Ammonia synthesis catalyst

Abstract

The present invention relates to a catalyst for producing ammonia with low energy; a process for producing said catalyst; and a process for producing ammonia with low energy, comprising the use of said catalyst.

Description

[Technical Field]

[0001] The present invention relates to a catalyst for producing ammonia with low energy, a process for producing said catalyst, and a process for producing ammonia with low energy comprising the use of said catalyst. [Background technology]

[0002] The industrial synthesis of ammonia has dramatically increased the world population from 1.6 billion in the early 1900s to approximately 7.7 billion today. This growth would not have been possible without rapid advances in food production, facilitated by the widespread use of ammonia-based fertilizers. Current ammonia production is 176 million tonnes (Mt) per year, resulting in approximately 500 Mt of CO2 (~1.8% of global CO2 emissions). The Haber-Bosch process for ammonia production (early 20th century) is recognized as one of the major chemical reactions ever developed, accounting for approximately 2% of the energy consumed on Earth. In addition to its importance as a fertilizer, ammonia has also attracted significant interest as a means of energy storage and transportation, namely as a way to store and transport hydrogen fuel. Ammonia has a much higher volumetric energy density than hydrogen, allowing it to be stored in the liquid phase under mild conditions and transported as is currently done. Furthermore, ammonia is also attracting attention as an alternative, carbon-free fuel source that does not contribute to CO2 emissions.

[0003] A major challenge in ammonia synthesis is activating N2, as the N-N triple bond is one of the most stable chemical bonds in all of chemistry. The current industrial process for ammonia production is the Haber-Bosch process (N2 + 3H2 → 2NH3), which requires high-pressure (>15 MPa (150 bar)) and high-temperature (>400 °C) reaction conditions with a large, centralized infrastructure. However, given the environmental need to reduce dependence on fossil fuels, a sustainable ammonia synthesis process that can be performed under low-pressure and low-temperature conditions and relies solely on renewable energy and feedstocks is desirable.

[0004] Typically, iron is used in industry as a catalyst for ammonia synthesis, although it is well understood that a variety of alternative transition metals, particularly Pt, Mo, Re, Co, Ru and / or Rh, are equally suitable catalysts.

[0005] Ammonia synthesis under low temperature and pressure conditions is a well-known academic topic [1-3]. Many catalysts for low-energy thermal ammonia synthesis have been invented. For example, Masashi Hattori and his coworkers discovered that CaFH is an excellent catalyst for ammonia synthesis at 0.1 MPa (1 bar) and 50 °C [4]. However, fabrication of such a complex system remains challenging.

[0006] Another alternative technology is electrochemical ammonia synthesis at room temperature and atmospheric pressure, but the technology is currently in its very early stages, and no electrocatalysts exist that can produce ammonia with high yield and faradaic efficiency [5].

[0007] We herein disclose novel catalysts and processes for low-energy ammonia synthesis via heterogeneous catalysis. This is achieved by novel atomic metal catalysts containing at least one single metal atom or cluster of metal atoms (e.g., double iron atomic catalysts) supported on the surface of a substrate, which is non-reactive to N2 reduction and is typically, but not exclusively, prepared by cluster beam deposition techniques [6].

[0008] Using the catalyst and process disclosed herein, ammonia can be synthesized at low temperatures (i.e., ≦250°C, preferably ≦50°C) and low pressures (i.e., ≦30 bar, preferably ≦0.1 MPa (1 bar)). Thus, the catalyst and production process paves the way for green hydrogen feedstocks (e.g., water electrolysis) and renewable energy (e.g., solar) power generation, providing a near-zero-carbon process for ammonia synthesis. Furthermore, the simple setup eliminates the need for complex infrastructure typically associated with current high-energy production processes, offering the potential for simple, local green ammonia production at the point of use (e.g., on a farm) using renewable energy-powered machinery; in this way, ammonia can be generated on demand and introduced into irrigation systems or stored as an ammonia solution for use as a fertilizer. Summary of the Invention

[0009] Statement of the Invention The invention, in its various aspects, is as set out in the appended claims.

