is commonly understood by a person skilled in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein may be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, shall prevail. Furthermore, the materials, methods, and examples are for illustrative purposes only and are not intended to be necessarily limiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Some embodiments of the invention are described herein by way of example only, with reference to the accompanying drawings. With specific reference now to the detailed drawings, it is emphasized that the details shown are by way of example and for the purpose of illustrative discussion of the embodiments of the invention. In this respect, the description accompanied by the drawings makes it evident to those skilled in the art how the embodiments of the invention can be implemented.

[0042] In the drawings: Petition 870250100702, dated 03 / 11 / 2025, p. 12 / 141 9 / 126

[0043] Figures 1A-1B are graphs showing the rate of nitrate formation and the % FE (Faradaic Efficiency) calculated for each CoPc / RuO2 composition at 0.1 V vs. RHE in 0.1 M Na2SO4 solution saturated with air (1A) and comparison of the remaining peroxide and nitrate formed at different RuO2 contents of the CoPc / RuO2 compound (1B).

[0044] Figures 2A-2E are X-ray diffraction patterns of (2A) 100% Ce, (2B) 100% Fe, (2C) 75% Ce:25% Fe, (2D) 50% Ce:50% Fe and (2E) 25% Ce:75% Fe.

[0045] Figures 3A-3D are scanning electron microscopy micrograms of the synthesized 50Fe:50Ce compound catalyst at 20Kx magnification (3A) and EDS mapping of oxygen (3B), iron (3C) and cerium (3D) on the synthesized 50Fe:50Ce compound catalyst at the same magnification.

[0046] Figure 4 is a scanning electron micrograph of the synthesized NiCo2S4.

[0047] Figures 5A-5D are bar graphs showing the production rate and faradaic efficiency of (5A) NH3; (5B) NO2-; and (5C) NH2OH from the reduction of NO3- at selected applied potentials for the NiCo2S4 catalyst mixed with 20 wt% Vulcan carbon in 0.1 M KOH saturated with Ar-containing 0.5 M NO3- electrolyte; (5D) Selectivity of NiCo2S4 as a function of the contribution of the faradaic efficiency of the products NH3, NO2-, NH2OH and other byproducts, possibly H2y.

[0048] Figures 6A-6E show micrographs XRD, SEM, and TEM diffraction of the Rh / C catalysts. Figure 6A is an X-ray diffraction pattern of the synthesized carbon and the 5 wt% Rh / C catalysts. Figures 6B-6C are scanning electron microscopy (SEM) micrographs in Petition 870250100702, dated 03 / 11 / 2025, page 13 / 141 10 / 126 two different magnifications. Figures 6D-6E are transmission electron microscopy (TEM) images of a 5 wt% Rh / C sample at two different magnifications. The inset in Figure 6E shows the particle size distribution of Rh.

[0049] Figure 7 presents a non-limiting schematic illustration of the electrochemical cell used for the nitrogen reduction reaction.

[0050] Figure 8 presents a non-limiting schematic illustration of the electrochemical cell used for the nitrogen reduction reaction.

[0051] Figures 9A-9B present non-limiting schematic illustrations of an electrochemical cell used for the electrochemical reduction of nitrogen to ammonia. DETAILED DESCRIPTION OF THE INVENTION

[0052] The present invention, in some embodiments, relates to a catalyst (e.g., electrocatalyst) comprising a transition metal oxide, as disclosed herein, and its uses for the electrochemical reduction of nitrogen to ammonia or for the electrochemical reduction of nitrogen oxide (e.g., a nitrate salt) to ammonia. The present invention, in some embodiments, is based on a surprising discovery that transition metal oxides (such as Ru or PdO oxide) are capable of electrochemically reducing nitrogen and nitrogen oxide to ammonia.

[0053] In some embodiments, the electrocatalyst of the invention has high activity. Petition 870250100702, dated 03 / 11 / 2025, page 14 / 141 11 / 126 electrocatalytic reduction of nitrogen. In some embodiments, the electrocatalytic reduction of nitrogen is carried out at ambient pressure and temperature in aqueous media, using air or pure nitrogen as nitrogen sources.

[0054] Furthermore, the present invention, in some of its embodiments, is based on a surprising discovery that the electrochemical reduction of nitrogen to ammonia, catalyzed by an electrocatalyst comprising (i) the transition metal oxide catalyst of the invention, (ii) an iron oxide-based catalyst TiO2 or (iii) a noble metal alloy catalyst (e.g., RuPt), is accompanied by the formation of nitrate as an intermediate. In some embodiments, the electrocatalyst of the invention is capable of reducing nitrogen oxide (e.g., nitrate or nitrite) to ammonia.

[0055] Before explaining at least one embodiment of the invention in detail, it should be understood that the invention is not necessarily limited in its application to the construction details and arrangement of components and / or methods presented in the following description and / or illustrated in the drawings and / or examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. The electrocatalyst 1. Metal oxide catalyst

[0056] According to some embodiments, the present invention provides an electrocatalyst comprising a transition metal oxide (also referred to herein as a “metal oxide catalyst”); wherein the transition metal oxide is characterized by an activity Petition 870250100702, dated 03 / 11 / 2025, p. 15 / 141 12 / 126 electrocatalytic comprising any of the following: (i) reduction of nitrogen to ammonia (referred to herein as “NRR activity”); (ii) reduction of nitrogen-based species to ammonia (referred to herein as “NO3RR activity”); (iii) oxidation of nitrogen to nitrogen-based species (referred to herein as NOR activity), wherein the nitrogen-based species is selected from nitrogen oxide, nitrate and nitrite, including any combination thereof and any salt thereof, or any combination of (i) to (iii). The term “electrocatalytic activity” is well known in the art and refers to the ability of a catalyst material to catalyze (i.e., initiate, induce, enhance and / or promote) a redox reaction upon application of voltage (i.e., to a working electrode containing the catalyst material).The reaction (also called an “electrochemical reaction”) occurs on the surface of a working electrode containing the catalyst material and in contact with an electrolyte, wherein the electrolyte (i.e., a liquid electrolyte) contains one or more species (i.e., a gas, an ion, and / or a molecule dissolved or dispersed in the electrolyte) that are reduced or oxidized during the reaction.

[0057] In some embodiments, the electrocatalyst of the invention comprises an electrocatalytically active material consisting essentially of transition metal oxide. In some embodiments, at least 95%, at least 90%, at least 97%, between 90 and 99%, between 90 and 99.9%, between 95 and 99%, between 95 and 99.9% by weight of the active electrocatalyst material consists of one or more species of transition metal oxide. In some embodiments, the electrocatalytically active material consists Petition 870250100702, dated 03 / 11 / 2025, page 16 / 141 13 / 126 essentially in a single species of transition metal oxide. In some embodiments, the electrocatalytically active material is devoid of iron oxide; TiO2; a metal in its elemental state or an alloy thereof; an oxide of any of the following elements: Sn, Pb, Bi, Hg and Cd, or any combination thereof.

[0058] In some embodiments, the transition metal oxide is or consists essentially of ruthenium oxide (e.g., RuO2), CeO2, or PdO. In some embodiments, the metal oxide catalyst is ruthenium oxide.

[0059] The term “devoid of”, as used herein, encompasses the fact that the material may comprise only trace amounts of the specific element or specific material, such that the specific element or specific material does not contribute to any electrocatalytic activity.

[0060] In some embodiments, the term “active electrocatalytic material” encompasses a part of the electrocatalyst capable of inducing electrocatalysis. For example, the electrocatalyst of the invention may be in the form of a first layer in contact with a second layer facing the environment, and the second layer is the transition metal oxide layer, as disclosed herein. Thus, electrocatalysis occurs on the surface of the second layer and is referred to herein as the “electrocatalytically active material”.

[0061] In some embodiments, the transition metal oxide is devoid of iron oxide as the only metal oxide. In some embodiments, the transition metal oxide is devoid of TiO2. In some embodiments, the transition metal oxide is devoid of a compound that Petition 870250100702, dated 03 / 11 / 2025, page 17 / 141 14 / 126 comprises iron oxide and TiO2. In some embodiments, the transition metal oxide is still devoid of an elemental metal or a salt thereof. In some embodiments, the transition metal oxide is also devoid of an oxide of any of the following elements: Sn, Pb, Bi, Hg, and Cd.

[0062] In some embodiments, the electrocatalyst has the form of a solid material (e.g., a powder, a film, a particle, a bulk material, a fiber, a porous matrix, a plurality of aggregated particles, etc.) with at least one average dimension of at least 1 µm, at least 100 µm, at least 1 mm, at least 1 cm, at least 10 cm, including any interval between these values. In some embodiments, the electrocatalyst is a particle (e.g., a substantially spherical particle of nano or micro size). In some embodiments, the particle is characterized by an average size between 10 and 500 nm, between 10 and 100 nm, between 50 and 500 nm, between 200 and 500 nm, between 1 and 500 µm, between 10 and 500 µm, between 1 and 50 µm, between 1 and 100 µm, including any range between these values.

[0063] In some embodiments, the electrocatalyst has the form of a film, a sheet, a bulk material, a fiber, a porous matrix, characterized by at least one average dimension (e.g., thickness, length, width) between 10 and 500 nm, between 10 and 100 nm, between 50 and 500 nm, between 200 and 500 nm, between 1 and 500 µm, between 10 and 500 µm, between 1 and 50 µm, between 1 and 100 µm, including any range between these values. Petition 870250100702, dated 03 / 11 / 2025, p. 18 / 141 15 / 126

[0064] In some embodiments, the transition metal oxide comprises or consists essentially of a transition metal selected from an element of the lanthanide series (e.g., Ce), an element of the actinide series, Fe, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, W, Re, Os, Ir, Pt, and Au, including any combination thereof. In some embodiments, the transition metal is selected from Ru, Pd, Co, Ni, Ce, Cu, Zn, Ru, Rh, Pd, Re, Ir, including any combination thereof. In some embodiments, the transition metal oxide comprises NiOx / Ni(OH)2, Co3O4 and mixed spinel Ni-Co oxides (e.g., NiCoO4). In some embodiments, the transition metal oxide is selected from ruthenium oxide (e.g., RuO2 and PdO, or both).

[0065] In some embodiments, the metal oxide catalyst is a compound. In some embodiments, the compound comprises a first transition metal oxide and a second transition metal oxide. In some embodiments, the first transition metal oxide and the second transition metal oxide are homogeneously distributed within the compound. In some embodiments, the first transition metal oxide and the second transition metal oxide are mixed within the compound.

[0066] In some embodiments, the compound has the form of a layered material. In some embodiments, the compound comprises an outer layer over a core. In some embodiments, the compound comprises an outer layer that surrounds the core. Petition 870250100702, dated 03 / 11 / 2025, page 19 / 141 16 / 126

[0067] In some embodiments, the outer layer consists essentially of transition metal oxide. In some embodiments, the core comprises or consists essentially of transition metal and / or a salt thereof. In some embodiments, the core comprises or consists essentially of transition metal oxide. In some embodiments, the outer layer comprises transition metal oxide nanoparticles.

[0068] In some embodiments, the core has the form of a particle (for example, a nano or micro-sized particle). In some embodiments, the core has the form of a substantially spherical particle. In some embodiments, the core has the form of a film, a bulk material, a fiber, a porous matrix, a plurality of aggregated particles, etc.

[0069] In some embodiments, the term shell refers to the sheathing domain that surrounds the core. By sheathed we mean a composition of two or more entities, namely, an entity that defines a shell (the surrounding entity, i.e., the shell) and the entity (or entities) that is at least partially enclosed in it. In some embodiments, the sheathing may conform to the exact contour of the core. In some embodiments, the core comprises or is made of a plurality of particles.

[0070] Particles coated with a layer can be characterized by a discrete inner and outer surface, in which the inner surface constitutes the boundary of the enclosed area or space. The enclosed area or space can Petition 870250100702, dated 03 / 11 / 2025, p. 20 / 141 17 / 126 to be isolated from the external area of ​​the space, which is delimited only by the external surface.

[0071] In the context of the present invention, the closure of the enclosing entity may depend on the size, shape, and chemical composition of the entity being enclosed within it, such that the enclosing entity may be closed to one entity and, at the same time, open to another entity. For example, the structures presented here are closed with respect to certain chemical entities that cannot pass through their enclosing layer, while the same closed structures are not closed with respect to other entities.

[0072] In some embodiments, the thickness of the outer layer is between 1 nm and 100 µm, between 1 nm and 10 µm, between 1 nm and 100 nm, between 10 nm and 100 nm, between 10 nm and 500 nm, between 10 nm and 1000 nm, between 100 nm and 1000 nm, between 1 nm and 1 µm, between 1 and 100 µm, between 10 and 100 µm, including any range between these values.

[0073] In some embodiments, the compound (also used herein as iron oxide compound TiO2) comprises or consists essentially of iron oxide (e.g., Fe11e oxide and / or Fe111 oxide) and TiO2, wherein the iron oxide forms the outer layer and the TiO2 is in the core. In some embodiments, the iron oxide is in the form of hematite. In some embodiments, the iron oxide is in the form of nanoparticles on a microparticulate TiO2 core; and wherein the molar ratio between Fe and Ti in the compound is between about 1:1 and 10:1, between about 1:1 and 5:1, between about 1.2:1 and 10:1, between about 1.5:1 and 10:1, between about 1.2:1 and 5:1, between about 1.2:1 and Petition 870250100702, dated 03 / 11 / 2025, p. 21 / 141 18 / 126 4:1, between approximately 2:1 and 10:1, between approximately 2:1 and 5:1, between approximately 2:1 and 4:1, including any range between these values.

[0074] In some embodiments, the iron oxide-TiO2 compound comprises (i) Fe2O3, Fe3O4 and / or Fe2O3FeO and (ii) TiO2. In some embodiments, the iron oxide-TiO2 compound comprises Fe2O3, Fe3O4 or Fe2O3FeO as the first metallic component and TiO2 as the second metallic component, in a molar ratio in the range of 1:9 to 9:1. In some embodiments, the molar ratio of the first metallic component to the second metallic component is in the range of 1:9 to 9:1, 2:9 to 9:1, 3:9 to 9:1, 4:9 to 9:1, 5:9 to 9:1, 6:9 to 9:1, 7:9 to 9:1, 8:9 to 9:1, 9:9 to 9:1, 1:9 to 9:2, 1:9 to 9:3, 1:9 to 9:4, 1:9 to 9:5, 1:9 to 9:6, 1:9 to 9:7, 1:9 to 9:8, or 1:9 to 9:9, including any intervals between them.

[0075] In some embodiments, the compound comprises or consists essentially of (i) iron oxide (e.g., FeO and / or Fe2O3 and / or TiO2) and, optionally, (ii) an additional transition metal and / or an additional transition metal oxide other than iron oxide or TiO2. In some embodiments, the additional transition metal is or comprises a metal from the lanthanide series (e.g., oxophilic lanthanides, such as Ce). In some embodiments and es, the additional transition metal oxide is or comprises a metal oxide from the lanthanide series (e.g., Ce oxide). Petition 870250100702, dated 03 / 11 / 2025, p. 22 / 141 19 / 126

[0076] In some embodiments, the compound comprises or consists essentially of iron oxide (for example, FeO and / or Fe2O3) and / or TiO2; and (i) the additional transition metal and / or the additional transition metal oxide that is not iron oxide or TiO2, and / or (ii) the co-catalyst, wherein the co-catalyst is as described herein (such as a catalyst capable of catalyzing the reduction of oxygen to peroxide (H2O2); or a catalyst capable of catalyzing the reduction of nitrate to ammonia).

[0077] In some embodiments, the compound is a Ce oxide and Fe oxide compound. In some embodiments, the Ce oxide and Fe oxide compound comprises CeFeO3. In some embodiments, the Ce oxide and Fe oxide compound comprises or consists essentially of (i) CeO2, (ii) CeFeO3 and, optionally, (iii) iron oxide (e.g., Fe3O4, Fe2O3). In some embodiments, the molar ratio between Ce and Fe in the cerium oxide and iron oxide compound is between 80:20 and 30:70, between 80:20 and 30:70, between 80:20 and 30:70, between 75:25 and 30:70, between 60:40 and 30:70, between 60:40 and 50:60, between 55:45 and 45:55, or approximately 50:50, including any interval between these values. In some embodiments, a molar ratio between Ce and Fe within the Ce oxide and Fe oxide compound Fe is approximately 50:50. In some embodiments, the weight ratio between Ce and Fe within the Ce oxide and Fe oxide compound is between 7:1 and 1.5:1, between 7:1 and 2:1, between 6.5:1 and 2:1, between approximately 6:1 and 1.5:1, between approximately 5:1 and 2:1, between approximately 4:1 and 2:1, between approximately 3:1 and 2:1, or approximately 2.5:1, including any range between these values. Petition 870250100702, dated 03 / 11 / 2025, p. 23 / 141 20 / 126

[0078] In some embodiments, the weight portion of CeFeO3 in the Ce oxide and Fe oxide compound is between 40 and 95%, between 40 and 90%, between 40 and 85%, between 40 and 80%, between 45 and 90%, between 50 and 95%, between 50 and 80%, including any interval between them.

[0079] In some embodiments, the weight ratio between CeFeOa and CeO2 in the cerium oxide and iron oxide compound is between about 0.8:1 and 10:1, between 1:1 and 8:1, between 1:1 and 6:1, between about 1:1 and 5:1, between about 5:1 and 2:1, between about 4:1 and 2:1, between about 3:1 and 2:1, or about 5:1, including any range between these values.

[0080] In some embodiments, the Ce oxide and Fe oxide compound is characterized by an XRD pattern comprising at least 3, at least 4, at least 5 or all of the peaks at: 22.7°, 32.3°, 39.8°, 46.3°, 57.8° and 67.6°, corresponding to CeFeO3.

[0081] In some embodiments, the Ce oxide and Fe oxide compound comes in the form of microparticles. In some embodiments, the Ce oxide and Fe oxide compound is characterized by an average particle size (based on SEM measurements) between 0.5 and 100 pm, between 0.5 and 25 pm, between 1 and 50 pm, including any range between these values.

[0082] In some embodiments, the Ce oxide and Fe oxide compound is a porous matrix. In some embodiments, the Ce oxide and Fe oxide compound is characterized by a porosity (e.g., determined by the BET method) between 20 and 90, between 50 and 90, between 50 and 80%, including any range between these values. Petition 870250100702, dated 03 / 11 / 2025, p. 24 / 141 21 / 126

[0083] In some embodiments, the outer surface of the metal oxide catalyst of the invention comprises a plurality of reactive oxygen species (ROS), also used herein as an “activated electrocatalyst”. The presence of ROS can be determined spectroscopically, for example, by surface-enhanced Raman spectroscopy (SERS), X-ray photoemission spectroscopy (XPS), XRD, FTIR, Raman.

[0084] In some embodiments, the ROS are selected from singlet oxygen, a peroxide (e.g., H2O2), a superoxide, a hydroxyl radical, or any combination thereof. In some embodiments, the ROS are in contact with the outer surface of the metal oxide. In some embodiments, the ROS are absorbed (e.g., physically absorbed) by the metal oxide. In some embodiments, the ROS are covalently bonded to the surface of the metal oxide.

[0085] In some embodiments, the metal oxide catalyst comprises or consists essentially of RuO2, characterized by NO3RR activity.

[0086] In some embodiments, the metal oxide catalyst comprises or consists essentially of a Ce oxide-Fe oxide compound, characterized by NO3RR activity and by NOx (i.e., nitrate and / or nitrite) reducing activity to hydroxylamine.

[0087] In some embodiments, the metal oxide catalyst comprises or consists essentially of iron oxide-TiO2 compound, and is characterized by NRR activity and / or NOR activity. In some embodiments, the metal oxide catalyst comprises or Petition 870250100702, dated 03 / 11 / 2025, page 25 / 141 22 / 126 consists essentially of Ni oxide, Co oxide and mixed spinel Ni-Co oxide and is characterized by NOR activity. 2. Metal chalcogenide catalyst

[0088] According to another embodiment, the present invention provides an electrocatalyst comprising a transition metal chalcogenide (also referred to herein as a “metal chalcogenide catalyst”); wherein the electrocatalyst is characterized by NO3RR activity. In some embodiments, the transition metal chalcogenide comprises copper sulfide, nickel sulfide or NiCo2S4. In some embodiments, the transition metal chalcogenide consists essentially of NiCo2S4.

[0089] In some embodiments, the transition metal chalcogenide is in the form of nanoparticles (e.g., nanoparticle cluster). In some embodiments, the transition metal chalcogenide is a crystalline material characterized by a crystallite size of about 40 nm.

[0090] In some embodiments, the transition metal chalcogenide is characterized by the XRD pattern, as disclosed herein.

[0091] In some embodiments, the transition metal chalcogenide is further characterized by NOx-reducing activity to hydroxylamine (e.g., nitrite-reducing activity to hydroxylamine). In some embodiments, under predefined conditions (e.g., about 1 M hydroxide in the liquid electrolyte), the transition metal chalcogenide is substantially devoid of NOx-reducing activity to hydroxylamine. Petition 870250100702, dated 03 / 11 / 2025, page 26 / 141 23 / 126 3. Rh Catalyst

[0092] According to another embodiment, the present invention provides an electrocatalyst comprising Rh (also referred to herein as “Rh catalyst”); wherein the electrocatalyst is characterized by NOR, NO3RR and / or NRR activity. In some embodiments, the Rh catalyst essentially consists of a carbon material (e.g., carbon matrix) doped with Rh (i.e., elemental Rh). In some embodiments, the Rh is incorporated or embedded in the carbon material. In some embodiments, the weight content of Rh in the Rh catalyst is between 1 and 30%, between 3 and 30%, between 3 and 25%, between 4 and 20%, between 3 and 15%, between 3 and 10%, between 3 and 7% or about 5%, including any range between these values.

[0093] In some forms, the Rh catalyst is characterized by the XRD pattern, as disclosed here.

[0094] In some embodiments, the carbon material of the Rh catalyst is in the form of microparticles. In some embodiments, the microparticles are in the form of sheets or flakes of e. In some embodiments, the microparticles are characterized by an average dimension (width and / or length) between 1 and 100 µm, between 10 and 100 µm, including any interval between (as determined by SEM).

[0095] In some embodiments, Rh is in the form of nanoparticles (NPs) within the Rh catalyst. In some embodiments, the Rh NPs are homogeneously distributed within the carbon microparticles. In some embodiments, the Rh NPs are characterized by an average particle size (as determined by STEM). Petition 870250100702, dated 03 / 11 / 2025, p. 27 / 141 24 / 126 between 5 and 30 nm, between 5 and 28 nm, between 5 and 15 nm, between 8 and 15 nm, between 10 and 15 nm, including any interval in between.

[0096] In some embodiments, the Rh catalyst is characterized by selective NOR activity that results in selective nitrate formation (optionally, wherein the selective NOR activity comprises at least 60% w / w, at least 70%, at least 80% or at least 90% w / w of nitrate of the total NOx species generated during NOR).

[0097] In some embodiments, the electrocatalyst of the invention consists essentially of a crystalline material. In some embodiments, at least 70%, at least 80%, at least 90%, at least 95%, between 70 and 100%, between 70 and 99%, between 70 and 97%, between 70 and 95%, between 70 and 90%, between 70 and 85% by weight of the electrocatalyst is a crystalline material.

