Pyrolysis composite catalyst

Abstract

This invention relates to a pyrolysis composite catalyst comprising electrocatalyst-active metal alloy nanoparticles and a nitrogen-doped carbonaceous matrix, wherein the matrix comprises pyrolysis products of a polyamide material. A one-step method for preparing the pyrolysis composite catalyst is also provided, along with the pyrolysis composite catalyst obtainable by this method and an electrode comprising the pyrolysis composite catalyst. The invention further relates to the use of the pyrolysis composite catalyst as an anode catalyst for the electrochemical oxygen evolution reaction in an electrochemical device, and to an electrochemical device comprising an electrode as defined herein.

Description

[0001] This application claims the benefit of European patent application EP23383098.3, filed on 26 October 2023.

[0002] This disclosure relates to the field of electrolysis, and more particularly to composite catalysts that can be used as catalysts in electrolyzers, and more specifically for the oxygen evolution reaction in the anode. Background Technology

[0003] Oxygen evolution reaction (OER) is an important reaction not only in water electrolysis but also in CO2 electrolysis, reversible fuel cells, and metal-air batteries. Therefore, it is expected that OER will play an important role in the design of high-efficiency energy conversion and storage devices.

[0004] Water electrolysis represents a well-known method for hydrogen production. Various water splitting methods are known in the art, such as liquid alkaline water electrolysis (AWE), proton exchange membrane (PEM) electrolysis, and anion exchange membrane (AEM) electrolysis.

[0005] The water splitting system comprises a half-cell with an electrode (anode) where the oxygen evolution reaction (OER) occurs, and another half-cell with an electrode (cathode) where the hydrogen evolution reaction (HER) occurs.

[0006] In the water splitting reaction, an electric current is applied to an electrochemical cell containing an electrolyte, typically an aqueous solution of an alkaline or acidic substance, where the conversion of electrical energy into chemical energy occurs at the electrode-electrolyte interface. The cell comprises two electrodes: an anode and a cathode. The OER reaction takes place at the anode.

[0007] The electrode reactions carried out in liquid alkaline and anion exchange membrane electrolyzers can be written as: Anode: 4OH - → 2H₂O + O₂ + 4e - Cathode: 4H₂O + 4e⁻ - → 2H2 + 4OH - For a PEM electrolyzer, the electrode reaction is as follows: Anode: 2H₂O → O₂ + 4H₂O + + 4e - Cathode: 4H + + 4e - → 2H2 Therefore, the oxygen evolution reaction (OER) is a fundamental process in electrochemistry, which involves the production of oxygen through the electrochemical decomposition of water molecules.

[0008] Water electrolysis, under both acidic and alkaline conditions, is kinetically limited by the oxygen evolution reaction (OER) at the anode, rather than by the hydrogen evolution reaction (HER) at the cathode. The equilibrium redox potential (Er) for water molecule decomposition is 1.23 V. For actual yield in an electrolyzer, a higher voltage is required to achieve a sufficiently high conversion rate due to the activation energies and kinetics of both OER and HER, as well as ohmic losses related to electrolytes, electrodes, and other factors. This additional voltage above 1.23 V is called the overpotential (η).

[0009] High catalytic activity is one of the requirements for the practical application of OER catalysts in water splitting units, and the catalytic materials are also required to exhibit long-term stability.

[0010] Alkaline electrolyzers are characterized by the robust performance, long lifespan, and low cost of their electrode materials (especially anode materials), which are primarily composed of abundant transition metals (Fe, Ni, Co, Cu, and Mn oxides) and carbon-based materials (nitrogen-doped carbon). A major obstacle to improving long-term durability is the high overpotential of the anode reaction, which leads to corrosion of the active phase and support materials.

[0011] The main drawback of proton exchange electrolyzers is the limitation on anode catalysts based on original key materials, as well as other device components such as separators and current collectors, due to the high durability required of materials in the highly corrosive environment associated with high electrode potentials. In PEM cells, the corrosive environment necessitates that the anode catalyst be based on a noble metal obtained through electrochemical oxidation.

[0012] AEM electrolysis is an emerging technology. The development of polymeric anion exchange membranes has garnered significant attention due to their application in alkaline fuel cells. However, they can also be used in water electrolysis systems, offering several advantages, such as: the use of transition metal-based catalysts instead of precious metal-based materials; the use of low-concentration alkaline solutions (or even distilled water) instead of high-concentration KOH solutions; cheaper membrane substrates (compounds containing quaternary ammonium ion exchange groups) compared to Nafion®-based membranes used in PEMs; reduced degradation due to CO2 interaction due to the absence of metal ions in the AEM structure; and greater versatility in equipment engineering design due to the absence of a corrosive liquid electrolyte.