[0010] According to a first aspect, there is provided an atomic metal catalyst, said catalyst comprising a plurality of metal atom clusters supported on the surface of a solid substrate, each metal atom cluster independently comprising or consisting of from about 1 to about 500, preferably from about 1 to about 100, more preferably from about 1 to about 50, even more preferably from about 1 to about 10, and most preferably from about 1 to about 6 metal atoms.

[0011] Preferably, each of the metal atom clusters comprises or consists of one or more metals selected from lead (Pb), silver (Ag), gold (Au), platinum (Pt), molybdenum (Mo), tungsten (W), rhenium (Re), cobalt (Co), ruthenium (Ru), rhodium (Rh), and iron (Fe). More preferably, the metal atom cluster comprises or consists of one or more metals selected from Pt, Mo, Re, Co, Ru, Rh, and Fe, and even more preferably, Mo, Re, Fe, and Pt atoms. In a particularly preferred example, the metal atom cluster comprises or consists of Fe atoms.

[0012] The atomic clusters may comprise individual atoms or mixtures or alloys containing multiple atoms. The metal atoms may be covalently or non-covalently modified and / or in oxidized or reduced form. Preferably, substantially all of the metal atom clusters comprise or consist of the same number and / or type of metal atoms.

[0013] In preferred embodiments, the metal atom clusters comprise or consist of a single metal atom, two metal atoms, or three metal atoms, which are referred to as single atom catalysts (SAC), double atom catalysts (DAC), and triple atom catalysts (TAC), respectively.

[0014] Particularly preferred are metal atom clusters containing two metal atoms, especially two Fe atoms, ie Fe DAC.

[0015] As will be readily apparent to those skilled in the art, the degree of surface coverage of the metal atom clusters on the surface of the substrate can be measured or calculated by a variety of methods, for example, surface coverage is typically measured by deposition beam current and projected surface area derived from X-ray photoelectron spectroscopy (XPS).

[0016] Preferably, said metal atom clusters cover 0.1 to 20%, more preferably 1 to 10%, and even more preferably 2 to 5% of the surface of the substrate.

[0017] The solid substrate on which the metal ion clusters are deposited and supported is not particularly limited, except that the substrate is typically non-reactive to N reduction. As will be readily understood, suitable solid substrates include, but are not limited to, silicon or carbon-based materials, oxides, hydrides, nitrides, or MXenes. However, in a preferred embodiment, the substrate is a carbon material, which may be doped with one or more heteroatom (i.e., nitrogen, sulfur, or oxygen)-containing dopants.

[0018] Preferably, the dopant comprises one or more nitrogen heteroatoms. More preferably, the substrate comprises a carbon material doped with pyridine and / or pyrrolic nitrogen atoms. The inclusion of such dopants prevents surface diffusion of the metal atom catalyst on the substrate.

[0019] Preferably, when a doped carbon material is used as the substrate, the dopant covers preferably 0.1 to 20%, more preferably 1 to 10%, and even more preferably 2 to 5% of the surface of the substrate. As will be readily apparent to those skilled in the art, the surface coverage of the dopant can be measured or calculated by a variety of methods. Examples of suitable methods include electron microscopy, surface spectroscopy (e.g., XPS), and, in the case of powder substrates, inductively coupled plasma mass spectrometry (ICP-MS).

[0020] As will be readily apparent to those skilled in the art, the atomic metal catalyst of the first aspect of the present invention may be formed by a conventional physical vapor deposition (PVD) process, such as evaporation, sputtering, or pulsed laser deposition. Such a PVD process may include a cluster deposition process, in which metal atom clusters are formed (e.g., by condensation in the gas phase) and then deposited on the surface of the substrate. Alternatively, the PVD technique may include an atom deposition process, in which individual metal atoms are deposited on the substrate surface and then metal atom clusters are formed.