[0098] In some embodiments, at least 70%, at least 80%, at least 90%, at least 95%, between 70 and 100%, between 70 and 99%, between 70 and 97%, between 70 and 95%, between 70 and 90%, between 70 and 85% of the metallic content of the electrocatalyst is in a crystalline state. Co-catalyst

[0099] In another aspect, a composite material is provided comprising the electrocatalyst (e.g., the metal oxide catalyst disclosed above) and a co-catalyst. In some embodiments, the composite material is characterized by NOR activity.

[0100] The term electrocatalyst, as used herein, encompasses any of the Rh catalysts, metal oxide catalysts and catalysts of Petition 870250100702, dated 03 / 11 / 2025, page 28 / 141 25 / 126 metallic chalcogenide disclosed above and the composite material disclosed below.

[0101] In some embodiments, the co-catalyst is in contact with or mixed with the electrocatalyst in the composite material. In some embodiments, the co-catalyst is located on the outer surface of the electrocatalyst (e.g., metal oxide catalyst) or is incorporated into the matrix formed by the electrocatalyst. In some embodiments, the co-catalyst is in the form of a layer on the electrocatalyst. In some embodiments, the composite material comprises an excess weight of the cocatalyst relative to the electrocatalyst. In some embodiments, the composite material consists essentially of the electrocatalyst (e.g., metal oxide catalyst) and the co-catalyst. In some embodiments, the electrocatalyst suitable for use in the composite material is a H2O2 disproportionation catalyst (optionally a H2O2 disproportionation metal oxide).

[0102] In some embodiments, the p / p ratio between the co-catalyst and the electrocatalyst in the composite material of the invention is between about 20:1 and about 1:1, between about 10:1 and about 1:1, between about 10:1 and about 2:1, between about 5:1 and about 1:1, between about 5:1 and about 2:1, between about 3:1 and about 1:1, including any range between these values.

[0103] In some embodiments, the w / w ratio between the cocatalyst and the metal oxide catalyst (e.g., RuO2, Ce oxide, Fe oxide) in the composite material of the invention is between about 1:1 and about 10:1, Petition 870250100702, dated 03 / 11 / 2025, p. 29 / 141 26 / 126 between about 1:1 and about 5:1, between about 1:1 and about 3:1, between about 2:1 and about 10:1, between about 2:1 and about 5:1, between about 2:1 and about 3:1, including any range between these values. In some embodiments, the w / w ratio between the cocatalyst (e.g., macrocyclic ring transition metal complex) and the metal oxide catalyst (e.g., RuO2) in the composite material of the invention is between about 2:1 and about 4:1. In some embodiments, the composite material consists essentially of (i) cophthalocyanine (as a cocatalyst) and RuO2 (as a metal oxide catalyst), in a cocatalyst:metal oxide catalyst weight ratio of about 3:1.

[0104] In some embodiments, the composite material consists essentially of the co-catalyst and RuO2 is characterized by NOR activity. In some embodiments, a working electrode (e.g., cathode) comprising the composite material is configured to generate nitrate from nitrogen (or a gas comprising it, such as air) in a liquid electrolyte (e.g., aqueous electrolyte) that is substantially devoid of nitrate.

[0105] In some embodiments, the co-catalyst is capable of catalyzing the reduction of oxygen to peroxide (H2O2) after its activation. In some embodiments, the co-catalyst is capable of generating ROS (e.g., H2O2) in situ after its exposure to oxygen and activation of the co-catalyst. In some embodiments, the activation of the co-catalyst is achieved by applying an electrical potential to it. In some embodiments, the electrical potential sufficient for the activation of the co-catalyst is between -1 Petition 870250100702, dated 03 / 11 / 2025, page 30 / 141 27 / 126 and 1 V, between -1 and 0.8 V, between -0.8 and 0.8 V, between -0.5 and 0.6 V, between -1 and 0.6 V, between -0.2 and 0.6 V relative to NHE, including any range between these values. In some embodiments, co-catalyst activation is performed by light excitation, irradiating the co-catalyst with light at a wavelength within the co-catalyst's absorption range (typically between about 300 and about 700 nm). In some embodiments, co-catalyst activation is performed by contact with an oxidant (e.g., H2O2, hypochlorite, peracid, organic / inorganic peroxide and / or hydrogen peroxide precursor, such as a percarbonate).

[0106] In some embodiments, the co-catalyst is a carbon catalyst capable of catalyzing the reduction of oxygen to H2O2 or water. In some embodiments, the co-catalyst is a metal oxide capable of catalyzing the reduction of oxygen to H2O2 or water. In some embodiments, the co-catalyst is a fluorophore. In some embodiments, the co-catalyst is a ROS-generating dye. In some embodiments, the co-catalyst comprises a macrocyclic ring. In some embodiments, the macrocyclic ring is selected from a phthalocyanine dye, a cyanine dye, a porphyrin dye, or any combination thereof. In some embodiments, the co-catalyst is or comprises a macrocyclic ring transition metal complex. In some embodiments, the co-catalyst is selected from a phthalocyanine dye, a cyanine dye, a porphyrin dye, including any transition metal complex, any salt, or any combination thereof.Dyes that generate color are known in the field. Petition 870250100702, dated 03 / 11 / 2025, p. 31 / 141 28 / 126 Additional ROS (such as xanthene (e.g., rose Bengal), curcumin-based dyes, etc.).

[0107] In some embodiments, the co-catalyst (i.e., a catalyst capable of catalyzing the reduction of oxygen to H2O2 or water) is a metal phthalocyanine complex. In some embodiments, the metal phthalocyanine complex comprises a transition metal cation. In some embodiments, the transition metal cation is a divalent or trivalent metal cation (e.g., Fe, Zn, Ni, Cu, Co, Pd, Pt, cation). In some embodiments, the co-catalyst is Co-phthalocyanine.

[0108] In some embodiments, a p / p ratio between the co-catalyst and the electrocatalyst (e.g., RuO2) disclosed above is an effective synergistic ratio. In some embodiments, the effective synergistic ratio refers to the NOR activity of the composite material.

[0109] The term synergism, or any grammatical derivative thereof, is defined as the simultaneous action of two or more compounds (e.g., cocatalyst and electrocatalyst) in which the electrochemical activity (e.g., NOR activity) of the combination is greater than the sum of the electrochemical activity of the individual components.

[0110] The higher term encompasses at least 20%, at least 50%, at least 100%, at least 3 times, at least 5 times, at least 10 times, at least 50 times more electrochemical activity, compared to the control (i.e., the electrochemical activity of the individual components), including any range in between. Ink composition Petition 870250100702, dated 03 / 11 / 2025, page 32 / 141 29 / 126

[0111] In another aspect, a composition is provided, comprising the electrocatalyst (i.e., Rh catalyst, metal oxide catalyst and metal chalcogenide catalyst, or the composite material disclosed above) in contact with a conductive material. In some embodiments, the composition consists essentially of the electrocatalyst (and optionally the co-catalyst) and the conductive material. In some embodiments, the composition is a solid or powder composition. In some embodiments, the transition metal oxide and the conductive material and, optionally, additional constituents of the composition are homogeneously mixed within the composition. In some embodiments, the composition is a coating composition or paint composition for coating an electrode with the electrocatalyst.

[0112] In some embodiments, the composition comprises the electrocatalyst and the conductive material in the form of particles (e.g., nanoparticles and / or microparticles). In some embodiments, the composition is a mixture.

[0113] In some embodiments, the composition (i.e., after its application to an electrode surface) is an electrically conductive material. In some embodiments, the composition is characterized by an electrical conductivity of at least 10⁻¹ S / m, at least 1 S / m, at least 10 S / m, at least 10² S / m, at least 10³ S / m, between 10⁻¹ and 10¹⁰ S / m, between 1 and 10¹⁰ S / m, between 10 and 10¹⁰ S / m, between 10 and 10⁸ S / m, between 10² and 10¹⁰ S / m, including any range between these values. Petition 870250100702, dated 03 / 11 / 2025, page 33 / 141 30 / 126

[0114] In some embodiments, the percentage by weight of the electrocatalyst in the composition (i.e., relative to the total weight of the dry constituents of the composition) is between 1 and 90% w / w, between 50 and 90% w / w, between 70 and 90% w / w, between 1 and 5% w / w, between 1 and 10% w / w, between 5 and 90% w / w, between 5 and 20% w / w, between 5 and 10% w / w, between 1 and 30% w / w, between 1 and 40% w / w, between 1 and 50% w / w, between 5 and 50% w / w, between 10 and 90% p / p, between 10 and 50% p / p, between 20 and 90% p / p, between 20 and 70% w / w, including any range between these values. In some embodiments, the relative percentage by weight of the conductive material (i.e., that which is not the electrocatalyst or co-catalyst) in the composition is between 1 and 50% w / w, between 1 and 5% w / w, between 1 and 10% w / w, between 5 and 50% w / w, between 5 and 20% p / p, between 5 and 30% p / p, between 5 and 10% p / p, between 1 and 30% p / p, between 1 and 40% p / p, between 1 and 50% p / p, between 5 and 50% p / p, between 10 and 50% p / p, between 10 and 30% p / p, between 20 and 50% p / p, between 20 and 40% p / p, including any interval between these values.

[0115] In some embodiments, the composition is a fluid (liquid) ink further comprising a solvent. In some embodiments, the solvent comprises a polar organic solvent (for example, a water-miscible organic solvent, such as an alcohol or a lower alcohol) and optionally further comprises an aqueous solvent. In some embodiments, a weight portion of the solid constituents (i.e., any of the following: the electrocatalyst, the cocatalyst and the conductive material) within the fluid ink is between 5 and 50%, between 10 and 50%, between 5 and 30%, between 20 and 70%, including any range between these values. Petition 870250100702, dated 03 / 11 / 2025, p. 34 / 141 31 / 126

[0116] In some embodiments, the fluid ink is characterized by a viscosity suitable for its deposition on at least one surface of a substrate. In some embodiments, the viscosity of the fluid ink is between 0.1 and 1,000,000, between 0.1 and 100,000, between 0.1 and 1000, between 0.1 and 100 Pa* at 25 °C, including any range between these values.

[0117] In some embodiments, the conductive material comprises a carbon material, a metal (e.g., metal mesh, metal particle or metal foam), a conductive metal oxide, a conductive ceramic material, a conductive polymer (e.g., an ionomer such as Nafion, a sulfonated fluoropolymer) or any combination thereof. In some embodiments, the conductive material is presented in the form of nanoparticles and / or microparticles.

[0118] In some embodiments, the carbon material comprises carbon black, activated carbon, graphite, carbon nanotubes, graphene, and any combination thereof. The carbon black may be selected from, but not limited to, Vulcan XC-72, Black Pearls 700, Black Pearls 800, Black Pearls 2000, Vulcan XC-605, Regal 350, Regal 250, Black Pearls 570, and Vulcan XC-68, or any combination thereof.

[0119] Throughout this document, the expression “deposited on at least one surface” is also referred to, for simplicity, as a coating on a substrate or the surface of a substrate.

[0120] In some forms, the term “coating”, or any grammatical derivative thereof, is Petition 870250100702, dated 03 / 11 / 2025, p. 35 / 141 32 / 126 defined as a coating that (i) is positioned above the substrate, (ii) is in contact with the substrate, and (iii) does not necessarily cover the substrate completely. In some embodiments, the term coating, or any grammatical derivative thereof, encompasses a single-layer coating or a plurality of coating layers.

[0121] In some embodiments, the electrocatalyst or the composition of the invention is deposited onto the substrate. In some embodiments, the deposition is carried out by printing, liquid coating, casting, molding, pressure molding, extrusion, non-electrolytic deposition, etc., including any combination thereof. Electrode

[0122] In another aspect of the invention, an electrode is provided comprising the electrocatalyst or the composition of the invention in contact with a substrate. In some embodiments, the electrocatalyst is incorporated into or within the substrate. In some embodiments, the composition of the invention takes the form of a coating bonded or adhered (stablely fixed) to a surface of the substrate. In some embodiments, the coating comprises dry constituents of the composition disclosed above. In some embodiments, the coating takes the form of a continuous layer. In some embodiments, the electrode essentially consists of the electrocatalyst in contact with the substrate.

[0123] In some embodiments, the electrocatalyst or composition of the invention is presented in the form of a layer (e.g., continuous layer) or coating on the substrate. In some embodiments, the Petition 870250100702, dated 03 / 11 / 2025, page 36 / 141 33 / 126 The coating has a thickness between 10 nm and 10 mm, between 1 and 1000 µm, between 0.1 and 1000 µm, between 0.1 and 100 µm, between 1 and 100 µm, between 100 nm and 10 µm, between 100 nm and 1 µm, between 100 nm and 100 µm, between 100 nm and 1 mm, between 1 µm and 10 mm, between 1 µm and 1 mm, between 1 µm and 500 µm, including any interval between these values. In some embodiments, the layer is characterized by a porosity between 10 and 80%, between 10 and 60%, between 10 and 50%, between 10 and 30%, between 10 and 20%, including any interval between.

[0124] The term substrate, as used herein, encompasses any material (i.e., electrically conductive material) used for the fabrication of electrodes. In some embodiments, the substrate comprises or consists essentially of organic or inorganic electrically conductive surfaces.

[0125] In some embodiments, the substrate is a conductive substrate. In some embodiments, the substrate (and / or the substrate material) is characterized by an electrical conductivity of at least 1 S / m, at least 10 S / m, at least 102 S / m, at least 103 S / m, between 105 and 1010 S / m, between 1 and 1010 S / m, between 10 and 1010 S / m, between 10 and 108 S / m, between 102 and 1010 S / m, between 103 and 1010 S / m, between 104 and 1010 S / m, between 105 and 1010 S / m, between 102 and 108 S / m, including any interval in between.

[0126] In some embodiments, the substrate is or essentially consists of a material selected from, but not limited to, carbon material (for example, carbon fiber, carbon black, activated carbon, graphite, carbon nanotubes, graphene and any combination thereof), a conductive metallic substrate (comprising a Petition 870250100702, dated 03 / 11 / 2025, page 37 / 141 34 / 126 metal or a metalloid in its elemental state, or a conductive metal oxide), a conductive polymer (for example, a conductive organic polymer, such as PANI, polyacetylene; polyphenylene vinylene; polypyrrole, polythiophene, polyphenylene sulfide), or any combination thereof. In some embodiments, the conductive metallic substrate is in the form of a sheet, a rod, a blade, a wire, etc.) or a porous material, such as: metal mesh (woven or non-woven), metal foam (for example, Ni foam, Sn foam, etc.).

[0127] In some embodiments, the carbon material is a woven or non-woven carbon fiber-based material (e.g., Toray paper, carbon fabric, carbon paper).

[0128] In some embodiments, the substrate is configured to facilitate gas flow through at least one dimension thereof (e.g., length and / or cross-section). In some embodiments, the substrate is a porous substrate. In some embodiments, the substrate is characterized by a porosity between 50 and 95%, between 50 and 90%, between 50 and 80%, between 60 and 90%, including any range between these values. In some embodiments, the substrate is a porous electrode (e.g., a mesh or foam). In some embodiments, the substrate is a non-porous substrate characterized by a porosity of less than 20%, less than 10%, less than 5%, including any range in between.

[0129] In some embodiments, the electrocatalyst or the composition of the invention is present in a concentration between 0.1% and 99%, between 5% and 99%, between Petition 870250100702, dated 03 / 11 / 2025, p. 38 / 141 35 / 126 0.1% and 5%, between 0.1% and 10%, between 0.1% and 20%, between 10% and 99%, between 2% and 10%, between 2% and 20%, between 2% and 30%, between 10% and 99%, between 10% and 90%, between 10% and 80%, between 20% and 99%, between 20% and 90%, between 20% and 80%, between 50% and 99%, between 50% and 90%, by total electrode weight, including any interval in between.

[0130] In some embodiments, the electrode is characterized by an electrocatalytically effective charge of the electrocatalyst between 0.5 and 10 mg / cm2, between 1 and 10 mg / cm2, between 1 and 5 mg / cm2, between 2 and 10 mg / cm2, between 2 and 5 mg / cm2 or about 4 mg / cm2, including any range between these values.

[0131] In some embodiments, the electrode comprises the electrocatalyst or the composition of the invention stably bonded to at least one surface of the substrate. In some embodiments, the term stably bonded refers to the ability of the electrode to maintain its structural integrity (i.e., to maintain its shape, chemical composition, charge and / or electrocatalytic activity, and not exhibit disintegration of the substrate composition) under operating conditions of electrocatalytic ammonia generation, as disclosed herein. Furthermore, the electrode must maintain its structural integrity for at least 3, at least 5, at least 10, at least 100, at least 500, at least 1000, at least 10,000 operating cycles, including any interval between these values.

[0132] In some embodiments, the electrode described here is characterized by an electrocatalytic activity selected from: (i) reduction of nitrogen to ammonia Petition 870250100702, dated 03 / 11 / 2025, page 39 / 141 36 / 126 (NRR activity); (ii) reduction of nitrogen-based species to ammonia (NO3RR activity), (iii) NOR activity, (iv) reduction of NOx (i.e., nitrate and / or nitrite) to hydroxylamine or any combination of (i) to (iv). In some embodiments, the electrode is a working electrode. In some embodiments, the electrode described herein comprises the electrocatalytically effective charge of the electrocatalyst characterized by an electrocatalytic activity selected from: (i) reduction of nitrogen to ammonia (NRR activity); (ii) reduction of nitrogen-based species to ammonia (NO3RR activity), (iii) NOR activity, (iv) reduction of NOx (i.e., nitrate and / or nitrite) to hydroxylamine or any combination of (i) to (iv).

[0133] In some embodiments, the electrode is a cathode. In some embodiments, the cathode is characterized by NRR activity and comprises or essentially consists of the electrocatalyst characterized by NRR activity. In some embodiments, the electrocatalyst characterized by NRR activity comprises any of the following: (i) RuO2, (ii) a compound of Ce oxide and Fe oxide, or a composite material comprising (i) or (ii) and the cocatalyst (e.g., CoPc). In some embodiments, the cathode with NRR activity is operable at a negative potential. In some embodiments, the cathode with NRR activity is operable at a negative potential between -0.2 and -0.4 V, between -0.25 and -0.35 V, approximately -0.35 V (e.g., for CoPc / RuO2) versus RHE.

[0134] In some embodiments, the NRR activity cathode is operable with the liquid electrolyte disclosed herein. In some embodiments, the liquid electrolyte for Petition 870250100702, dated 03 / 11 / 2025, p. 40 / 141 37 / 126 NRR further comprises (i) one or more peroxide species (e.g., H2O2) and (ii) a nitrate anion or a salt thereof dissolved therein.

[0135] In some embodiments, the concentration of one or more peroxide species in the liquid electrolyte (e.g., liquid alkaline electrolyte) is between 1 and 1000 uM, between 50 and 1000 uM, between 10 and 200 uM, between 50 and 200 uM, between 50 and 500 uM, including any interval between these values.

[0136] In some embodiments, the nitrate concentration in the liquid electrolyte is in the range between 500 uM and 2 M, from 0.01 M to 2 M, from 0.1 M to 2 M, from 0.2 M to 1 M, from 0.1 M to 1 M, from 0.2 M to 0.5 M or about 0.5 M.

[0137] In some embodiments, the liquid electrolyte for NRR is further saturated with a mixture of nitrogen and oxygen (e.g., oxygen content between 5 and 30%, as disclosed above) and, optionally, one or more additional gases. In some embodiments, the liquid electrolyte for NRR is further saturated with air.

[0138] In some embodiments, the cathode is characterized by NO3RR activity and comprises or essentially consists of the electrocatalyst characterized by NO3RR activity. In some embodiments, the electrocatalyst characterized by NO3RR comprises a metal oxide catalyst (e.g., RuO2, composed of Ce oxide and Fe oxide), a metal oxide catalyst composed of a co-catalyst (e.g., RuO2 co-catalyst, such as CoPc), or a metal chalcogenide catalyst (e.g., NiCo2S4). In some embodiments, the NO3RR activity cathode is operable at a negative potential between 0 and -0.6 V, Petition 870250100702, dated 03 / 11 / 2025, page 41 / 141 38 / 126 between -0.05 and -0.45 V, between -0.3 and -0.5 V, approximately -0.3 V (e.g., for NiCo2S4), approximately -0.45 V (e.g., for Ce-Fe oxide compound), approximately -0.35 V (e.g., for RuO2-CoPc) or approximately -0 V (e.g., RUO2) versus RHE. The operable cathodic potential may vary depending on the pH of the electrolyte.

[0139] In some embodiments, the NO3RR activity cathode is operable with a liquid electrolyte comprising between about 0.1 and 1M of metal hydroxide (and / or characterized by a pH between 10 and 14). In some embodiments, the NO3RR activity cathode is operable with a liquid electrolyte comprising between about 0.001 and 1M, or between 0.1 and 1M of metal sulfate (and is optionally characterized by a pH value of about 7). In some embodiments, the electrocatalyst is NiCo2S4 and the concentration of metal hydroxide in the liquid electrolyte is about 1 M. In some embodiments, the liquid electrolyte further comprises between about 0.1 and 1 M of KCl. In some embodiments, the liquid electrolyte comprises at least 10, at least 100, at least 400, at least 500, at least 1000 µM of nitrate, between 0.1 mM and 1 M, between 0.1 M and 1 M, including any range between these values. In some embodiments, the liquid electrolyte is further saturated with nitrogen.

[0140] In some embodiments, the NO3RR activity cathode comprising a metal oxide catalyst (e.g., RuO2) has a nitrate generation rate of about 170 μg h-1cm-2 with a faradaic efficiency (FE) of about 17%. In some embodiments, the NO3RR activity cathode comprising a metal oxide catalyst (e.g., Ce oxide-Fe oxide compound) Petition 870250100702, dated 03 / 11 / 2025, p. 42 / 141 39 / 126 has a nitrate generation rate of approximately 21,000 μg h⁻¹cm⁻² with a faradaic efficiency (FE) between 80 and 100%.

[0141] In some embodiments, the cathode comprising NiCo2 S4 as an electrocatalyst is characterized by the activity of reducing nitrite to ammonia.

[0142] In some embodiments, the cathode comprising RuO2 / co-catalyst (e.g., CoPc) iron oxide-TiO2 compound, Ni oxide, Co oxide and NiCo oxide mixed spinel is characterized by NOR activity.

[0143] In some embodiments, the cathode is characterized by NOx-reducing activity to hydroxylamine and comprises or essentially consists of the electrocatalyst characterized by NOx-reducing activity to hydroxylamine. In some embodiments, the electrocatalyst characterized by NOx-reducing activity to hydroxylamine comprises a compound of Ceoxide of Fe or NiCo2 S4. In some embodiments, the cathode with NOx-reducing activity to hydroxylamine is operable at a negative potential between -0.1 and -0.5 V, between -0.05 and -0.45 V, between -0.3 and -0.5 V, about -0.3 V, -0.5 V, about 0.45 V (e.g., for the cerium oxide and iron oxide compound) vers. RHE.