[0013] In addition, in CO2 electrolysis, the cathode reaction has the following general formula: x CO2 + n H + + n e - →Product+ y H2OCO2 reduction (CO2R) Similarly, in water splitting, the anodic reaction in electrochemical CO2 reduction is typically the oxygen evolution reaction (OER): 2H₂O → O₂ + 4H + + 4e - Oxygen evolution reaction (OER) at the anode For the purpose of summarizing, the following is the overall response: x CO2 + y H2O → Products + z O2CO2 electrolysis Reference WO2022264112 describes a catalyst comprising nanoparticles made of a metal alloy and a porous matrix, wherein the nanoparticles are embedded and uniformly distributed within the porous matrix. The porous matrix contains nitrogen-doped carbon, which is typically formed through the pyrolysis / decomposition of a suitable metal precursor, wherein the organic ligands of the organometallic and / or coordination compounds used as the precursor form the porous matrix upon decomposition.

[0014] A series of MOF-templated catalysts with embedded Co-Ni alloy nanoparticles are described in Chem Eng Sci 166 (2017) 66-76 for the hydrogenation of phenol to cyclohexanol.

[0015] In Appl Surface Sci 299 (2014) 19-28, ordered mesoporous carbon (OMC) modified with nitrogen from polyarylamide precursors is described. Summary of the Invention

[0016] One object of the present invention is to provide a pyrolysis composite catalyst that exhibits high catalytic activity in the oxygen evolution reaction and is therefore suitable as a catalyst on the anode of an electrolyzer. This composite catalyst operates at a suitable overpotential and is cost-effective.

[0017] Therefore, according to a first aspect of the present invention, a pyrolysis composite catalyst is provided, comprising: i) Electrocatalytically active metal alloy nanoparticles; and ii) A nitrogen-doped carbonaceous matrix, wherein the nitrogen content of the matrix, as determined by elemental analysis, is 0.1% to 5% as a percentage of dry weight based on the total weight of the composite catalyst; The matrix comprises pyrolysis products of polyamide materials; The metal alloy nanoparticles are present at a weight percentage of 10% to 70% based on the total weight of the composite catalyst.

[0018] In a second aspect, the present invention provides a one-step method for preparing a pyrolysis composite catalyst, comprising contacting two or more alloy precursors selected from metal salts and metal complexes with a polyamide material under pyrolysis conditions, wherein the metal salts and metal complexes comprise two or more metals selected from the group consisting of Co, Fe, Cu, Ti, V, Cr, Mn, Ni, Zn, Ir, Ru, Os, Au, Nb, Mo, and W; wherein the pyrolysis temperature is 700-1000℃, and the pyrolysis heating rate is 1-10℃ / min.

[0019] Another aspect of the invention relates to a pyrolysis composite catalyst that can be obtained by the one-step method described herein.

[0020] In another aspect, the present invention provides a method for producing electrodes, the method comprising the following steps: a) A pyrolysis composite catalyst is prepared by contacting two or more alloy precursors selected from metal salts and metal complexes with a polyamide material at a pyrolysis temperature of 700-1000℃ and under pyrolysis conditions, wherein the metal salts and metal complexes include two or more metals selected from the group consisting of Co, Fe, Cu, Ti, V, Cr, Mn, Ni, Zn, Ir, Ru, Os, Au, Nb, Mo and W, and the polyamide material contains 2 to 20% by weight of nitrogen, wherein the pyrolysis heating rate is 1-10℃ / min; b) Cool to room temperature to collect the pyrolysis composite catalyst; and c) The pyrolysis composite catalyst is loaded onto a conductive substrate or an ion exchange membrane.

[0021] Another aspect of the invention relates to an electrode that can be obtained by the above method, preferably for use as an anode in an OER.

[0022] On the other hand, electrodes for OER in an electrolyzer according to the invention are provided, particularly anodes, which contain a pyrolysis composite catalyst supported on a conductive substrate or an ion exchange membrane to form a MEA (membrane electrode assembly) or CCM (catalyst-coated membrane).

[0023] On the other hand, this relates to the use of the pyrolysis composite catalyst described herein in alkaline water electrolysis (AWE), anion exchange membrane electrolysis (AEM), proton exchange membrane (PEM) electrolysis, or CO2 electrolysis.

[0024] Another aspect of the invention relates to the use of the pyrolysis composite catalyst as an anode material in the oxygen evolution reaction (OER). This aspect can also be expressed as the use of the pyrolysis composite catalyst as an anode catalyst material for the electrochemical oxygen evolution reaction in an electrochemical device.