[0021] Thus, according to a second aspect of the present invention, there is provided a method for preparing a catalyst of the first aspect of the present invention by PVD, wherein the metal atom clusters are formed by a cluster deposition process or the metal atom clusters are formed after being deposited as single atoms on the surface of a substrate.

[0022] In some embodiments, the PVD process is selected from cluster deposition, evaporation deposition, sputter deposition, or pulsed laser deposition.

[0023] Advantageously, the atomic metal catalyst is deposited by a cluster deposition process, preferably a cluster beam deposition process, since such a process allows for precise control over the size of the deposited metal atom clusters. Thus, according to a preferred embodiment of the second aspect of the present invention, there is provided a method for preparing the catalyst of the first aspect by cluster deposition of a plurality of metal atom clusters onto the surface of a solid substrate, the metal ion clusters comprising or consisting of 1 to 10 metal atoms, the method comprising the steps of: (i) providing a cluster beam deposition source including a plasma sputtering and gas condensation chamber, a mass filter chamber, and a deposition chamber; (ii) placing a metal catalyst target containing or consisting of metal atoms in the condensation chamber; (iii) placing a solid substrate in a deposition chamber; (iv) performing a magnetron sputtering step in the condensation chamber, sputtering the metal catalyst target with a plasma to release metal atoms, followed by a condensation step, in which the released atoms are cooled in an inert gas to form positively charged metal ion clusters; (v) separating and selecting metal ion clusters based on size in said mass filter chamber; and (vi) depositing the metal ion clusters of selected size on the surface of the substrate in the deposition chamber;

[0024] As will be readily apparent to one skilled in the art, in step (iv), the metal catalyst target can be sputtered with a plasma obtained from any one or combination of an inert gas (e.g., argon) and / or a reactive gas. When a reactive gas such as O2 or N2 is used, the sputtered particles from the metal catalyst target can undergo a chemical reaction during the sputtering and deposition process, resulting in the deposition of, for example, metal oxide or metal nitride clusters on the substrate surface.

[0025] In a preferred embodiment, the metal catalyst target is sputtered with an inert gas (eg, helium, neon, argon) plasma, most preferably an argon plasma.

[0026] Preferably, the clusters are formed in step (iv) by condensation under pressure of helium gas cooled to about 80 to about 120K.

[0027] Preferably, the metal catalyst target comprises or consists of one or more metals selected from lead (Pb), silver (Ag), gold (Au), platinum (Pt), molybdenum (Mo), tungsten (W), rhenium (Re), cobalt (Co), ruthenium (Ru), rhodium (Rh), and iron (Fe). The metal catalyst target may be a single element or a mixture or alloy containing multiple elements. The metal catalyst target may comprise covalently or non-covalently modified metal atoms and / or may be in oxidized or reduced form. More preferably, the metal catalyst target comprises or consists of one or more metals selected from Pt, Mo, Re, Co, Ru, Rh, and Fe. Even more preferably, the metal catalyst target comprises or consists of one or more metals selected from Mo, Re, Fe, or Pt atoms, most preferably Fe atoms.

[0028] In a preferred embodiment, metal ion clusters containing or consisting of one, two, or three metal atoms, most preferably iron atoms, are deposited on the surface of the substrate, i.e., SAC, DAC, or TAC are formed. Most preferably, DAC is formed by the deposition of metal ion clusters containing or consisting of two iron atoms.

[0029] Preferred features regarding the substrate are as described above in relation to the first aspect.

[0030] In a preferred embodiment, the cluster beam deposition source provided in step (i) further comprises an ion optics chamber disposed between the gas condensation chamber and the mass filter chamber, and in such an embodiment, the method comprises extracting and focusing the metal ion clusters in the optics chamber between steps (iv) and (v).

[0031] The atomic metal catalysts of the first aspect of the present invention may be used to catalyze a variety of different chemical reactions. In particular, they can catalyze the synthesis of ammonia (NH) via the reduction of N at low temperatures and pressures.