[0144] In some embodiments, the cathode with NOx-reducing activity for hydroxylamine is operable with a liquid electrolyte comprising between about 0.1 and 1 M of metal hydroxide. In some embodiments, the liquid electrolyte comprises at least 100, at least 500, at least 1000 µM, between 0.1 mM and 1 M, between 0.1 M and 1 M of nitrate or nitrite, including any range between these values. Petition 870250100702, dated 03 / 11 / 2025, p. 43 / 141 40 / 126

[0145] In some embodiments, the cathode with NOx-to-hydroxylamine reducing activity comprising the metal oxide catalyst (e.g., Ce oxide-Fe oxide compound) has a hydroxylamine generation rate of about 1000-1300 μg h-1cm-2 with a faradaic efficiency (FE) of about 12%.

[0146] In some embodiments, the cathode of NOx reduction activity to hydroxylamine consists essentially of NiCo2 S4 as electrocatalyst and is operable at a negative potential of about -0.3 V vers. RHE (for NO2- reduction activity to hydroxylamine), about -0.5 V vers. RHE or about -0.25 V vers. RHE (for NO3- reduction activity to hydroxylamine).

[0147] In some embodiments, the NO2- to hydroxylamine reduction activity cathode comprising NiCo2 S4 has a hydroxylamine generation rate of about 3000 μg h-1cm-2 with a faradaic efficiency (FE) of about 18%.

[0148] In some embodiments, the electrode is an anode. In some embodiments, the anode is characterized by NOR activity and comprises or consists essentially of the electrocatalyst characterized by NOR activity. In some embodiments, the electrocatalyst characterized by NOR activity comprises the Rh catalyst or the composite material.

[0149] In some embodiments, the anode is operable at a potential between 0.1 and 2.0 V, between 1.6 and 1.8 V, between 1.5 and 1.7 V, about 0.1 V (for RuO2 / CoPc) or about 1.7 V (for Rh / C) versus RHE, including any range between these values. In some embodiments, the Petition 870250100702, dated 03 / 11 / 2025, p. 44 / 141 The 41 / 126 anode comprising the Rh catalyst has a nitrate generation rate of about 20 to 50 μg h-1cm-2 with a faradaic efficiency (FE) between about 20 and 30%.

[0150] In some embodiments, the anode is operable with a liquid electrolyte comprising between about 0.1 and 1 M of metal hydroxide (OH-) or metal sulfate (SO42-). In some embodiments, the liquid electrolyte is further saturated with air or with a mixture of nitrogen and oxygen, wherein the oxygen content of the mixture is between 5 and 30%, between 15 and 30%, between 15 and 25%, including any range between these values. The device

[0151] In another aspect of the invention, an apparatus (for example, an electrochemical cell) is provided comprising a first chamber(s) and a second chamber(s), each configured to contain a liquid electrolyte; wherein (i) one of the first chamber(s) and the second chamber(s) comprise a working electrode and the other comprises a counter electrode; or (ii) wherein the first chamber(s) and the second chamber(s) comprise a working electrode; and wherein the working electrode is the electrode disclosed above. In some embodiments, the apparatus is configured to carry out, induce or catalyze an electrochemical reaction. In some embodiments, the electrochemical reaction is selected from NRR, NOR, NO3RR, nitrate / nitrite reduction to hydroxylamine and nitrite reduction to ammonia, or any combination thereof.

[0152] In some embodiments, the working electrode is the cathode described above, operable at a negative potential. In some embodiments, the negative potential varies Petition 870250100702, dated 03 / 11 / 2025, p. 45 / 141 42 / 126 between 0 and -0.6, or between approximately -0.05 and -0.5 V, including any range between those values.

[0153] In some embodiments, the working electrode is the anode described above, operable at a positive working electrode potential. In some embodiments, the positive working electrode potential varies between 0.1 and 2.0 V, or about 1.7 V, including any range between these values.

[0154] In some embodiments, the liquid electrolyte (also referred to herein as an “electrolytic solution”) is or comprises an aqueous solution. In some embodiments, the liquid electrolyte comprises an organic solvent and further comprises an oxidant (for example, H2O2, hypochlorite, peracid, organic / inorganic peroxide and / or hydrogen peroxide). The terms “liquid electrolyte” and “electrolyte” or “electrolytic solution” are used herein interchangeably.

[0155] In some embodiments, the liquid electrolyte comprises between about 0.1 and 1 M, or about 0.1 M, between about 0.001 M and 5 M, between about 0.05 M and 1 M, between about 0.05 M and 5 M of a metal hydroxide (for example, alkali metal hydroxide, such as KOH, NaOH or LiOH), including any range between these values. In some embodiments, the liquid electrolyte comprises between about 0.1 and 1 M, or about 0.1 M, between about 0.001 M and 5 M, between about 0.05 M and 1 M, between about 0.05 M and 5 M of a metal sulfate (SO42-). In some embodiments, the liquid electrolyte comprises between about 0.5 and 1 M of KCl. In some embodiments, the liquid electrolyte is saturated with nitrogen. In some forms, the liquid electrolyte Petition 870250100702, dated 03 / 11 / 2025, p. 46 / 141 43 / 126 is saturated with a nitrogen / oxygen mixture (as disclosed below) or with air. In some embodiments, the liquid electrolyte is a supersaturated solution.

[0156] In some embodiments, the liquid electrolyte is a liquid alkaline electrolyte. In some embodiments, the liquid alkaline electrolyte has a pH value of at least pH 11, or at least pH 12, or at least pH 13. In some embodiments, the liquid alkaline electrolyte has a pH value between 10 and 14, between 11 and 14, or between 11 and 13, including any range between these values.

[0157] In some embodiments, the liquid alkaline electrolyte (e.g., for NRR) optionally further comprises (i) a nitrate salt or a nitrite salt and / or one or more peroxide species dissolved therein, wherein the concentration of (i) and / or (ii) is as described herein.

[0158] In some embodiments, the liquid electrolyte comprises a gas dissolved therein, wherein the gas comprises nitrogen, or a combination of nitrogen and oxygen (e.g., oxygen content between 5 and 30%, as disclosed above) and, optionally, one or more additional gases. In some embodiments, the gas is air. In some embodiments, the gas concentration in the liquid electrolyte is the maximum concentration of the specific gas, predetermined by the solubility of the specific gas in the specific liquid electrolyte and by the temperature of the liquid electrolyte. In some embodiments, the liquid electrolyte is saturated with air.

[0159] In some embodiments, the liquid electrolyte comprises a salt selected from a nitrate salt and a nitrite salt. In some embodiments, the liquid electrolyte is an alkaline electrolyte that further comprises a salt Petition 870250100702, dated 03 / 11 / 2025, p. 47 / 141 44 / 126 of nitrate or a nitrite salt dissolved in it. In some embodiments, the liquid electrolyte is supersaturated with the nitrate salt or the nitrite salt.

[0160] Figure 9A presents a schematic illustration of an apparatus (e.g., electrochemical cell) used for the electrochemical reduction of nitrogen to ammonia.

[0161] The apparatus 100 comprises an anode 101 located within a first chamber or container 110 and a cathode 102 located within a second chamber or container 120. The first and second chambers or containers 110 and 120 are configured to contain a liquid electrolyte 130. The length of the anode 101 and cathode 102 is sufficient for them to be immersed in the liquid electrolyte 130. Optionally, each of the anodes 101 and cathodes 102 is configured to be in contact with the liquid electrolyte (for example, so that at least 90% of the surface of the electrode coated with electrocatalyst is in contact with or immersed in the liquid electrolyte). The cathode 102 and the anode 101 are electrically connected to each other and can be connected to a power supply. The first chamber 110 is configured to contain a gas-pressurized liquid electrolyte (i.e., an electrolyte pressurized with a gas, wherein the gas is as described herein).The first chamber 110 and, optionally, the second chamber 120 are configured to maintain a pressure between 500 and 5000 mm Hg, or between 500 and 2000 mm Hg.

[0162] In some embodiments, apparatus 100 is an electrochemical cell, in which the first chamber 110 is a first half-cell and the second chamber 120 is a second Petition 870250100702, dated 03 / 11 / 2025, pp. 48 / 141 45 / 126 half-cell of the electrochemical cell, wherein the first chamber 110 is in liquid (e.g., fluid) communication with the second chamber 120. In some embodiments, the power supply is configured to generate a current (e.g., direct current or alternating current) at a predefined voltage sufficient for the operation of the apparatus 100.

[0163] In some embodiments, the device is operable at an electrical potential that varies between 1 and 3 V, between 1.5 and 2.5 V, between 1.7 and 2.3 V, between 1.5 and 2.3 V, including any interval between these values.

[0164] In some embodiments, the power supply is configured to generate a current (e.g., direct current). In some embodiments, the current is between 1 mA and 10 A, between 1 mA and 10 A, between 1 mA and 5 A, including any range between these values.

[0165] In some embodiments, anode 101 is the NOR activity anode disclosed above. In some embodiments, anode 101 comprises or essentially consists of the electrocatalyst characterized by NOR activity (for example, Rh catalyst or metal oxide catalyst, as disclosed above). In some embodiments, the electrocatalyst characterized by NOR activity comprises any of the following: Rh / C, Rh / C compound iron oxide-TiO2, Ni oxide, Co oxide (for example, Co3O4) and mixed spinel Ni-Co oxide, as disclosed above.

[0166] The first chamber 110 may have a valve or a pump 116 (also referred to as “first gas inlet”) configured to induce gas flow. Petition 870250100702, dated 03 / 11 / 2025, page 49 / 141 46 / 126 for the first chamber. The first gas inlet 116 may be in fluid communication with the liquid electrolyte 130 through a channel 117, so as to induce the flow of a gas (e.g., nitrogen, air or a mixture of oxygen and nitrogen) into the liquid electrolyte 130 to generate the gas-pressurized liquid electrolyte.

[0167] In some embodiments, the gas comprises a mixture of nitrogen and oxygen, wherein the oxygen content of the mixture is between 5 and 30%, between 15 and 30%, between 15 and 25%, including any range between these values. In some embodiments, the gas is or comprises air.

[0168] The first gas inlet 116 may be located at the top of the first chamber 110. The first gas inlet 116 may include a tube of various shapes and sizes, connected, fixed or integrally formed with the first chamber 110. The appliance 100 may be connected to a gas supply unit (not shown) that allows gas to be supplied through the first gas inlet.

[0169] The first chamber 110 and / or the second chamber 120 can be fitted with an overpressure control valve (optionally positioned at the top of the first / second chamber).

[0170] The first chamber 110 may have a valve or a pump (also referred to as “first liquid inlet”) 115 configured to induce a flow of liquid into the first chamber 110. The first chamber 110 may be filled with a predefined volume of liquid electrolyte via the liquid inlet 115. In some Petition 870250100702, dated 03 / 11 / 2025, p. 50 / 141 47 / 126 modes, the predefined volume of liquid electrolyte is such that anode 101 is immersed in it.

[0171] The first chamber 110 is fluidly connected to the second chamber 120 via a channel 140. The channel 140 may be located below the surface of the predetermined volume of liquid electrolyte 130 in the first chamber 110 and the second chamber 120. The channel 140 is configured to support a flow of liquid electrolyte from the first chamber 110 to the second chamber 120. The channel 140 may comprise a unidirectional flow element (e.g., valve or pump) 145 configured to generate a flow of liquid electrolyte from the first chamber 110 to the second chamber 120. In some embodiments, the unidirectional flow element 145 is located downstream of the first chamber 110 and upstream of the second chamber 120 at any location within the channel 140. In some embodiments, the unidirectional flow element 145 is a unidirectional pump.

[0172] Apparatus 100 may comprise a gas exchanger (or degassing unit) downstream of the first chamber 110 and upstream of the second chamber 120. The gas exchanger may be located anywhere within the channel 140, such as downstream of the unidirectional flow element 145. The gas exchanger is configured to substantially remove a gas (e.g., oxygen) dissolved in the liquid electrolyte of the first chamber before it enters the second chamber. The gas exchanger may be in the form of a vacuum-based degasser (configured to remove the gas dissolved in the liquid electrolyte) or a gas purge unit configured to feed an inert gas (such as nitrogen or argon) to the electrolyte. Petition 870250100702, dated 03 / 11 / 2025, page 51 / 141 48 / 126 liquid, thus replacing the gas (for example, a mixture of nitrogen and oxygen, such as air) in the liquid electrolyte with the inert gas.

[0173] In some embodiments, cathode 102 is the NO3RR activity cathode disclosed above. In some embodiments, cathode 102 comprises the electrocatalyst characterized by NO3RR activity, such as the metal oxide catalyst (e.g., RuO2, Ce oxide-Fe oxide compound) or the metal chalcogenide catalyst (e.g., NiCo2s4), disclosed above.

[0174] Apparatus 100 is configured to generate ammonia through simultaneous or subsequent reactions: NOR at anode 101 in the first chamber 110 to convert nitrogen (from the gas fed into the liquid electrolyte 130 through the first gas inlet 116) into nitrate; and NO3RR at cathode 102 in the second chamber 120 to generate ammonia from the nitrate obtained in the first chamber. 110. Apparatus 100 is configured to transfer the nitrate generated during NOR in the liquid electrolyte 130 in the first chamber 110 to the second chamber 120, where the nitrate undergoes NO3RR at the cathode 102 to generate ammonia. Apparatus 100 is configured to generate a flow of liquid electrolyte 130 within channel 140 to transfer the nitrate from the first chamber 110 to the second chamber 120. The flow can be generated via the unidirectional flow element 145.

[0175] The second chamber 120 contains a heating or cooling element and a temperature controller configured to maintain a predetermined temperature of the liquid electrolyte 130 in the second chamber 120. Petition 870250100702, dated 03 / 11 / 2025, page 52 / 141 49 / 126

[0176] The second chamber 120 may have an ammonia outlet 126. The ammonia outlet 126 may be located at the top of the second chamber 120. The ammonia outlet 126 may allow ammonia (and / or H2) to exit the second chamber 120. The ammonia outlet 126 may also allow other gases involved in ammonia synthesis, for example, nitrogen, hydrogen, to exit the second chamber. 120. The ammonia outlet 126 may be in fluid communication (e.g., through a channel or a tube) with the first liquid inlet 115. The apparatus 100 may be configured to generate a gas flow from

[0177] The ammonia outlet 126 may be in fluid communication with an ammonia capture unit. In some embodiments, the ammonia capture unit may have an ammonia trap. The ammonia trap may be in the form of a container configured to hold an acid (e.g., sulfuric acid). The ammonia collector may have an inlet, allowing a gas (e.g., ammonia and other gases) exiting the ammonia outlet 126 to enter an ammonia collector. The ammonia collector may have an outlet that allows gases (e.g., nitrogen and hydrogen) to exit it. In some embodiments, the ammonia capture unit may have a gas separation unit configured to separate (e.g., through a membrane, sorption, cryogenic distillation apparatus, etc.) ammonia from additional gases such as N2 and H2. In some embodiments, the ammonia capture unit may even be in fluid communication with a gas tank.

[0178] The ammonia capture unit may be in fluid communication (e.g., through a channel) Petition 870250100702, dated 03 / 11 / 2025, page 53 / 141 50 / 126 or a tube) with the first liquid inlet 115. Apparatus 100 can be configured to generate a gas flow from the ammonia capture unit through the first liquid inlet 115 to the first chamber 110. Apparatus 100 can be configured to feed a gas obtained from the ammonia capture unit (e.g., H2, N2, or both) into the first chamber 110, to obtain the liquid electrolyte 130 saturated with the gas (e.g., H2).

[0179] The second chamber 120 may have a one-way flow element 125 (e.g., valve or pump) configured to allow liquid electrolyte 130 to exit the second chamber 120. The valve or pump 125 may also be in fluid communication with a channel 160 configured to allow liquid electrolyte 130 to re-enter the first chamber 110 via the valve / pump 115. The channel 160 may be in the form of a tube that supports a one-way flow of liquid electrolyte 130 from the second chamber 120 to the first chamber 110. The channel 160 may be in fluid communication with the ammonia separation unit 150 located downstream of the one-way flow element. 125 and upstream of the valve / pump 115.

[0180] The ammonia separation unit 150 is configured to separate liquid electrolyte from ammonia in order to obtain a liquid electrolyte with an ammonia content of less than 0.1%, less than 0.01%, less than 1000 ppm, less than 100 ppm or less than 10 ppm. The ammonia separation unit 150 may have a heating element and, optionally, a condenser. The ammonia separation unit 150 may also be in communication Petition 870250100702, dated 03 / 11 / 2025, page 54 / 141 51 / 126 fluid with the ammonia capture unit and the gas separation unit described above.

[0181] Figure 9B presents an alternative configuration of the apparatus. As shown in Figure 9B, the first gas inlet 116 may be in fluid communication and upstream of the anode 101. The apparatus 100 may be configured to generate a gas flow from the first gas inlet 116 through the anode to the liquid electrolyte 130. The anode 101 may be composed of a porous material configured to support gas flow (e.g., metal mesh, metal foam, or a porous carbon material) from it. The anode 101 may be configured to support gas flow through at least one dimension (e.g., length, width) thereof.

[0182] Figure 7 presents a schematic illustration of an apparatus (e.g., electromechanical cell) used for the electrochemical reduction of the nitrogen-based species to ammonia, wherein the nitrogen-based species comes from nitrogen, nitrogen oxide, nitrate, and nitrite, including any combination and any salt thereof.

[0183] Apparatus 100 may have a working electrode (e.g., a cathode) 110 and an anode 120. Apparatus 100 may have a chamber or a container 105 configured to hold the liquid electrolyte. The working electrode 110 and the anode 120 may be arranged separately from each other in chamber 105.

[0184] In some embodiments, the thickness of the cathode is greater than the thickness of the anode, where the greater thickness comprises 2 times, 5 times, 10 times, 20 times, 50 Petition 870250100702, dated 03 / 11 / 2025, page 55 / 141 52 / 126 times, 100 times greater thickness, including any intervals in between. Increasing the cathode thickness is essential to increase the electrocatalytic surface area in contact with the gas and thus improve the electrocatalytic performance of the instantaneous apparatus.

[0185] In some embodiments, the cathode thickness is between 0.1 mm and 100 cm, between 0.2 mm and 20 cm, between 0.2 mm and 1 m, including any range between these values.

[0186] In some embodiments, the width or cross-sectional dimension of the electrochemical cell can vary between several centimeters and several meters.

[0187] In some embodiments, ammonia can be synthesized on the outer surface of the working electrode 110, where the outer surface faces the liquid electrolyte.

[0188] Apparatus 100 may have an electrode separation membrane 125. The electrode separation membrane 125 may be disposed in chamber 105. The electrode separation membrane 125 may be disposed in chamber 105 between cathode 110 and anode 120 and may electrically separate cathode 110 and anode 120, for example, by dividing chamber 105 to define a cathode zone 112 and an anode zone 114.

[0189] Chamber 105 may have a gas inlet 130 (also referred to as the “first gas inlet”). The gas inlet 130 may be located in a lower part of chamber 105, for example, in the cathode zone 112. The gas inlet 130 may include a tube of various shapes and sizes, either connected, fixed, or integrally formed. Petition 870250100702, dated 03 / 11 / 2025, p. 56 / 141 53 / 126 with chamber 105. Gas inlet 130 can allow gas (e.g., nitrogen, air, or a mixture of oxygen and nitrogen) to enter chamber 105. Optionally, the gas can be humidified with water vapor.

[0190] Appliance 100 can be connected to a gas supply unit 150, allowing gas to be supplied through gas inlet 130. Gas can enter the gas supply unit 150 and, optionally, the gas can be humidified in the gas supply unit 150.

[0191] Apparatus 100 may have an ammonia outlet 160. The ammonia outlet 160 may be located in chamber 105, for example, in the cathodic zone 112. The ammonia outlet 160 may allow ammonia to exit chamber 105. The ammonia outlet 160 may also allow the generated hydrogen gas to exit chamber 105. The ammonia outlet 160 may also allow other gases involved in ammonia synthesis, for example, nitrogen, air, or water, to exit chamber 105.

[0192] Apparatus 100 may have an ammonia collector 170. The ammonia collector 170 may be in the form of a container configured to hold an acid (e.g., sulfuric acid). The ammonia collector 170 may have an inlet 180, allowing a gas (e.g., ammonia and other gases) exiting the ammonia outlet 160 to enter the ammonia collector 170. The ammonia collector 170 may have a first outlet 190 that allows ammonia to exit. The first outlet 190 may be located at the bottom of the ammonia collector 170. The first outlet 190 may include a valve that allows control of the ammonia flow rate exiting the outlet 190. The ammonia collector 170 may have a second outlet 200 Petition 870250100702, dated 03 / 11 / 2025, page 57 / 141 54 / 126 which allows gases (e.g., nitrogen and hydrogen) to exit it. Outlet 200 may be located at the top of ammonia collector 170.

[0193] Chamber 105 may have another gas inlet 210 (also referred to as a “second gas inlet”). Inlet 210 may be located at the bottom of chamber 105, for example, in the anode area 114. Gas inlet 210 may include a tube of various shapes and sizes, connected, fixed, or integrally formed with chamber 105. Gas inlet 210 may also allow gases (e.g., nitrogen and hydrogen) exiting the second outlet 200 to re-enter or recirculate back into chamber 105.

[0194] Appliance 100 may have a gas outlet 220. The gas outlet 220 may be located in chamber 105, for example, in the anode zone 114. The gas outlet 220 may allow gases (for example, gases involved in ammonia synthesis, such as nitrogen or water) to exit chamber 105. The gas outlet 220 may include a tube of various shapes and sizes, connected, fixed, or integrally formed with chamber 105. Optionally, the gases exiting chamber 105 through the gas outlet 220 may be allowed to re-enter or recirculate to chamber 105 through the gas inlet 130.

[0195] Apparatus 100 may have several components of the apparatus disclosed here, such as any of the valves, sensors, blowers, fans, shock absorbers or pumps, etc.

[0196] In some embodiments, apparatus 100 is an electrochemical cell and is configured to synthesize ammonia at a rate (in mol cm-2s-1) of 1 x 10-8, at least 5 Petition 870250100702, dated 03 / 11 / 2025, p. 58 / 141 55 / 126 x 10-8, at least 1 x 10-9, 2 x 10-9, at least 3 x 10-9, 4 x 10(-9), at least 5 x 10(-9), including any value and interval thereafter, for example, at a pressure of 1 atm. According to one aspect of some embodiments of the present invention, an electrolysis cell is provided with an electrocatalyst comprising the composition disclosed in one embodiment thereof. In some embodiments, the electrocatalyst is the cathode.

[0197] The term electrochemical cell or cell, as used herein, generally refers to a device that converts chemical energy into electrical energy, or electrical energy into chemical energy. Electrochemical cells typically have two or more electrodes and an electrolyte, wherein electrode reactions occurring on the electrode surfaces result in charge transfer processes. Examples of electrochemical cells include, but are not limited to, batteries and electrolysis systems.

[0198] In some embodiments, the electrochemical cell is configured to synthesize ammonia at a rate of 1 x 10-12 mol s-1cm-2a 1 x 10-6 mol s-1cm-2a 1 atm N2.

