Transition metal carbide catalysts for the reduction of carbon monoxide and carbon dioxide

Abstract

Disclosed is a method for the catalytic reduction of CO2 and / or CO, the method comprising steps of (i) providing an electrolytic cell containing at least one reaction chamber that has at least one anode and at least one cathode and at least one electrolyte between the anode and the cathode, wherein the at least one cathode comprises at least one catalyst comprising at least one carbide of one or more transition metal selected from the group consisting of Nb, W, Mo, V, Ti, Hf, Ta, Cr, Zr, Sc and Y; (ii) providing CO2 and / or CO in the electrolytic cell; and (iii) applying electrical potential to the electrolytic cell so that the CO2 and / or CO undergoes a reduction reaction at the cathode. Also disclosed are electrolytic cells and chemical reactors containing the disclosed transition metal carbide catalysts.

Description

FIELD

[0001] The disclosure relates to the reduction of carbon dioxide and carbon monoxide by electrolysis and new transition metal catalysts therefor.INTRODUCTION

[0002] Since the start of the 20 th< century the world climate has been changing more noticeably. The balance in nature is lost due to dramatic increasing CO 2 emissions by burning of carbonaceous fuels which results in global warming. An urgent effort is needed to overcome this problem to reduce the ratio of CO 2 and turn it into fuel and other useful chemical products. On the other hand, the large-scale use of unsustainable fossil fuels for energy led to an energy crisis in the world and increasing the amount of CO 2 in the atmosphere. Due to this, the world climate is changing day by day and scientific effort is needed to overcome the emission of CO 2 in the air by converting the already present CO 2 into green energy fuels. Previous experimental and theoretical research concluded that conversion of CO 2 into valuable products can be achievable, but not yet efficient for commercialization. In the whole process of CO 2 reduction reaction (CO 2 RR), the catalyst plays a key role in capturing CO 2 and converting it into valuable chemical products and fuels. CO 2 is a chemically stable molecule and this makes its electrolytic reduction challenging with high reduction overpotential, poor product selectivity and low current efficiency. To address this challenge, researchers and scientists have been exploring novel catalysts which can overcome these issues and speed up the electrolytic process (Ebbesen & Mogesen, J. Power Sources 2009, 193:349; Fu et al, Energy & Environmental Sci 2010, 3:1382).

[0003] In CO 2 RR the catalysts play a key role in the conversion of CO 2 into valuable products. In previous decades many experimental studies have been done for electrolytic CO 2 RR on different metal catalysts. For example pure Cu, Ag, Au, and Pt catalysts have been studied as catalysts for the CO 2 reduction reaction. However, their application for the commercial purposes is not enough due to poor product selectivity, low faradic efficiency and high overpotential that is needed. It is well known that the Cu is a widely used catalyst for the reduction of CO 2 to CH 4 but its overpotential is high (~0.9 V) and moreover it produces 15 different carbon containing products which require large amount of energy for their separation. In addition to pure Cu, polycrystalline Cu was also used for the application of CO 2 RR and it produces great amount of C 2 and C 3 aldehydes as well as ethylene.

[0004] In addition to pure metal electrocatalysts, metal oxide catalysts i.e. TiO 2 have been studied by DFT methods and considered impressive and more efficient catalysts for CO 2 conversion to CH 3 OH and CH 4 products (Ramesha, ACS Catalysis, 2014, 4:3249). In another study RhO 2 is predicted to be a novel candidate for the formation of formic acid at -0.20 V onset potential. However, stability and electron conductivity of oxides as cathode materials are a challenge that limits the application of oxides for CO 2 RR. There are numerous research studies that have been conducted to explore novel catalyst materials for the CO 2 RR. Materials studied by DFT (density functional theory) include graphene-based materials, metals, metal oxides, zeolites, sulfides, and metal organic frameworks. The utilization of catalysts for large scale production is however still a challenge and improved methods are required to overcome this problem.SUMMARY

[0005] The present disclosure provides methods to overcome the above deficiencies of the prior art. The need to explore alternative materials for catalysis of CO 2 RR and CORR arises from the imperative to develop efficient and sustainable methods for converting carbon monoxide and carbon dioxide into valuable products. Traditional catalysts may have limitations in terms of activity, selectivity, efficiency, or cost. By searching for other materials, the aim is to identify catalysts that can enhance the performance of CO 2 RR and CORR processes, making them more economically viable and environmentally friendly.

[0006] In particular, in light of the challenge of finding good electrocatalysts for CO 2 and CO reduction, the disclosure provides certain transition metal carbides that are useful catalysts for CO 2 RR and CORR.

[0007] An aspect of the invention relates to a method for catalytic electrolytic reduction of CO 2 and / or CO, the method comprising (a) providing an electrolytic cell containing at least one reaction chamber that has at least one anode and at least one cathode and at least one electrolyte between the anode and the cathode, wherein the at least one cathode comprises at least one catalyst comprising at least one carbide of one or more transition metal selected from the group consisting of Nb, W, Mo, V, Ti, Hf, Ta, Cr, Zr, Sc and Y; (b) providing CO 2 and / or CO in the electrolytic cell; and (c) applying electrical potential to the electrolytic cell; whereby the CO 2 and / or CO undergoes at least one reduction reaction at the cathode.

[0008] Another aspect relates to an electrolytic cell for the reduction of carbon dioxide and / or carbon monoxide, comprising: an anode; a cathode, the cathode comprising a catalyst comprising at least one carbide selected of a transition metal selected from Nb, W, Mo, V, Ti, Hf, Ta, Cr, Zr, Sc and Y, and a power supply connected to the anode and the cathode.

[0009] The invention further relates to a chemical reactor comprising at least one electrolytic cell as described herein; and a power supply connected to the electrolytic cell.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows in (A) exemplary CO 2 RR at a transition metal carbide surface; (B) schematic representation of transition metal carbides. FIG. 2 shows a comparison of adsorption energies of different species onto the clean surface of TMCs. FIG. 3 shows a free energy diagram for methane formation via the Mars-van Krevelen (MVK) mechanism on the surface of NbC. FIG. 4 shows a theoretical volcano for the formation of Methane from the scaling relations MVK mechanism. FIG. 5 shows proposed mechanism for CO 2 reduction reaction. FIG. 6 shows a free energy diagram for HER on metals side. FIG. 7 shows a free energy for VC and green line indicate the formation of formic acid at 0V onset potential. FIG. 8 shows limiting potential required for the formation of methanol, methane, formic acid, CO and methanediol. FIG. 9 shows a theoretical volcano plot for the formation of HCOOH. FIG. 10 shows a free energy diagram for the methanol formation on WC. FIG. 11 shows a theoretical volcano plot for methanol formation. FIG. 12 shows a box plot analysis of required onset potential for formic acid, methanol, and Methane for each TMC. FIG. 13 shows a comparison of CO2RR onset potential for different product formation on TMCs studied herein with similar metal-based catalysts previously reported for formic acid, methanol, and methane. FIG. 14 shows adsorption of different species of CORR on clean surface TMCs. FIG. 15 shows methane formation of CORR via MVK mechanism. FIG. 16 shows emission of methane from MoC catalyst via MVK mechanism and spontaneous filling of carbon vacancy with the carbon of CO without any additional onset potential. FIG. 17 shows theoretical activity volcano for the methane production of CORR via MVK mechanism. FIG. 18 shows HER on 7 TMCs in CORR. CrC and NbC have the same free energy value, so their bars overlap each other. FIG. 19 shows a flow chart of mechanism of CORR towards methane and methanol formation via surface mechanism. FIG. 20 shows a CORR free energy diagram of WC for the formation of methanol. FIG. 21 shows a CORR free energy diagram of TaC for the formation of Methane. FIG. 22 shows onset potential values required for each candidate for the formation of methane and methanol. The *CH 4 shown in green is methane formation via MvK mechanism and the CH 4 shown in pink is methane formation via the conventional mechanism. FIG. 23 shows in a) schematic diagram of carbon migration from sublayer to vacancy where large atoms indicate the metal atom and smaller atoms indicate carbon atoms of TMCs; b) represents NEB calculated diffusion barrier of carbon from sublayer to vacancy and dotted line shows threshold of calculated diffusion barrier. FIG. 24 shows estimated diffusion barrier of MoC for carbon migration from sublayer to first layer vacancy. DESCRIPTION

[0011] In the following, exemplary embodiments of the invention will be described, referring to the figures. These examples are provided to provide further understanding of the invention, without limiting its scope.

[0012] In the following description, a series of steps are described. The skilled person will appreciate that unless required by the context, the order of steps is not critical for the resulting configuration and its effect. Further, it will be apparent to the skilled person that irrespective of the order of steps, the presence or absence of time delay between steps, can be present between some or all of the described steps.

[0013] As used herein, including in the claims, singular forms of terms are to be construed as also including the plural form and vice versa, unless the context indicates otherwise. Thus, it should be noted that as used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0014] Throughout the description and claims, the terms "comprise", "including", "having", and "contain" and their variations should be understood as meaning "including but not limited to" and are not intended to exclude other components.

[0015] The present invention also covers the exact terms, features, values and ranges etc. in case these terms, features, values and ranges etc. are used in conjunction with terms such as about, around, generally, substantially, essentially, at least etc. (i.e., "about 3" shall also cover exactly or "substantially constant" shall also cover exactly constant).

[0016] The term "at least one" should be understood as meaning "one or more", and therefore includes both embodiments that include one or multiple components. Furthermore, dependent claims that refer to independent claims that describe features with "at least one" have the same meaning, both when the feature is referred to as "the" and "the at least one".

