EP-4739820-A2 - ELECTROLYTIC AMMONIA PRODUCTION USING TRANSITION METAL OXIDE CATALYST ENHANCED WITH A TRANSITION METAL DOPANT

Abstract

The invention relates to a process and a system for electrolytic production of ammonia. The process comprises feeding nitrogen to an electrolytic cell, where it comes in contact with a novel cathode surface, wherein said surface consists of a catalyst comprising at least one transition metal oxide doped with at least one transition metal dopant, the electrolytic cell comprising a proton donor and running a current through said electrolytic cell, whereby nitrogen reacts with protons to form ammonia.

Inventors

• SKÚLASON, Egill
• HÖSKULDSSON, Árni Björn

Assignees

• Atmonia EHF.
• Fujitsu Limited

Dates

Publication Date

20260513

Application Date

20240702

Claims (1)

1. P15340PC00 CLAIMS 1. A process for producing ammonia, said process comprising: a. feeding N 2 to an electrolytic cell that comprises at least one source of protons, b. allowing the N 2 to come into contact with a cathode surface in the electrolytic cell, wherein the cathode surface comprises at least one catalyst surface comprising at least one transition metal oxide doped with at least one type of transition metal dopant is selected from the group consisting of: Hafnium Oxide doped with Molybdenum and/or Osmium, Iridium Oxide doped with Rhenium, Molybdenum Oxide doped with Tantalum and/or Tungsten and/or Hafnium and/or Niobium and/or Nickel and/or Osmium and/or Ruthenium and/or Titanium and/or Vanadium and/or Zirconium, Iridium and/or Rhenium, Niobium Oxide doped with Molybdenum and/or Titanium, and/or Tungsten, Osmium Oxide doped with Rhenium and/or Tungsten and/or Molybdenum, Platinum Oxide doped with Rhenium, Rhenium Oxide doped with Cobalt and/or Molybdenum, Rhodium Oxide doped with Rhenium, Ruthenium Oxide doped with Rhenium, Tantalum Oxide doped with Vanadium and/or Niobium, Titanium Oxide doped with Rhenium and/or Tungsten, Vanadium Oxide doped with Rhenium and Tungsten Oxide doped with Cobalt and/or Molybdenum and/or Niobium and/or Tantalum, and, c. running a current through said electrolytic cell, whereby nitrogen reacts with protons to form ammonia. 2. The process according to the preceding claim, wherein said at least one transition metal oxide doped with at least one type of transition metal dopant is selected from the group consisting of: Hafnium Oxide doped with Molybdenum or Osmium, Iridium Oxide doped with Rhenium, Molybdenum Oxide doped with Tantalum or Tungsten or Hafnium or Niobium or Nickel or Osmium or Ruthenium or Titanium or Vanadium or Zirconium, Iridium or Rhenium, Niobium Oxide doped with Molybdenum or Titanium, or Tungsten, Osmium Oxide doped with Rhenium or Tungsten or Molybdenum, Platinum Oxide doped with Rhenium, Rhenium Oxide doped with Cobalt or Molybdenum, Rhodium Oxide doped with Rhenium, Ruthenium Oxide doped with Rhenium, Tantalum Oxide doped with Vanadium or Niobium, Titanium Oxide doped with Rhenium or Tungsten, Vanadium Oxide doped with Rhenium and Tungsten Oxide doped with Cobalt or Molybdenum or Niobium or Tantalum. P15340PC00 3. The process according to the preceding claim, wherein said at least one transition metal oxide doped with at least one type of transition metal dopant is selected from a group consisting of: Molybdenum Oxide doped with Tungsten or Osmium or Titanium or Vanadium, Osmium Oxide doped with Molybdenum and Rhenium Oxide doped with Molybdenum. 4. The process according to any of the claims 1 to 3, wherein the surface coverage of the transition metal dopant atoms on the metal oxide surface is selected to range from 1- 15% or range from 20-30% or range from 45% to 55% or range from 70% to 80%. 5. The process according to any of the claims 1 to 3, wherein the transition metal dopant covers over 98% of the metal oxide surface, effectively creating a dopant surface layer. 6. The process according to any of the preceding claims, wherein the catalyst surface comprises a mixture of two or more transition metal oxides doped with two or more different transition metals. 7. The process according to any of the preceding claims, wherein the catalyst comprises a rutile crystal structure. 8. The process according to any of the preceding claims, wherein the catalyst surface comprises at least one surface having a (110) facet. 9. The process according to any of the preceding claims, wherein ammonia is formed in the electrolytic cell at an electrode potential less than -1.0 V relative to the reversible hydrogen electrode (RHE) or at an electrode potential less than -0.5 V relative to the reversible hydrogen electrode (RHE). 10. The process according to any of claims 1 to 9, wherein a cyclic varied potential is used that fluctuates between an active potential and a resting potential to generate a cyclic varied potential through the electrolytic cell. 11. The process according to any of the preceding claims, wherein said electrolytic cell comprises one or more aqueous electrolytic solution. P15340PC00 12. The process according to any of claims 1 to 11, wherein said electrolytic cell comprises an electrolytic solution comprising an organic protic or aprotic solvent or a miscible mixture thereof, or preferably a water-miscible organic solvent. 