[0199] In some embodiments, the electrochemical cell is configured to synthesize ammonia (from an aqueous solution of nitrite or nitrate electrolytic, or from a liquid electrolyte comprising nitrogen) at a rate of 1 x 10⁻¹² mol s⁻¹cm⁻², 1 x 10⁻⁶ mol s⁻¹cm⁻², 5 x 10⁻¹² mol s⁻¹cm⁻², 1 x 10⁻⁷ mol s⁻¹cm⁻², 10 x 10⁻¹¹ mol s⁻¹cm⁻², 1 x 10⁻⁷ mol s⁻¹cm⁻², 1 x 10⁻¹⁰ mol s⁻¹cm⁻², 1 x 10⁻⁷ mol s⁻¹cm⁻², 10 x 10⁻¹⁰ mol s⁻¹cm⁻², 1 x 10⁻⁷ mol Petition 870250100702, dated 03 / 11 / 2025, page 59 / 141 56 / 126 s-1cm-2, 1 x 10-11mol s-1cm-2a 1 x 10-8mol s-1cm-2, or 1 x 1010mol s-1cm-2a 1 x 10-8mol s-1cm-2, at least 6 x 10-11mol s-1cm-2, at least 6.5 x 10-11mol s-1cm-2, including any interval between these values.

[0200] In some embodiments, the electrochemical cell is configured to synthesize ammonia with a faradaic efficiency at a cathodic electrical potential in the range of 4% to 50%, 1% to 25%, 1% to 20%, 1% to 15%, 1% to 10%, 3% to 30%, 5% to 30%, 5% to 25%, 5% to 20%, 5% to 15% or 5% to 10%, including any range between them.

[0201] In some embodiments, the faradaic efficiency of the electrochemical cell is at least 4%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 30% or at least 40%, including any range in which the electrical potential is between 0.3 and -0.5 V relative to the standard hydrogen reference electrode (SHE).

[0202] In some embodiments, the faradaic efficiency of the electrochemical cell is at least 4%, at least 5%, at least 10%, at least 30%, wherein the electrical potential is between about -0.2 and about -0.3 V relative to the standard hydrogen reference electrode (SHE).

[0203] Apparatus 100 can be used to synthesize hydrogen.

[0204] Apparatus 100 can be used to synthesize ammonia by NRR using the liquid electrolyte described herein. In some embodiments, the liquid electrolyte for NRR further comprises (i) one or more peroxide species (e.g., H2O2) and (ii) a nitrate anion or a salt thereof dissolved therein. Petition 870250100702, dated 03 / 11 / 2025, p. 60 / 141 57 / 126

[0205] In some embodiments, the concentration of one or more peroxide species in the liquid electrolyte is between 1 and 1000 uM, between 50 and 1000 uM, between 10 and 200 uM, between 50 and 200 uM, between 50 and 500 uM, including any range between these values.

[0206] In some embodiments, the nitrate concentration in the liquid electrolyte is in the range of 0.0001 M to 0.1 M, 0.01 M to 2 M, 0.001 M to 5 M, 0.001 M to 0.1 M, 0.05 M to 1 M, 0.1 M to 1 M, 0.05 M to 5 M, about 0.1 M to about 1 M, including any range between these values.

[0207] In some embodiments, the liquid electrolyte for NRR is further saturated with In some embodiments, the liquid electrolyte comprises a gas dissolved within it, wherein the gas comprises nitrogen, or a combination of nitrogen and oxygen (e.g., oxygen content between 5 and 30%, as disclosed above) and, optionally, one or more additional gases. In some embodiments, the gas is air.

[0208] In some embodiments, the appliance 100 does not have a gas inlet 130 and / or a gas supply unit 150. In some embodiments, the appliance 100 does not have a gas inlet 130 and / or a gas supply unit 150, and the liquid electrolyte is an alkaline electrolyte that further comprises a nitrate salt or a nitrite salt dissolved within it and is substantially nitrogen-free.

[0209] In some embodiments, the working electrode 110 (e.g., cathode) is the electrode of the invention. In some embodiments, the working electrode 110 (e.g., cathode) is the electrode of the invention. Petition 870250100702, dated 03 / 11 / 2025, p. 61 / 141 58 / 126 example, cathode) is selected from an iron oxide-TiO2 compound or a noble metal compound comprising at least two noble metals.

[0210] In some embodiments, the noble metal compound comprises a first noble metal and a second noble metal, wherein the molar ratio of the first noble metal to the second noble metal is in the range of 1:9 to 9:1, 2:9 to 9:1, 3:9 to 9:1, 4:9 to 9:1, 5:9 to 9:1, 6:9 to 9:1, 7:9 to 9:1, 8:9 to 9:1, 9:9 to 9:1, 1:9 to 9:2, 1:9 to 9:3, 1:9 to 9:4, 1:9 to 9:5, 1:9 to 9:6, 1:9 to 9:7, 1:9 to 9:8, or 1:9 to 9:9, including any interval between them.

[0211] In some embodiments, the noble metal compound is a layered material comprising a first layer in contact with a second layer, wherein the first layer comprises or consists essentially of the first noble metal, and wherein the second layer comprises or consists essentially of the second noble metal. In some embodiments, the noble metal compound is an alloy.

[0212] In some embodiments, the noble metal compound is in the form of a coating, where the coating is as described herein. In some embodiments, the noble metal compound is in the form of particles, the particles having a size in the range of 1 nm to 50 μn, 3 nm to 50 μn, 5 nm to 50 μn, 10 nm to 50 μn, 25 nm to 50 μn, 50 nm to 50 μn, 100 nm to 50 μn, 250 nm to 50 μn, 500 nm to 50 μn, 1 nm to 900 nm, 1 nm to 800 nm, 1 nm to 500 nm, 1 nm to 250 nm or 1 nm to 100 nm, including any interval between them.

[0213] In some forms, the noble metal comprises Ru, Rh, Pd, Ag, Re, Ir, Pt and Au, or any Petition 870250100702, dated 03 / 11 / 2025, p. 62 / 141 59 / 126 combination thereof. In some embodiments of the present invention, the noble metal comprises ruthenium (Ru) and platinum (Pt), wherein the molar ratio of Ru to Pt is in the range of 1:10 to 10:1, respectively.

[0214] In some embodiments, the Ru:Pt molar ratio within the noble metal compound is 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, respectively, including any value and range between them.

[0215] In exemplary embodiments, the noble metal compound consists essentially of Ru and Pt, where the molar ratio of Ru to Pt is about 1:1 (±20%).

[0216] The exemplary non-limiting anode 120 comprises nickel (Ni), iron, zinc, cobalt, chromium, titanium or any oxide or a combination thereof.

[0217] In some embodiments, the apparatus 100 is configured to synthesize ammonia. In some embodiments, the apparatus 100 is configured to synthesize ammonia from a liquid electrolyte comprising a nitrate salt or a nitrite salt dissolved therein. In some embodiments, the apparatus 100 is configured to synthesize ammonia from a supersaturated liquid electrolyte comprising a nitrate salt or a nitrite salt dissolved therein, reducing the nitrate salt or a nitrite salt at the working electrode 110 (e.g., cathode); wherein the working electrode 110 comprises an electrocatalyst selected from (i) the electrocatalyst of the invention, (ii) iron oxide-TiO2 compound, or (iii) the noble metal compound, as described above. In some Petition 870250100702, dated 03 / 11 / 2025, page 63 / 141 In modes 60 / 126, apparatus 100 is configured to synthesize ammonia by applying a voltage to the working electrode.

[0218] In some modes, the voltage is between 0.5 and 0, between 0.5 and -2 V, between 0.4 and -2 V, between 0.3 and -2 V, between 0.1 and -2 V, between 0.3 and -0.5 V, including any range between these values. In some modes, the voltage is a negative voltage.

[0219] In some embodiments, the negative voltage is at least -0.05 V, at least -0.1 V, at least -0.15 V, at least -0.2 V, between -0.05 and -2 V, between -0.1 and -2 V, between -0.1 and -1 V, between -0.05 and -0.5 V, between -0.1 and -0.5 V, between -0.1 and -0.7 V, including any interval between them relative to the standard hydrogen reference electrode (SHE).

[0220] In some embodiments, the working electrode 110 is an activated electrode, wherein the activated electrode is as described above. In some embodiments, the working electrode 110 is subjected to activation before each operating cycle. In some embodiments, the working electrode 110 is activated by contact with an oxidizing solution comprising an effective amount of an oxidant (e.g., between 100 ppm and 20% w / w), such as a hypochlorite, a peroxide (such as H2O2), a peracid or a precursor thereof. In some embodiments, the oxidizing solution comprises a ROS (e.g., singlet oxygen, superoxide, hydroxyl radical, etc.). In some embodiments, the working electrode 110 is activated by its exposure to oxygen or air and by the application to the working electrode of a potential above 0.5 V, above 0.7 V, above 0.8 V, above 0.9 V, above 1 V, between 0.5 and 2 V, between 0.7 and 2 V, between 0.8 and 2 V, Petition 870250100702, dated 03 / 11 / 2025, page 64 / 141 61 / 126 between 1 and 2 V, including any range between these values.

[0221] In some embodiments, the working electrode 110 also includes the co-catalyst. In some embodiments, the working electrode 110 is activated by the activation of the co-catalyst, as disclosed herein.

[0222] The dimensions of each component of the apparatus are selected to be sufficient for a given desired fluidization and to provide sufficient contact time to provide, for example, a desired level of water / nitrogen consumption and / or ammonia regeneration.

[0223] Conditions can be monitored using any type of suitable monitoring device, for example, a computer-implemented system. Variables that can be tracked include, but are not limited to, pH, temperature, electrical potential, conductivity, turbidity, gas flow rate at each inlet or outlet, concentration of the alkaline solution. These variables can be recorded throughout the apparatus 100.

[0224] A monitoring device, a control unit or a controller (e.g., computer) may also be used to monitor, control and / or automate the operation of the various components of the apparatus described herein, such as any of the valves, sensors, dams, blowers, fans, dampers, pumps, etc.

[0225] The present apparatus of the invention may be a system, a method and / or a computer program product. The computer program product may Petition 870250100702, dated 03 / 11 / 2025, p. 65 / 141 62 / 126 comprise a computer-readable storage medium. The computer-readable storage medium may have embedded program code. The computer-readable storage medium may be a tangible device that can retain and store instructions for use by an instruction-executing device. The computer-readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof.A non-exhaustive list of more specific examples of computer-readable storage media includes the following: a laptop disk, a hard disk drive, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash memory), static random access memory (SRAM), portable compact disc read-only memory (CDROM), a digital versatile disc (DVD), a memory card, a mechanically encoded device such as punched cards or structures protruding into a slot with instructions recorded on them, and any suitable combination of the above.A computer-readable storage medium, as used herein, should not be interpreted as being transient signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., pulses of light). Petition 870250100702, dated 03 / 11 / 2025, page 66 / 141 63 / 126 that pass through a fiber optic cable), or electrical signals transmitted through a wire.

[0226] The computer-readable program instructions described herein may be downloaded to the respective computing / processing devices from a computer-readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network may comprise copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer-readable program instructions from the network and forwards the computer-readable program instructions for storage on a computer-readable storage medium within the respective computing / processing device.

[0227] The computer-readable program instructions for performing operations of the present invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state configuration data, or source code or object code written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++, or similar, and conventional procedural programming languages ​​such as the C programming language or Petition 870250100702, dated 03 / 11 / 2025, page 67 / 141 64 / 126 similar programming languages. Computer-readable program instructions can be executed entirely on the user's computer, partially on the user's computer as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on the remote computer or server. In the last scenario, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (e.g., via the Internet using an Internet service provider).In some embodiments, electronic circuits including, for example, programmable logic circuits, field-programmable gate arrays (FPGAs) or programmable logic arrays (PLAs) can execute computer-readable program instructions using state information from the computer-readable program instructions to customize the electronic circuits in order to realize aspects of the present invention. Ammonia synthesis

[0228] In some embodiments, ammonia can be synthesized using the electrolytic cell described herein.

[0229] In one aspect, a process for synthesizing ammonia from a gas comprising nitrogen is provided, the process comprising: (i) providing a liquid electrolyte (e.g., the aqueous electrolyte described herein) to the apparatus of the invention (e.g., electrochemical cell as illustrated in Figures 9A-B) Petition 870250100702, dated 03 / 11 / 2025, page 68 / 141 65 / 126 comprising the anode and cathode; (ii) generate a gas flow to the electrolyte in contact with the anode; and (iii) generate a positive electrical potential in the apparatus; thus obtaining ammonia; wherein the anode has the activity NOR and the cathode has the activity NO3RR, as disclosed herein.

[0230] In some embodiments, the method of synthesizing ammonia from nitrogen or a gas comprising it (referred to herein as the “NRR method”) comprises: filling the liquid electrolyte into the first and second chambers of the electrochemical cell of the invention; generate a flow of a gas comprising nitrogen in the first chamber; To generate a liquid flow from the first chamber to the second chamber, an electric current is applied to the electrochemical cell; in response to the applied electric current, the electrochemical cell generates nitrate in the first chamber (via NOR at the anode) and ammonia in the second chamber (via NO3RR at the cathode).

[0231] In some embodiments, the gas flow is generated by feeding a pressurized gas through the first gas inlet, or by using a pump (e.g., as the first gas inlet 116) in fluid communication with a vessel comprising the gas and configured to feed the gas from the vessel to the first chamber. In some embodiments, the method comprises generating a gas flow to the first chamber to saturate the liquid electrolyte in the first chamber with the gas. In some embodiments, the gas flow is directed to the liquid electrolyte volume (e.g., through a tube entering the liquid electrolyte volume). Petition 870250100702, dated 03 / 11 / 2025, page 69 / 141 66 / 126

[0232] In some embodiments, the gas flow is generated through the first gas inlet in fluid communication with the anode, wherein the anode comprises a porous material configured to support the flow of gas through it.

[0233] In some embodiments, the liquid flow is generated through the unidirectional flow element 145 (e.g., a liquid pump). In some embodiments, the gas further comprises between 5 and 30%, between 10 and 30%, between 10 and 25% v / v of oxygen, including any range between these values. In some embodiments, the gas is or comprises a mixture of oxygen and nitrogen, wherein the oxygen content of the gas is as described above. In some embodiments, the gas is air.

[0234] In some forms, the electric current is generated by the power supply. In some forms, the electric current is a direct current. In some forms, the device is operated with a positive electric potential. In some forms, the positive electric potential is between 1 and 3 V, between 1.5 and 3 V, between 1.5 and 2.5 V, between 1.7 and 3 V, between 1.7 and 2.5 V, between 1.7 and 2.3 V, between 1.7 and 2 V, including any interval between these values.

[0235] In some embodiments, the liquid flow has a flow rate between 0.01 and 5 ml / min, between 0.01 and 1 ml / min, between 0.01 and 0.5 ml / min, between 0.1 and 1 ml / min, between 0.1 and 0.5 ml / min, including any interval between these values.

[0236] In some embodiments, the gas flow is carried out at a flow rate between 1 ml / min and 1000 L / min, between 1 Petition 870250100702, dated 03 / 11 / 2025, p. 70 / 141 67 / 126 ml / min and 100 L / min, between 0.1 L / min and 10 L / min, including any interval between these values.

[0237] In some embodiments, the gas flow generation step and the liquid flow generation step are performed simultaneously or subsequently (for example, the gas flow is generated before the liquid flow). In some embodiments, the gas flow generation step is performed simultaneously with the electric current application step (and before the liquid flow generation step), where the gas flow is maintained for a sufficient time to generate a predetermined nitrate concentration. In some embodiments, the predetermined nitrate concentration is at least 300, at least 400, at least 500 µM, or between 0.01 and 2 M nitrate, including any range between these values.

[0238] In some embodiments, the electric current application stage and the liquid flow generation stage are performed simultaneously or subsequently. In some embodiments, the electric current application stage is performed before the liquid flow generation stage.

[0239] In some embodiments, the liquid electrolyte further comprises an ion selected from hydroxide, halide (e.g., chloride), sulfate, nitrite, and nitrate, including any combination thereof. In some embodiments, the liquid electrolyte is an aqueous electrolyte comprising between 0.01 and 2M of at least one ion selected from hydroxide and sulfate and optionally further comprises any of the following: halide (e.g., chloride), nitrite, and nitrate. Petition 870250100702, dated 03 / 11 / 2025, page 71 / 141 68 / 126

[0240] In another aspect, a process for synthesizing ammonia from nitrate or nitrite via NO3RR is provided, the process comprising: (i) providing a liquid electrolyte (e.g., aqueous electrolyte) comprising a nitrate salt or a nitrite salt to the electrochemical cell of the invention comprising the working electrode (with NO3RR activity) and the counter electrode, as disclosed herein; and (ii) applying an electrical potential to the electrochemical cell under suitable conditions to generate ammonia; thereby obtaining ammonia.

[0241] In some embodiments, an ammonia synthesis process is provided, the process comprising: (i) supplying the liquid electrolyte to the electrochemical cell, wherein a working electrode comprises the electrocatalyst of the invention (comprising a transition metal oxide that is not iron oxide and / or TiO2), and simultaneously or subsequently bringing the liquid electrolyte into contact with a gas comprising or consisting essentially of air, nitrogen or a mixture of oxygen and nitrogen; and (ii) applying an electrical potential to the electrochemical cell under suitable conditions to generate ammonia; thereby obtaining ammonia.

[0242] In some embodiments, an ammonia synthesis process is provided, the process comprising: (i) supplying the supersaturated alkaline electrolyte solution to the electrochemical cell of the invention comprising the cathode as the working electrode and, simultaneously or subsequently, bringing the supersaturated alkaline electrolyte into contact with a gas comprising or consisting essentially of air, nitrogen or a mixture of Petition 870250100702, dated 03 / 11 / 2025, page 72 / 141 69 / 126 oxygen and nitrogen; and (ii) apply a cathodic electrical potential to the electrochemical cell under suitable conditions to generate ammonia; thus obtaining ammonia.

[0243] In some embodiments, the electrical potential comprises a negative cathodic potential of at least -0.05 V, at least -0.1 V, or between -0.05 and -0.6 V, between -0.05 and -0.5 V, between -0.05 and -0.4 V relative to the RHE, including any range between these values. In some embodiments, ammonia synthesis is carried out at a low electrical potential. In some embodiments, the low electrical potential is necessary to avoid the competing hydrogen evolution reaction.

[0244] In some embodiments, the electric potential comprises a positive cathodic potential of at least 0 V, at least 0.05 V, or between 0.05 and 0.3 V, between 0.05 and 0.2 V, or about 0.1 V relative to the RHE, including any interval between them.

[0245] In some embodiments, the electric potential comprises a positive anodic potential (e.g., for NOR using Rh / C as an electrocatalyst) of at least 1 V, at least 1.5 V, or between about 1.5 and about 2 V, between about 1.5 and about 1.9 V, between about 1.5 and about 1.8 V, between about 1.5 and about 1.7 V, between 1.6 and 1.7 V, or approximately 1.7 V relative to the RHE, including any range between these values.

[0246] Ammonia is synthesized using the liquid electrolyte as described above. In some embodiments, the synthesis of ammonia from gas comprising or consisting essentially of air, nitrogen, a mixture of oxygen and nitrogen, or a mixture of Petition 870250100702, dated 03 / 11 / 2025, page 73 / 141 70 / 126 nitrogen and hydrogen and, optionally, oxygen, is carried out by (i) activating the working electrode, as disclosed below, thereby generating a nitrogen oxide (e.g., comprising nitrite and / or nitrate) in the liquid electrolyte (e.g., supersaturated alkaline electrolyte); and (ii) subsequently applying a negative electrical potential to the working electrode, thereby reducing the nitrogen oxide to generate ammonia.

[0247] In some embodiments, the synthesis of ammonia from gas comprising or consisting essentially of air, nitrogen or a mixture of oxygen and nitrogen is carried out (i) by applying a positive electrical potential to the working electrode, thereby generating a nitrogen oxide (for example, comprising nitrite and / or nitrate); and (ii) by subsequently applying a negative electrical potential to the working electrode, thereby reducing the nitrogen oxide to generate ammonia.

[0248] In some embodiments, step (i) is performed under conditions (e.g., normal pressure, temperature as disclosed herein, etc.) and for a period of time sufficient to convert at least 5%, at least 10%, at least 20%, at least 50%, at least 70%, at least 80%, at least 90%, at least 95% of the initial nitrogen content of the electrochemical cell into nitrogen oxide, including any interval in between. In some embodiments, the positive electrical potential of step (i) is at least 0.5 V, at least 1 V, at least 2 V, between 0.5 and 5 V, between 1 and 5 V, between 1 and 2 V, between 0.5 and 3 V, between 1 and 3 V relative to RHE, including any interval in between. Petition 870250100702, dated 03 / 11 / 2025, page 74 / 141 71 / 126

[0249] In some embodiments, step (ii) is carried out under conditions (e.g., normal pressure, temperature as disclosed herein, etc.) and for a period of time sufficient to convert at least 20%, at least 50%, at least 70%, at least 80%, at least 90%, at least 95% of the nitrogen oxide generated in step (i), including any interval in between. In some embodiments, the negative electrical potential of step (ii) is as described above.

[0250] In some embodiments, ammonia synthesis is carried out at a temperature of 5°C to 150°C, 5 to 80°C, 5 to 10°C, 5 to 20°C, 5 to 30°C, 30°C to 70°C, 30°C to 65°C, or 30°C to 150°C, including any range between them.

[0251] In some embodiments, ammonia synthesis is carried out at a temperature of 10 to 30°C. In some embodiments, ammonia synthesis is carried out at a temperature of 10 to 50°C.

[0252] In some embodiments, ammonia synthesis is carried out at a pressure of 500 to 2000 mm Hg. In some embodiments, synthesis is carried out at a pressure of 500 to 1000 mm Hg.

[0253] In some embodiments, ammonia synthesis is carried out at room temperature. In some embodiments, ammonia synthesis is carried out at room pressure. In some embodiments, ammonia synthesis is carried out at room pressure and room temperature.

[0254] In some applications, the term “ambient pressure” is intended to mean approximately 740 mm Hg to approximately 780 mm Hg. Petition 870250100702, dated 03 / 11 / 2025, page 75 / 141 72 / 126

[0255] In some embodiments, the method further comprises a preliminary activation step of the working electrode, wherein the preliminary step is performed before performing step i. In some embodiments, the preliminary step is performed before performing step ii. In some embodiments, the preliminary step is performed under suitable conditions to obtain the activated electrode. The presence of radical species on the surface of the activated electrode can be determined as described above.

[0256] In some embodiments, the preliminary activation step of the working electrode comprises contacting it with an oxidizing solution comprising an effective amount of an oxidant (for example, between 100 ppm and 20% w / w), such as a hypochlorite, a peroxide (such as H2O2), a peracid or a precursor thereof. In some embodiments, the oxidizing solution comprises a ROS (e.g., singlet oxygen, superoxide, hydroxyl radical, etc.) or an agent configured to generate ROS.