[0017] The present disclosure is based on surprising discoveries that have identified that certain transition metal carbides, when used as a catalyst in the electrolytic reduction of CO 2 and CO, allow for efficient reduction to produce valuable small compounds at low temperatures and pressure and using low applied potential. Given the ever-increasing levels of CO 2 in the global atmosphere and concomitant need to find ways to achieve a carbon neutral energy technology, these catalysts can be used to facilitate the conversion of CO and CO 2 into valuable carbon-containing fuels.

[0018] In general, the catalysts can be used to reduce CO and / or CO 2 to produce hydrocarbons or oxygenates having from 1 to 3 carbon atoms. Exemplary products include methane, methanol, methanediol, formaldehyde, formic acid, ethanol, ethylene glycol, ethanediol, propane and propanol.

[0019] Accordingly, the disclosure provides means in the form of methods and systems for electrolytic conversion of CO and / or CO 2 at low temperature and pressure. Compounds such as short-chain alkanes and oxygenates (e.g. alcohols and acids) having from 1 to 3 carbon atoms can be produced using the disclosed transition metal carbides. Through selection of appropriate catalysts, catalyst surface and appropriate applied voltage, the reduction reaction can be geared to produce compounds of particular interest.

[0020] In an aspect, the present disclosure is based on the investigation of the capability of transition metal carbides (TMCs) to catalyze the conversion of CO and CO 2 into valuable organic compounds that can for example be used as valuable fuel. The results are based on studies that delve into the electronic intricacies of TMCs, unraveling their potential to drive the transformation of CO and CO 2 .

[0021] One distinct advantage of the transition metal carbide catalysts described herein is their unique usefulness to drive the CO and CO 2 reduction reactions via the Mars van Krevelen reaction mechanism. This is not possible on most other catalysts surfaces and explains in part the unique chemistry possible by using these catalysts.CO 2 Reduction Reaction (CO 2 RR)

[0022] A total of 11 TMCs have been analyzed using Density Functional Theory (DFT) to explore the reactivity of the reduction of CO 2 to produce formic acid, methane, methanediol and methanol. The diagram shown in FIG. 1 depicts the reduction of CO 2 to produce these chemicals on a TMC surface.

[0023] DFT is a quantum mechanical methodology that accounts for the interaction between electrons and the nucleus. The input is the atomic structure of the molecular system of interest and the output is the ground state energy of the system. The reaction mechanism of CO 2 reduction to CH 4 on a stepped Cu(211) surface was first proposed by Peterson et al (Energy Environ Sci 2010, 3:1311). The free energy of adsorbed intermediates on the catalyst surface were calculated using a thermochemical model (TCM). The same approach has been successfully applied on several other electrolytic systems, including water oxidation on transition metal oxides, N 2 electroreduction on transition metal surfaces, transition metal nitrides and transition metal oxides, hydrogen evolution reaction (HER) on transition metal nitrides and CO 2 RR on transition metals and transition metal oxides.

[0024] The need to explore alternative materials for the CO 2 RR arises from the imperative to develop efficient and sustainable methods for converting carbon dioxide into valuable products. Traditional catalysts may have limitations in terms of activity, selectivity, efficiency, or cost. By searching for other materials, researchers aim to identify catalysts that can enhance the performance of CO 2 RR processes, making them more economically viable and environmentally friendly. The surface chemistry of TMCs is comparable to precious Pt-group metals which was already described by Levy and Boudart (Science 1973, 181:185). In previous studies these TMCs have been used for wide range of reactions such as CO oxidation, hydrogenation, methane dry reforming, desulfurization, conversation of methane to gas and water gas shift reaction. Hence these materials have received great attention for application in catalysis.

[0025] Utilizing advanced quantum mechanical simulations and computational models, the present disclosure is based on an exploration of the binding energies and reaction pathways of TMCs (CrC, HfC, MoC, YcC, ScC, NbC, ZrC, TaC, TiC, WC, and VC), with a focus on their suitability for catalyzing CO 2 reduction. In this research a complete and comprehensive analysis for above mentioned TMCs (100) was conducted.

[0026] Previous studies have used DFT calculations to model the CO 2 RR. The first mechanism was implemented on Cu (211) to reduce the CO 2 to CH 4 , and the free energies of the adsorbed intermediates was successfully calculated explicitly. The model used for this system was a thermochemical model (TCM) and this model was also successfully applied for numbers of electrolytic activities i.e. N 2 reduction reaction, hydrogen evolution reaction and CO 2 RR on various transition metals. The phenomena of applied potential studied using the computational hydrogen electrode (CHE) and other parts of electrolytic parts such that pH dependence and solvent effects are neglected. In another study the TCM-CHE was applied to study the CO 2 RR on RuO 2 surface (Karamad et al, Acs Catalysis 2015, 5:4075). The same model (TCM-CHE) and methodology can be used to study the CO 2 RR on 11 TMCs as shown herein. The full mechanism on each candidate of TMCs has been studied and the minimum energy pathway for producing formic acid, methane, methanol, CO and methanediol calculated.

[0027] In the following Example 1 it is described how DFT calculations can be used to describe the interaction of CO 2 with TMC surfaces and predict the reaction pathway for CO 2 RR on TMC. Two mechanisms were considered, the Mars-van Krevelen mechanism (MvK) and conventional surface mechanism, to study the CO 2 RR towards methane and methanol production on TMCs surfaces, The analysis reveals that specific TMCs exhibit remarkable catalytic activity for CO 2 reduction, surpassing the performance of conventional catalysts. The electronic structure of these TMCs plays a pivotal role in facilitating the conversion of CO 2 into valuable chemical products, offering a glimpse into the potential applications of these materials in renewable energy technologies. Exploring the performance of a range of TMCs, it has been found that the VC is the best candidate for the formation of formic acid with 0 V required onset potential, WC is the best candidate to produce methanol with -0.36 V onset potential, and MoC is the best candidate to produce methanediol with the potential limiting steps of -0.58 V.CO reduction reaction (CORR)

[0028] The disclosure also shows that transition metal carbides (TMCs) are capable of catalyzing the conversion of CO into valuable organic compounds via CORR.

[0029] Protonation along the reaction pathway from CO to CH 4 and CH 3 OH on 11 transition metal carbides have been calculated, including CrC, HfC, MoC, NbC, TaC, ScC, TiC, VC, WC, YC and ZrC with (100) facets. These facets of TMCs are considered the most stable structure with the 1:1 TM:C ratio and cubic crystallography.

[0030] Two mechanisms were considered, the Mars-van Krevelen mechanism (MvK) and conventional surface mechanism, to study the CORR towards methane and methanol production on TMCs surfaces. In Mars-van Krevelen mechanism, carbon vacancy is generated with the formation of methane and then vacancy is filled with the Carbon of CO with the release of water molecule at reliable onset potential values and later on Climbing Image Nudged Elastic Band (Cl-NEB) has been done to estimate the activation energy of migration of carbon atom from second layer to first layer to fill the carbon vacancy. In conventional surface mechanism the interaction of CO gas molecule on the surface of TMCs with different sides is studied. All aspects of each mechanism are calculated explicitly, and free energy diagrams are drawn for each adsorbed species on the surface of catalyst. Thermochemical model was implemented to obtain the trends of CORR on each TMCs surface.

[0031] Employing Density Functional Theory (DFT) the 11 TMCs were thus explored for the conversion of CO to methane and methanol formation via both Mars-van Krevelen (MvK) and conventional surface mechanism. Free energy diagrams were also constructed for the CO adsorption and its further electrochemical protonation to predict onset potentials values for methane and methanol formation. The study results are shown herein in Example 2. Results reveal that MoC is the best candidate for the formation of methane through MvK mechanism with the onset potential of - 0.22 V. NbC, WC, VC, TiC, ZrC, HfC and TaC are also showing formation of methane with corresponding onset potentials of -0.39, -0.41, -0.44, -0.46, -0.58, -0.62, -0.83 V respectively. In addition, via conventional surface mechanism WC exhibited the lowest onset potentials of -0.34 V suggesting superior catalytic activity for methanol formation among the studied TMCs catalysts. VC, NbC, TiC CrC, ZrC, MoC and HfC were also explored good candidates for methanol formation with the corresponding onset potential values of -0.42, -0.44, -0.59, -0.67, -0.84, -0.87, -0.9 V respectively. The studied TMCs via conventional surface mechanism are also promising for methane formation, with TaC showing lowest onset potential value -0.32 V for methane formation. Similarly, NbC and VC are also showing promising catalytic activity for methane formation with the corresponding onset potential values of -0.35 and -0.42 V. The Climbing Image Nudge Elastic Band (CI-NEB) calculations confirmed migration of carbon atom from sublayer to first surface is difficult to fill the carbon vacancy created via MvK mechanism. Overall, the findings indicate due to CO spontaneously adsorption, less poisoning, less over potential and high product selectivity TMCs are excellent choice for CORR to produce valuable products such as methane and methanol.Electrolytic cells

[0032] In general, an electrolytic cell is a chemical reactor where chemical reactions take place, driven by an applied electric potential. An electrolytic cell in the present context is therefore an electrolytic cell that undergoes a redox reaction when electrical potential is applied to the cell.

[0033] Design of electrolytic cells is known in the art. Examples of suitable electrolytic cells include H-type cells, polymer electrolyte membrane (PEM) flow cells, microfluidic flow cells, solid oxide electrolytic cells and DEMS cells. It should be appreciated that the transition metal carbides disclosed herein can be adapted for use in any type of electrolytic cell. Examples of suitable electrolytic cells are described in Liang et al. (Journal of CO2 Utilization, 2020, 35:90-105).

[0034] In an H-type cell, the cathodic and anodic compartments are typically separated by an ion-exchange membrane that allows ions to flow across while preventing reaction products from being reoxidized at the anode. There can be a reference electrode present in the cathodic compartment. In these cells, there is a liquid electrolyte solution at the cathode and anode, and CO 2 gas is typically streamed into the cathodic compartment.