[0025] Another aspect of the present invention relates to an electrochemical device including the anode of the present invention. Attached Figure Description

[0026] Non-limiting examples of this disclosure will now be described with reference to the accompanying drawings, in which: Figure 1 j = 10 mA / cm 2 Chronopotential curves of PACoFeP2 and PACoFeZnP3 in 0.1 M NaOH.

[0027] Figure 2 OER polarization curves of PACoFeP2 and PACoFeZnP3

[0028] Figure 3 XRD patterns of PACoFeP2 and PACoFeZnP3 catalysts Detailed Implementation

[0029] Unless otherwise stated, all terms used in this application shall be understood in their ordinary meaning as known in the art. Further more specific definitions of certain terms used in this application are set forth below and are intended to apply throughout the specification and claims.

[0030] When using numerical ranges in this invention, this includes the values ​​of the extreme values ​​of the range.

[0031] The terms "weight percentage," "volume percentage," or "molar" are used. A "percentage" refers to the percentage of a component by weight, volume, or moles, based on the total weight, total volume, or total number of moles of the material comprising that component, respectively. In a non-limiting example, 10 grams of component in 100 grams of material constitutes 10% by weight of the component. Therefore, when referring to metal alloy nanoparticles contained in a composite catalyst, the term "weight percentage (%w / w)" is estimated by determining the amount of metal alloy nanoparticles relative to the total weight of the composite catalyst and multiplying the resulting value by 100.

[0032] The term “water splitting,” or any variation thereof, describes the chemical reaction in which water is separated into oxygen and hydrogen under the influence of an electric current.

[0033] When used in the claims or description in conjunction with any of the terms “comprising,” “including,” “containing,” or “having,” the use of the words “a” or “an” can mean “a,” but it is also consistent with the meanings of “one or more,” “at least one,” and “one or more.”

[0034] The words “comprising” (and any form of inclusion, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”), or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional unlisted elements or method steps; and include cases where “composes of”.

[0035] Composite catalyst

[0036] As described above, the present invention relates to a pyrolysis composite catalyst, comprising: i) Electrocatalytically active metal alloy nanoparticles; and ii) A nitrogen-doped carbonaceous matrix, wherein the nitrogen content of the matrix, as determined by elemental analysis, is 0.1% to 5% as a percentage of dry weight based on the total weight of the composite catalyst; The matrix comprises pyrolysis products of polyamide materials; The metal alloy nanoparticles are present at a weight percentage of 10% to 70% based on the total weight of the composite catalyst.

[0037] According to some embodiments, optionally in combination with any of the embodiments above or below, the electrocatalytically active metal alloy nanoparticles have a particle size of 0.1 nm to 60 nm as determined by high-resolution transmission electron microscopy (HRTEM).

[0038] In some embodiments, optionally in combination with any of the embodiments described above or below, the composite catalyst has a surface area of ​​80 m² as determined by the Brunauer-Emmett-Teller (BET) method. 2 / g to 300 m 2 / g, preferably 90m 2 / g to 280 m 2 / g, more preferably 100 m 2 / g to 250 m 2 / g.

[0039] In some embodiments, optionally in combination with any of the embodiments described above or below, the nitrogen-doped carbonaceous matrix has an average pore size of 0.1 nm to 17 nm, preferably 1 nm to 15 nm, more preferably 2 nm to 12 nm, as determined by the Barret-Joyner-Halenda (BJH) method.

[0040] As described above, in the pyrolysis composite material, the metal alloy nanoparticles are present at a weight percentage of 10% to 70% based on the total weight of the composite catalyst. According to some embodiments, the metal alloy nanoparticles are present at a weight percentage of 12% to 60%, preferably 17% to 40%, and even more preferably 20% to 30%.

[0041] The pyrolysis composite catalyst of the present invention comprises: i) electrocatalytically active metal alloy nanoparticles; and ii) a nitrogen-doped carbonaceous matrix, wherein the metal alloy nanoparticles are embedded within the carbonaceous matrix. Embedding is achieved through physical embedding or / and covalent bonding or / and joining of the nanoparticles with the carbonaceous matrix. Preferably, the nanoparticles are dispersed in the matrix and retained therein by physical retention.

[0042] Some specific embodiments involve pyrolysis composite catalysts, which include: i) Electrocatalytically active metal alloy nanoparticles with particle sizes ranging from 0.1 nm to 60 nm, as determined by high-resolution transmission electron microscopy (HRTEM); and ii) Nitrogen-doped carbonaceous matrix; The nitrogen-doped carbonaceous matrix can be obtained by the pyrolysis of polyamide materials; The metal alloy nanoparticles are present at a weight percentage of 10% to 70% based on the total weight of the composite catalyst. The metal alloy nanoparticles are embedded within the carbonaceous matrix.