[0257] In some embodiments, the preliminary activation step of the working electrode comprises exposing the working electrode to oxygen or a gas mixture comprising oxygen (e.g., air), applying to the working electrode a potential above 0.5 V, above 0.7 V, above 0.8 V, above 0.9 V, above V, between 0.5 and 2 V, between 0.7 and 2 V, between 0.8 and 2 V, between and 2 V, including any interval in between. In some embodiments, the application is for a period of time between 1 and 2 h, including any interval in between. In some embodiments, the application is made at a temperature between 5 and 100 °C, including any interval in between. In some Petition 870250100702, dated 03 / 11 / 2025, page 76 / 141 In 73 / 126 modes, exposure of the working electrode to oxygen is achieved by introducing a gas comprising oxygen (e.g., air or pure oxygen) into the liquid electrolyte.

[0258] In some embodiments, the preliminary step and subsequent steps i-ii are performed sequentially, consecutively, or simultaneously. In some embodiments, the preliminary step and subsequent steps i-ii are performed sequentially or consecutively, forming an operating cycle. In some embodiments, the invention process comprises the simultaneous performance of a plurality of operating cycles.

[0259] The dimensions of each component of the apparatus are selected to be sufficient for a given desired fluidization and to provide sufficient contact time to provide, for example, a desired level of nitrate or nitrite / nitrogen consumption and / or ammonia generation. Ammonia generation can be determined by measuring the volume of gas emerging from the apparatus of the invention or, alternatively, by means of UV-Vis colorimetric spectroscopy. The concentration of nitrate or nitrite in the liquid electrolyte can be determined spectroscopically (for example, by measuring the UV absorption of the aqueous electrolyte solution).

[0260] In some embodiments, ammonia synthesis is characterized by a faradaic efficiency at a cathodic (e.g., negative) electrical potential in the range of 4% to 50%, 1% to 25%, 1% to 20%, 1% to 15%, 1% to 10%, 3% to 30%, 5% to 30%, 5% to 25%, 5% to 20%, 5% to 15% or 5% to 10%, including any range between them. Petition 870250100702, dated 03 / 11 / 2025, page 77 / 141 74 / 126

[0261] In some embodiments, the synthesis of ammonia is characterized by a faradaic efficiency of at least 4%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 30% or at least 40%, including any range in which the electrical potential is between -0.1 and -0.5 V.

[0262] In some embodiments, the synthesis of ammonia is characterized by a faradaic efficiency of at least 4%, at least 5%, at least 10%, at least 30%, wherein the electrical potential is between about -0.2 and about -0.3 V.

[0263] In some embodiments, the synthesis of ammonia is characterized by a rate of ammonia production in the range of 1 x 10-11mol s-1cm-2a 1 x 10-7mol s-1cm-2, 5 x 10-11mol s-1cm-2a x 10-17cm-2a 10 x 10-11mol s-1cm-2a 1 x 10-7mol s-1cm-2a, 1 x 10-10mol s-1cm-2a 1 x 10-7mol s-1cm-2a 1 x 10-10mol s-1cm-2a 1 x 10-17mol s-1cm-2a s-1cm-2a 1 x 10—8 mol s-1cm-2, or 1 x 10-10mol s-1cm-2a 1 x 10-8mol s-1cm-2, including any interval between them. General

[0264] The terms comprise, including, include, having and their conjugates mean including, but not limited to. The term consisting of means including and limited to. The term consisting essentially of means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and innovative characteristics of the claimed composition, method or structure. Petition 870250100702, dated 03 / 11 / 2025, page 78 / 141 75 / 126

[0265] The word exemplar is used here to mean serving as an example, instance, or illustration. Any modality described as exemplary should not necessarily be interpreted as preferable or advantageous in relation to other modalities and / or exclude the incorporation of characteristics of other modalities.

[0266] The word optionally is used here to mean is provided in some embodiments and is not provided in other embodiments. Any specific embodiment of the invention may include a plurality of optional features, unless such features conflict.

[0267] As used in this document, the singular forms a, an and the include plural references, unless the context clearly indicates otherwise. For example, the term a compound or at least one compound may include a plurality of compounds, including mixtures thereof.

[0268] Throughout this descriptive report, various embodiments of the present invention may be presented in a range format. It should be understood that the range description is intended solely for convenience and brevity and should not be interpreted as an inflexible limitation of the scope of the invention. Thus, the description of a range should be considered as having specifically disclosed all possible sub-ranges as well as individual numerical values ​​within that range. For example, the description of a range such as 1 to 6 should be considered as having specifically disclosed sub-ranges such as 1 to 3, 1 Petition 870250100702, dated 03 / 11 / 2025, page 79 / 141 76 / 126 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5 and 6. This applies regardless of the range width.

[0269] Whenever a numerical interval is indicated here, it must include any number quoted (fractional or integral) within the indicated interval. The expressions “ranging / intervals between” a first number indicated and a second number indicated and “ranging / intervals from” a first number indicated “to” a second number indicated are used here interchangeably and must include the first and second numbers indicated and all fractional and integral numbers between them.

[0270] As used in this document, the term “method” refers to ways, means, techniques and procedures for performing a given task, including, but not limited to, those ways, means, techniques and procedures known or readily developed from ways, means, techniques and procedures known to professionals in the chemical and electrochemical fields.

[0271] In cases where a convention analogous to “at least one of A, B and C, etc.” is used, such a construction is generally intended to be understood in the sense that a specialist in the field would understand the convention (for example, “a system that has at least one of A, B and C” would include, but not be limited to, systems that have only A, only B, only C, A and B together, A and C together, B and C together and / or A, B and C together, etc.). Petition 870250100702, dated 03 / 11 / 2025, pp. 80 / 141 77 / 126

[0272] Experts in the technical field will also understand that virtually any disjunctive word and / or phrase that presents two or more alternative terms, whether in the description, claims or drawings, should be understood as encompassing the possibilities of including one of the terms, either of the terms or both terms. For example, the sentence A or B will be understood as including the possibilities of A or B or A and B.

[0273] It is important to emphasize that certain features of the invention, which are described, for greater clarity, in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, several features of the invention, which are described, for brevity, in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as appropriate in any other described embodiment of the invention. Certain features described in the context of several embodiments should not be considered essential features of those embodiments unless the embodiment is inoperative without those elements. EXAMPLES

[0274] Reference is now made to the following examples, which, together with the descriptions above, illustrate some embodiments of the invention in a non-limiting manner. Material characterizations

[0275] X-ray powder diffraction (XRD) analysis of the samples was performed using a Rigaku Smart Lab SE diffractometer. For infrared spectra by Petition 870250100702, dated 03 / 11 / 2025, page 81 / 141 Fourier transform infrared (FT-IR) spectroscopy of the synthesized catalysts was performed using the KBr pellet method on a Bruker vertex70 instrument. Raman spectroscopy was performed using a Kratos AXIS-HS spectrometer with a 532 nm laser and a monochromatic Al Ka ​​source, as well as the Horiba Scientific XploRA ONE™ micro-Raman system from Japan. To determine the iron content in the electrolyte, inductively coupled plasma optical emission spectroscopy (ICPOES) was performed using a Spectro Arcos optical emission spectrometer. For X-ray photoelectric spectroscopy (XPS) analysis, which provides information on the electronic / chemical states and elemental composition of the catalyst, a Nexsa spectrometer equipped with a monochromatic Al Ka ​​X-ray source was used. A JEOL JSM-35 CF scanning electron microscope (SEM) was used for morphological analysis of the materials. Electrochemical measurements Quantification of nitrate / nitrite

[0276] The nitrate / nitrite concentration in the electrolyte was determined using a UV-Visible spectrophotometer. Absorbance at 300 and 350 nm was measured for nitrate (NOa-) and nitrite (NO2-), respectively. A calibration curve was generated based on the known nitrate / nitrite concentrations in 0.1 M KOH solution. The nitrate formation rate and its faradaic efficiency were calculated using Equations 3 and 4. Rate of formation of NO3- or NO2- = (C x V) / (t x A) (3) FE% = (3 x F x Cx V) / (Qx MW) (4) Petition 870250100702, dated 03 / 11 / 2025, page 82 / 141 79 / 126

[0277] C is the concentration of NO3- or NO2- in μM; V is the sample volume in mL; t is the electrolysis time in hours; A is the active electrode area in cm²; Q is the applied charge in coulombs; MW is the molecular weight of NO₃⁻ (62.004 g mol⁻¹) or NO₂⁻ (46.005 g mol⁻¹); and F is the Faraday constant. 96485 C mol-1. Ammonia quantification

[0278] The ammonia concentration in the samples was determined using a UV-Visible spectrophotometer, employing the indophenol blue method. Initially, approximately 200 μL of each sample were diluted to a final volume of 2.0 mL. This dilution was performed using a 0.1 M potassium hydroxide (KOH) solution containing 5 wt% salicylic acid and 5 wt% sodium citrate dissolved in a 1 M sodium hydroxide (NaOH) solution. In the next step, 1 mL of 0.05 M sodium hypochlorite (NaOCl) followed by 0.2 mL of 1 wt% sodium nitroprusside (Na2[Fe(CN)(õ)NO]) were added to the mixture. The reaction mixture was then stored in a dark place for 1 hour to ensure completion of the reaction before measuring the absorbance at 655 nm. For calibration purposes, a series of ammonia standards with known concentrations were prepared in 0.1 M KOH solution. These standards were subjected to the same procedure to construct a calibration curve.The rate of ammonia formation and the faradaic efficiency (FE) were calculated using equations 3 and 4, respectively. These calculations incorporated the molecular weight of ammonia, which is 17.031 g / mol. EXAMPLE 1 Petition 870250100702, dated 03 / 11 / 2025, page 83 / 141 80 / 126

[0279] The present invention, in some embodiments, relates to the electrocatalytic reduction of nitrogen to ammonia under ambient reaction conditions, with the reaction mechanism detailed by the formation of nitrate or NOx. Another feature of the present invention is to provide a suitable electrochemical cell configuration, preferably with high efficiency and low cost. This invention comprises an electrochemical cell composed of an electrochemical cell, water-based electrolytic solutions with different ionic strengths (free water molecules), and specific catalysts in which the NRR occurs at low overpotentials. The same system is constructed for the production of NOx, followed by the formation of ammonia. This provides the ability to store the NOx and produce ammonia on demand.Catalysts such as platinum-ruthenium alloy (PtRu), ruthenium (Ru), palladium (Pd), and iron (Fe)-based oxides (RuOx, PdOx, and FeOx), and water-based electrolytes with a smaller number of free water molecules, thus facilitating the solubility of N2 with limited HER activity, are used in the present invention. Preliminary electrochemical tests were performed in a standard three-electrode cell composed of catalyst-coated carbon paper as the working electrode, a metallic / graphitic counter electrode, and a suitable reference electrode. Water-based electrolytes, such as 0.1 M KOH, were used for the preliminary studies, and high-purity nitrogen gas was purged during the reaction. The cell outlet was connected to an acid-containing trap to collect the ammonia formed during the eNRR. Materials and methods Petition 870250100702, dated 03 / 11 / 2025, page 84 / 141 81 / 126

[0280] The required amount of commercial PdO or RuOo was dispersed by ultrasound (30 minutes) in a mixture of isopropyl alcohol (IPA) and water (1:1 v / v) with the addition of 15% by weight of Nafion ionomer to prepare the catalyst ink. The required amount of prepared catalyst ink was dripped onto a Teflon-coated Toray carbon electrode holder, followed by drying to fabricate the working electrode with a catalyst load of 4 mg / cm2.

[0281] Electrochemical techniques, such as linear sweep voltammetry and chronoamperometry, were employed to optimize the potential effect and achieve maximum ammonia production and NOx formation for each catalyst. The NO3 RR activity of these catalysts with optimized applied potential was also studied in detail using commercially available NOx sources, such as nitrate salts, employing the same electrochemical configuration described above. From a commercial standpoint, the results were also verified by conducting the electrochemical test in a prototype three-electrode electrochemical reactor, composed of an anode compartment and a cathode compartment separated by a suitable ion-conducting membrane with a suitable reference electrode. NOx and ammonia formation was verified and quantified by UV-visible spectrophotometric analysis.The nitrate in the electrolyte was analyzed directly by UV, and the absorption value at 3000 nm was considered for NOx quantification. The ammonia in the electrolyte and trap was analyzed by the method of... Petition 870250100702, dated 03 / 11 / 2025, page 85 / 141 82 / 126 salicylate and the cumulative value was reported as the total ammonia production.

[0282] NRR activity is verified by linear scanning voltammetry (LSV) analysis. The detailed electrochemical study of NH3 generation was evaluated by combining the electrochemical techniques LSV and chronoamperometry (CA) with the commercial electrocatalyst RuPt-black. The currents measured in electrolytes saturated with N2- were higher than those measured in electrolytes saturated with Ar due to the contribution of NRR. Therefore, the performance of NRR was evaluated in the region of -0.045 V to -0.85 V. The chronoamperometry measurement was performed for 1 hour at various potentials (-0.045, -0.25, -0.45, -0.65 and 0.85 V vs NHE). In CA, it was observed that the current increased with the external potential. The extent of NH3 production and the faradaic efficiency (FE) were evaluated by UV-vis absorption spectroscopy.

[0283] The rate of NH3 formation increased with increasing negative potential. The maximum NH3 production achieved was 3.4 μgh-1cm-2 at -0.25 V vs. NHE above, where the rate decreased due to the competitive formation of the hydrogen evolution reaction (HER). The FE at -0.25 V is 4.3%.

[0284] In the next step, the electrode was oxidized at 0.65 V and then the NRR activity was checked at different potentials, i.e., -0.045, -0.25, -0.45 V vs NHE. After electrode oxidation, NH3 formation and FE rate increased slightly. The NH3 formation rate increased to 4.2 μgh-1cm-2 at -0.25 V vs. NHE with FE of 5.7%. Petition 870250100702, dated 03 / 11 / 2025, p. 86 / 141 83 / 126

[0285] The inventors further demonstrated that it is possible to significantly increase the rate of ammonia production using the electrode with 4-5 mg / cm2 of electrocatalyst charge: (i) first generating NOx species in situ by applying a positive electrode potential (approximately +1.8 V vs. RHE for one hour) and (ii) subsequently applying a negative electrode potential of only -0.1 V vs. RHE to reduce the NOx species to ammonia. The reduction rate of the 2nd step was approximately 147 µg / h / cm2, which is more than ten times faster than the reaction rate of less than 10 µg / h / cm2 obtained by the direct reduction of N2 to NH3. The observed reduction rate of the 1st step was approximately 50 µg / h / cm2. [028 6] The RR activity of NO3 from RuOx is evaluated in 0.1 M KOH saturated with Ar containing 0.1 M NaNO3 in a wider potential window in a standard three-electrode cell configuration. The chronoamperometry (CA) experiment was performed in a wider potential window for 30 minutes and ammonia formation after CA at each potential was quantified by the salicylate method. The RuOx electrocatalyst showed a maximum ammonia production rate of 1680 μgh-1cm-2 with FE of 35% at -0.35 V vs RHE.

[0287] NOx formation during NRR was evidenced with both RuOx and PdOx. After evaluating the NRR activity of RuOx and PdOx in saturated N2 and 0.1 M KOH electrolyte, the sample was collected from the electrolyte and analyzed for NOx formation. Both RuOx and PdOx lead to NOx formation, as evidenced by a fairly high absorbance value for the sample. Petition 870250100702, dated 03 / 11 / 2025, page 87 / 141 84 / 126 electrolyte compared to the 0.1 M KOH blank. This interesting finding adds new insights into the NRR mechanism and the facilitated electrochemical synthesis of ammonia with less energy investment. EXAMPLE 2

[0288] 10 mg of RuO2 were added to 12 mL of 0.1M KOH, followed by purging with N2 for 3 hours. The resulting 0.1M KOH electrolyte containing nitrate was used for the synthesis of ammonia. This experiment was carried out in an Ar atmosphere to avoid the contribution of NRR. The catalyst charge is 4.4 mg cm-2. NO3RR activity of RuO2 in 0.1 M Na2SO4.

[0289] The effect of electrolysis time for NO3 RR (also called NitRR) was studied with the aim of limiting the energy required for the reaction. CA experiments were carried out in 0.1 M KOH containing 0.1 M NaNO3 at 0.25 V vs. RHE using the catalyst RuO2. The ideal electrolysis time is 20 minutes, above which no effect on the faradaic efficiency of ammonia formation is observed. After 30 minutes of electrolysis, the remaining nitrate concentration was calculated to be 24.4 mM. An NH3 production rate (gh-1cm-2) of approximately 1500–4650 and an FE of [missing value] were observed. 10-32%.

[0290] NOx formation during NRR was also observed in RuO2. This interesting finding clearly demonstrates the formation of oxygenated nitrogen species (nitrate) by applying a very small excess potential (50 mV).

[0291] The activity of RuO2NO3RR in 0.1 M Na2SO4 containing 0.1 M NaNO3 is described in detail in Example 7. Petition 870250100702, dated 03 / 11 / 2025, page 88 / 141 85 / 126 NOR electrochemistry using RuO2 catalyst.

[0292] This experiment was performed with a catalyst loading of 3.7 mg cm-2 in 0.1 M KOH. The nitrate concentration reported is after the experiment CA for 30 minutes at each potential. Table 1: V vs. RHE Nitrate concentration (mM) 0.05 2.88 -0.05 9.61 -0.15 2.32 -0.25 2.54 -0.35 4.41 -0.45 2.18 -0.55 8.198 Formation of nitrate (chemical) under ambient conditions using RuO2 catalyst.

[0293] 5 mg of RuO2 were dispersed in a known volume of 0.1 M KOH in separate containers and then purged with N2 / Ar / N2 +Ar / N2 with the addition of peroxide. The sample was then analyzed for nitrate. After the addition of H2O2, the resulting nitrate concentration was approximately 51 mM.

[0294] A vigorous reaction was observed immediately after the addition of RuO2 to 0.1 M KOH containing 200 μM of peroxide, validating the surface reaction with H2O2. The possible reaction is a decomposition of the peroxide into water and oxygen via a hydroxyl radical mechanism initiated on the surface of the RuO2. This process may leave Petition 870250100702, dated 03 / 11 / 2025, page 89 / 141 86 / 126 activated oxygen fragments that facilitate the oxidation of nitrogen to nitrate.

[0295] In summary, the electrochemical reduction of nitrogen to ammonia was demonstrated using PtRu, RuOx, Fe2O3-TiO2 and PdOx catalysts in an electrolyte (supersaturated saline solution) without free water molecules through a mechanism associated with nitrate (NO3-) formation. Furthermore, hydrogen evolution (HER) is also suppressed by the use of electrolytes with a lower quantity of water molecules. EXAMPLE 3 H2O2 mediated NOR-NO3 RR of RuO2 and compound RUO2 / C0PC

[0296] Cobalt(II) phthalocyanine with a minimum purity of 97%, sodium nitroprusside dihydrate, salicylic acid, and sodium hypochlorite solution with available chlorine content ranging from 11% to 15% by weight, as well as sulfuric acid with 96% w / w, were purchased from SigmaAldrich. The chemicals used in this study, namely isopropyl alcohol (2-propanol), ruthenium oxide (RuO2), sodium sulfate (Na2SO4), and Nafion ionomer, were obtained from Bio-Lab Ltd-Jerusalem, Strem Chemicals, Riedel-De Haen Ag Seelze-Hannover, and Ion power, respectively. Sodium citrate dihydrate (> 99% by weight) and sodium nitrate were purchased from Merck. Teflon-coated Toray carbon sheet was purchased from Fuel Cell Store. All compounds used in this study were of analytical grade and were employed without further purification. High-purity deionized water with a resistivity of 18.2 MΩ cm was used in all experiments. Preparation of the working electrode Petition 870250100702, dated 03 / 11 / 2025, pp. 90 / 141 87 / 126

[0297] The CoPc / RuO2 ink was prepared by mixing 1 mg of RuO2 with 3 mg of CoPc and 15% by weight of Nafion ionomers in a glass vial, adding 400 μL of water and isopropyl alcohol (1:1 v / v) to the mixture. This paste was sonicated for 30 minutes to ensure homogeneity and coated onto a pre-weighed, Teflon-coated Toray carbon sheet (active area 1 x 1 cm2). The electrode was dried at 80 °C for 1 hour. The total catalyst charge calculated from the electrode weight was ~4 mg cm-2. Peroxide-induced nitrate formation in RuO2

[0298] The activity of ruthenium oxide in the chemical oxidation of nitrogen to nitrate in the presence of peroxide was evaluated in a 0.1 M Na2SO4 solution. The experiment was performed by continuously purging air at a flow rate of 100 mL / min in 5 mg of RuO2 dispersed in a 200 μM peroxide solution containing 0.1 M NaSO4 at room temperature for 5 hours. For comparison, a control experiment without a ruthenium oxide catalyst was performed. Nitrate concentrations of 49.51 and 65.6 μM were obtained under an N2 atmosphere. The nitrate concentration increased to 140.1 ± 6.3 μM when exposed to a mixture of 75% N2 and 15% O2. When the oxygen concentration in the mixture was adjusted to 5% and 10%, the resulting nitrate concentrations were 75.3 μM and 101.3 μM, respectively.Although the chemical formation mechanism of nitrate involves the disproportionation reaction of peroxide on the RuO2 surface, this variation in nitrate yield at different oxygen levels indicates the impact of oxygen on the chemical formation of nitrate, through the oxygen radical anion O2_*. At the same time, in the presence of air, it produces 179.8 ± 15.7 μM. The inventors. Petition 870250100702, dated 03 / 11 / 2025, pp. 91 / 141 88 / 126 observed a linear correlation between the amount of RuO2 and the rate of nitrate formation in the air atmosphere, a first-order study regarding the number of functional catalytic active sites that control peroxide disproportionation and N2 adsorption after nitrate formation. Proposed reaction pathways

[0299] Based on the experimental results obtained, mechanistic insights are proposed regarding the promotion of eNOR by the peroxide formed in situ and the subsequent electron-α reduction of the nitrate formed to ammonia. As presented in Equations 6 to 16, the overall reaction pathway can be best described in three individual reactions with multiple elementary reaction steps. Step 1: Peroxide formation (electrochemical process)

[0300] The reduction of oxygen to peroxide can be induced using various metal-centered phthalocyanines. The Co metal center of the macrocyclic rings interacts with O2 present in the air, forming an adduct in the first step (equation 6). The successive transfer of electrons from the Co11 metal atom to oxygen leads to the formation of an oxidized Co111 metal center (equation 7).