[0035] In PEM flow cells, CO and / or CO 2 can be streamed directly at the cathode or it can be provided by dissolved bicarbonate. There can be either a liquid phase at both electrodes, a gas phase at the cathode and liquid at the anode or a humified gas phase at both electrodes. Typically, there is a gas diffusion electrode at the cathode and possibly also at the anode.

[0036] In microfluidic flow cells, an electrolyte channel is provided between a cathode and an anode, with a stream of CO and / or CO 2 gas delivered at the cathode. Instead of utilizing a membrane, the cathode and anode are separated by the diffusion of products.

[0037] Solid state electrolysis cells can improve the kinetics of reactions and achieve high efficiency. In these cells, there is a solid electrolyte to facilitate transfer of ions, with a membrane separating the cathode and anode. The cells can operate at high temperatures if needed, e.g. at or above 600°C, such as high as 700°C, 800°C or 900°C, even as high as 1000°C.

[0038] The transition metal carbide catalysts disclosed herein can be provided in any suitable form in the electrolytic cell of interest, depending on its design and intended use. Thus, the catalysts can be provided as a coating, film, as a powder, dopant etc., and in forms such as microparticles, nanoparticles such as zero- dimensional (OD), one-dimensional (1D), two-dimensional (2D) and three- dimensional (3D) nanoparticles, nanotubes, nanosheets, heterostructures, a single atom catalyst, a dual-atom catalyst and a triple-atom catalyst.

[0039] Transition metal arbides can have the general 1:1 (TMC:C) stoichiometry, e.g. VC, MoC, WC, NbC etc. Other stoichiometries are however also possible.

[0040] Thus, the skilled person will appreciate that the carbides may have an alternative stoichiometry, e.g. (TM) 2 C or other stoichiometries. Such stoichiometries are also within scope of the present disclosure. Further, chemical compounds as described herein are provided by their chemical formula irrespective of their phase or state. In particular, compounds that are present in their gaseous state when present in a pure and isolated form at room temperature (such as CO or CO 2 ) are herein described by their chemical formula. For example, carbon monoxide and carbon dioxide is herein described as CO and CO 2 , whether present as a gas, as individual molecules, in clusters, bound to surfaces or present as a solute, and the same applies to other molecular species described herein.

[0041] A mixture of CO and CO 2 can be provided in the electrolytic cell. During such operation of the cell, both CORR and CO2RR reactions will take place with products formed depending on the type of catalyst used (i.e., which TMC) and the applied voltage.

[0042] Alternatively, only CO or only CO 2 can be provided in the cell. This may be preferable, as it will be easier to control the respective reaction (CORR or CO2RR) for the type of TMC being used in the cell.

[0043] The proton donor in the electrolytic reactions can be any suitable substance that is capable of donating protons in the electrolytic cell. The proton donor can for example be water or it can be in the form of an acid, such as any suitable organic or inorganic acid. The proton donor can be provided in an acidic, neutral or alkaline aqueous solutions. The proton donor can also, or alternatively, be provided by H 2 oxidation at the anode. In other words, hydrogen can be considered as a source of protons: H 2 <=> 2(H +< + e -< )

[0044] The electrolytic cell can in general comprises at least three general parts or components, a cathode electrode, an anode electrode and an electrolyte.

[0045] The electrolytic reduction of carbon dioxide is the conversion of carbon dioxide to more reduced chemical species using electrical energy.

[0046] The different parts or components can be provided in separate containers, or they can be provided in a single container. The electrolyte can be a solid or an aqueous solution in which ions are provided, for example in a dissolved form in an aqueous solution when present. When provided as an aqueous solution, the aqueous solution can be a neutral, an alkaline or an acidic solution.Sources of CO 2 and CO

[0047] Carbon dioxide (CO 2 ) can be provided by a source such as any one of bicarbonate (HCO 3 -< ), carbonate (CO 3 -2< ) and / or carbonic acid (H 2 CO 3 ). For example, bicarbonate and carbonate can be provided as bicarbonate or carbonate salts, either in pure form as a solid or in solution, or in a mixture into a solution, that can preferably be an aqueous solution. A mixture of bicarbonate, carbonate and carbonic acid will reach equilibrium in solution. Therefore, the relative concentration of these species will depend on pH of an aqueous solution.

[0048] An alternate source of CO and CO 2 is the gaseous form of the compounds, CO(g) and CO 2 (g). Gaseous CO and CO 2 can be provided as a sole source of CO and / or CO 2 , or it can be provided as a supplement to other sources of CO or CO 2 in the cell. In the case of CO 2 , this includes the aforementioned bicarbonate, carbonate and carbonic acid.

[0049] Other or additional sources of CO and CO 2 are possible. For example, direct injection of CO 2 gas is possible by bubbling CO 2 directly into an electrolyte solution.

[0050] Alternatively, dissolved carbonate salts (e.g., sodium carbonate, Na 2 CO 3 ) in water can be used to provide a source of CO 2 .

[0051] An alternative source can be provided from industrial CO 2 Emissions. Capturing CO 2 from industrial processes such as cement production, steel manufacturing, or chemical production can also form a source of CO 2 . Further, chemical reactions that release CO 2 can be a source of CO 2 .

[0052] Certain microbial processes, such as fermentation, produce CO 2 as a byproduct and can serve as a source of CO 2 . The CO 2 can also be provided through photocatalytic production.

[0053] Another source is represented by CO 2 captured from fossil fuel-based power plants (coal, natural gas, oil) which produce large amounts of CO 2 .

[0054] Yet another source can be CO 2 generated from burning biomass such as agricultural waste, forestry residues, or bioenergy crops. Further, CO 2 emitted from the incineration of municipal solid waste can be captured as a source of CO 2 .

[0055] Through advanced capture technologies, CO 2 can be captured directly from the ambient air.

[0056] Carbon monoxide can be provided e.g. from microbial production, decomposition of metal carbonyls, thermal decomposition of formic acid, reforming reactions, water-gas shift reaction or gasification of biomass or coal.Catalysts

[0057] In general terms, the catalyst on the electrode surface should ideally have the following characteristics: It should (a) be chemically stable, it should (b) not become reduced or otherwise consumed during the electrolytic process, it should facilitate the formation of carbon-containing products, and (d) use of the catalyst should lead to the production of minimal amount of hydrogen gas. The catalysts disclosed herein fulfil these characteristics.

[0058] A catalyst can comprise one or more stabiliser that serves the role of preventing degradation of the catalyst. Suitable stabilisers should be more stable to degradation than the metal carbide(s) being employed, but otherwise are inert with respect to the catalytic reactions taking place on the electrode surface. Exemplary stabilisers include, but is not limited to, metal oxycarbides, metal oxynitrides, bimetallic oxides and the like.

[0059] The transition metal carbides can be provided as a film, i.e. as a thin layer (e.g., as few layers or as a monolayer) on a stable and conductive surface.

[0060] The catalysts disclosed herein are transition metal carbide catalysts. The catalysts can generally contain one or more transition metal carbide, or any mixture of transition metal carbides.

[0061] The transition metal carbide can preferably be selected from the group consisting of carbides of Nb, W, Mo, V, Ti, Hf, Ta, Cr, Zr, Sc and Y. The preferable catalyst composition can be varied depending on the intended use, i.e. the reactant being provided (CO or CO 2 ) and the desired product(s) formed in the electrolytic cell.

[0062] For formation of methane from CO 2 , the suitable catalyst can comprise a transition metal carbide of a transition metal selected from Nb, W, Mo, V, Ti, Hf, Zr and Ta, or alternatively Nb and Ti.

[0063] For formation of formic acid from CO 2 , the suitable catalyst can comprise a transition metal carbide of a transition metal selected from Cr, Hf, Mo, Nb, Zr, Ta, Ti, W and V.

[0064] For formation of methanol from CO 2 , the suitable catalyst can comprise transition metal carbide of a transition metal selected from the group consisting of Cr, Hf, Mo, Nb, Zr, Ta, Ti, W and V.

[0065] For formation of methanediol from CO 2 , the suitable catalyst can comprise a transition metal carbide of a transition metal selected from the group consisting of V and Mo.

[0066] For formation of methane from CO, the suitable catalyst can comprise a transition metal carbide of a transition metal selected from Mo, Nb, W, V, Ti, Zr, Hf, Cr, Sc, Y and Ta, or alternatively selected from Mo, Ta, Nb and V.

[0067] For formation of methanol from CO, the suitable catalyst can comprise a transition metal carbide of a transition metal selected form W, V, Nb, Ti, Cr, Zr, Mo and Hf, the preferable choice of which can be W.

[0068] An advantage of the present invention is that the process can be suitably operated using suitable electrolytes in solid or liquid form. An electrolyte solution can be non-aqueous or aqueous. For example, an electrolyte solution can comprise, or consist of an aqueous solutions containing dissolved electrolytes (salts). Thus, in certain embodiments of the process and system, the electrolytic cell comprises one or more aqueous electrolytic solutions, in one or more cell compartments. Individual cell compartments can be separated by suitable barriers, such as membranes that allow electrolytes to pass through.

[0069] Solid and liquid electrolytes may comprise any of various typical inorganic or organic salts such as but limited to soluble salts of e.g. chloride, nitrate, chlorate bromide, etc. e.g. sodium chloride, potassium chloride, calcium chloride, ammonium chloride, and other suitable salts. The electrolyte may also comprise any one or a combination of, alkali or alkaline earth metal oxides, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, rubidium hydroxide and cesium hydroxide.