[0032] Thus, according to a third aspect, there is provided a process for the production of ammonia, the process comprising: (i) disposing in a reactor a catalyst bed comprising an atomic metal catalyst according to the first aspect of the present invention; (ii) passing one or more sources of nitrogen (N2) and one or more sources of hydrogen (H2) over said catalyst bed; (iii) obtaining a product stream containing ammonia (NH3) Includes:

[0033] Step (ii) is preferably carried out at a temperature of not more than 250° C., more preferably not more than 200° C., even more preferably not more than 150° C. Alternatively or additionally, step (ii) is preferably carried out at a temperature of not less than 20° C., more preferably not less than 30° C.

[0034] In exemplary embodiments, step (ii) may be carried out at a temperature ranging from about 20° C. to about 250° C., e.g., from about 30° C. to about 75° C., or from about 30° C. to less than about 50° C. Furthermore, in preferred embodiments, step (ii) is carried out at a pressure of about 3 MPa (30 bar) or less, more preferably about 2 MPa (20 bar) or less, even more preferably about 1 MPa (10 bar) or less, and even more preferably about 0.5 MPa (5 bar) or less. For example, step (ii) may be carried out under standard atmospheric pressure conditions, i.e., about 0.1 MPa (1 bar).

[0035] Step (ii) can also be carried out at subatmospheric pressure, for example, catalytic N reduction at a pressure of about 250 to about 750 Pa (2.5 to 7.5 mbar), more preferably about 500 Pa (5 mbar), is exemplified.

[0036] In a preferred embodiment, the catalyst bed is reduced prior to step (ii). Catalyst reduction can be achieved, for example, by exposure to H2 at elevated temperatures (e.g., up to about 400°C).

[0037] Preferably, the one or more hydrogen sources are prepared from green hydrogen feedstocks, for example, hydrogen can be prepared from water by electrolysis.

[0038] Preferably, the process of the present invention is powered by renewable energy, non-limiting examples of which include solar and wind power. The combination of renewable energy and the use of green hydrogen feedstocks allows for the preparation of ammonia through a zero-carbon process.

[0039] Preferred features of each aspect of the invention may be as described in relation to any of the other aspects.

[0040] Throughout this description and the claims, the words "comprise" and "contain," as well as variations of these words, such as "comprising" and "comprises," mean "including but not limited to," and do not exclude other moieties, additives, ingredients, integers, or steps. Throughout this description and the claims, the word "and / or" includes any and all combinations of one or more of the associated listed elements. Throughout this description and the claims, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, it is understood that the specification contemplates both the plural and the singular unless the context otherwise requires. Throughout this description and the claims, the word "about" means ±5%, alternatively ±2%, unless the context otherwise requires.

[0041] Throughout the description and claims of this specification, the term "metal atom cluster" and variations thereof include single metal atoms and aggregates of multiple metal atoms, unless the context dictates otherwise.

[0042] All documents cited in this specification, including any patents or patent applications, are hereby incorporated by reference. No admission is made that any document is prior art. Further, no admission is made that any prior art is part of the general knowledge in the art.

[0043] Other features of the present invention will become apparent from the following examples. Generally speaking, the present invention extends to any novel one or any novel combination of the features disclosed in this specification (including the accompanying claims and drawings). Accordingly, it is understood that any feature, integer, property, compound, or chemical moiety described in connection with a particular aspect, embodiment, or example of the present invention is also applicable to any other aspect, embodiment, or example described herein, except where inconsistent therewith.

[0044] Additionally, unless stated otherwise, features disclosed herein may be replaced by alternative features that serve the same or similar purpose.