[0301] Finally, the charge transfer from the Co5+ metal atom to the Ü2õ- occurs with a sequential addition of protons from the electrolyte, resulting in the electrochemical generation of H2O2, as shown in equation 8. The rate of the electron / proton transfer process is increased by the N present in the macrocyclic ring. [PcCo11] + O2 θ [PcCo5+......Ο2δ-] (6) [PcCo5+......Ο2δ-] + H+^ [PcCo111......O2H]+(7) Petition 870250100702, dated 03 / 11 / 2025, page 92 / 141 89 / 126 [PcCo111......O2H]++ H++ 2e- ^ [PcCo11] + H2O2 (8) Step 2A: Peroxide disproportionation (autocatalytic process)

[0302] Although the peroxide formed on the surface of CoPc is sufficiently stable at neutral pH, it can undergo disproportionation upon contact with a catalyst such as RuO2 (e.g., Ru-based salts or Ru-clamp complexes). Therefore, it can end up in reactions that form hydroxyl ions, which involves the deactivation of the catalyst, as shown in Equation 9. Based on these studies, the possible disproportionation of the peroxide can occur following the Heber-Weiss mechanism, as follows: H2 O2 θ HO2-+ H+(9) HO2-+ H2 O2 ^ *OH + H2 O + O2 (10)

[0303] According to Herber-Weiss, peroxide can readily form peroxyl ions and protons, as shown in Equation 9. In the next step, this formed peroxyl ion reacts further with another neighboring peroxide present in the electrolyte, resulting in hydroxyl radical, water, and oxygen (equation 10). The inventors assume that RuO2 induces a catalytic reaction of the hydroxyl radical and molecular N2. Step 2B: Formation of RuO(OH)2 (autocatalytic process)

[0304] The highly reactive hydroxyl radical formed on the surface of RuO2 through the disproportionation of the peroxide interacts back with the free reactive sites of ruthenium oxide, resulting in the cleavage of the Ru-O double bond. Thus, ruthenium oxyhydroxide [RuO(OH)2] is formed, as described in equation 11. RuO2 + *2OH ^ RuO(OH)2 + O2 (11) Petition 870250100702, dated 03 / 11 / 2025, page 93 / 141 90 / 126 Step 2C: Formation of nitrate (the * denotes the species adsorbed on the surface) RuO(OH)2 + *N2 - RuOOH + *NNOH (12) *NNOH + RuOOH - *N + *NO + H2 O + Ru (13) *NO + RuO(OH)2 - *NOOH + RuOOH (14) *NOOH + RuOOH - *NOOOH + H2 O + Ru (15)

[0305] The subsequent reaction of the formed ruthenium oxyhydroxide (RuO(OH)2) with the N2 adsorbed at the Ru site of RuO2 produces *NNOH and RuOOH (equation 12). This RuOOH phase further oxidizes *NNOH, leading to the formation of *N, *NO, metallic Ru, and water (equation 13). The formation of metallic ruthenium was confirmed using XRD analysis of the electrode after NOR. In the next step, the *NO species reacts with the new ruthenium oxyhydroxide (RuO(OH)2), converting it to *NOOH (equation 14). Then, RuOOH further oxidizes *NOOH to *NOOOH with a simultaneous reduction of Ru4+ to metallic Ru. Steps 12-15 are repeated for the conversion of another *N formed in the reaction of equation 13 to NO3-. The overall chemical fixation of N2 to NO3 is shown below. 16O2 + 32H+ + 32e- - 16H2 O2 (16) 16H2 O2 - 8*OH + 8H2 O + 8O2 + 8H+ (17) 4RuO2 + 8*OH - 4RuO(OH)2 + 2O2 (18) 4RuO(OH)2 + N2 - 2HNO3 + 3H2 O + 4Ru (19)

[0306] Thus, any peroxide-generating cocatalyst, together with a metallic peroxide disproportionation catalyst (e.g., Ru-based salt or a complex thereof, such as a Ru-pincer complex), can be used in the composite material characterized by NOR activity, as described herein. Petition 870250100702, dated 03 / 11 / 2025, pp. 94 / 141 91 / 126 Peroxide-forming activity of CoPc, RuO2 and compounds

[0307] The formation of peroxide versus water in the oxygen reduction reaction (ORR) was measured in a selected CoPc / RuO2 compound and its components in a potential window of 1.0-0.0 V vs. RHE using a rotating ring disc electrode (RRDE). The observed peroxide yield of CoPc is 82.5% at 0.1 V vs. RHE, which is higher than RuO2 (60.8%). The CoPc / RuO2 compound catalyst with a composition of 25% RuO2 and 75% CoPc produced a peroxide percentage of 36.4% at the same potential. The ORR current of the selected compound is higher than that of CoPc and RuO2 with the same charge, but the same could not be detected in the Pt ring, indicating that the peroxide formed is reacting with N2 present in the air before being oxidized and detected in the ring. PT.

[0308] The inventors concluded that the peroxide concentration produced by the compound electrocatalyst is lower than the corresponding peroxide concentration produced by the RuO2 electrocatalyst alone, which implies that about 30% of the peroxide formed participates in the proposed mechanism of electro-oxidative fixation of N2 to NO3-assisted by radicals.

[0309] To study the effect of composition on NOR yield, we optimized the RuO2 to CoPc ratio of the catalyst and measured the corresponding NO3 formation rate in 0.1 M air-saturated Na2SO4 electrolyte under selected potentials. The nitrate formation rate and corresponding FE for each composition are shown in Figure 1A. For 100% CoPc, the nitrate yield rate of Petition 870250100702, dated 03 / 11 / 2025, pp. 95 / 141 92 / 126 A concentration of 12.1 ± 1.0 μg h⁻¹cm⁻² was measured with an FE of 1.3%. In the composite containing 25 wt% RuO₂ in CoPc, a significant increase to 71.1 ± 4.2 μg h⁻¹cm⁻² was observed, while the concentration of the 100% RuO₂ catalyst was only 4.1 μg h⁻¹cm⁻². This supports the synergistic effect of CoPc and RuO₂.

[0310] To complete the picture, we quantified the residual hydrogen peroxide after the oxidation reaction with nitrogen using a Pt ring and spectrophotometry, comparing it with the nitrate concentration measured in Figure 1B. It was found that the exclusive use of CoPc resulted in a high residual peroxide concentration of 135.3 μM and a minimal nitrate concentration (21.0 μM), aligning with the limitations of CoPc in the disproportionation of peroxide, which leads to nitrate formation. In contrast, the addition of 25% RuO2 to CoPc significantly improved the performance, leaving only 38.4 μM of peroxide and increasing the nitrate concentration to 127.4 μM. Consequently, the study identifies a mixture of 25% RuO2 and 75% CoPc as the ideal composition to produce peroxide and oxidize nitrogen to nitrate effectively. Potential effect on nitrate formation

[0311] The influence of applied potential on nitrate formation was studied using an optimized catalyst composition of 25% RuO2 and 75% CoPc. Potentiodynamics were recorded from LSV measurements in Ar and air atmospheres. The highest current observed under air is mainly attributed to ORR with an initial potential of 0.42 V vs. RHE. Chronoamperometry (CA) electrolysis experiments were performed at selected applied potentials of 0.4 to 0.0 V vs. RHE for 1 h. Currents of Petition 870250100702, dated 03 / 11 / 2025, pp. 96 / 141 93 / 126 Oxygen reduction begins at 0.35 V vs. RHE under Ar. The maximum nitrate yield rate of 73.6 μg h⁻¹cm⁻² was obtained at 0.1 V vs. RHE with FE of 2.0%. This higher yield is attributed to a peroxide production of 36.4% at the same potential. Considering the higher nitrate formation rate, the applied potential of 0.1 V vs. RHE was selected as the optimized one for further electrochemical stability measurements. Reduction of nitrate formed into ammonia

[0312] The nitrate formed via in situ peroxide-induced electroreduction was subsequently converted to high-value ammonia by its electroreduction using a RuO2 catalyst-based electrode (charge was 4 mg / cm2). To optimize the applied potential of eNO3RR, chronoamperometry studies were performed at selected applied potentials in 1000 μM NaNO3 containing 0.1 M Na2SO4 solution for 30 minutes under an Ar atmosphere. The maximum ammonia yield rate of 168.4 μg.h-1cm-2 with 17.6% FE was achieved at an optimized potential of -0.35 V vs. RHE. The nitrate is accumulated using a CoPc / RuO2 composite electrode (electrode area of ​​2x2 cm2) for 1 hour at 0.1 V vs. RHE under an air atmosphere.

[0313] The total nitrate concentration is quantified as 1081.7 μM and this resulting nitrate was subjected to electroreduction to ammonia at the RuO2 electrode at -0.35 V vs. RHE for 30 minutes under an Ar atmosphere. The calculated ammonia formation rate is 147.2 ± 13.7 pg.h-1cm2 with 13.8 ± 1.7% FE, which is 30 times greater than direct eNRR using RuO2 catalyst in saturated N2 0.1 M Na2SO4 at 0.35 V vs. RHE (4.9 μg h-1cm-2). Furthermore, the change in nitrate concentration of 227.3 μM after the eNO3RR well Petition 870250100702, dated 03 / 11 / 2025, page 97 / 141 94 / 126 coincides with the concentration of ammonia generated of 223.4 μM, which indicates efficient conversion of the nitrate formed into ammonia.

[0314] In summary, the chemical formation of nitrate from ruthenium oxide catalyst was studied in a 0.1 M Na2SO4 solution under an air atmosphere in a peroxide environment. The peroxide-forming capacity of cobalt phthalocyanine (CoPc) at lower potentials is utilized by combining it with the RuO2 catalyst to perform in situ chemical NOR. The nitrate-forming capacity of this mixture in the peroxide region via the peroxide radical mechanism was experimentally validated in detail. This catalyst mixture of 25% RuO2 with 75% CoPc showed 36.4% peroxide production at 0.1 V Vs.RHE in neutral medium under an air atmosphere. The same mixture showed a nitrate formation rate of 71.11±4.21 μg h-1cm-2. 2.14% FE at a much lower potential of 0.1 V vs. RHE under air. The nitrate formation under this very low applied potential is attributed to CoPc-induced in situ peroxide formation, which is even more disproportionate and forms nitrate on the RuO2 surface, in turn converting RuO2 to metallic Ru. This formed nitrate is converted to more valuable ammonia using the RuO2 catalyst with an ammonia formation rate of 147.23±13.71 μg h-1cm-2 and 13.76±1.68% FE at -0.35 V vs. RHE. Furthermore, the CoPc / RuO2 composite catalyst showed stability for up to 5 consecutive nitrate formation cycles. EXAMPLE 4 Effect of N2 on the electrochemical reaction of nitrate reduction. Petition 870250100702, dated 03 / 11 / 2025, pp. 98 / 141 95 / 126

[0315] The inventors also set out to study the reduction of nitrogen to ammonia in the presence of nitrate in the electrolytic solution. It was observed that the rate of N2 reduction in the presence of nitrate (0.01 M to 1.0 M) and under an air atmosphere (at 1 atm and 20 °C) was 3 orders of magnitude greater than that of a similar reaction using an electrolytic solution without nitrate and about 50% greater than the reduction under Ar. The authors hypothesized that the reduction in NOa” results in the formation of metallic nitride, providing Na reduction sites in the Mars-van Krevelen NRR mechanism. EXAMPLE 5 Cerium ferrite compounds

[0316] Cerium(III) nitrate hexahydrate (99.9%+ Ce) and iron(III) nitrate nonahydrate (98+%) were purchased from Strem Chemical Inc. Polyvinylpyrrolidone (PVP), along with potassium hydroxide, sodium citrate dihydrate (more than 99% by weight), sodium nitroprusside dihydrate, ammonium chloride, and salicylic acid were purchased from Sigma Aldrich. Sulfuric acid (95-98% by weight), isopropyl alcohol, and sodium hypochlorite solution (containing 11-15% by weight of available chlorine) were purchased from Honeywell, Bio-Lab Ltd. (Jerusalem) and Thermo Scientific, respectively. Vulcan XC-72 carbon was obtained from Cabot Corporation. Both the Nafion® 115 membrane and the Nafion® ionomer (a 5% by weight solution in a mixture of lower aliphatic alcohols and water) were purchased from Fuel Cell Store. Ultra-high purity water with a resistivity of 18 MΩ cm was used in all tests. Petition 870250100702, dated 03 / 11 / 2025, pp. 99 / 141 96 / 126 experiments. All chemicals were used in their original state, without any further processing. Synthesis of the CeO2 / CeFeO3 compound catalyst

[0317] The synthesis of CeO2 / CeFeO3 compounds was carried out using a polyol-assisted microwave method, chosen for its inherent polarity which facilitates rapid and localized heating at the molecular level. Polyvinylpyrrolidone (PVP) was used as an encapsulating agent to uniformly polydisperse Ce and Fe throughout the compound mixture. An aqueous solution of PVP (MW=31,000) was prepared by dissolving 4 g of PVP in 100 ml of deionized water at 80 °C. Different molar ratios of iron nitrate and cerium nitrate were added to a specific volume of water, well mixed, and added to the polymer solution, followed by continuous stirring for 2 hours with a magnetic stirrer. This mixture was microwave-treated at a power of 1000 W for 15 minutes until complete evaporation of the water. The resulting dry solid was washed with water until no nitrate content was detected in the UV-Visible analysis.The resulting powder was calcined in an Ar atmosphere at 500 °C for 3 hours, resulting in the desired CeO2 / CeFeO3 compound catalysts. Pure cerium oxide and iron oxide catalysts were synthesized using the same methodology, without the addition of iron nitrate or cerium nitrate salt.

[0318] Electrochemical measurements were performed in a double-chamber H-type cell using a standard three-electrode configuration. A mercury / mercury oxide (Hg / HgO) electrode served as a reference, Petition 870250100702, dated 03 / 11 / 2025, pages 100 / 141 97 / 126 while a nickel strip (with 99.9% purity) was used as a counter electrode.

[0319] To prepare the working electrode, 80% by weight of the CeO2 / CeFeOa compound catalyst was mixed with 20% by weight of Vulcan XC-72 carbon. This mixture was then added to 2 mL of a 1:1 solution of isopropanol (IPA):water and 15% by weight of Nafion® ionomer. The resulting mixture was sonicated for 30 minutes to ensure homogeneity. The homogenized catalyst dispersion was then dropped onto Teflon-coated Toray carbon paper with an active area of ​​1x1 cm². After drying, this paper was used as a working electrode, maintaining a total catalyst load (catalyst + Vulcan carbon) of 2 mg / cm² for all experiments. Electrochemical tests were performed using a BioLogic potentiostat / galvanostat workstation (VSP / VMP 3B-20). The electrochemical nitrate reduction reaction (eNO3RR) activity of the catalyst was evaluated in a 0.1 M KOH electrolyte saturated with argon containing 0.1 M KNO3. The 0.1 M solution KOH was used as an anolyte and a pre-treated Nafion®115 membrane was used as a separator. Argon gas was purged for 30 minutes before each experiment. To collect ammonia, a 1 mM H2SO4 acid trap was connected to an outlet of the electrochemical cell. All reported potentials were referenced relative to the reversible hydrogen electrode (RHE), with pH adjustments made using the Nernst equation, as described in Equation 2. E(RHE) = E(Hg / HgO) + (0.059 xpH) (2) Petition 870250100702, dated 03 / 11 / 2025, pages 101 / 141 98 / 126 Physicochemical characterization of CeO2 / CeFeO3 compound catalysts

[0320] The CeO2 / CeFeO3 composite catalyst with three different atomic ratios of cerium / iron, pure cerium oxide, and iron oxides were analyzed by XRD to determine their crystallinity and phase purity. The phase distribution in these compounds was examined using Expert High Score Plus software. For the catalyst with In a 100% by weight cerium XRD pattern (Figure 1a), the XRD pattern revealed the presence of a CeO2 phase with characteristic diffraction peaks (JCPDS 01-018-0792). These peaks were observed at values 2θ values ​​of 28.5°, 33.1°, 47.4°, 56.3°, 59.1°, 69.4°, 76.7°, 79.1°, and 88.4°, corresponding to the (111), (200), (311), (222), (400), (331), (420), and (422) planes of a cubic structure, respectively. The introduction of 25% iron to pure CeO2 (Figure 1c) resulted in the formation of 51% CeFeO3 with an orthorhombic phase (JCPDS 00-022-016). This was confirmed by diffraction patterns at 2θ values ​​of 22.7°, 32.3°, 39.8°, 46.3°, 57.8%, and 67.6%, which align with planes (110), (112), (202), (004), (024), and (224). Figures 2D and 2E illustrate the XRD patterns for composites with 50 and 75% iron, leading to 75% and 32% CeFeO3 phase, along with 15% and 29% CeO2, respectively. A decrease in cerium content reduced the formation of the CeFeO3 phase to 43%, with a corresponding 19% increase in the magnetite (Fe3O4) phase of the iron oxide. The cerium-containing catalyst, illustrated in Figure 2B, consisted of a mixture of maghemite (CeFeO3), magnetite (Fe3O4), and hematite (FemO18), correlating with JCPDS files 00-039-1346, 01-088-0315, and 96-901-5504. Among these iron oxides, the maghemite phase was Petition 870250100702, dated 03 / 11 / 2025, pp. 102 / 141 99 / 126 is predominant, constituting 72%, with the remaining 38% being a combination of magnetite and hematite phases. The average crystallite sizes were calculated using the Scherer formula for the compound catalysts 100% Ce, 75% Ce:25% Fe, 50% Ce:50% Fe, 25% Ce:75% Fe and 100% Fe are 20.4 nm, 141.4 nm, 89.2 nm, 157.1 nm, and 127.5 nm, respectively.

[0321] The Raman spectroscopy study investigated the local crystalline symmetry and defects / disorders in the metal oxides of the compound catalysts. Raman spectra were recorded in a range of 50 to 2000 cm⁻¹ using a 532 nm laser. For the catalyst with 100% by weight cerium, a single Raman shift was observed at 452 cm⁻¹, originating from the symmetrical T2γ vibration of the Ce-O-Ce bond. In contrast, the catalyst without cerium (100% Fe) showed distinct Raman bands, including A1γ and Eγ bands of Fe₂³⁻ at 197 (shift of 226 cm⁻¹) and 264 cm⁻¹ (shift of 249 cm⁻¹), respectively,19 and T2γ bands at 373 cm⁻¹ (shift of 365). Furthermore, the bands observed at 268, 755, and 1288 cm⁻¹ in catalysts containing 50, 75, and 100% iron was attributed to the Eg and A1g bands of magnetite, corroborating the conclusions of the XRD analysis. Notably, these bands were absent in the catalyst with 25% Fe, aligning with expectations based on the XRD analysis. FT-IR spectra further confirmed the formation of cerium ferrite compounds in the mixture. The absorption bands at 550 and 696 cm⁻¹, associated with metal-oxygen (Fe-O) stretching, were evident in the sample with 100% Fe, which has two different Fe-O bonds, one Fe₂O₃ and the other Fe₃O₄. The peak at 975 cm⁻¹ corresponded to the characteristic Ce-Fe bond in the CeFeO₃ phase. Petition 870250100702, dated 03 / 11 / 2025, pp. 103 / 141 100 / 126 was particularly prominent with the addition of 50% Fe. Furthermore, the peaks at 3453 and 1623 cm⁻¹ indicated the presence of adsorbed water molecules, while the peak at 1384 cm⁻¹ was attributed to C=C elongation, likely originating from a trivial amount of carbon due to thermal oxidative removal from the PVP polymer during high-temperature calcination.

[0322] Scanning electron microscopy (SEM) micrographs of the synthesized catalysts reveal a spongy morphology in all compound catalysts. The distinct morphology observed in the compound is largely due to the inclusion of PVP in the synthesis process. PVP plays a critical role as a coating agent, not only facilitating the uniform dispersion of particles but also stabilizing them, which contributes significantly to the unique structural characteristics of the compound. The homogeneous distribution of metal oxides in the compounds is further confirmed by energy-dispersive X-ray spectroscopy (EDS) mapping. This is particularly evident in the 50Fe:50Ce samples, as illustrated in Figure 3.

[0323] For the 100% Ce catalyst, the elemental composition of 84.5% Ce and 15.5% O aligns closely with the theoretically calculated composition of 81.4% Ce and 18.6% O. Similarly, the 100% Fe catalyst exhibits an average elemental composition of 69.7% Fe and 30.3% O, which is in accordance with the theoretical values ​​of 70.3% Fe and 29.7% O, based on XRD data. The inclusion of 25% Fe results in a composition of 70.3% Ce, 11.4% Fe, and 18.4% O. This corresponds to the calculated values ​​of 69.2% Ce, 11.7% Petition 870250100702, dated 03 / 11 / 2025, pp. 104 / 141 101 / 126 of Fe and 19.1% of O, corresponding to phase mixtures of 51% CeFeO3 and 49% CeO2. Furthermore, the addition of 50% and 75% Fe produces compositions of 56.9% Ce, 32.1% Fe and 20.1% O and 42.9% Ce, 35.4% Fe and 21.8% O, respectively. These values ​​also correspond well to the compositions calculated for their respective compound oxide mixtures.

[0324] Chronoamperometric electrolysis was performed on several catalyst systems for one hour at seven potentials selected between 0.05 V and -0.55 V relative to RHE in a 0.1 M argon-saturated KOH solution containing 0.1 M KNO3. With the pure CeO catalyst (Figure 6e), the ammonia formation rate increased sharply to 4040.5 μg h-1cm-2 at -0.45 V vs. RHE, approaching saturation, while the faradaic efficiency started high at 75.2% at 0.05 V vs. RHE and decreased to 48.2% at -0.55 V vs. RHE. The maximum observed ammonia yield rate was 4132.5 μg h-1cm-2 with a faradaic efficiency of 48.2% at -0.55 V vs. RHE.

[0325] The introduction of 25% Fe into the catalyst, which consists of 51% CeFeO3 and the remainder CeO2, resulted in an increase in the ammonia yield rate at higher applied potentials. Unlike CeO2, the faradaic efficiency peaked at 81.2% at -0.35 V vs. RHE, which is 31% higher than the pure CeO2 system. The maximum rate for this compound was 3693.9 μg h-1cm-2 at -0.55 V vs. RHE, only 10.6% lower than that of pure CeO2, suggesting that the CeFeO3 phase significantly increases the faradaic efficiency for ammonia with minimal impact on the yield rate. Furthermore, this compound exhibited a high hydroxylamine rate in Petition 870250100702, dated 03 / 11 / 2025, pp. 105 / 141 102 / 126 lower potentials (below -0.25 V vs. RHE), decreasing to 71.0 μg h⁻¹cm⁻² at -0.25 V and then increasing at higher potentials. Faradaic efficiencies for nitrite and hydroxylamine were higher at lower potentials and decreased as the potential increased. Given the relatively high yield rates and efficiencies, -0.45 V vs. RHE was determined as the optimized potential.

[0326] The 50Ce:50Fe compound catalyst achieved a peak ammonia yield rate of 3911.5 μg h-1cm2 at -0.55 V vs. RHE. Its highest FE, of 89.1%, was achieved at -0.35 V vs. RHE, slightly exceeding the efficiency at 0.25 V vs. RHE. When compared to the 75Ce:25Fe mixture, the inclusion of 50% Fe led to the best faradaic efficiency of 89.1% at -0.35 V vs. RHE and ammonia yield, likely due to a 75% CeFeO3 e-phase in the composition. Considering the relative rate and FE, the potential of -0.45 V vs. RHE was considered optimized. In this ratio, the efficiency of hydroxylamine increased by 30% at lower potentials and its yield rate doubled at -0.55 V vs. RHE, a change attributable to the presence of 10% of the new Fe3O4 phase in the mixture.