[0043] In some embodiments, optionally in combination with any of the embodiments above or below, the metal alloy includes two or more metals selected from the group consisting of cobalt (Co), iron (Fe), copper (Cu), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), zinc (Zn), iridium (Ir), ruthenium (Ru), osmium (Os), gold (Au), niobium (Nb), molybdenum (Mo), and tungsten (W); preferably two or more metals selected from the group consisting of Co, Fe, Zn, Cu, and Ni; particularly preferred are metal alloys selected from Co-Fe alloys, Ni-Fe alloys, Co-Ni alloys, Co-Fe-Zn alloys, Co-Fe-Ni alloys, and Cu-Fe alloys.

[0044] According to some embodiments, optionally in combination with any of the embodiments above or below, the nitrogen-doped carbonaceous matrix has a nitrogen content of 0.1% to 5% by dry weight, as determined by elemental analysis, preferably 0.2% to 4.8%, more preferably 0.3% to 3%.

[0045] According to some embodiments, optionally in combination with any of the embodiments above or below, the nitrogen-doped carbonaceous matrix has an average pore size of 0.1 nm to 17 nm as determined by the Barret-Joyner-Halenda (BJH) method.

[0046] As described in this article, the nitrogen-doped carbonaceous matrix contains the pyrolysis products of polyamide materials.

[0047] In some embodiments, optionally in combination with any of the embodiments described above or below, the nitrogen-doped carbonaceous matrix comprises graphene sheets and carbon shell structures, such as fullerene-like cavities.

[0048] Nitrogen-containing carbon nanostructures exhibit promising catalytic activity for the oxygen evolution reaction (OER). However, methods for preparing nitrogen-doped carbon structures containing graphene, carbon shells, or fullerene-like carbons typically rely on very demanding processes and multi-step procedures involving the high-temperature production of carbon materials followed by the introduction of nitrogen into the carbon structure using NH3, amines, urea, or melamine. In this paper, nitrogen-doped carbon nanostructures are readily prepared from polyamide materials.

[0049] In some embodiments, optionally in combination with any of the embodiments described above or below, the polyamide material (i.e., a polymeric material containing repeating amide groups (R-CO-NH-R') as part of the polymer backbone) can be any known natural or synthetic polyamide material. Examples of suitable polyamide materials include aliphatic polyamides, such as nylon 6 (i.e., prepared by ring-opening polymerization of the monomer caprolactam), nylon 66 (i.e., a polyamide made from the monomers hexamethylenediamine and adipic acid); polyphthalamides, such as PA 6T (obtained by the reaction of hexamethylenediamine and terephthalic acid); and aromatic polyamides, such as those obtained by the reaction of p-phenylenediamine and terephthalic acid.

[0050] Polyurethane polymers are typically prepared by reacting polyisocyanates (especially diisocyanates) with hydroxyl-rich compounds (such as glycols and polyester and polyether polyols). The recycling and reuse of polyurethane chemical components in new product manufacturing is of interest. A general aim of polyurethane chemical recycling is to recover polyols (one of its components), which can be used as valuable raw materials to manufacture new polyurethane foams.

[0051] The chemical depolymerization of polyurethane can be achieved through processes such as hydrolysis, hydroglycolysis, ammonolysis, glycolysis, and acidolysis.

[0052] In the acid hydrolysis method used for recycling polyurethane foam, polyamide sub-products can be recovered in addition to polyols. These polyamide sub-products can be used as raw materials for preparing the pyrolysis composite catalyst of this invention.

[0053] Therefore, according to some embodiments of the present invention, the polyamide material is obtained from a polyurethane material, which may be waste polyurethane material or fresh polyurethane material.

[0054] In the experimental section of this disclosure, different polyurethane materials were used as raw materials for preparing polyamides, which were then used to prepare the pyrolysis composite catalyst of the present invention. Therefore, a mixture of waste polyurethane, polyurethane prepared from TDI (toluene diisocyanate), polyurethane prepared from MDI (methylene diphenyl diisocyanate), and polyurethane prepared from TDI (which has undergone a deammoniation process to remove TDA (toluene diamine) derived from isocyanates present in the foam) was used.

[0055] Therefore, according to some embodiments, optionally in combination with any of the embodiments described above or below, polyamide materials can be obtained from polyurethane foam. Preferably, polyamide can be obtained by acid hydrolysis of polyurethane material.