[0070] An aqueous electrolyte solution can preferably comprise carbonate, bicarbonate or carbonic acid as a source of CO 2 . Such an aqueous electrolyte solution can also further comprise one or more organic or inorganic acids. Inorganic acids can include mineral acids that include but are not limited to, hydrochloric acid, nitric acid, phosphoric acid, sulphuric acid, boric acid, hydrofluoric acid, hydrobromic acid, and perchloric acid. The electrolyte can alternatively be provided as a protic or aprotic, non-aqueous solution. For example, the electrolyte can be provided as an ionic liquid, i.e. as a molten salt, for example a sodium chloride salt.

[0071] Depending on the substance composition of the catalyst, a suitable surface crystal structure may be preferred. Various different crystal structures exist for transition metal carbides and different structures can be obtained at different growth conditions. It is within scope of the skilled person to select appropriate surface crystal structures.

[0072] Further, it is possible that a catalyst contains more than transition metal carbide, such as two or more or three or more transition metals. For example, a transition metal carbide can be doped by a small amount of a second (or more) transition metal. Alternatively, a catalyst can contain one or more layer of a transition metal carbide that is provided over one or more layers of another transition metal carbide.

[0073] In certain embodiments of the invention, the catalyst surface is provided as a pure transition metal carbide, i.e. the catalyst comprises a single transition metal carbide, i.e. the catalyst for example does not contain a mixture of transition metal carbides or one transition metal carbide that is coated by one or several layers of a second (or more) transition metal carbides.

[0074] Thus, as will be apparent to the skilled person, the catalyst according to the invention can comprise a single transition metal carbide. The catalyst can alternatively comprise, or consist of, a mixture of two or more transition metal carbides. Such mixed transition metal carbides can comprise a single crystal structure or polycrystalline structures, for example a rocksalt structure. The mixed transition metal carbides can also comprise a mixture of transition metal carbides that are of different crystal structures and / or carbide with different catalytic facets. Accordingly, such mixed transition metal carbides can further comprise a single, or a mixture of, facets. Mixed transition metal carbide catalysts can be grown or manufactured separately and then assembled into mixed catalysts comprising the different metal carbides, wherein the carbides in the mixture have the same or different crystal structures.

[0075] As described in more detail herein, running a current through the electrolytic cell leads to a chemical reaction in which carbon monoxide (CO) and / or carbon dioxide (CO 2 ) is reduced in a series of steps to ultimately form one or more valuable short chain organic products, including for example methane, methanol, formic acid and methanediol. The running of current is achieved by applying a voltage to the cell. An advantage of the disclosed transition metal carbide catalysts is the possibility of performing electrolytic production of these valuable products at a low electrode potential under conditions of low temperature and / or gas pressure, which is beneficial in terms of energy efficiency and required equipment.

[0076] An electrolytic cell can be operated at an ambient gas pressure of about 1 atmosphere. The electrolytic cell can also be operated at higher pressure, i.e. pressure that is greater than ambient pressure. For example, the cell can be operated at a pressure of up to 50 atmospheres (atm), up to 40 atmospheres, up to 30 atmospheres, up to 20 atmospheres or up to 10 atmospheres. In some embodiments, the electrolytic cell is operated at a pressure that is in the range of 1 to 30 atmospheres, in the range of 1 to 20 atmospheres, in the range of 1 to 10 atmospheres, in the range of 1 to 5 atmospheres or in the range of 1 to 3 atmospheres. The electrolytic cell can also be operated at a pressure that is in the range of 2 to 20 atmospheres, in the range of 3 to 20 atmospheres, in the range of 4 to 20 atmospheres, or in the range of 5 to 20 atmospheres, such as at about atmospheres, about 6 atmospheres, about 7 atmospheres, about 8 atmospheres, about 9 atmospheres, about 10 atmospheres, about 11 atmospheres, about 12 atmospheres, about 13 atmospheres, about 14 atmospheres, about 15 atmospheres, about 16 atmospheres, about 17 atmospheres, about 18 atmospheres, about 19 atmospheres or about 20 atmospheres.

[0077] The electric potential can be applied as a constant or variable electric potential. Pulsed electric fields generated by pulsed potentials can be varied by adjusting a number of parameters such as electric field intensity, rise time of voltage pulses, number of pulses, frequency of pulses, pulse wave shape, treatment time (i.e. the length of time the pulse sequence is applied, resulting in from a product of the number of pulses and the duration of each pulse).

[0078] In certain useful embodiments, the cell is operated at an electrode potential that is less than (i.e., less negative) than about -2.0V, less than about -1.5V, less than about -1.0 V, less than about -0.9 V, less than about -0.7 V, less than about -0.6 V, less than about 0.5 V, less than about -0.4 V, less than about -0.3 V or less than about - 0.2 V. In some embodiments, the cell is operated at electrode potential in the range of about -1.0 V to about 0.0 V, such as in the range of about -0.7V to about 0.0V, about - 0.5 V to about 0.0 V, or in the range of about -0.3 V to about 0.0 V. The upper limit (i.e., more negative potential limit) of the range can be about -0.3 V, about -0.4 V, about -0.5 V, about -0.6 V, about -0.7 V, about -1.0V, about -1.5V or about -2.0V. The lower limit (i.e. less negative potential limit) of the range can be as high as about +1.0V, about +0.5V, about 0.0 V, about -0.1 V, about -0.2 V, or about -0.3 V.

[0079] A high (more positive) or low (more negative) potential may be applied to the electrolytic cell before and / or after operation of the cell to produce products from CO / CO 2 . For example, it may be beneficial to increase voltage to a more positive potential (e.g., a voltage greater than 0.0V) to free the surface of the catalyst / electrode from adsorbents that may have an adverse effect on its operation. After such cleaning, the electrolytic cell can be operated under normal production potential.

[0080] During operation of the cell, the composition of products obtained in the reduction of CO and / or CO 2 can be altered / controlled by selective adjustment of applied potential for any given catalyst surface. Thus, the data provided herein shows that depending on the relative binding energies of adsorbed intermediates the selectivity of the electrolytic cell changes depending on the applied voltage.

[0081] The temperature of the cell may be varied as needed. One advantage of the present catalysts is that the CO 2 RR and CORR reactions can be carried out at low temperature, such as at or near ambient room temperature. However, it will be appreciated that the temperature may be adapted and / or adjusted as needed.

[0082] For example, solid state electrolytic cells can operate at high temperatures of up to or close to 1000°C, and the catalysts described can be used at such high temperatures.

[0083] In general therefore, the temperature of the electrolytic cell, and in particular the temperature at the cathode of the cell, can be in the range of 0°C to 1000°C, in the range of 0°C to 900°C, 0°C to 800°C, 0°C to 700°C, 0°C to 600°C, 0°C to 500°C, 0°C to 400°C, 0°C to 300°C, 0°C to 200°C, 0°C to 100°C or 0°C to 50°C. In some embodiments, the temperature is in the range of 0°C to 50°C, 5°C to 45°C, 10°C to 40°C, 15°C to 35°C, or 20°C to 30°C.

[0084] An advantage of the present invention is the specificity and efficiency of product formation over side-product (such as H 2 ) formation, which is a challenge due to the competing binding energies of hydrogen and oxygen on the catalyst surface. In certain embodiments, less than about 50% moles H 2 are formed compared to moles of the desired product formed, and preferably less than about 40% moles H 2 , less than about 30% moles H 2 , less than about 20% moles H 2 , less than about 10% moles H 2 , less than about 5% moles H 2 , less than about 2% moles H 2 , or less than about 1 % moles H 2 .

[0085] Further, reaction conditions (choice of catalyst, applied potential in particular) can be set so that one reaction product is selectively formed over other reaction products. This means that the reaction predominantly or even completely leads to the formation of one particular reaction product (e.g., methane, methanol, formic acid, methanediol).

[0086] The reaction pathway of CO and CO 2 reduction depends on the relative energies of reaction intermediates. Thus, the pathway can depend on the system within which the reaction takes place, including the chemical composition of the catalysis and the catalytic surface being used in the reaction.

[0087] The active part of an industrial heterogeneous catalyst is most commonly a solid surface, e.g. a transition metal or transition metal carbide or mixture of transition metal carbides. The surface offers a favourable energy path from reactants to products, by binding reactants and reaction intermediates. The binding energy of reactants to the surface must be strong enough to produce reaction intermediates, but weak enough to allow products to leave the surface, allowing more reactions to take place on the surface. The consequence is that for a reaction, there will be an optimum binding energy for an intermediate, such that both stronger and weaker binding leads to lower activity. A result of this phenomenon is a reaction relationship called the volcano-shaped relationship, or commonly referred to as a Volcano plot.

[0088] Catalyst activity can in general be modified by altering the local electronic structure by strain, ligand, substitution and / or alloying. These alterations can result in changes in binding energies of reaction intermediates, and thereby a change in the thermodynamics of the overall reaction profile. Thereby it may be possible to adapt the reaction profile to specifically obtain desired reaction products.