[0045] The invention will now be described, by way of example only, with reference to the following examples and the following figures. [Brief explanation of the drawings]

[0046] [Figure 1] Schematic diagram of a size-selective cluster beam source that combines magnetron sputtering and gas condensation techniques; [Figure 2] STEM image of iron dimers deposited on a graphene oxide coated TEM grid; [Figure 3] N1s XPS spectra of Fe dimer on N-doped carbon (Fe2-NC), N-doped carbon (NC) alone, and Fe dimer on carbon (Fe2-C); [Figure 4] N1s XPS spectra of Fe2-NC system under different conditions; [Figure 5] Fe L-edge NEXAFS of Fe2-NC and Fe2-C systems under different conditions; [Figure 6]N1s peak of N-doped carbon under different conditions. The temperature (T) is below room temperature (rt), and the flow rates of H2 and N2 are sccm; [Figure 7] Partial mass spectra of the Fe2-NC system (upper spectrum) and the Fe2-C system (lower spectrum). H2 and N2 flow rates are in sccm, and the partial pressures of the mass signals are in mbar; [Figure 8] Catalytic activity of Fe-TiH2 powder for ammonia production (200 °C; 10 bar). The metal loading of Fe clusters on TiH2 powder is normalized to 0.1%. The products were analyzed every hour by gas chromatography.

[0047] material and method The metal catalysts produced in this project were fabricated using cluster beam deposition technology (equipment manufactured by Swansea) at the new Swansea Satellite Nanolab at Diamond Light Source (B07).

[0048] The cluster beam deposition source (Figure 1) is a vacuum-based magnetron sputtering gas condensation source equipped with a transverse time-of-flight mass filter [7]. The metal target is sputtered by a DC argon plasma; hot metal atoms are condensed into clusters under the pressure of helium gas cooled to ~100 K with liquid nitrogen. Positively charged clusters are extracted and focused into a mass filter by ion optics for size selection. The mass filter resolution is approximately 1 in 20 atoms, and the transmission efficiency of the selected mass exceeds 50%. In this project, a series of atomic metal catalysts (Fe and Pt) were fabricated, including single atoms, dimers, and trimers of the metals. The atomic catalysts were deposited on transmission electron microscope (TEM) grids (graphene oxide-coated grids, 3 mm diameter) for TEM characterization [8] (surface coverage of 1%), XPS, and near-edge X-ray absorption fine structure (NEXAFS) studies [9] (surface coverage of 3%–4%). To prevent surface diffusion of atomic catalysts, N-doping of carbon (graphene oxide) (5% surface coverage) was also performed before Fe deposition. These materials were imaged by scanning transmission electron microscopy (STEM) at Swansea University and Diamond Light Source.

[0049] Near-atmospheric pressure XPS and NEXAFS experiments were performed at the B07 beamline at Diamond Light Source. Atmospheric pressure XPS and NEXAFS were performed at temperatures between room temperature and 400 °C, 10 -4 This study was carried out to verify the catalytic activity of various atomic catalysts for thermochemical ammonia synthesis by exposing the samples to pure N2 and N2 + H2 in the pressure range from 0 to 10 mbar. The adsorbed reaction intermediates (e.g., * The ion-dependent oxidation states of the NHx and NHx molecules were monitored in real time via the chemical shifts of the N 1s core level. The chemical / oxidation states were investigated by monitoring the Fe 2p core level.

[0050] In a further example, magnetron sputtering was used to deposit a thin layer of iron clusters (maximum cluster size approximately 1 nm) on TiH particles (average particle size 20 μm) enclosed in a metal cup equipped with a stirring mechanism. A high-pressure reactor was then used to measure the catalytic activity of the iron cluster-coated TiH particles for ammonia production, and the products were analyzed using gas chromatography or liquid chromatography. Specifically, after diluting the catalyst with SiC powder to improve heat transfer, the reaction was tested at 200 °C and 1 MPa (10 bar) in a mixture of N (10 ml / min) and H (30 ml / min).

[0051] result Figure 2 shows an image of Fe dimers after deposition, created by cluster beam deposition. These dimers have an impact energy of 9 eV per atom, so they can split into single atoms upon surface collision. The bright spots shown in the STEM image are Fe dimers and single atoms.