[0056] Preparation method of composite catalyst

[0057] A second aspect of the invention relates to a one-step method for preparing a composite catalyst. The method includes contacting a polyamide material with two or more alloy precursors selected from metal salts and metal complexes under pyrolysis conditions, wherein the metal salts and metal complexes comprise two or more metals selected from the group consisting of Co, Fe, Cu, Ti, V, Cr, Mn, Ni, Zn, Ir, Ru, Os, Au, Nb, Mo, and W; wherein the carbonization temperature is 700-1000 °C, and the pyrolysis heating rate is 1-10 °C / min. The method further includes a step of cooling to room temperature to collect the resulting composite catalyst.

[0058] According to some embodiments, optionally in combination with any of the embodiments above or below, the metal alloy precursor is a metal salt and metal complex comprising a metal selected from the group consisting of Co, Fe, Cu, Ti, V, Cr, Mn, Ni, Zn, Ir, Ru, Os, Au, Nb, Mo and W; preferably Co, Fe, Zn, Cu and Ni; particularly preferred are metal alloys selected from Co-Fe alloys, Ni-Fe alloys, Co-Ni alloys, Co-Fe-Zn alloys, Co-Fe-Ni alloys and Cu-Fe alloys.

[0059] In some specific embodiments, optionally in combination with any of the embodiments described above or below, the metal alloy precursor is a metal salt and metal complex selected from CoCl2, FeCl3, ZnCl2, CuCl2, NiCl2.

[0060] According to some embodiments, optionally in combination with any of the embodiments above or below, the method includes contacting a mixture of two metal alloy precursors under pyrolysis conditions, wherein the atomic-to-metal ratio of the metal alloy precursors is 4:1 to 1:4, preferably 3:1 to 1:3, more preferably 1:1.

[0061] In some specific embodiments, optionally in combination with any of the embodiments described above or below, the method includes contacting a mixture of three metal alloy precursors under pyrolytic conditions. Therefore, when the metal alloy comprises three metal atoms, according to the following formula: (A x B y ) n C z A, B, and C are different metal atoms; The ratio between x and y is 4:1 to 1:4, preferably 3:1 to 1:3, and more preferably 1:1; and The ratio between n and z is 1:2 to 10:1, preferably 1:1 to 5:1.

[0062] According to some specific embodiments, optionally in combination with any of the embodiments above or below, the method includes contacting a mixture of a metal precursor and a polyamide material at a weight ratio of 3:1 to 1:3, more preferably 1:1, under pyrolysis conditions.

[0063] In some embodiments, optionally in combination with any of the embodiments above or below, the nitrogen content of the polyamide material is determined by elemental analysis to be 2% to 20% by weight, preferably 5% to 15% by weight, and more preferably 6% to 12% by weight.

[0064] In some embodiments, optionally in combination with any of the embodiments described above or below, polyamides can be obtained from polyurethane foams. Therefore, in some embodiments, polyamides can be obtained by acid hydrolysis of polyurethane materials.

[0065] In some embodiments, optionally in combination with any of the embodiments described above or below, the acidolysis process includes contacting the polyurethane material with an acid solution, preferably derived from an organic acid, more preferably at least one dicarboxylic acid or at least one carboxylic acid derivative (e.g., succinic acid, succinic anhydride, phthalic anhydride, phthalic acid, maleic anhydride, adipic acid, and glutaric acid), preferably in the presence of at least one polyether polyol, at least one free radical generator suitable for initiating free radical polymerization (e.g., methyl ethyl ketone peroxide, cumene hydroperoxide, di-tert-butyl hydroperoxide, or ethylbenzene hydroperoxide), and a carbonyl-containing carbon-unsaturated monomer (which has undergone a grafting reaction), and decomposing at least a portion of the polyurethane material into a recycled feedstock composition containing polyamide compounds.

[0066] In some embodiments, optionally in combination with any of the embodiments above or below, the carbonization temperature is 700°C to 1000°C, preferably 720°C to 960°C, more preferably 800°C to 920°C; particularly preferred is a carbonization temperature of 900°C; and wherein the pyrolysis heating rate is 1°C / min to 10°C / min, preferably 2°C / min to 5°C / min, particularly preferably 3.3°C / min, up to reaching 900°C.

[0067] Another aspect of the invention relates to a composite catalyst that can be obtained in one step as described above.

[0068] Electrode for OER

[0069] In another aspect, the present invention provides a method for producing electrodes, the method comprising the following steps: a) Prepare composite catalysts according to the one-step method described herein; b) Load the composite catalyst obtained in a) onto a conductive substrate or a polymer film.