[0089] Exemplary embodiments in accordance with the present disclosure include the following: 1. A method for catalytic electrolytic reduction of CO 2 and / or CO, the method comprising: a. providing an electrolytic cell containing at least one reaction chamber that has at least one anode and at least one cathode and at least one electrolyte between the anode and the cathode, wherein the at least one cathode comprises at least one catalyst comprising at least one carbide of one or more transition metal selected from the group consisting of Nb, W, Mo, V, Ti, Hf, Ta, Cr, Zr, Sc and Y; b. providing CO 2 and / or CO in the electrolytic cell; and c. applying electrical potential to the electrolytic cell; whereby the CO 2 and / or CO undergoes at least one reduction reaction at the cathode. 2. The method of clause 1, wherein the catalyst is provided as a surface coating, a film, a microparticle, nanotubes, nanosheets, heterostructure, dopant and / or a nanoparticle. 3. The method of any one of the previous clauses, wherein the temperature at the at least one cathode is in the range of 0°C to 300°C, 0°C to 200°C, 0°C to 100°C, 0°C to 50°C 5°C to 45°C, 10°C to 40°C, 15°C to 35°C, or 20°C to 30°C. 4. The method of any one of the previous clauses, wherein the electrolytic cell comprises gas diffusion electrodes at the anode and / or the cathode. 5. The method of any one of the previous clauses, wherein the electrolytic cell further comprises at least one reference electrode. 6. The method of any one of the previous clauses, wherein the electrolytic reduction reaction results in formation of at least one alkane, lower alcohol or acid having from 1 to 3 carbon atoms. 7. The method of any one of the previous clauses, wherein the electrolytic reduction reaction results in formation of at least one product selected from methanol, methane, methanediol, formic acid, formaldehyde, ethanol, ethane, ethylene glycol, ethanediol, propane and propanol. 8. The method of any one of the previous clauses, wherein CO 2 and / or CO are provided in gaseous form into the electrolytic cell, and wherein the gas pressure at the at least one cathode is in the range of about 1 atm to 40 atm, 5 atm to 30 atm, or 10 atm to 20 atm. 9. The method of any one of the previous clauses 1 to 8, wherein the gas pressure at the at least one cathode is ambient pressure of about 1 atm. 10. The method of any one of the previous clauses, wherein the electrical potential applied to the electrolytic cell is in the range of -2.0 V to +1.0 V using a reversible hydrogen electrode (RHE) as a reference. 11. The method of any one of the previous clauses, wherein molar production of hydrogen (H 2 ) compared with CO 2 and / or CO reduction in the electrolytic cell is less than 50%. 12. The method of any one of the previous clauses, wherein the electrolyte solution comprises at least one source of CO 2 selected from carbonate (CO 3 2-< ), carbonate salts, bicarbonate (HCO 3 -< ) and carbonic acid (H 2 CO 3 ). 13. The method of any one of the previous clauses, wherein CO and / or CO 2 is provided in the solution by a stream of gas. 14. The method of any one of the previous clauses, wherein CO 2 only is provided in the electrolytic cell, and wherein the carbide is a carbide of a transition metal selected from Nb, W, Mo, V, Ti, Hf, Zr and Ta, the catalytic reduction resulting in formation of methane. 15. The method of any one of the previous clauses, wherein CO 2 only is provided in the electrolytic cell, wherein the carbide is a carbide of a transition metal selected from the group consisting of Nb and Ti, the catalytic reduction resulting in formation of methane. 16. The method of any one of the previous clauses 1-13, wherein CO 2 only is provided in the electrolytic cell, and wherein the carbide is a carbide of a transition metal selected from the group consisting of Cr, Hf, Mo, Nb, Zr, Ta, Ti, W and V, the catalytic reduction resulting in the formation of formic acid. 17. The method of any one of the previous clauses 1-13, wherein CO 2 only is provided in the electrolytic cell, and wherein the carbide is a carbide of a transition metal selected from the group consisting of Cr, Hf, Mo, Nb, Zr, Ta, Ti, W and V, the catalytic reduction resulting in formation of methanol. 18. The method of any one of the previous clauses 1-13, wherein CO2 only is provided in the electrolytic cell, and wherein the carbide is a carbide of a transition metal selected from the group consisting of V and Mo, the catalyst reduction resulting in formation of methanediol. 19. The method of any one of the previous clauses 1-13, wherein CO only is provided in the electrolytic cell, and wherein the carbide is a carbide of a transition metal selected from the group consisting of Mo, Nb, W, V, Ti, Zr, Hf, Cr, Sc, Y and Ta, the catalytic reaction resulting in formation of methane. 20. The method of the previous clause, wherein the carbide is a carbide of a transition metal selected from Mo, Ta, Nb and V. 21. The method of any one of the previous clauses 1-13, wherein CO only is provided in the electrolytic cell, and wherein the carbide is a carbide of a transition metal selected from the group consisting of W, V, Nb, Ti, Cr, Zr, Mo and Hf, the catalytic reaction resulting in formation of methanol. 22. The method of the previous clause, wherein the carbide is a carbide of W. 23. An electrolytic cell for the reduction of carbon dioxide and / or carbon monoxide, comprising: an annode; and a cathode, the cathode comprising a catalyst comprising at least one carbide selected of a transition metal selected from Nb, W, Mo, V, Ti, Hf, Ta, Cr, Zr, Sc and Y,. 24. The electrolytic cell of the previous clause, wherein the catalyst is provided as a surface coating, a film, a microparticle, nanotubes, nanosheets, nanoarrays, nanoribbons, heterostructure, dopant, a nanoparticle, zero- dimensional (0D), one-dimensional (1D), two-dimensional (2D) and three- dimensional (3D), a single atom catalyst, a dual-atom catalyst and a triple-atom catalyst. 25. The electrolytic cell of any one of the previous two clauses, wherein the catalyst is provided as a pure carbide of a transition metal selected from Nb, W, Mo, V, Ti, Hf, TaC, Cr, Zr, Sc and Y. 26. The electrolytic cell of any one of the previous three clauses, wherein the transition carbide is a carbide of a transition metal selected from V, Nb and W. 27. The electrolytic cell of any one of the previous four clauses, wherein the electrolytic cell comprises gas diffusion electrodes at the anode and / or the cathode. 28. The electrolytic cell of any one of the previous five clauses, wherein the electrolytic cell further comprises at least one reference electrode. 29. A chemical reactor comprising at least one electrolytic cell as set forth in any one of clauses 23-28; and a power supply connected to the electrolytic cell.

[0090] The invention will now be exemplified by the following non-limiting Examples.Example 1 CO2RR Computational method

[0091] The interaction of CO 2 with TMC surfaces and formation of different intermediates were studied by DFT calculations with Generalized Gradient Approximation (GGA) using RPBE exchange correlation function. The tool used for these calculations was ab initio simulation package (VASP) and cutoff energy was 450 eV with the 4×4×1 Monkhorst-Pack K-point mesh until energy differences are converged within 10 -4< eV. The Projector augmented wave (PAW) method was implemented due to full wavefunction by utilizing computationally efficient pseudopotentials, significantly reducing computation time. The surface of TMCs were considered in the rocksalt (RS) crystallographic structure with the texture orientation of (100). The electrodes modelled consisting of 5 layers with each layer made of 4 atoms of carbon and 4 atoms of metal, 40 atoms in total in the unit cell of each TMC structure. The boundary condition was periodic with 20 Å vacuum along the z direction to avoid self-interaction of neighboring layers. The bottom two layers were fixed, and the top 3 layers were allowed to fully relax together with any adsorbates on the surface as shown in figure 1B, where a schematic representation of TMC is shown. The smaller spheres indicate carbon atom and larger spheres metal atoms. The dotted line shows how bottom two layers are fixed.

[0092] The binding energy of an adsorbate was calculated according to the equation 1: ΔE ads = E adsorbate / TMC slab − E TMC slab − E adsorbate

[0093] Here E (adsorbate / TMC slab) is the total energy of the system with an adsorbate on the TMC slab, E (TMC slab) is the total energy of the pristine TMC slab, and E(adsorbate) is the total energy of the adsorbate. The negative ΔE ads corresponds to the exothermic adsorption phenomenon.

[0094] The Computational hydrogen electrode model as proposed by Norskov et al was used to calculate the free energy diagram for CO 2 RR and / or CORR along different paths at certain applied potential. According to this method at room temperature kinetic barrier is negligible for the proton coupled electron step and the potential limiting step is the most positive energy difference between the two adjacent steps.

[0095] The reaction free energy of an adsorbate for CO 2 RR at any arbitrary potential U vs RHE and any arbitrary pH was calculated by equation: Δ G U RHE = Δ G U RHE = 0 + neU RHE eU RHE = eU RHE + 2.3 k b TpH where U RHE is the applied potential referred against the standard hydrogen electrode (SHE), n is number of electrons, e is the elementary charge , k b is the Boltzmann constant and T is the Temperature. By putting eq (2) into eq(3) we will get : Δ G U RHE = Δ G U RHE = 0 + n eU RHE = eU RHE + 2.3 k b TpH

[0096] Generally overpotential are independent of pH of electrolyte so in this study we will consider pH = 0. Hence for each elementary step ΔG (U = 0) is calculated by Δ G U = 0 = ΔE DFT + ΔE ZPE − T Δ S + ΔE 0 K → T + ΔE sol

[0097] Where ΔG is the Gibbs free energy, ΔE DFT is the electronic energy calculated by DFT, ΔE ZPE is the zero-point energy correction and TΔS is entropy differences between the gas phase and adsorbed species calculated by vibrational frequencies for the adsorbed species, ΔE sol is the adsorbate stabilization term due to the solvent and we have not included in this study. ΔE 0K→T is the change in internal energy because of temperature. The value of the gas phase is taken from the thermodynamic tables from textbooks.Results and discussion

[0098] The thermochemical model was employed to predict reaction pathways and onset potentials for the CO 2 RR on the (100) facets of the RS structure of TMCs. From the earlier transition metals, 11 carbides including CrC, HfC, MoC, YcC, ScC, NbC, ZrC, TaC, TiC, WC, and VC were selected for this investigation, as the later transition metals form carbides in structures other than the RS. In the initial phase, the adsorption free energy of all species were systematically tested on both the metal and carbon sites of each metal carbide. This investigation revealed that the carbon sites are particularly more active for adsorption compared to the metal sites. We have undertaken a comprehensive exploration involving the absorption of various species to analyze their poisoning effects on TMCs, as illustrated in Fig 2.