[0327] For the 25Ce:75Fe catalyst system, the ammonia yield rate dropped to 3101.6 μg h⁻¹cm⁻² at 0.55 V vs. RHE, which is 20.7% less than the 50Ce:50Fe mixture, reflecting the reduced content of the CeFeO₃ phase. The absence of Ce in the compound led to the lowest ammonia yield rate of 1912.8 μg h⁻¹cm⁻² at 0.55 V vs. RHE compared to other catalyst ratios, highlighting the role of Ce in increasing ammonia production. On the other hand, this compound achieved the highest nitrite yield rate of 3146.7 μg h⁻¹ Petition 870250100702, dated 03 / 11 / 2025, pp. 106 / 141 103 / 126 cm-2a -0.55 V vs. RHE, indicating a preference for nitrite formation in the Fe2Oa / Fe3O4 phases.

[0328] The ammonia rate distribution and overall faradaic efficiency of the catalyst systems at 0.45 V vs. RHE were tested. The CeO2 and CeFeO3 phases exhibited higher ammonia yield rates, as evidenced by the increased yields with 25-100% Ce in the mixture. Furthermore, the formation of the CeFeO3 phase was highly selective towards ammonia, with the 50Ce:50Fe mixture containing 75% CeFeO3 phases achieving a maximum ammonia FE of 88.5%. Additionally, the presence of iron (Fe2O3 / Fe3O4) altered the selectivity towards ammonia hydroxylamine, as the hydroxylamine FE% increased with the additional Fe. Considering the higher ammonia efficiency and the significant CeFeO3 content, the 50% Ce and 50% Fe mixture was chosen for stability studies at -0.45 V vs. RHE.

[0329] It is postulated that catalytic performance The superior properties of the compound CeFeO3se are largely due to intrinsic defects in its perovskite structure, especially oxygen vacancies. In ABO3-type perovskite oxides, such as CeFeO3, these oxygen vacancies are not mere imperfections, but act as... critical facilitators of increased catalytic activity. The mixed valence of iron—where Fe2+ and Fe3+ states coexist—leads to the formation of these vacancies as the material compensates for charge imbalances. These vacancies effectively act as active catalytic sites that facilitate various electron transfer reactions. In the context of nitrate reduction to ammonia, oxygen vacancies provide Petition 870250100702, dated 03 / 11 / 2025, pp. 107 / 141 104 / 126 sites for adsorption and activation of nitrate ions, thus reducing activation energies and allowing for improved kinetics for the conversion process. This mechanism highlights the importance of structural defects in optimizing the efficiency and selectivity of catalysts in electrochemical reactions.

[0330] The inventors confirmed the stability of the CeO2 / CeFeOa-based electrode for at least 25 repetitive eNOaRR cycles, resulting in a nearly constant ammonia generation rate.

[0331] Further stability tests indicate that the CeO2 / CeFeO3 compound maintains stable performance for 25 hours in eNO3RR cycles. Online mass spectrometry confirmed the absence of gases such as N2O, NO and N2, with only H2 being released during the reaction.

[0332] To this end, various ratios of CeO2 / CeFeO3 compound catalysts were synthesized using a microwave-assisted method and comprehensively characterized by XRD, FT-IR, Raman, SEM, EDS and XPS techniques. Characterization results indicated that a 50% Ce to 50% Fe ratio resulted in a compound with a predominant phase of 75% CeFeO3, complemented by 15% CeO2 and 10% Fe3O4. Electrochemical evaluations of nitrate reduction for the synthesized compound catalysts demonstrated that the introduction of Fe, forming the 75% CeFeO3 phase, notably increased the faradaic efficiency of ammonia to 88.2%, along with an appreciable yield rate of 3223.9 μg h-1cm-2. This CeFeO3 phase also restricts parasitic HER to 3.1%, while the remainder is destined for nitrite and hydroxylamine. Petition 870250100702, dated 03 / 11 / 2025, pp. 108 / 141 105 / 126 Effect of N2 on the electrochemical reaction of nitrate reduction.

[0333] The CeFeOa catalyst along with 20% Vulcan XC-72 carbon was coated onto a Teflon-coated Toray carbon electrode and used as the working electrode. Preliminary experiments were performed in an H-type electrochemical cell using 0.1 M KOH containing 0.1 M KNO3 solution as the electrolyte. Hg / HgO and a Ni strip (99.9% purity) were used as the reference and counter electrodes, respectively. A pre-treated Nafion® 115 membrane was used as a separator. Ar and N2 gases were purged for 30 minutes before the corresponding experiment.

[0334] Chronoamperometry was performed at 8 different potentials of -0.05 V Vs.RHE. As the potential increases, the rate tends to increase further with a sudden decrease in efficiency. Interestingly, the same experiment was performed under a nitrogen atmosphere (CeFeO3 has no activity for NRR), and the FE tends to be stable with increasing rate.

[0335] The rate under N2 atmosphere was 35% higher than in Ar atmosphere, with FE% relatively stable at 0.4 5 V vs. RHE in 0.1 M KOH containing 0.1 M NO3-.

[0336] Furthermore, we varied the nitrate concentration from 0.01 M to 0.5 M in 0.1 M KOH solution, keeping the applied potential constant at -0.45 V vs. RHE. The rate of ammonia formation increases with increasing nitrate concentration, but the faradaic efficiency reaches saturation after 0.1 M KNO3 under an N2 atmosphere. The same trend was also observed under an Ar atmosphere. As previously noted, ammonia formation was observed at approximately Petition 870250100702, dated 03 / 11 / 2025, pp. 109 / 141 106 / 126 47% greater under a N2 atmosphere using a solution of 0.5 M KNO3 in 0.1 M KOH. Effect of N2 on eNO2 RR and eNH2 OHRR

[0337] As we observed a higher yield of ammonia in the reduction of nitrate under an N2 atmosphere, we tried the same with nitrite and hydroxylamine. Here, the rate of ammonia formation observed under an N2 atmosphere was almost equal to that observed under an Ar atmosphere. Effect of hydroxyl ion concentration (in the presence of N2 / Ar)

[0338] The rate of ammonia formation increases 4.19 times when increasing the OH- concentration from 0.01 M to 0.1 M. Further increasing the concentration to 1.0 M, the rate of ammonia formation increased 1.28 times, becoming saturated. The same trend was observed with the rate of NO2- formation. The rate of hydroxylamine formation increased up to a hydroxyl concentration of 0.1 M, then decreased slowly. These results showed that changes in process selectivity were highly influenced by alterations in hydroxyl ion concentration.

[0339] The inventors observed that increasing the concentration of the supporting electrolyte suppresses the HER and increases ammonia formation. Here, the change from the Volmer HER mechanism to the Hyrovsky mechanism may also be possible by increasing the concentration of -OH. Due to the higher rate of ammonia formation, the concentration of 1 M KOH was optimized. Cationic effect on the supporting electrolyte

[0340] The inventors tested the influence of different chloride salts added to the electrolyte (in Petition 870250100702, dated 03 / 11 / 2025, pp. 110 / 141 107 / 126 final concentration of 1 M) at the rate of ammonia formation during NO3RR in an atmosphere of Ar and N2. Cation: 0.5 M KNO3 in 1.0 M LiCl, 1.0 M KCl, 1.0 M NaCl (35.0 mL); Anolyte: 1.0 M LiCl, 1.0 M KCl, 1.0 M NaCl solution (35.0 mL).

[0341] It was found that the rate of ammonia formation increased with increasing cation size of the supporting electrolyte. The rate of ammonia formation increases more than five times in NaCl than in LiCl, which was reflected in the conductivity measurement (71 mS for NaCl and 13.7 mS for LiCl). The highest rate of ammonia formation was observed in KCl under an N2 atmosphere of 8272.95 μg / h / cm2 and an FE of about 78%. EXAMPLE 6 Electrochemical reduction of nitrate to ammonia under ambient conditions using NiCo2S4 nanoparticles Materials

[0342] Cobalt(II) acetate tetrahydrate (Co(OCOCH3)2·4HO) and sulfur (99+%) were purchased from Strem Chemicals. Nickel(II) acetate tetrahydrate (Ni(OCOCH3)2·4H2O, 98%), potassium hydroxide, isopropyl alcohol, sulfuric acid (96% by weight), sodium nitroprusside dihydrate, salicylic acid, hydroxylamine hydrochloride, hydrochloric acid (37% by weight), and sodium hypochlorite solution (11-15% by weight of available chlorine) were purchased from Sigma Aldrich. Sodium citrate dihydrate (>99% by weight) and sodium hydroxide were obtained from Merck. The Nafion® 115 membrane and Nafion® ionomer (5% by weight solution in a mixture of lower aliphatic alcohols and water) were purchased from Fuel Cell Store. Vulcan XC-72 carbon (Cabot) was purchased from Cabot. All Petition 870250100702, dated 03 / 11 / 2025, pp. 111 / 141 108 / 126 The chemicals used in this work were of analytical grade and ultrapure water (resistivity of 18.2 kΩ cm) was used in all experiments. Synthesis of trimetallic nickel-cobalt sulfide spinel (NiCo2 S4)

[0343] 10 mmol of nickel(II) acetate tetrahydrate, 20 mmol of cobalt(II) acetate tetrahydrate and 40 mmol of sulfur were added to 60 mL of water. The resulting mixture was transferred to a Teflon beaker in a hydrothermal reactor and the hydrothermal reaction was carried out at 160 °C for 8 hours. The catalyst was obtained after centrifugation, washing three times with water, drying at 50 °C overnight and finally calcination at 400 °C (heating ramp of 5 °C min-1) for 2 hours under an argon atmosphere.

[0344] Catalyst-coated Toray carbon paper, a strip of nickel (99.9% pure), and Hg / HgO were used as working, counter, and reference electrodes, respectively. The required weight of synthesized catalyst (80% by weight) and Vulcan XC-72 carbon (20% by weight) was dispersed in a 1:1 v / v ratio of IPA and water mixture by ultrasound. The resulting homogeneous catalytic ink was dropped onto a 1 cm² active area of ​​Toray carbon and dried to prepare the working electrode. The BioLogic potentiostat / galvanostat workstation (VSP / VMP 3B-20) was used to perform the electrochemical tests. The RR activity of eNOa from the prepared catalysts was tested in 0.1 M KOH containing 0.5 M KNOa under an Ar atmosphere. Nitrite analysis Petition 870250100702, dated 03 / 11 / 2025, pp. 112 / 141 109 / 126

[0345] The sample was analyzed for nitrite (NO2-) using a UV-Vis spectrophotometer and the absorbance at A wavelength of 350 nm was used to estimate the concentration of NO2-. A standard calibration curve was made using a 0.1 M KOH standard sample containing a series of known concentrations of NO2-. The NO2(-) rate and the corresponding FE were estimated by applying the concentration and molecular weight (46.0055 g mol-1) of NO2- to equations 2 and 3. Hydroxylamine analysis

[0346] A colorimetric method based on a chemical reaction of potassium ferricyanide (KaFe(CN)6) with hydroxylamine (NH2OH) under alkaline pH was used to quantify the NH2OH formed during eNOaRR, following a slightly modified procedure reported elsewhere. 1.5 mL of 25 wt% KOH solution and 2 mL of 3 mM K3Fe(CN)6, prepared with 0.1 M potassium chloride, were added to 1 mL of electrolyte sample and UV-Vis spectra were recorded after 15 minutes of waiting. The absorbance value at 425 nm was noted to quantify the NH2OH concentration. The yield rate and FE were obtained by applying the concentration and molecular weight (33.03 g mol-1) of NH2OH to equations 1 and 2, respectively.

[0347] The XRD pattern of the synthesized NiCo2S4 powder was obtained to examine its phase purity and crystallinity. Diffraction peaks at 2Θ values ​​of 16.26°, 26.70°, 26.70°, 31.47°, 36.01°, 38.28°, 47.49°, 50.44°, 55.12°, 59.85°, 62.47°, 65.07°, 69.16°, 77.96° and 88.84° are assigned to (111), (220), (311), (222), (400), (422), (511), (440), (531), (620), (533), (444), (731) and (800), which are characteristic of the cubic phase of NiCo2S4 and the peaks of Petition 870250100702, dated 03 / 11 / 2025, pp. 113 / 141 110 / 126 diffraction observed correspond to JCPDS no. 20-0782. The presence of an insignificant amount of the CoS2 phase is evidenced by the existence of two additional diffraction peaks at 2Θ values ​​of 39.37° and 45.84°, which are attributed to the (211) and (220) planes of the cubic CoS2 phase (JCPDS no. 9008393). The Scherrer equation (D=kX / B cosΘ) was applied to the (311) plane of NiCo2 s4 located at 31.47° to calculate the crystallite size. The crystallite size of the synthesized NiCo2S4 is calculated to be 39.73 nm.

[0348] The morphological characteristics of NiCo2 S4 samples were analyzed by SEM, as shown in Figure 4. SEM micrographs revealed the nanometric cubic morphology of the NiCo2 S4 sample. The elemental composition was analyzed by EDX spectroscopy. EDX analysis revealed that only Ni, Co, and S are present in the sample, with weight percentages of 23.0, 39.9, and 37.0%, respectively. Furthermore, the elemental composition was also analyzed by ICP-OES, and the results (Ni (19.8 wt%), Co (33.3 wt%), and S (47 wt%)) corroborate the EDX analysis. The combined analysis of XRD, Raman, SEM, and ICP-OES evidenced the formation of the NiCo2 S4 nanostructure from the synthesis route of the material adopted in this study.

[0349] Before evaluating NO3RR activity, the electrochemically active surface area (ECSA) of the NiCo2S4 catalyst mixed with 20 wt% Vulcan carbon was quantified by double layer capacitance (Cdl). ECSA represents the extent of availability of electrochemically active catalytic sites and is an important parameter that determines the activity of catalysts. This analysis exhibited an ECSA of 0.622 cm2e Petition 870250100702, dated 03 / 11 / 2025, pp. 114 / 141 111 / 126 0.317 cm2 for the working electrode consisting of 80% by weight of NiCo2S4 + 20% by weight of Vulcan carbon (4 mg cm-2) and 20% by weight of Vulcan carbon (0.8 mg cm-2), respectively. In the working electrode with 80% by weight of NiCo2S4 + 20% by weight of Vulcan carbon, an ECSA of 0.305 cm2 is due to the presence of the active catalyst NiCo2S4 and is available for NO3RR.

[0350] To further investigate the RR activity of NO3 and the selectivity of the product of this catalyst, a constant potential electrolysis was performed in a potential range of -0.05 V to -0.50 V relative to RHE (Figure 3b). The observed current response is relatively stable at all applied potentials, which can be attributed to the electrochemical stability of these catalysts. Generally, the rate of NH3 formation increases with the applied potential. The FE reaches a maximum of 64% with an NH3 yield rate of 3793.0 μg h-1 cm-2 at -0.3 V vs. RHE. More interestingly, only a small deviation in the FE is observed, regardless of the applied potential. This is attributed to NO3RR being as fast as the competing HER, even at higher applied potentials of e and es on this catalyst.As discussed earlier, the RR of eNO3 is a complex process with several proton-coupled electron transfer (PCET) steps that occurs through more than one intermediate and byproducts. Careful analysis of the electrolyte sample after electrolysis reveals the formation of NO2- and NH2OH, in addition to NH3. As shown in Figure 5B, NO2- formation peaked at -0.25 V vs. RHE with a yield rate of 9411 μg h-1cm-2 (FE 17.6%), and the rate remains nearly constant below -0.25 V vs. RHE, but the... Petition 870250100702, dated 03 / 11 / 2025, pages 115 / 141 112 / 126 FE drops to 7.5% at -0.50 V vs. RHE. Similarly, the quantification of NH2OH showed a sharp increase in FE with a value of 10.0% (the yield rate is 1286 μg h⁻¹cm⁻² at -0.25 V vs. RHE, as shown in Figure 5C). Interestingly, the lowest rate of 425.0 μg h⁻¹cm⁻² with the lowest FE of 2.8% was obtained with an applied potential of -0.30 V vs. RHE.

[0351] Based on the above results, the product selectivity analysis was performed as a function of the FE and the corresponding results are presented in Figure 5D. This analysis clearly shows that more than 50% (average of 59.85%) of the total applied charge is used for the final NH3 product. However, this analysis may be misleading, because the remainder of the charge is not wasted. Unlike the more expected competing cathodic side reaction, which produces evolving H2 gas, NO2- and NH2OH are essential byproducts in this multi-step reaction, which is expected to proceed to ammonia under prolonged reduction. This indicates the suitability of the nanostructured NiCo2s4 catalyst for eNO3RR. An average of 12.82% and 5.28% of the applied electrical charge is used for the formation of NO2- and NH2OH, respectively, in the widest potential window tested. Furthermore, an average charge of 22% is used for the formation of other products besides NH3, NO2- and NH2OH, probably for HER.Specifically, at -0.3 V vs. RHE, FE values ​​of 64.01, 13.65, 2.77, and 19.55 were achieved for NH3, NO2, NH2OH, and other products, respectively. In other words, the FE of the total nitrate reduction products is 80.43%, which signifies the NO3RR performance of the NiCo2S4 electrocatalysts. This confirms that H2 is the only gaseous byproduct. Petition 870250100702, dated 03 / 11 / 2025, pp. 116 / 141 113 / 126 released during the NO3 RR, an online mass spectrometry analysis was performed during the electrolysis of NO3 at -0.3 V. Several possible gaseous products, including N2O, N2, NO2, NO, and H2, were monitored, and it was found that only H2 is being released due to competitive HER during the NO3RR over time. Considering the higher FE for NH3 and the lower FE for NH2OH with a moderate NH3 yield rate of 3793 μg h-1cm-2, the -0.3 V vs. RHE is proposed to be optimized as an applied potential for a longer eNO3RR electrolysis using NiCo2S4.

[0352] We studied the effect of NO3- and OH- concentration on the NO3RR activity of NiCo2S4 catalysts at an optimized applied potential of -0.3 V vs. RHE. The current increases with increasing NO3- concentration in 0.1 M KOH supporting electrolyte, indirectly signifying the dependence of NO3RR performance on NO3- concentration. The ammonia formation rate increases with NO3- concentration up to the highest concentration tested, and a maximum NH3 formation rate of 3793.3 μg h-1 cm-2 was achieved with 0.5 M NO3-. The FE reaches a maximum of 67.25% with 0.5 M NO3- and remains almost constant beyond this concentration. The corresponding formation rate of NO2- and NH2OH is presented in Table 3. This analysis shows that NO3RR is controlled by mass transport in relation to NO3- concentration.The increasing trend in the current, the rate of ammonia formation and FE is also seen with increasing OH- concentration while keeping the nitrate ion concentration constant (0.5 M NO3-) (Figure 5c ed). A maximum ammonia formation rate of 8513.0 μg h-1 cm-2 with FE of 73.21% was achieved using 1 M KOH containing 0.5 M NO3-. Petition 870250100702, dated 03 / 11 / 2025, pp. 117 / 141 114 / 126 This is 66% higher compared to the ammonia formation rate of 0.1 M KOH containing 0.5 M NO3-. Furthermore, as shown in Table 3, NH2OH formation is prevented with 1 M KOH, thus increasing the selectivity of NO3- reduction to NH3. The better performance with 1 M KOH may be due to suppressed HER. Table 2. Formation rate of NO2- and NH2OH and FE during NO3RR in 0.1 M KOH containing various concentrations of NO3-. Nitrate concentration (M) NO2- yield rate (pg h-1 cm-2) FE (%) NH2 OH yield rate (pg h-1 cm-2) FE (%) 0.01 301.81 2.24 - - 0.1 2237.83 8.85 - - 0.2 4186.94 12.07 1367.21 13.61 0.3 5208.07 14.07 145.41 1.30 0.4 5588.77 13.21 269.51 2.11 0.5 8744.44 13.66 425.34 2.78 Table 3. Formation rate of NO2- and NH2OH and FE during NO3RR in 0.1 M KOH containing various concentrations of OH- containing 0.5 M NO3- Concentration of OH- (M) Yield rate of NO2- (pg h-1 cm-2 FE (%) Yield rate of NH2OH (pg h-1 cm-2) FE (%) 0.1 8744.44 13.66 425.34 2.78 Petition 870250100702, dated 03 / 11 / 2025, pp. 118 / 141 115 / 126 0.5 4817.26 5.48 584.02 3.81 1.0 2584.23 2.06 0 0 Nitrite (NO2) reduction using NICO2S4

[0353] The nitrite reduction of the NiCo2S4-based electrode was tested using 0.5 M KNO2 in 0.1 M KOH electrolyte (under an Ar atmosphere). The results are presented in the table below: Table 4: V vs. RHE NH3 production rate (pg h-1 cm-2) FE (%) NH2OH production rate (pg h-1 cm2) FE (%) -0.10 2341.92 92.37±5.1 973.83 13.20±5.0 -0.30 4762.87 80.95 3113.10 18.19 -0.50 8327.35 61.57 4412.10 11.21

[0354] As is evident from the table above, the rate of hydroxylamine generation is higher for NO2RR than for NO3RR.

[0355] To this end, the NiCo2S4 nanostructure was constructed for the electrochemical reduction of nitrate under ambient conditions. Systematic experimental results revealed the suitability of NiCo2S4 for the efficient electrochemical conversion of NO3- with high product selectivity towards the desired NH3. A maximum ammonia yield rate of 37 93 μg h-1cm-2 with an FE of 64% was achieved at -0.3 V vs. RHE using the developed NiCo2S4 catalysts. Petition 870250100702, dated 03 / 11 / 2025, pp. 119 / 141 116 / 126 EXAMPLE 7 Electrochemical oxidation of nitrogen (eNOR) reaction using Rh supported on carbon nanosheets (Rh / C) as a catalyst. Materials

[0356] Rhodium (III) acetylacetonate 97% and anhydrous ruthenium (IV) oxide (99.9+% Ru) were purchased from Strem Chemical INC Inc and used as received. Anhydrous phloroglucinol (99%) was purchased from Acros Organics. Potassium hydroxide, sodium citrate dihydrate (> 99% by weight), sodium nitroprusside dihydrate, ammonium chloride, and salicylic acid were purchased from Sigma Aldrich. Sulfuric acid (95-98% by weight), isopropyl alcohol, and sodium hypochlorite solution (11-15% by weight available chlorine) were purchased from Honeywell, Bio-Lab Ltd. (Jerusalem) and Thermo Scientific, respectively. Vulcan XC-72 was purchased from Cabot. Ultrapure water with a resistivity of 18 MΩ cm was used in all experiments. All chemicals were used as received. Synthesis of a carbon-supported rhodium catalyst

[0357] Rhodium (III) acetylacetonate with different required weight percentages was thoroughly mixed with phloroglucinol using a mortar and pestle. The resulting mixture was calcined at 700 °C for 2 hours with a temperature increase of 10 °C per minute under an Ar atmosphere. The calcined samples were labeled as 5% by weight Rh / C, 20% by weight Rh / C, and 40% by weight Rh / C, with additions of 5% by weight, 20% by weight, and 40% by weight Rh. Petition 870250100702, dated 03 / 11 / 2025, pages 120 / 141 117 / 126 respectively. In addition, a pure carbon sample was also synthesized, without rhodium acetylacetonate, following the same procedure. All electrochemical measurements were performed in a single-chamber cell with a regular three-electrode configuration. Mercury / mercurous oxide (Hg / HgO) and nickel foil (99.9% pure) were used as reference and counter electrodes, respectively. The required weight of Rh / C catalyst was added with 2 mL of a 1:1 (v / v) mixture of IPA: water and 15% by weight of Nafion® ionomer. This mixture was sonicated for 30 minutes to achieve homogeneity. This catalyst dispersion was poured onto Toray Teflon-coated carbon paper with an active area of ​​1x1 cm², dried, and used as a working electrode. A total catalyst load (Rh / C) of 4 mg cm⁻² was maintained throughout this study. The BioLogic potentiostat / galvanostat workstation (VSP / VMP 3B-20) was used to perform the electrochemical tests. The eNOR activity of the catalyst was measured in a 0.1 M KOH electrolyte in Ar, N₂, and air atmospheres. The respective gas was purged 30 minutes before each experiment. An additional acid trap was used for the eNOaRR to collect ammonia. Physicochemical characterization of synthesized Rh / C catalysts

[0358] Three different Rh / C catalysts were synthesized with varying Rh contents. ICP-OES elemental analysis of these catalysts revealed Rh contents of 5.6, 20.7, and 40.5 wt%, designated as 5 wt% Rh / C, 20 wt% Rh / C, and 40 wt% Rh / C, respectively. The XRD standard of the synthesized carbon and of Petition 870250100702, dated 03 / 11 / 2025, pages 121 / 141 118 / 126 A 5 wt% Rh / C solution was recorded to assess phase purity and crystallinity. As shown in Figure 6, the carbon XRD standard exhibited only two diffraction peaks characteristic of graphitic carbon, thus confirming the synthesis of a pure carbon phase. On the other hand, the 5 wt% Rh / C catalysts exhibited a series of diffraction peaks at 2Θ values ​​of 40.01°, 49.20°, 70.0°, 84.3°, and 89.2°. These were assigned to the (111), (200), (220), (311), and (222) planes, which are characteristic of the face-centered cubic phase of Rh. In addition, a broad diffraction peak centered at 24.8° was assigned to the hexagonal (002) plane of the conductive carbon support. XRD analysis confirms the structure of a pure Rh / C phase prepared in this work.