[0070] Suitable carrier materials are commercially available or can be prepared using conventional methods known to those skilled in the art. Therefore, according to some embodiments, optionally in combination with any of the embodiments described above or below, the conductive substrate is selected from glassy carbon, paper carbon, cloth carbon, and anion exchange membranes. Alternatively, in some other embodiments, optionally in combination with any of the embodiments described above or below, the carrier material is an ion exchange membrane.

[0071] Those skilled in the art will know suitable methods for loading composite catalysts onto conductive substrates or ion exchange membranes. In some embodiments, optionally in combination with any of the embodiments described above or below, the loading step includes adding an appropriate amount of ink containing a dispersion of the catalyst in a solvent and an ionomer.

[0072] In some embodiments, optionally in combination with any of the embodiments described above or below, a water electrolyzer is provided, comprising: an electrolytic cell containing an electrolyte in the form of an aqueous electrolyte solution or a polymer membrane; a first electrode (anode) containing an electrocatalyst as described herein or manufactured by a method as defined herein; a second electrode (cathode); and a voltage source providing a current density to electrochemically decompose water, thereby forming oxygen and hydrogen at the anode and cathode, respectively. The first electrode and the second electrode are electrically connected to the power source. The water electrolyzer may include one or more operating features, elements, or conditions, and / or include a device or features thereof having one or more features as described, shown, or required herein. In an exemplary embodiment, an ion exchange unit may also be provided between the first and second electrodes in the water electrolyzer.

[0073] The first electrode and the second electrode can be formed of semiconductor or conductive materials, respectively. The composite catalyst is disposed on at least one side of the first electrode.

[0074] An aqueous electrolyte solution can be used as a water supply source for water splitting reactions. The aqueous electrolyte solution may include, for example, 0.1M-1M NaOH. The pH of the aqueous electrolyte solution can be between 12 and 14.

[0075] When a voltage is applied between the first and second electrodes in a water splitting system, the following reaction can occur: oxygen is produced in the first electrode containing a composite catalyst, and hydrogen is produced in the second electrode.

[0076] In some embodiments, optionally in combination with any of the embodiments described above or below, a system for the electroreduction of CO and / or CO2 to produce multicarbon compounds is provided, comprising: an electrolyzer configured to receive a liquid electrolyte and CO and / or CO2 gas; an anode containing an electrocatalyst as defined herein or manufactured by methods defined herein; a cathode containing a copper-containing electroreduction catalyst; and a voltage source providing a current density to electrochemically convert CO and / or CO2 gas in contact with the cathode into the multicarbon compounds and induce an oxygen evolution reaction at the anode. The system may also include one or more operating features, elements, or conditions, and / or include devices or features thereof having one or more features as described, shown, or required herein.

[0077] The composite catalyst of the present invention can be used as an oxygen evolution catalyst with improved catalyst properties under alkaline conditions.

[0078] As described above, one aspect of the present invention relates to an electrochemical device comprising the electrodes as defined in the claims. According to some specific embodiments, the electrochemical device is a water electrolyzer for electrolyzing and splitting water into hydrogen and / or oxygen, wherein the device comprises: - Electrodes as defined above; - A container for holding electrolytes; - Counter electrode; and - A power supply configured to apply a voltage between the electrodes.

[0079] Throughout the specification and claims, the word "comprising" and variations thereof are not intended to exclude other technical features, additives, components, or steps. Other objects, advantages, and features of the invention will become apparent to those skilled in the art upon reading this specification, or may be learned by practicing the invention. Although only a few embodiments are disclosed herein, other substitutions, modifications, uses, and / or equivalents are possible. Furthermore, all possible combinations of the described embodiments are covered. Therefore, the scope of this disclosure should not be limited to the specific embodiments but should be determined solely through a reasonable reading of the appended claims.

[0080] The following embodiments and accompanying drawings are provided by way of illustration and are not intended to limit the invention. Furthermore, the invention encompasses all possible combinations of the specific and preferred embodiments described herein.

[0081] Example

[0082] Example 1. Acid hydrolysis of polyurethane foam

[0083] The polyurethane foam was acid-hydrolyzed according to the procedure described in DE19512778C1.

[0084] DE19512778C1 discloses a reaction mixture comprising a dicarboxylic acid or a derivative thereof, a polyether polyol with a functionality of 3, a free radical generator, and a carbonyl-containing carbon-unsaturated monomer (which has undergone a grafting reaction); polyurethane waste is added, and the resulting mixture is reacted at a temperature of 140°C to 250°C (preferably 170°C to 220°C) for a reaction time of 1 hour to 10 hours to form a dispersion. Optionally, the polyol dispersion can be deaminated by a glycidyl ether reaction.