[0099] The findings reveal positive binding energies of H, O, and OH species for most TMCs rendering a lower likelihood of poisoning, with the exceptions being ScC and YcC. However, these materials (ScC and YcC) have been selected only for investigation within the framework of the Mars-van Krevelen (MvK) mechanism. Adsorption of other key species such as COOH, OCHO, CO, and CO 2 was found to be exergonic for most of these surfaces and the products formed corresponding the required onset are mentioned in Table 1.

[0100] For the direct adsorption of CO 2 , we found out that most of these surfaces do not bind CO 2 exergonically except HfC, ScC, YcC, and ZrC, demonstrating a Gibbs free energy of -0.25, -1.05, -1.99, -0.25 eV, respectively. To investigate the interaction of CO 2 with these metal carbides, two mechanisms were explored: the Mars-van Krevelen (MvK) mechanism and direct adsorption on clean surface (the conventional method).1. CO 2 RR Pathways via Mars-van Krevelen (MvK) mechanism

[0101] In actual experiments, it is important to observe that Transition Metal Carbides (TMCs) often exhibit a significant number of defects, such as carbon vacancies, primarily due to the inherent difficulty in achieving complete stoichiometry. To better facilitate CO 2 we assume the carbon vacancy is generated by emission of one CH 4 molecule. In the MvK mechanism the cycle starts from the surface protonation as a result CH 4 is released, carbon vacancy is formed which should be filled with atmospheric CO 2 where the C atom of CO 2 fills the vacancy of TMCs, and two oxygen atoms is reduced to two water molecules as mentioned in equation 6. In this procedure, sustained protonation on the metal carbides results in the attachment of four protons to the carbon of the surface atom of the metal carbides, leading to the release of CH 4 . The reaction following this method to fill the vacancy is expressed as: V <mprescripts / > <none / > C ac + CO 2 + 4 H + + e − → 2 H 2 O + *

[0102] NbC emerges as the optimal candidate for CH 4 formation, via a predicted onset potential of -0.39 V and its free energy diagram is shown in Fig 3.

[0103] The other promising candidates for CH 4 production through the MvK mechanism are WC, MoC, VC, and TiC with limiting potential of -0.41, -0.44, -0.44, -0.46 V, respectively as shown in figure S1. The limiting potential required for methane formation on the surface of ScC and YC are -1.24 and - 1.68 V, respectively.

[0104] For most of these surfaces it is relatively facile to form methane and then fill the vacancy with atmospheric CO 2 and complete the catalytic cycle. In the MvK there is a possibility of migration of the vacancy to the bulk which means migration of the C atoms from the bulk to the surface. If this process is facile (thermodynamically and kinetically) it can contribute to further reduction of C atoms of the material and conversion of the carbide to its pure metal, rendering material instability. Therefore, it is crucial to investigate this phenomenon carefully. It is noted that in NbC carbon migration barrier is very high, approximately 2.96 eV which means that there is no concern about migration of carbon atom from second layer to first layer due to high migration barrier and catalyst is stable under ambient condition. Similarly for other promising candidates WC and VC the diffusion barrier for carbon atom is calculated 1.94 and 2.40 eV respectively.2. CO 2 RR Pathways via the conventional method

[0105] In the first step of CO2RR two possible intermediates, OCHO and COOH, can be formed by the first electron proton step as shown in Fig 5, the purposed mechanism of CO 2 reduction. In this study it is concluded that in most cases COOH adsorption is more energetically favorable as compared to OCHO as shown in Fig 2. Adsorption of OCHO is favorable on the HfC and VC only. In case of COOH adsorption, the C atom of COOH binds with C atom of TMC surface, 1 st< oxygen atom of COOH bind with TMC atom and 2 nd< O atoms binds with H atoms. Similarly, for OCHO, the C atom of OCHO binds with C atom of TMC surface but H binds with the C atom of OCHO, and two O atoms binds with metal atom of metal carbide surface.a. The selectivity between CO 2 RR versus HER.

[0106] The first step of protonation provides the information of selectivity towards CO 2 RR and HER. If proton binds the metal site more preferentially than the carbon site, this will be indication of HER, which is not the case for these TMCs studied here. Fig 6 shows the free energy diagram for HER where proton binding energies on all of the TMCs are endergonic and thus should not be of concern. (*COOH or *OCHO) adsorption vs hydrogen adsorption for CrC, HfC, MoC, NbC, ZrC, TiC and VC shows more tendency towards CO 2 RR rather than HER. Table 1 summarizes the predicted onset potentials for CO2RR towards different products. Table 1: Onset potential (V) for CO 2 RR towards various products and intermediates (* means that these products are not formed on these catalysts) Catalyst Formic acid CO Methanol Methanediol Methane HER on Metal side (MH) CrC-1.670.00-0.53*unstable-0.66HfC-0.460.00-0.69*-0.52-1.60MoC-0.58-0.12-0.87-0.58-0.87-0.75NbC-0.40-0.29-0.44*unstable-0.67ZrC-0.790.00-0.83*-0.83-TaC-0.25*-0.69*-0.69-0.37TiC-0.90-0.06-0.4*-0.9-WC-0.31-0.20-0.36*-0.69-0.38VC0.000.00-1.08-1.08*-0.90 b. CO 2 RR pathways towards formation of Formic acid (HCOOH) and CO

[0107] In the second protonation step formic acid and CO are the main products before the formation of methane, methanol and methanediol. The reactions follow protonation steps as:         *COOH or *OCHO + H +< + e -< → *HCOOH         *COOH or *OCHO + H +< + e -< → *CO + H 2 O

[0108] We found out that VC does not bind *HCOOH intermediate on its surface and this catalyst has the potential to produce aqueous formic acid with 0 V onset potential as shown in the free energy Fig 7 and volcano plot in Figure 9 and thus this candidate is the best TMC to produce formic acid.

[0109] In addition to VC, other carbides like WC, HfC, TaC, and NbC are explored as good candidates to produce formic acid with small onset potentials of -0.25 V, - 0.31 V, -0.40 V, and -0.46 V, respectively as shown in Fig 8 and in the volcano plot of Fig 9. The asterisk (*) in Fig 8 indicate that mentioned products in specific color are formed with 0V onset potential.

[0110] The CrC, HfC, ZrC, TaC, and VC are expected to spontaneously convert CO 2 to CO. These materials are promising for CO 2 conversion to CO at 0 V. MoC, NbC, TiC, and WC are also good candidates for the formation of CO with appropriate onset potential of -0.12, -0.29, -0.06, and -0.20 V, respectively as shown in Table 1.c. CO2RR Pathways towards formation of Methanol

[0111] CO2RR towards methanol formation involves 6 protons-electron transfer steps via 5 (A-E) pathways as shown in table 2. In this work, we have investigated two routes to produce methanol, one route is *COOH to *HCOOH and another route is *COOH to *CO+H2O. Table 2: Pathways for Methanol formation (e+H +< ) steps Pathways 1 2 3 4 5 6 A *COOH*HCOOH*H 2 COO H*CH 2 O+H 2 O*CH 2 OHCH 3 OH (aq)B *OCHO*HCOOH*H 2 COO H*CH 2 OH+ OHCH 3 OH (aq)+ *OHH 2 OC *COOH*HCOOH*H 2 COO H*CH 2 OH+ OH*CH 2 OH + H 2 OCH 3 OH (aq)D *COOH*HCOOH*H 2 COO H*CH 3 O+O H*CH 3 O +H 2 OCH 3 OH (aq)E *COOH*CO+H 2 O*COH or CHO*CHOH or * CH 2 O*CH 2 OH or *CH 3 OCH 3 OH (aq)

[0112] The route followed through COOH to CO+H2O is more promising as compared to the other one because in this route we have required less onset potential. For seven TMCs (CrC, HfC, MoC, NbC, ZrC, TiC, and WC) the COOH path is favorable, while for TaC and VC the OCHO path is more favorable for methanol formation. The potential limiting step for methanol on each metal is shown in Table 1 and volcano plot of Fig 9. The mechanisms for methanol are not the same for all TMCs and we simplify these free energy diagrams and volcanos by only including the most energetically favorable reaction steps that exist in the minimum free energy pathways. The surfaces of HfC, WC, MoC, ZrC, TiC, and CrC followed path E (mentioned in table 2), NbC followed path C, TaC followed path B, and VC followed path A as mentioned in Table 2 for the formation of methanol. In the volcano plot Fig 9 and data in Table 1 it is clearly shown that the WC is the best candidate for the methanol formation with the potential limiting step of -0.36 V. The free energy diagram for the WC is shown in Fig 10. In addition to WC the studied TiC, NbC, and CrC are also good candidates for methanol formation with corresponding onset potential of -0.40 V, -0.44 V, and -0.53 V, respectively as shown in the volcano plot in Fig 11.d. CO2RR Pathways towards formation of methanediol and methane

[0113] In this analysis each carbide has specific onset potential for each product as shown for VC in Fig.7, i.e. MoC and VC are promising candidates for the formation of methanediol with the potential limiting steps of -0.58 V and -1.08 V, respectively. The path followed by methanediol are 4 steps as COOH / OCHO → HCOOH → H 2 COOH → CH 2 (OH) 2 . On the other TMCs, further protonation of H 2 COOH intermediate breaks it into other intermediates (as mentioned in Table 2) and thus methanediol formation cannot be achieved.