[0359] The SEM micrographs presented in Figures 6B and 6C reveal the sheet-like morphology of the carbon support. Morphological analysis also showed a uniform dispersion of Rh nanoparticles over the carbon matrix. This uniform dispersion was expected to provide better exposure of the active sites for N2 adsorption with full utilization of the metallic active sites. This could result in greater NO3- formation per gram of the active precious metal Rh. Only Rh and C were detected in the EDX elemental analysis of these catalysts with 5.8% and 94.2%, respectively, corresponding well to the ICP-OES analysis.

[0360] Scanning transmission electron microscopy (STEM) images are shown in Figures 6D and 6E at different magnifications. These images further validate the layered carbon structures in which Rh metals were uniformly dispersed. The particle size Petition 870250100702, dated 03 / 11 / 2025, pages 122 / 141 The 119 / 126 of the Rh metal is shown in Figure 6E, and the particle size distribution histogram is included (see inset). The average particle size of Rh, determined by e, was 12.6 nm, which corresponds to the crystal size of 13.2 nm calculated from the Rh / C XRD standard using the (111) plane of Rh. Activity of the electrochemical oxidation reaction of nitrogen from Rh / C

[0361] The inventors observed a current A 48% higher LSV was recorded in a N2 atmosphere with a positive change in current above 1.5 V vs. RHE compared to the voltammogram of the same electrode in an Ar atmosphere. The higher currents observed under N2 are attributed to eNOR activity in Rh / C. Electrolysis by chronoamperometry (CA) was performed at each selected potential to find an ideal potential for a longer electrolysis period. A maximum NO3(-) formation rate of 21.3 μg h-1cm-2 with an FE of 28.2% was obtained at 1.7 V vs. RHE. An applied potential of 1.7 V vs. RHE is considered ideal due to the maximum ammonia formation rate, despite the Highest FE of 37.2% obtained at 1.6 V vs. RHE.

[0362] The eNOR activity of the other two compositions (20 and 40 wt% Rh supported on carbon) was also studied to examine the ideal Rh content. The current increases in the wider potential region with an increase in Rh content from 5 to 20 and 40 wt% supported on C. Therefore, Rh is directly related to the increase in current through a greater number of active catalytic sites, promoting eNOR.

[0363] Potential optimization of 20 and 40 wt% Rh / C revealed the maximum NO3- formation rate Petition 870250100702, dated 03 / 11 / 2025, pages 123 / 141 120 / 126 9.4 μg h⁻¹cm⁻² (FE 13.9%) and 2 4.1 μg h⁻¹cm⁻² (FE 4.5%) at 1.7 V vs. RHE, as observed for 5 wt% Rh / C. This teaches us that, regardless of the Rh content, the ideal potential for longer electrolysis is 1.7 V vs. RHE. This observation is attributed to the undesirable dominance of the competing oxygen evolution (OER) reaction over eNOR at an applied anodic potential above 1.7 V vs. RHE.

[0364] Catalysts with 5 wt% Rh / C offered efficient Rh utilization with the highest NO3- formation rate of 94.9 μg h-1mgRh-1 at 1.7 V vs. RHE compared to the other two catalysts, namely 20 wt% Rh / C (36.2 μg h-1mgRh-1) and 40 wt% Rh / C (14.8 μg h-1mgRh-1). Furthermore, the FE was also higher for this catalyst. For this purpose, 5 wt% Rh / C was considered ideal.

[0365] In order to understand the mechanical pathway of eNOR and the possibility of using nitrogen present in the air without the need for pure N2, the eNOR activity of 5 wt% Rh / C was evaluated in 0.1 M KOH saturated with air. A positive change in current was observed in an air atmosphere, which signifies eNOR kinetics. At 1.7 V vs. RHE, a maximum NO3- formation rate of 47.0 μg h-1cm-2 (FE 30.9%) was achieved. This is about 50% higher than the results obtained with N2 under identical operating conditions. This enhanced eNOR kinetics in the presence of air is attributed to the combined oxygen- and hydroxide-mediated conversion of N2 to NO3- over Rh / C catalysts.

[0366] The stability of 5 wt% Rh / C was evaluated in air and in N2-saturated with 0.1 M KOH at an optimized potential of 1.7 V vs. RHE. Each cycle represents 1 hour of Petition 870250100702, dated 03 / 11 / 2025, pp. 124 / 141 121 / 126 eNOR electrolysis and new electrolytes were used in each cycle. A stable NO3- formation rate of ~20 and ~45 μg h-1cm-2 was observed in N2 and air atmospheres, respectively, over the five consecutive cycles. The XRD pattern recorded for the electrode before and after electrolysis showed no phase change, oxide, or nitride formation. ICP analysis of these solutions showed no signs of Rh after continuous polarization. Conversion of nitrate generated electrochemically via eNOR to NH3 via eNO3RR

[0367] In the second stage of the proposed route for ammonia synthesis, electrochemically generated NO3- was converted to NH3 via eNO3RR. In order to find a suitable eNO3RR catalyst, the eNO3RR activity of Rh / C catalysts at 5, 20 and 40 wt% was measured in KOH. 0.1 M saturated with Ar containing simulated KNO3 electrolyte at 1.0 mM at selected applied potentials. The NH3 formation rate and FE of the Rh / C catalysts were compared with the eNO3RR performance of the RuO2 catalyst under similar test conditions.

[0368] Among the three different catalysts Rh / C, the 40 wt% Rh / C catalyst showed the highest ammonia formation rate of 25.4 μg h⁻¹cm⁻², while the 20 wt% and 5 wt% Rh / C catalysts showed the lowest ammonia formation rates of 11.9 and 3.7 μg h⁻¹cm⁻², respectively, at 0 V vs. RHE. However, the ruo2 catalyst resulted in an NH₃ formation rate of 8.2 μg h⁻¹cm⁻² at 0 V vs. RHE, surpassing the eNO₃RR performance of the three Rh / C catalysts. Furthermore, the faradaic efficiency of 40 wt% Rh / C was three times higher. Petition 870250100702, dated 03 / 11 / 2025, pp. 125 / 141 122 / 126 lower than that of RuO2 (11.9%) at 0 V vs. RHE when tested with the same metallic catalyst load (1.6 mg cm⁻²). Therefore, the RuO2 catalyst was selected as a suitable catalyst for the reduction of electrochemically generated nitrate at an ideal applied potential of 0 V vs. RHE.

[0369] eNOR was performed for different durations, such as 1, 3, 5, 10, and 24 hours at 1.7 V vs. RHE, using a 5 wt% Rh / C catalyst in 0.1 M air-saturated KOH solutions. Nitrate concentrations were recorded as 79.9, 206.6, 347.4, 428.2, and 496.0 μM during the selected electrolysis time applied. With a longer eNOR duration, nitrate accumulates in the electrolyte. After 10 h of eNOR, the detected nitrate concentration was 428.2 μM, which increased slightly to 496.0 μM after 24 h. Before and after eNOaRR, the nitrite concentration decreased from 490.9 to 283.2 μM, corresponding to the concentration of ammonia produced (283.6 μM). These results depict the successful quantitative indirect electrochemical conversion of N2 to NH3 through the synthesis of NO3-. The ammonia formation rate shown above is 2.73 times greater than the direct reduction of N2 via eNRR to RuO2, accompanied by a 22.3-fold improvement in FE (16.5 μg h-1cm-2 and FE of 0.26%).This demonstrates the advantage of a combined eNOR and eNO3RR cycle approach shown in this work for large-scale ammonia synthesis under ambient conditions. Continuous synthesis of NH3 through the coupling of eNOR and eNO3RR.

[0370] The electrochemical conversion of N2 to NH3 via the formation of NO3- was demonstrated in two steps, Petition 870250100702, dated 03 / 11 / 2025, pages 126 / 141 123 / 126, that is, oxidation of N2 to NO3- in the first step via eNOR, followed by the reduction of the NO3- formed to NH3 via eNO3RR. However, this two-step process may not be suitable for practical application due to the energy consumption in each step separately, due to the high energy consumption and HER and OER during eNOR and eNO3RR.

[0371] Thus, the inventors propose an alternative electrochemical cell for the synthesis of ammonia from nitrogen, suitable for continuous operation mode (illustrated in Figure 9). Figure 9 shows a single electrochemical cell configured to produce ammonia at the cathode and generate nitrate at the anode, which is pumped to the cathode side. The required applied voltage is similar to the voltage designated for each reaction (~2 V). After a sufficient electrolysis time, the supporting electrolyte saturated with N2 / Ar (containing the electrochemically formed NO3-) from the first anode chamber is fed into the second cathode chamber, where it undergoes reduction to ammonia. This combined approach to ammonia synthesis will be energetically superior to the current eNRR, and is therefore suitable for an alternative industrial ammonia synthesis.

[0372] Furthermore, the inventors have successfully designed and implemented an exemplary cell for the efficient synthesis of ammonia from nitrogen. As the reduction of nitrogen is accompanied by the massive generation of hydrogen, the proposed cell design efficiently recycles the resulting hydrogen. The inventors surprisingly observed that the introduction of a nitrogen / hydrogen mixture into the cell increased the reaction rate and, consequently, the overall FE of the process. Petition 870250100702, dated 03 / 11 / 2025, pages 127 / 141 124 / 126

[0373] A non-limiting exemplary apparatus of the invention (electrochemical cell), as designed and implemented by the inventors, is shown in Figure 8.

[0374] Figure 8 shows a non-limiting configuration of a cell fabricated by the inventors incorporating a 3D / thick electrode for the cathode in a centrifuge tube. A Pt-Black coated disc-shaped Ni foam is used as the anode. O-rings are used as spacers between the anode and cathode. This also helps to direct the gas flow through the center, rather than the sides.

[0375] A cylindrical carbon felt coated with catalyst is used as the cathode, and a Ni foam is placed below as a current collector. The anode and cathode connections to the potentiostat terminals were fabricated using Ni wires. Springs are introduced to induce compression of the carbon felt.

[0376] The electrolyte purged with nitrogen is circulated through the cell using a peristaltic pump. External nitrogen is also carried through the cell along with the electrolyte via the inlet. Inside the cell, during NRR, NH3 and H2 are produced and transported to a 1 mM H2SO4 trap via the gas outlet, where the NH3 is retained. The H2 and excess N2 are recirculated back into the cell.

[0377] An optional gas flow within the cell is as follows: initially, nitrogen flow is induced through the cell, where it undergoes reduction to ammonia at the cathode. The protons in the electrolyte are also reduced, forming hydrogen. The anode can oxidize some of the hydrogen back. Petition 870250100702, dated 03 / 11 / 2025, pp. 128 / 141 125 / 126 to protons. Through the gas outlet, the resulting gases, excess nitrogen, formed ammonia and hydrogen are directed to an ammonia trap, where the ammonia is retained and the remaining gases are recirculated to the cell.

[0378] The inventors observed that the addition of hydrogen (e.g., external hydrogen or recycled hydrogen from NRR or NO3RR) to the gas stream (comprising nitrogen) entering the supersaturated electrolytic solution (in this case, 50% by weight of CaBra) substantially increases the reaction rate and efficiency of the electrochemical reaction.

[0379] The reaction conditions were as follows: Cathode = Pt-Ru on carbon cloth, 4.09 mg / cm2; Anode = Pt black on Teflon-coated Toray carbon paper, 3.6 mg / cm2; Na:Ha flow rate = 2:1 (100 ccpm:50 ccpm).

[0380] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Thus, the intention is to cover all alternatives, modifications and variations that fall within the spirit and general scope of the appended claims.

[0381] All publications, patents and patent applications mentioned in this specification are incorporated herein by reference in the descriptive report, to the extent that each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. Furthermore, the citation or identification of any reference in this application shall not be construed as an admission that such reference is available as Petition 870250100702, dated 03 / 11 / 2025, pp. 129 / 141 126 / 126 prior technique to the present invention. To the extent that section headings are used, they should not be interpreted as necessarily limiting. Petition 870250100702, dated 03 / 11 / 2025, pages 130 / 141

Claims

1 / 8 CLAIMS 1. An electrochemical cell comprising a first chamber in liquid communication with a second chamber, characterized in that: the first chamber comprises an anode and is configured to contain a liquid electrolyte pressurized with a gas comprising nitrogen; the second chamber comprises a cathode; the anode comprises an electrocatalyst defined by the activity of nitrate oxidation reaction (NOR) to convert nitrogen to nitrate; the electrochemical cell is configured to transfer nitrate from the first chamber to the second chamber; and wherein the cathode comprises an electrocatalyst defined by the activity of nitrogen reduction reaction (NO3RR) to convert nitrate in the second chamber to ammonia.

2. Electrochemical cell, according to claim 1, characterized in that each of the cathodes and anodes has an electrocatalytically effective charge of the electrocatalyst between 0.5 and 10 mg / cm2.

3. Electrochemical cell, according to claim 1 or 2, characterized in that the electrochemical cell is operable at a predefined voltage between 1.5 and 2.5 V.

4. Electrochemical cell, according to claim 2, characterized in that the cathode and anode are connectable to a power supply configured to provide the predefined voltage; and in which the transfer is made by a pump configured to generate a flow of liquid electrolyte from the first chamber to the second chamber.

5. Electrochemical cell of any one of claims 1 to 4, characterized in that the electrocatalyst defined by the NOR activity and the electrocatalyst defined by the NO3RR activity are present in the form of a coating in contact with an external surface of the anode and cathode, respectively.

6. Electrochemical cell, according to claim 5, characterized in that the coating further comprises an electrically conductive material.

7. Electrochemical cell, according to claim 6, characterized in that the electrically conductive material comprises a conductive carbon material, a conductive ceramic material, a conductive polymer, a conductive metal oxide, or any combination thereof.

8. Electrochemical cell of any one of claims 1 to 7, characterized in that the electrocatalyst defined by the NOR activity comprises carbon material doped with Rh (Rh / C).

9. Electrochemical cell of any one of claims 1 to 8, characterized in that the electrocatalyst defined by the NO3RR activity comprises any one of the following: RuO2, a compound of cerium oxide and iron oxide, and a transition metal chalcogenide.

10. Electrochemical cell, according to claim 9, characterized in that the transition metal chalcogenide comprises any of the following: NICO2S4, copper sulfide and nickel sulfide.

11. Electrochemical cell, according to claim 9, characterized in that the molar ratio between Ce and Fe in the cerium oxide and iron oxide compound is about 1:

1.

12. Electrochemical cell of any one of claims 1 to 11, characterized in that the first chamber comprises a first gas inlet configured to direct gas to the liquid electrolyte; wherein the electrochemical cell further comprises a unidirectional flow element selected between a pump and a valve and located downstream of the first chamber and upstream of the second chamber.

13. Working electrode, characterized in that it comprises an electrocatalyst bonded to an electrode surface, wherein: the electrocatalyst comprises any of the following: (a) a transition metal oxide; (b) a transition metal chalcogenide; and (c) Rh-doped carbon material (Rh / C); the electrocatalyst is defined by an electrocatalytic activity selected from: (i) nitrogen-to-ammonia reducing (NRR) activity; (ii) NO3RR activity; and (iii) NOR activity, or any combination of (i) to (ii); and wherein said transition metal oxide is devoid of Ti oxide, a metal in its elemental state, or a salt thereof.

14. Working electrode according to claim 13, characterized in that said transition metal oxide comprises a transition metal selected from (i) Ru, Ce, Co, Ni, Fe, Pd, Sc, V, Cr, Mn, Cu, Zn, Y, Zr, Nb, Mo, Tc, Rh, Ag, Cd, W, Re, Os, Ir, Au and Pt; and (ii) a combination of iron oxide and the transition metal oxide.

15. Working electrode, according to claim 13 or 14, characterized in that the transition metal oxide comprises any of the following: RuO2, CeFeO3 and PdO; and in that the transition metal chalcogenide comprises any of the following: NiCo2S4, copper sulfide and nickel sulfide.

16. Working electrode, according to any one of claims 13 to 15, characterized in that the electrocatalyst is a RuO2 co-catalyst compound, wherein the co-catalyst is defined by the oxygen-peroxide reduction activity; and wherein the electrode is a cathode.

17. Working electrode, according to any one of claims 13 to 15, characterized in that the weight content of Rh in said Rh / C is between 3 and 20%, wherein said carbon material is in the form of microparticles and said Rh is in the form of nanoparticles.

18. Working electrode, according to any one of claims 16 to 17, characterized in that the electrocatalyst is any one of the following: (i) an electrocatalyst defined by the activity NOR consisting essentially of: Rh / C or the co-catalyst compound RuO2 any one of the following: a carbon material doped with Rh (Rh / C), composed of iron oxide TiO2, Ni oxide, Co oxide and mixed spinel Ni-Co oxide; and Petition 870250100627, dated 03 / 11 / 2025, p. 8 / 26 5 / 8 (ii) an electrocatalyst defined by the activity NO3RR consisting essentially of: RuO2, composed of Ce oxide-Fe oxide or the transition metal chalcogenide.

19. Working electrode, according to any one of claims 13 to 18, characterized in that the said electrocatalyst is in the form of a coating further comprising a conductive material; and wherein the concentration of said electrocatalyst in said coating is between 50 and 90% w / w.

20. Working electrode, according to claim 19, characterized in that said conductive material is a particulate matter comprising carbon particles, elemental metal particles, conductive metal oxide particles or any combination thereof.

21. Working electrode, according to any one of claims 13 to 20, being: (i) an anode, and characterized in that the electrocatalyst attached to a surface of the anode comprises Rh / C; or (ii) a cathode, and wherein the electrocatalyst attached to a surface of the cathode comprises any of the following: RuO2, a compound of Ce oxide and Fe oxide or the transition metal chalcogenide.

22. An electrochemical cell comprises a working electrode according to any one of claims 13 to 21 and a counter electrode in contact with a liquid electrolyte; characterized in that said electrochemical cell is configured to carry out a selected reaction between NRR, NOR and NO3RR. Petition 870250100627, dated 03 / 11 / 2025, page 9 / 26 6 / 8 23. Electrochemical cell, according to claim 22, characterized in that the working electrode comprises Rh / C and the electrochemical cell is configured to perform NOR after the application of an anodic potential in a range between about 1.5 and about 1.7 V relative to the RHE.

24. Electrochemical cell, according to claim 22, characterized in that the working electrode comprises the co-catalyst compound RuO2 and the electrochemical cell is configured to perform NOR by applying a cathodic potential in a range between 0 and 0.3 V relative to RHE.

25. Electrochemical cell, according to claim 22, characterized in that the working electrode comprises any of the following: RuO2, co-catalyst compound RuO2, compound of Ce oxide and Fe oxide or the transition metal chalcogenide, and the electrochemical cell is configured to perform NO3RR after the application of a negative cathodic potential.

26. Electrochemical cell, according to claim 25, characterized in that the negative cathodic potential is between -0.05 V and -0.6 V relative to the RHE.

27. Electrochemical cell, according to claim 25 or 26, characterized in that said electrolytic solution is saturated with nitrogen.

28. Electrochemical cell, according to claim 23 or 24, characterized in that said electrolytic solution is saturated with a gas comprising nitrogen and oxygen, optionally wherein said electrolytic solution further comprises a nitrate salt.

29. Electrochemical cell of any of claims 22 to 28, characterized in that said electrolytic solution comprises between 0.01 and 2 M of one or more ions selected from chloride, hydroxide and sulfate.

30. Ammonia synthesis method, characterized in that it comprises: (i) generating a flow of a gas comprising nitrogen in the first chamber of the electrochemical cell of any of claims 1 to 12, wherein the electrochemical cell is in contact with the liquid electrolyte, and (ii) applying electric current to the electrochemical cell, thereby inducing NOR at the anode to obtain nitrate within the first chamber; and (iii) generating a flow of nitrate from the first chamber to the second chamber to reduce said nitrate at the cathode, thereby generating ammonia.

31. Method according to claim 30, characterized in that the gas further comprises between 10 and 30% v / v of oxygen; and in that said electric current comprises a potential between 1.5 and 2.5 V.

32. A method according to claim 30 or 31, characterized in that the gas enters the first chamber through the first gas inlet, and in that the gas flow is sufficient to saturate the liquid electrolyte in the first chamber with the gas.

33. Method according to claim 32, characterized in that the nitrate flow is generated Petition 870250100627, dated 03 / 11 / 2025, page 11 / 26 8 / 8 through the unidirectional flow element; optionally, wherein the first gas inlet is in fluid communication with the anode, wherein the anode is configured to support the gas flow.

34. A method for any one of claims 30 to 33, characterized in that the nitrate flow rate is between 0.1 and 3 ml / min; and wherein said method is carried out at a temperature between 5 °C and 100 °C.

35. A method according to any one of claims 30 to 34, characterized in that the liquid electrolyte comprises between 0.01 and 2 M of one or more ions selected from chloride, hydroxide, and sulfate.

36. Method, according to any one of claims 30 to 35, characterized in that step (ii) and step (iii) are performed simultaneously. Petition 870250100627, dated 03 / 11 / 2025, page 12 / 26

Images