13. The process according to any of the preceding claims, wherein said nitrogen is fed to the electrolytic cell by bubbling nitrogen gas to the electrolytic solution in contact with said cathode surface. 14. The process of any of the preceding claims, wherein the source of protons in the formation of ammonia is water splitting at the anode or H2 oxidation reaction at the anode. 15. The process of any of the preceding claims operated at a temperature in the range from -10° C to 80° C, preferably in the range 20° C to 50°C, more preferably in the range 25°C to 30°C. 16. The process of any of claims 1 to 15, wherein the process is operated at a pressure selected to be in the range of 1 to 30 atmospheres, preferably in the range of 1-20 atmospheres, preferably in the range of 1-10 atmospheres, more preferably in the range of 1-5 atmospheres. 17. A system for generating ammonia, the system comprising at least one electrolytic cell, which comprises at least one cathode having at least one catalytic surface, wherein the at least one catalytic surface comprises at least one transition metal oxide doped with at least one type of transition metal dopant selected from the group consisting of: Hafnium Oxide doped with Molybdenum and/or Osmium, Iridium oxide doped with Rhenium, Molybdenum Oxide doped with Tantalum and/or Tungsten and/or Hafnium and/or Niobium and/or Nickel and/or Osmium and/or Ruthenium and/or Titanium and/or Vanadium and/or Zirconium, Iridium and/or Rhenium, Niobium Oxide doped with Molybdenum and/or Titanium, and/or Tungsten, Osmium Oxide doped with Rhenium and/or Tungsten and/or Molybdenum, Platinum Oxide doped with Rhenium, Rhenium Oxide doped with Cobalt and/or Molybdenum, Rhodium Oxide doped with Rhenium, Ruthenium Oxide doped with Rhenium, Tantalum Oxide doped with Vanadium and/or Niobium, Titanium Oxide doped with Rhenium and/or Tungsten, Vanadium Oxide doped with Rhenium and Tungsten Oxide doped with Cobalt and/or Molybdenum and/or Niobium and/or Tantalum. P15340PC00 18. The system according to the preceding claim, wherein said at least one transition metal oxide doped with at least one type of transition metal dopant is selected from the group consisting of: Hafnium Oxide doped with Molybdenum or Osmium, Iridium Oxide doped with Rhenium, Molybdenum Oxide doped with Tantalum or Tungsten or Hafnium or Niobium or Nickel or Osmium or Ruthenium or Titanium or Vanadium or Zirconium, Iridium or Rhenium, Niobium Oxide doped with Molybdenum or Titanium, or Tungsten, Osmium Oxide doped with Rhenium or Tungsten or Molybdenum, Platinum Oxide doped with Rhenium, Rhenium Oxide doped with Cobalt or Molybdenum, Rhodium Oxide doped with Rhenium, Ruthenium Oxide doped with Rhenium, Tantalum Oxide doped with Vanadium or Niobium, Titanium Oxide doped with Rhenium or Tungsten, Vanadium Oxide doped with Rhenium and Tungsten Oxide doped with Cobalt or Molybdenum or Niobium or Tantalum. 19. The system according to the preceding claim, wherein said at least one transition metal oxide doped with at least one type of transition metal dopant is selected from a group consisting of: Molybdenum Oxide doped with Tungsten or Osmium or Titanium or Vanadium, Osmium Oxide doped with Molybdenum and Rhenium Oxide doped with Molybdenum. 20. The system according to any of claims 17 to 19, wherein the catalyst surface comprises a mixture of two or more transition metal oxides doped with two or more different transition metals. 21. The system according to any of claims 17 to 20, wherein the catalyst comprises a rutile structure. 22. The system according to any of claims 17 to 21, wherein the catalyst surface comprises at least one surface having a (110) facet. 23. The system according to any of claims 17 to 22, wherein said electrolytic cell comprises one or more electrolytic solutions. 24. The system according to the preceding claim, wherein said electrolytic cell comprises an acidic, neutral or alkaline aqueous solution. P15340PC00 25. The system of claim 23, wherein said electrolytic cell comprises an electrolytic solution comprising an organic protic or aprotic solvent, or a miscible mixture thereof, preferably a water-miscible organic solvent. 26. The system according to any of claims 17 to 25, wherein the system is configured to produce ammonia in the electrolytic cell at an electrode potential of less than -1.0 V relative to the reversible hydrogen electrode (RHE) or preferably at an electrode potential of less than -0.5 V, relative to the reversible hydrogen electrode (RHE). 27. The system according to any of claims 17 to 26, wherein a cyclic varied potential is used that fluctuates between an active potential and a resting potential to generate a cyclic varied potential through the electrolytic cell.