[0114] In this research through conventional method, TiC and NbC are considered suitable candidate for the formation of methane with the onset potential values of - 0.4 V, -0.44 V respectively, and interestingly these candidates have same onset potential for the formation of methanol. In addition, HfC, MoC, ZrC, TaC, and WC are also suitable for the formation of methane with the required onset potential value of -0.69, -1.06, -0.83, -0.72, and -0.69 V, respectively, but these materials are more selective towards formic acid formation as compared to methane with onset potentials of -0.46, -0.58, -0.79, -0.25, and -0.41 V, respectively.e. Deviation of Onset potential

[0115] Box plots are plotted to estimate the required onset potential for each candidate for the formation of formic acid, CO, methane, and methanol (methandiol not included due to insufficient data for box plot). This gives a complete road map and picture to the experimentalist to adjust the potential according to the requirements of each product. The formation of methane in this analysis included the pathways towards MvK mechanism. Scale of box plot is mentioned in Fig12. In the box plot analysis, we have included onset potential of each product for each candidate. WC shows capability to produce 4 products i.e formic acid, CO, methane, and methanol below the outset potential of -0.41 V. The minimum onset potential of WC lies at -0.08 V and maximum is at -0.41 V and deviation of data is towards the minimum side from its mean position. VC shows its minimum at 0 V onset potential due to formation of formic acid on this onset potential, but its maximum is high due to formation of methanol at -1.08 V.

[0116] In addition, NbC is interesting as its maximum lies at -0.44 V and its minimum at - 0.39 V, and between maximum and minimum potential four products are formed. HfC also shows good result as its minimum at 0 V and maximum is at -0.69 V and its median value of onset potential deviate towards the minimum side in the box plot similarly behavior is also noted for the ZrC but its maximum lies at -0.83 which is higher than HfC, NbC and WC.f. Comparison of CO 2 RR onset potential for TMCs studied in this work with some other metal-based catalysts previously reported.

[0117] The results obtained for these TMCs were compared with previously studied metal-based catalysts as shown in Fig 13. In this research work except CrC other TMCs show less required onset potential as compared to previously studied TMOs, Pristine metals and dopant Transition metals. HfC, MoC, NbC, and TiC offer selectivity towards formic, methanol and methane and are better than previously studied oxides of the same parental metal (HfO 2 , NbO 2 , TiO 2 , RuO 2 and (TiO2) 3 / Ag and pristine Ti). The conclusion drawn from figure 13 shows that the findings from the TMCs for CO 2 RR are more novel than previously studied metals.References of figure 13

[0118] 1. Tayyebi, E., et. al., (2018), The Journal of Physical Chemistry C, 122(18), 10078-10087. 2. Li, F., et. al., (2021). International Journal of Hydrogen Energy, 46(24), 12886-12896. 3. Atrak, N., et. al., (2021). Applied Surface Science, 570, 151031. 4. Kim, S. et. al., (2016). Acs Catalysis, 6(3), 2003-2013. 5. Li, H., et. al., (2020). ACS catalysis, 10(20), 11814-11821. 6. Wannakao, S., et. al., (2017). The Journal of Physical Chemistry C, 121(37), 20306-20314. 7. Back, S., et. al., (2015). Acs Catalysis, 5(2), 965-971. 8. Hazarika, J., er. al., (2019). Electrochimica Acta, 328, 135053. 9. Zhao, Y., et. al., (2021). Small, 17(16), 2006590. Example 2 CORR Computational details

[0119] In all computational analysis Vienna ab initio simulation (VASP) package was employed. Density functional theory was applied with exchange correlation function of (RPBE) with the 4×4×1 Monkhorst-Pack K-point mesh. These exchange correlation functions are suitable for transition metals in generals and for TMCs. With the VASP code calculation cutoff energy was 450 eV were used to expand the valence electron density. All studied TMCs consist of rocksalt (RS) with the texture orientation of (100) facets. The slab model consists of 5 layers and 40 atoms, and each layer has 4 carbon atoms and 4 metal atoms as shown in Figure 1B. The upper three layers are allowed to relax during the optimization and bottom two layers were fixed. To avoid the self-interaction of slabs with neighbors layers all adsorptions were modeled on fully relaxed slabs of TMCs with the vacuum of 20 Å along z direction and along x and y axis boundaries conditions were periodic.Results and Discussion

[0120] Density functional theory approach was used to investigate the catalytic activity of transition metal carbide (TMCs) surfaces with a (100) crystallographic orientation (RS) for CO reduction reaction (CORR) through comprehensive modeling of adsorption energies and reaction pathways for a range of candidates including CrC, HfC, MoC, ScC, YcC, NbC, ZrC, TaC, TiC, WC, VC. In the first step all species were adsorbed on the clean surface of each fully relaxed TMCs surface. To investigate the adsorption free energies of each species on both metal and carbon sites the results conclude that carbon sites are more active than metal sites. Before starting the CORR mechanism study of CO adsorption comparison to other species is mandatory. This analysis offers insights into the stability of these surfaces concerning susceptibility to poisoning of protons, O, and OH, by comparing the adsorption CO 2 and CO on pristine surfaces. This study reveals that TMCs are more favorable for CO study as compared to CO 2 and hydrogen evolution reaction (HER) as shown in Fig14. The results demonstrate binding energies of H, O, and OH species on each of TMC surfaces, indicating less poisoning, except in the cases of ScC and YcC and less poisoning of these species are more favorable for CORR mechanism. The vacancy poisonous of H, OH and O were already studied in previous research work. In this study two mechanisms were used to investigate the activity CORR on the TMCs surface. In the first mechanism we have done a complete analysis of MvK mechanism and in the second mechanism we have studied the conventional surface mechanism of CO activity on the clean surface of the TMCs.Mars-van Krevelen (MvK) mechanism towards Methane formation

[0121] The MvK mechanism provides a framework for understanding the redox chemistry occurring on catalyst surfaces as the results of vacancy occurring. Vacancy generation in TMCs can occur due to two primary reasons. Firstly, there's the notable presence of defects, particularly carbon vacancies, within the crystal lattice structure. These vacancies arise mainly from the challenges in achieving precise stoichiometry during synthesis, where some carbon atoms are inevitably missing from the intended composition. Secondly, another mechanism contributing to vacancy generation involves the emission of carbon in the form of methane with protons. This process occurs during certain reaction conditions, where carbon atoms are released from the TMC structure in the form of methane gas when reacting with protons. In this analysis we have drawn a complete picture of MvK mechanism how CH 4 is released with continue protonation and vacancy is generated and this vacancy is filled with carbon atom of CO and O is transferred into to water molecule. The reaction followed by this mechanism is expressed by using the Kröger-Vink notation:         * + 2(H +< + e -< ) → CH 4(g) + C< Vac     eq (7)          C< Vac +CO (g) + 2(H +< + e -< ) → H 2 O + *     eq (8)

[0122] This cycle will continue with the emission of CH 4 molecules and vacancy is filled with the carbon of CO and releasing water molecules as shown in the Fig 15 where (a) represents clean surface (b) represents formation of methane (c) carbon vacancy is created mentioned in read circle (d) represents adsorption of CO in the gas form and carbon of CO is fixed in the carbon vacancy to fill the vacancy (e) represents again protonation and oxygen of CO is converted into water and again surface is clean.

[0123] CrC, HfC, MoC, ScC, YcC, NbC, ZrC, TaC, TiC, WC,and VC were comprehensively studied through MvK mechanism. The results indicate that MoC is the best candidate for the formation of methane through MvK mechanism with the onset potential of - 0.22 V and more interestingly, vacancy is filled with the carbon atom of CO and water is released spontaneously without any additional applied onset potential as shown in the free energy diagram Fig 16. The analysis of activity volcano plot also show MoC is promising catalyst among all the studied catalysts located at the top of the volcano plot as shown in fig 17.

[0124] In addition to MoC there are also other promising candidates for the formation of methane with ideal onset potential. NbC, WC, VC, TiC, ZrC, HfC and TaC show formation of methane with corresponding onset potentials of -0.39, -0.41, -0.44, -0.46, -0.58, -0.62, -0.83 V, respectively, and these materials filled the carbon vacancy spontaneously by adsorbing CO to make a clean structure and releasing water molecule without any additional potential. Other catalysts, CrC, YcC and ScC, are also good candidates for methane formation and these catalysts required small onset potential to fill the vacancy from the carbon atom of CO with onset potentials of -0,82, -0.61, and -0.65 V, respectively. The results concluded from the MvK mechanism is that only one product methane can be formed through this mechanism by the conversion of CO.CORR conventional mechanism towards Methanol and Methane

[0125] The conversion of CO to methanol via conventional mechanism for CO reduction reaction is a promising strategy for both mitigating greenhouse gas emissions and producing valuable chemicals. To obtain the most stable CO adsorption configuration on the TMCs three different sites, metal, carbon, and bridge (between metal and carbon) sites were investigated for CrC, HfC, MoC, NbC, ZrC, TaC, TiC, WC, and VC and due to high Gibbs free energy values ScC and YcC were not considered for methanol and methane activity. TMCs have unique surface reactivity and electronic properties due to the presence of carbon in CO and catalyst which create the great interaction between catalyst and reactants for methanol and methanol formation. The findings conclude that carbon sites of TMCs were the most active and optimal sites for CORR mechanism. Interestingly all studied material show spontaneous adsorption of CO at 0V onset potential as shown in Fig 16. Before any catalytic activity the starting steps of protonation provide information about the direction of reaction towards HER or CORR. In this study 7 carbides show adsorption of H on metal site as shown in the fig 7, but this adsorption is weaker compared to the adsorption energy of CO and hence CORR is favorable and dominant over HER on TMCs.