[0085] A dispersion containing polyamide particles in a liquid polyol is obtained. The polyamide solid particles (PA) are separated from the liquid phase by centrifugation.

[0086] Table 1 shows the nitrogen content as a percentage of dry weight based on the total weight of polyamide, as determined by elemental analysis.

[0087] Table 1

[0088] Example 2. Preparation of composite catalyst

[0089] Polyamide and the corresponding metal salt (polyamide to metal ratio 1:1) were ground in a mortar until a homogeneous mixture was obtained. This mixture was then pyrolyzed at high temperatures (1000°C, 900°C, 800°C), wherein it was maintained under N2 for 1 or 2 hours. Temperature ramps were also achieved by stopping at 500°C for 30 minutes, then increasing to 900°C and holding for 1 hour. The pyrolysis heating rate was 3.3°C / min in all samples.

[0090] Table 2. Details of Catalytic Synthesis

[0091] in: PATDI is a polyamide obtained as in Example 1, derived from TDI polyurethane foam. PAS is a synthetic polyamide obtained by the equimolar reaction of toluene diamine (TDA) with dicarboxylic acid. PAMDI is a polyamide obtained through the acid hydrolysis of MDI polyurethane foam. PATDIdes are polyamides obtained through the acid hydrolysis of TDI polyurethane foam, which have undergone a deamination process to eliminate TDA. PANY is a commercially available polyamide, nylon 6,6, linear, obtained from MERCK. PA12 is a commercially available polyamide; polyamide 12 was obtained from MERCK. PANOM is a commercially available polyamide, Nomex, obtained from MERCK.

[0092] Example 3. Electrochemical Characterization

[0093] Electrochemical characterization was performed in a conventional three-electrode electrochemical cell connected to an Autolab PGSTAT302 potentiostat. The catalyst was analyzed in the oxygen evolution reaction (OER) using a rotating ring-disk electrode (RRDE) as the working electrode (with a dye prepared from the useful catalyst deposited thereon), glassy carbon as the counter electrode, and a reversible hydrogen electrode (RHE) as the reference electrode.

[0094] Some catalyst powder was ultrasonically treated in ethanol to obtain a concentration of 10 mg·mL⁻¹ -1 The catalyst ink solution was prepared by mixing 5 wt% Nafion solution. 20 μL of the catalyst ink was deposited onto a glassy carbon disk (5 mm in diameter, 0.196 cm²) of a rotating ring-disk electrode (RRDE). 2In this process, the working electrode (WE) is prepared.

[0095] Measurements were performed using 0.1M or 1M NaOH as the carrier electrolyte and saturated with Ar. For OER measurements, the electrode was rotated at 1600 rpm, and cyclic voltammetry was recorded between 1.1V and 1.8V at a scan rate of 5 mV / s. The ring disk was maintained at a control potential of 0.4V to detect oxygen formation and distinguish it from oxide formation on the catalyst.

[0096] IrO2 catalyst was used as a reference, which was at 10 mA / cm 2 It has an overpotential (η) of 0.399 V at a current density: η = 1.23 - E OER (10 mA / cm 2 ) = 0.399V Calculating the Tafel slope allows us to obtain a direct correlation between the current change and the applied potential (Table 2). Lower Tafel slope values ​​indicate that the catalytic current increases more rapidly when a higher potential is applied. The obtained values ​​are 54–69 mV / dec, even lower than the values ​​for IrO2 (70 mV / dec).

[0097] Table 3. Overpotential (η) and Tafel slope values ​​of the catalyst

[0098] By maintaining 10 mA / cm 2 The current density was measured for 18 hours and the potential evolution was recorded. The stability of the PACoFeP2 and PACoFeZnP3 catalysts was measured using chronopotentialography in 0.1 M NaOH. The results are as follows: Figure 1 As shown.

[0099] In addition, PACoFeP2 and PACoFeZnP3 were analyzed using 1M NaOH as the electrolyte. Under these conditions, the overpotentials generated by both catalysts were observed to be lower than those of iridium oxide using this electrolyte (Table 4 and...). Figure 2 ).

[0100] Table 4. Overpotential values ​​in 1M NaOH

[0101] Example 4. Physicochemical Characterization

[0102] The composite catalyst sample was characterized using X-ray diffraction (XRD) in an X'Pert Pro PAN analytical diffractometer. XRD diffraction patterns were obtained by studying different crystal phases of the catalyst, in which graphite-like structures and cobalt alloys were detected in all cases. Figure 3 ).