Description

P15340PC00 ELECTROLYTIC AMMONIA PRODUCTION USING TRANSITION METAL OXIDE CATALYST ENHANCED WITH A TRANSITION METAL DOPANT FIELD OF INVENTION The disclosure is within the field of process chemistry, and specifically relates to the production of ammonia with electrolytic methods using novel doped transition metal oxide catalysts for the cathode surface. BACKGROUND Ammonia is a high value chemical owing to its use in fertilizers, with an annual production of 175 million tonnes, but its potential as an energy storage material and a carbon-free maritime fuel have recently gained attention. For more than a century, ammonia has been produced via the Haber-Bosch process, in which nitrogen and hydrogen gases react over a promoted Fe/Ru catalyst at a temperature exceeding 400°C and pressure upwards of 150 bar; N2(g) + 3H2(g) → 2NH3(g) This leads to substantial carbon emissions, owing mostly to the production of hydrogen gas via steam reforming, but also to the extreme reaction conditions rendering the process highly energy consuming. These are in stark contrast to the ambient conditions at which the enzyme nitrogenase in bacteria naturally catalyses nitrogen reduction from solvated protons, electrons and atmospheric nitrogen; N2(g) + 8H+ + 8e- → 2NH3(g) + H2(g) This natural process of nitrogen fixation has inspired the search and development of catalysts that can work at (much milder) ambient conditions. However, as is common knowledge, the search for a suitable catalyst for a specific reaction is both challenging and complex, wherein a search needs to be based on factors such as availability, cost, stability, activity, and selectivity of the catalyst material under the desired operational conditions. In particular, the realisation of the electrochemical nitrogen reduction reaction (NRR) using solid catalytic electrodes in an aqueous solution, with the protons coming from water splitting at the anode, has been an active field of research, both computationally and experimentally [1]. Despite the research interest and recent efforts, little progress has been made in finding a suitable catalyst for NRR with the main culprit being the competing hydrogen evolution reaction (HER), as most of the materials that are active towards the NRR are more selective towards HER, especially at higher overpotentials. This leads to extremely low Faradaic efficiencies, i.e., most of the P15340PC00 electrical energy supplied to the system is being wasted on the HER rather than being utilized for the NRR. To emphasize the challenge of finding a suitable NRR catalyst, a few examples from the literature and from previous efforts by the applicants are discussed below. Out of the pure transition metals, namely, Sc, Y, Ti, Zr Re, Os, Co, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, V, Nb, Ta, Cr, Mo, W, and Fe it has been predicted (with computational studies) that none of the pure transition metals is capable of catalysing the NRR because of the facile H2 formation. [2] The linear scaling relations of adsorption energies for the pure metals in the periodic table predict that they are not able to catalyse this reaction. Some of these predictions have been verified in experiments, namely for Ru, Rh and Re, with strict protocols used to avoid false positive results. [3] In fact, it is safe to say that efficient ammonia synthesis in an aqueous solution verified with strict experimental protocols remains a challenge, with the literature littered with likely false positives [3,4,5]. Recent efforts by the present applicants have focused on novel ceramics materials, i.e., using transition metal nitride (TMN), transition metal oxide (TMO) and transition metal sulphide (TMS) catalyst surfaces, as disclosed in WO2015189865, WO2019053749 and WO2020110155, respectively,. Despite these efforts, most investigated materials still catalyse HER over NRR. The identification of a promising catalyst is one of the steps needed to realise electrochemical NRR at low to moderate overpotentials. The present invention seeks to ameliorate these problems by providing novel catalyst compounds capable of catalysing the electrochemical nitrogen reduction reaction (NRR) at mild operational conditions such as in an aqueous solution, using low to moderate overpotentials/voltage. References: [1] Guo, W., Zhang, K., Liang, Z., Zou, R., and Xu, Q. (2019). Electrochemical nitrogen fixation and utilization: theories, advanced catalyst materials and system design. Chem. Soc. Rev.48, 5658-5716. [2] Skúlason, E., Bligaard, T., Gudmundsdóttir, S., Studt, F., Rossmeisl, J., Abild-Pedersen, F., Vegge, T., Jónsson, H., and Nørskov, J.K. (2012). A theoretical evaluation of possible transition metal electro-catalysts for N2 reduction. Phys. Chem. Chem. Phys.14, 1235-1245. [3] Andersen, S.Z., Colic, V., Yang, S., Schwalbe, J.A., Nielander, A.C., McEnaney, J.M., Enemark-Rasmussen, K., Baker, J.G., Singh, A.R., Rohr, B.A., et al. (2019). A rigorous electrochemical ammonia synthesis protocol with quanti