[0126] After adsorption of CO gas exogenically on the surface of TMCs the subsequent protonation initiates the electrochemical process. These steps lead to formation of two intermediates, *CHO and *COH making the beginning of the pathways towards the methanol and methane formation as shown in the flow chart of mechanism of CORR in Fig 19.Methanol formation

[0127] In CORR there are 4 protonation steps for methanol formation, and each material has different type of pathways corresponding to its minimum energy path. After the spontaneously adsorption of CO on surface of catalysts each reaction followed by 4 protonation steps and all possible pathways towards methanol are:         *CO + H +< + e -< → *COH or *CHO     eq (9)         *CHO or COH + H +< + e → *CH 2 O or *CHOH     eq (10)         *CH 2 O or CHOH + H +< + e -< → *CH 2 OH or *CH 3 O     eq (11)         *CH 2 OH or CH 3 O+ H +< + e -< → *CH 3 OH (aq)     eq (12)

[0128] In the investigated CORR mechanism on TMCs we have done full complete reaction mechanism study on each candidate of 9 TMCs surface but we only show here minimum energy pathways in free energy diagrams of each candidate for ease of understanding. In this analysis, WC exhibited the lowest onset potentials of -0.34 V suggesting superior catalytic activity for methanol formation among the studied TMCs catalysts. The reaction followed by WC towards methanol formation at minimum energy level was *CO → *CHO → *CH 2 O → *CH 3 O → *CH 3 OH (aq) as shown in the free energy diagram of fig 20.

[0129] The DFT calculations also provide valuable insights into the CO reduction reaction selectivity towards methanol formation on VC, NbC and TiC with onset potential values -0.42, -0.44 and -0.59 V, respectively. The reaction pathway followed by NbC is same as followed by WC. The reaction pathway followed by VC is *CO → *CHO → *CH 2 O → *CH 2 OH → *CH 3 OH (aq) and for TiC is followed by *CO → *CHO → *CHOH → *CH 2 OH → *CH 3 OH (aq). In addition, CrC, ZrC, MoC and HfC were also considered good candidates for methanol formation with the onset potential values of -0.67, -0.84, -0.87, -0.9 V, respectively. CrC follows the same pathway as followed by TiC but potential is little higher as compared to TiC for methanol formation. The reaction followed by ZrC and HfC are *CO → *COH → *CHOH → *CH 2 OH → *CH 3 OH(aq) and for MoC reaction pathway are *CO → *COH → *CH 2 O → *CH 3 O → *CH 3 OH (aq) and here we have shown free energy diagram of the promising candidate WC. Out of 9 TMCs only one candidate, TaC, was not suitable for methanol formation because before the formation of methanol, the *CH 2 OH intermediate split into two intermediate, *CH 2 and *OH towards the methane formation.Methane formation

[0130] For methane formation through CORR on the studied TMCs there are 6 protonation steps with different pathways corresponding to minimum energy values. All possible pathways followed as         *CO + H +< + e -< → *COH or *CHO     eq (13)         *CHO or COH + H +< + e -< → *CHOH or *CH 2 O or *C     eq (14)         *CHOH or *CH 2 O or *C or + H +< + e → *CH 2 OH or *CH     eq (15)         *CH 2 OH or *CH + H +< + e -< → *CH 2 or *CH 3 + OH     eq (16)         *CH 2 or *CH 3 + OH + H +< + e -< → *CH 3      eq (17)         *CH 3 + H +< + e -< → CH 4 (g)     eq (18)

[0131] Similarly, as for methanol formation we have also done complete reaction mechanism study for methane formation on 9 TMCs. As can be seen in the Fig 21, TaC show lowest onset potential of -0.32 V for methane formation. This suggests that among all the studied materials TaC catalyst is highly efficient for electrochemical conversation of CO into methane and low onset potential indicates that this catalyst requires less energy for CO to methanol formation as compared to other studied catalysts. The reaction pathways followed by TaC is *CO → *CHO → *CHOH → *CH 2 OH→ *CH 3 + OH→ *CH 4 + OH as shown in the Fig 21.

[0132] Like TaC two other catalysts, NbC and VC, also show promising catalytic activity for methane formation with the corresponding onset potential of -0.35 and -0.42 V, respectively. The reaction pathways followed by NbC and VC are *CO → *CHO —► *CH 2 O → *CH 2 OH→ *CH 2 → *CH 3 → *CH 4 and both catalysts have same path towards the methane formation. Among all the studied TMCs, TiC and WC catalysts show moderate catalytic activity for methane formation with the onset potential of - 0.59 and -0.67 V, respectively, and reaction pathways are *CO → *CHO → *CHOH → *CH→ *CH 2 → *CH 3 → *CH 4 which are same for both catalysts. In addition, HfC, MoC, CrC and ZrC also show their catalytic activity for methane formation with the onset potential of -1.0, -1.01, -1.12 and -1.23 V, respectively. HfC followed the same path as followed by TaC, CrC followed the same bath as followed by TiC and WC, MoC followed reaction pathway as *CO → *CHO → *CHOH → *CH 2 OH→ *CH 2 → *CH 3 → *CH 4 and ZrC has slightly different pathway which is *CO → *CHO → *CH 2 O → *CH 3 +O→ *CH 4 . The onset potential values of HfC, MoC, CrC and ZrC are more than threshold values we have in mind but for the formation of methane via the MVK mechanism these materials show promising results as shown in Fig 22 where onset potential values required for each candidate for the formation of methane and methanol is shown. Methane formation is shown via conventional surface mechanism, while notation of *CH 4 with satiric (*) indicate methane formation via MVK mechanism. ScC and YcC are not suitable for methane and methanol formation via surface mechanism therefore their bars are missing. Similarly, TaC is not producing stable methanol, so its bar is missing in this figure.Carbon vacancy migration and stability

[0133] NEB have been calculated to estimate the diffusion barrier (E a ) of carbon atom from the sublayer to the first layer (surface) when CH 4 is released during the MvK mechanism. This could be led to formation of all carbon atoms into methane and whole TMCs can decompose into parental metal. The energy difference ΔE were calculated as ΔE = E vac,2 - E vac,1 where E vac,2 is the energy of vacancy generated in sublayer and E vac,1 is the energy of vacancy generated in first layer and this energy difference determines the stability of carbon vacancy at the catalytic surface. In the findings, all materials show diffusion barrier greater than threshold value 1 eV as shown in Fig 23 and these migration energy values revel that all the studied TMCs have stable surface vacancy without migration of carbon atom from sublayer to first layer, and thus should be stable.

[0134] A promising candidate, MoC shows carbon migration energy value of 1.89 eV as shown in the Fig 24 rendering good stability.

Claims

1. A method for catalytic electrolytic reduction of CO2 and / or CO, the method comprising: a. providing an electrolytic cell containing at least one reaction chamber that has at least one anode and at least one cathode and at least one electrolyte between the anode and the cathode, wherein the at least one cathode comprises at least one catalyst comprising at least one carbide of one or more transition metal selected from the group consisting of Nb, W, Mo, V, Ti, Hf, Ta, Cr, Zr, Sc and Y; b. providing CO2 and / or CO in the electrolytic cell; and c. applying electrical potential to the electrolytic cell; whereby the CO2 and / or CO undergoes at least one reduction reaction at the cathode.

2. The method of claim 1, wherein the electrolytic reduction reaction results in formation of at least one product selected from methanol, methane, methanediol, formic acid, formaldehyde, ethanol, ethane, ethylene glycol, ethanediol, propane and propanol.

3. The method of any one of the previous claims 1, wherein the gas pressure at the at least one cathode is ambient pressure of about 1 atm.

4. The method of any one of the previous claims, wherein the electrical potential applied to the electrolytic cell is in the range of -2.0 V to +1.0 V using a reversible hydrogen electrode (RHE) as a reference.

5. The method of any one of the previous claims, wherein CO2 only is provided in the electrolytic cell, and wherein the carbide is one or more carbide of a transition metal selected from Nb, W, Mo, V, Ti, Hf, Zr and Ta the catalytic reduction resulting in formation of methane.

6. The method of any one of the previous claims, wherein CO2 only is provided in the electrolytic cell, wherein the carbide is one or more carbide of a transition metal selected from the group consisting of Nb and Ti, the catalytic reduction resulting in formation of methane.

7. The method of any one of the previous claims 1-4, wherein CO2 only is provided in the electrolytic cell, and wherein the carbide is one or more carbide of a transition metal selected from the group consisting of Cr, Hf, Mo, Nb, Zr, Ta, Ti, W and V, the catalytic reduction resulting in the formation of formic acid.

8. The method of any one of the previous claims 1-4, wherein CO2 only is provided in the electrolytic cell, and wherein the carbide is one or more carbide of a transition metal selected from the group consisting of Cr, Hf, Mo, Nb, Zr, Ta, Ti, W and V, the catalytic reduction resulting in formation of methanol.

9. The method of any one of the previous claims 1-4, wherein CO2 only is provided in the electrolytic cell, and wherein the carbide is a carbide of a transition metal selected from the group consisting of V and Mo, the catalyst reduction resulting in formation of methanediol.

10. The method of any one of the previous claims 1-4, wherein CO only is provided in the electrolytic cell, and wherein the carbide is one or more carbide of a transition metal selected from the group consisting of Mo, Nb, W, V, Ti, Zr, Hf, Cr, Sc, Y and Ta, the catalytic reaction resulting in formation of methane.

11. The method of the previous claim, wherein the carbide is a carbide of a transition metal selected from Mo, Ta, Nb and V.

12. The method of any one of the previous claims 1-4, wherein CO only is provided in the electrolytic cell, and wherein the carbide is one or more carbide of a transition metal selected from the group consisting of W, V, Nb, Ti, Cr, Zr, Mo and Hf, the catalytic reaction resulting in formation of methanol.

13. The method of the previous claim, wherein the carbide is a carbide of W.

14. An electrolytic cell for the reduction of carbon dioxide and / or carbon monoxide, comprising: an anode; and a cathode, the cathode comprising a catalyst comprising at least one carbide of a transition metal selected from Nb, W, Mo, V, Ti, Hf, Ta, Cr, Zr, Sc and Y.

15. A chemical reactor comprising at least one electrolytic cell as set forth in claim 14; and a power supply connected to the electrolytic cell.

Images