[0103] In the JEOL JEM 2100, the composite catalyst was also analyzed by transmission electron microscopy (TEM). Images obtained by TEM showed that metal alloy particles were embedded in a nitrogen-doped carbonaceous matrix, some of which had graphene sheet and carbon shell structures, such as fullerene-like cavities.

[0104] The BET specific surface area and chemical composition are shown in Table 5. The composite material exhibits a type IV isotherm, a typical characteristic of mesoporous materials. Its BET specific surface area ranges from 84 to 287 m². 2 / g, depending on the starting polymer used. The pore size distribution of these composites indicates the formation of mesopores with an average pore size of 4 nm.

[0105] Table 5. BET specific surface area, average pore size and chemical composition.

[0106]

[0107] References cited in this application

[0108] DE19512778.

Claims

1. A pyrolysis composite catalyst, comprising: i) Electrocatalytically active metal alloy nanoparticles; and ii) A nitrogen-doped carbonaceous matrix, wherein the nitrogen content of the matrix, as determined by elemental analysis, is 0.1% to 5% as a dry weight percentage based on the total weight of the pyrolysis composite catalyst; The matrix comprises pyrolysis products of polyamide materials; The metal alloy nanoparticles are present at a weight percentage of 10% to 70% based on the total weight of the composite catalyst.

2. The pyrolysis composite catalyst according to claim 1, wherein the particle size of the electrocatalytically active metal alloy nanoparticles, as determined by high-resolution transmission electron microscopy (HRTEM), is from 0.1 nm to 60 nm.

3. The pyrolysis composite catalyst according to any one of claims 1 to 2, wherein the surface area of ​​the composite catalyst, as determined by the Brunauer-Emmett-Teller (BET) method, is 80 m². 2 / g to 300 m 2 / g.

4. The pyrolysis composite catalyst according to any one of claims 1 to 3, wherein the average pore size of the nitrogen-doped carbonaceous matrix, as determined by the standard Barret-Joyner-Halenda (BJH) method, is from 0.1 nm to 17 nm.

5. The pyrolysis composite catalyst according to any one of claims 1 to 4, wherein the metal alloy comprises two or more metals selected from the group consisting of Co, Fe, Ti, V, Cr, Mn, Ni, Zn, Ir, Ru, Os, Au, Nb, Mo and W.

6. The pyrolysis composite catalyst according to any one of claims 1 to 5, wherein the nitrogen-doped carbonaceous matrix comprises graphene sheets and fullerene-like cavities.

7. The pyrolysis composite catalyst according to any one of claims 1 to 6, comprising: i) Electrocatalytically active metal alloy nanoparticles with particle sizes ranging from 0.1 nm to 60 nm, as determined by high-resolution transmission electron microscopy (HRTEM); and ii) Nitrogen-doped carbonaceous matrix, The nitrogen-doped carbonaceous matrix can be obtained by the pyrolysis of polyamide materials. The metal alloy nanoparticles are present at a weight percentage of 10% to 70% based on the total weight of the composite catalyst. The metal alloy nanoparticles are embedded within the carbonaceous matrix.

8. A one-step method for preparing a pyrolysis composite catalyst, comprising contacting two or more alloy precursors selected from metal salts and metal complexes with a polyamide material under pyrolysis conditions, wherein the metal salts and metal complexes comprise two or more metals selected from the group consisting of Co, Fe, Cu, Ti, V, Cr, Mn, Ni, Zn, Ir, Ru, Os, Au, Nb, Mo, and W; wherein the pyrolysis temperature is 700-1000℃, and the pyrolysis heating rate is 1-10℃ / min.

9. The one-step method of claim 8, wherein the polyamide material is obtained by acid hydrolysis of polyurethane foam.

10. A pyrolysis composite catalyst, which can be obtained by the method of any one of claims 8 to 9.

11. An electrode comprising the pyrolysis composite catalyst according to any one of claims 1 to 7.

12. The electrode of claim 11, wherein the pyrolysis composite catalyst is supported on a conductive substrate or an ion exchange membrane to form a MEA (membrane electrode assembly) or a CCM (catalyst-coated membrane).

13. Use of the pyrolysis composite catalyst according to any one of claims 1 to 7 as an anode catalyst for the electrolytic oxygen removal reaction in an electrochemical device.

14. An electrochemical device comprising the electrode according to any one of claims 11 to 12.

15. The electrochemical device of claim 14, wherein the device is a water electrolyzer for electrolyzing and splitting water into hydrogen and / or oxygen, wherein the device comprises: - The electrode according to any one of claims 11 to 12; - A container for holding electrolytes; - Counter electrode; and - A power supply configured to apply a voltage between the electrodes.

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