[0052] Three samples were tested for ammonia synthesis: Fe dimers on an N-doped carbon (graphene oxide) support (Fe2-NC), the N-doped carbon support itself (NC), and Fe dimers on an undoped carbon support (Fe2-C). Figure 2 shows the N1s XPS spectra of these samples under vacuum conditions. The deposition chamber of the cluster source was evacuated with N2 gas after cluster deposition, and the samples were then transferred (in air) to the beamline for measurement. The N in the bare NC system is from the N-doping process. Both pyridinic and pyrrolic N are found on the surface of this support. The addition of Fe dimers on N-doped carbon results in Fe-N x This introduces a new peak corresponding to the species. This suggests that Fe dimers are highly active in N fixation. When the NC system is modified with Fe dimers, N molecules are adsorbed on the surface of those dimers. This can also be confirmed in experiments with the Fe-C system, where no N is injected into the chamber. Here, no N doping is performed, and the surface N is derived from the chamber evacuation process and air movement.

[0053] All samples were tested for ammonia synthesis under a mixed gas atmosphere of N and H gases after reduction in H at temperatures up to 400 °C. Figure 4 shows the evolution of the N1s peak under various conditions for the Fe-NC system. When N was introduced into the chamber, the Fe-N x / NH x The intensity of increases. This is because the N-N triple bond is split and the Fe-N x or NH x This indicates the formation of a species. The intensity of this peak decreases as the N2 in the chamber is depleted.

[0054] The reduction process of the Fe dimer catalyst on N-doped carbon and bare carbon was monitored by Fe L-edge NEXAFS spectra, as shown in Figure 5. In the samples after deposition of metal atom clusters, Fe 2+ and Fe 3+ Both states were observed. 3+ is immediately dissolved in H2 atmosphere (e.g., 500 Pa (5 mbar), temperature 300 °C or higher). 2+ can be reduced to Fe 2+ Reduction to Fe was also achieved in the Fe2-NC system. In the case of the Fe2-C system, subsequent reduction cycles resulted in Fe 3+ Fe 2+ This suggests that there is a change in the surface morphology (e.g., sintering) or atomic configuration during the heating process.

[0055] The presence of the N 1s peak (NC sample) before reduction, shown in Figure 6, indicates successful N doping into carbon (graphene oxide). This peak disappears during the reduction process. The formation of ammonia is detected during this process, which means that the bond between the doped N atom and the carbon support is not strong enough to prevent N from forming NH3 in the H2 atmosphere. The N peak cannot be recovered by reintroducing N2 gas, as there is no catalyst to split the N-N bond.

[0056] As shown in Figure 7, the catalytic activity of the Fe dimer was monitored by mass spectrometry. The mass of ammonia is 17 amu. However, because water (18 amu) also produces a secondary signal at 17 amu, 17 amu is not a good indicator of ammonia formation. Because ammonia produces a strong signal at 16 amu in mass spectrometry, 16 amu is used here as an indicator of ammonia. The "NH3" signal, shown in pink, was obtained by subtracting the water contribution at 17 amu. Mass spectrometry was performed at 5 mbar pressure in the main chamber. For the Fe2-NC system, the ammonia synthesis reaction can be triggered by introducing a minimal N2 flow rate (1 sccm) into the chamber at temperatures <50 °C. Successful ammonia synthesis can be confirmed by an increase in both the 16 amu and "NH3" signals (above). In high-temperature tests, the Fe2-C system exhibits similar behavior to the Fe2-NC system with regard to ammonia formation.

[0057] Figure 8 shows the catalytic activity of the Fe-TiH particle system for ammonia production. It is noteworthy that the catalyst was observed to stabilize (as indicated by a decrease in catalytic activity) during the first 2 hours of reaction before stabilizing over the remaining measurement time (7 hours).

[0058] summary Using cluster beam deposition techniques, we have successfully synthesized and deposited Fe catalysts with low atomic numbers (1, 2, and 3 atoms). To date, Fe dimers have been tested for ammonia synthesis on two different supports: carbon and N-doped carbon. Both the Fe2-NC and Fe2-C systems exhibit catalytic activity for the reduction of N2 to ammonia. Compared to the Fe2-C system, the Fe2-NC system is much more stable, as seen when subjected to high-temperature reduction cycles. The Fe dimers can catalyze this reaction at as low a pressure as 5 mbar, with higher pressures expected to result in higher yields, and at temperatures <50 °C.

[0059] Furthermore, Fe catalysts obtained by depositing Fe clusters (maximum cluster size approximately 1 nm) onto TiH2 particles by magnetron sputtering were shown to be catalytically active for ammonia production under conditions milder than those used in the conventional Haber-Bosch process.

[0060] References [1] Rod, TH, Logadottir, A., & Norskov, JK The Journal of Chemical Physics, 2000, 112(12), 5343-5347. [2] Wang, P., Chang, F., Gao, W., Guo, J., Wu, G., He, T., & Chen, P. Nature chemistry, 2017, 9(1), 64-70. [3] Ogura, Y., Tsujimaru, K., Sato, K., Miyahara, SI, Toriyama, T., Yamamoto, T., & Nagaoka, K. ACS Sustainable Chemistry & Engineering, 2018, 6(12), 17258-17266. [4] Hattori, M., Iijima, S., Nakao, T., Hosono, H., & Hara, M. Nature communications, 2020, 11(1), 1-8. [5] Singh, AR; Rohr, BA; Schwalbe, JA; Cargnello, M.; Chan, K.; Jaramillo, TF; Chorkendorff, I.; Norskov, JK ACS Catalysis 2016, 7, (1), 706-709. [6] Palmer, RE, Cai, R., & Vernieres, J. Accounts of Chemical Research, 2018, 51(9), 2296-2304. [7] Pratontep, S., Carroll, S. J., Xirouchaki, C., Streun, M., & Palmer, R. E. Review of Scientific Instruments, 2005, 76(4), 045103. [8] Niu, Y., Schlexer, P., Sebok, B., Chorkendorff, I., Pacchioni, G., & Palmer, R. E. Nanoscale, 2018, 10(5), 2363-2370. [9] Held, G., Venturini, F., Grinter, D. C., Ferrer, P., Arrigo, R., Deacon, L., ... & Scott, S. Journal of synchrotron radiation, 2020, 27(5), 1153-1166.

Claims

1. An atomic metal catalyst comprising a plurality of metal atom clusters supported on the surface of a solid substrate, wherein each metal atom cluster independently contains about 1 to about 500 metal atoms, or is composed of such clusters.

2. The atomic metal catalyst according to claim 1, wherein each metal atom cluster independently contains or consists of about 1 to about 10 metal atoms.

3. The atomic metal catalyst according to claim 1 or 2, wherein each of the metal atomic clusters comprises or consists of one or more metals selected from: lead (Pb), silver (Ag), gold (Au), platinum (Pt), molybdenum (Mo), tungsten (W), rhenium (Re), cobalt (Co), ruthenium (Ru), rhodium (Rh), and iron (Fe).

4. The atomic metal catalyst according to claim 3, wherein each of the metal atom clusters contains or consists of one or more metals selected from Pt, Mo, Re, Co, Ru, Rh, and Fe.

5. The atomic metal catalyst according to claim 4, wherein each of the metal atom clusters contains or consists of Fe atoms.

6. The atomic metal catalyst according to claim 1, wherein the metal atom cluster covers 0.1 to 20% of the surface of the substrate.

7. The atomic metal catalyst according to claim 1, wherein the substrate is silicon or a carbon-based material, oxide, hydride, nitride or MXene.

8. The atomic metal catalyst according to claim 7, wherein the substrate is a carbon material.

9. The atomic metal catalyst according to claim 8, wherein the carbon material is doped with one or more heteroatom-containing dopants, and optionally the dopants cover 0.1 to 20% of the substrate surface.

10. A method for producing a catalyst according to Claim 1, wherein the method is a cluster deposition process of forming metal atom clusters and then depositing them on the surface of the substrate; or the method is an atomic deposition process of depositing individual metal atoms on the surface of the substrate and then forming metal atom clusters.

11. The method according to claim 10, comprising depositing a plurality of metal atoms and / or metal atom clusters on the surface of a solid substrate by a cluster deposition, evaporation deposition, sputter deposition or pulsed laser deposition process, wherein each metal atom cluster independently contains or consists of about 1 to about 500 metal atoms.

12. The method according to claim 11, wherein each metal atom cluster independently contains or consists of about 1 to about 10 metal atoms.

13. The method according to claim 10, wherein the method is a cluster deposition process and the method comprises the following steps: (i) To provide a cluster beam deposition source including a plasma sputtering and gas condensation chamber, a mass filter chamber and a deposition chamber; (ii) Placing a metal catalyst target containing or consisting of metal atoms in a condensation chamber; (iii) Placing a solid substrate in a deposition chamber; (iv) Performing a magnetron sputtering step in which the metal catalyst target is sputtered with plasma in the condensing chamber to release metal atoms, and then performing a condensation step in which the released atoms are cooled in an inert gas to form positively charged metal ion clusters; (v) Separating and selecting metal ion clusters based on size in the mass filter chamber; and (vi) Depositing the metal ion cluster of the selected size onto the surface of the substrate within the deposition chamber.

14. The method according to claim 13, wherein the metal atom target comprises or consists of one or more metals selected from: lead (Pb), silver (Ag), gold (Au), platinum (Pt), molybdenum (Mo), tungsten (W), rhenium (Re), cobalt (Co), ruthenium (Ru), rhodium (Rh), and iron (Fe).

15. The method according to claim 14, wherein the metal atom target comprises or consists of one or more metals selected from Pt, Mo, Re, Co, Ru, Rh, and Fe.

16. The method according to claim 15, wherein the metal atom target contains or consists of Fe atoms.

17. The method according to claim 10, wherein the substrate is silicon or a carbon-based material, oxide, hydride, nitride or MXene.

18. The method according to claim 17, wherein the substrate is optionally a carbon material doped with one or more heteroatom-containing dopants.

19. The method according to any one of claims 13 to 18, wherein in step (iv), the metal catalyst target is sputtered with an inert gas, preferably argon, or plasma, and / or in step (iv), the cluster is formed by condensing in a pressure of helium gas cooled to about 80 to about 120 K.

20. The method according to any one of claims 13 to 18, wherein in step (vi), a metal ion cluster containing one, two, or three metals is deposited on the surface of the substrate.

21. A method for producing ammonia, the following: (i) Placing a catalyst bed containing the atomic metal catalyst described in claim 1 within the reactor; (ii) One or more nitrogen atoms (N ２ ) Source and one or more hydrogen (H ２ ) Passing the source over the catalyst bed; (iii) Ammonia (NH ３ Obtain a product stream that includes ) A method that includes this.

22. The method according to claim 21, wherein step (ii) is carried out at a temperature in the range of about 20°C to about 250°C and / or at a pressure of about 3 MPa (30 bar) or less.

23. The method according to claim 22, wherein step (ii) is carried out at a temperature in the range of about 30°C to about 75°C and / or at a pressure of about 1 MPa (10 bar) or less.

24. The catalyst bed is reduced before process (ii) and optionally heated to a temperature of approximately 400°C. ２ The method according to any one of claims 21 to 23, which is reduced by exposure to.

25. The method according to any one of claims 21 to 23, wherein one or more hydrogen sources are prepared from green hydrogen raw materials, and / or the method is driven by renewable energy.

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