Electrodeposition method and product

Abstract

An electrocatalyst comprising CuNiFe nanoparticles on a conductive substrate is described where the nanoparticles comprise less than 5 at % Fe. The electrocatalyst may comprise part of an electrode wh

Description

Field of invention The invention relates to an electrodeposition method suitable for depositing a conformal layer of single or multi metallic systems, and products made from such electrodeposition. Background Water splitting is a sustainable technology to produce hydrogen, a net-zero fuel, offering energy independence and a profitable route to store renewable energy. In water electrolysers, the cathodes reduce protons and the anodes oxidize hydroxyl anions to complete the reaction. Water reduction occurs at ~0V while oxidation at anode occurs at 1,23V, putting anodes under high oxidative duress. The oxidative duress caused by applied oxidative potential is amplified due to production of protons, which lower local pH causing metal catalyst to leach out causing system failure. As water oxidation reaction is most common anodic reaction in all types of electrolysers, the similar system failure, very high cell potentials, and smaller yield is observed in CO2 conversion reaction. CO2 utilization is a core strategy of decarbonization energy sector, sustainment of circular carbon economy, and reuse of anthropogenic carbon. In order to achieve a smooth energy transition, it is very important to produce highly active, stable, robust, and economical anodes. Most of the anodes used for electrolysers belong to noble group of metals like IrO, RuO or Platinum group. As activity, stability, cost, and availability are most critical merits that need consideration while designing an anode for oxygen evolution reaction (OER), these choices perform better but fail at being cost-effective and active. Nickel and iron-based anodes are very commonly used for alkaline electrolysis and outperform IrO in turnover numbers but lack the long-time stability and corrosion resistance. It was revealed that presence of impurity iron in electrolyte was responsible for higher OER activity. The hypothesis was further established on testing different NiFe combinations and Ni in a pure iron free electrolyte. The tests confirmed the synergetic cooperation between the two metal sites for enhanced OER. However, the stability issue is still a big challenge. The cost is also increased by using multi-step, complex reaction of synthesis and activation. Summary The invention provides, in a first aspect, an electrocatalyst comprising a conductive substrate comprising thereon a layer of CuNiFe nanoparticles, wherein the CuNiFe nanoparticles comprise less than 5% Fe. The product of the invention is a CuNiFe-based, robust, stable, and scalable anode that is suitable for alkaline electrolysers for hydrogen, and / or carbon dioxide conversion to fuels. The catalyst offers unique and unprecedented stability for anodes under high oxidative (corrosive) currents for more than 500 hours without any decay. The anode also excels over current state-of-art anodes in overpotential, harboring <400 mV at 100 mA / cm2 current. Experimental work has shown that the electrocatalyst works very well as an anode both in half- and full-cell setups. The product of the invention also has a unique tendency to act as a bifunctional catalyst, with initial results mirroring platinum activity for hydrogen generation in an alkaline full cell. The invention also provides, in a second aspect, a method for depositing metal on a substrate, the method comprising providing a three-electrode cell comprising: a working electrode, wherein the working electrode is the substrate on which metal is to be deposited; a counter electrode; a reference electrode; and metal ions in an acidic aqueous solution; - subjecting the working electrode to a pulsed current in which each cycle comprises an ON state and an OFF state, wherein the OFF state comprises at least about 0.01 seconds at about zero current in every cycle, thereby depositing the metal on the working electrode. The invention also provides, in a third aspect, a substrate having deposited thereon a metal, the metal having been deposited according to the method of the second aspect; the substrate having deposited thereon the metal may be an electrocatalyst. The preparation method according to the invention and suitable for making the product of the invention is suitable for scale-up without adding complex process steps. There is no need for addition of any harsh or expensive additives and the method can complete in 5 minutes at SATP. The method is scalable and retains all the material properties at larger deposition areas. The invention also provides the use of the electrocatalyst of the invention as the anode and / or cathode in a process for alkaline water electrolysis. The invention also provides the use of the electrocatalyst of the invention as the anode and / or cathode in a process for CO2 reduction. The inventors have developed a single step pulsed electrodeposition method which is able to fabricate a strongly adhered, copper-rich, stable, and scalable CuNiFe anode. The electrolytic bath comprises simple metal ions and slightly acidic pH. No additives or complex treatments are required, and the thin film is obtained in -165 seconds irrespective of the dimension needed. The film is corrosion resistant for -500 hours at 100m A / cm2. The method is also suitable for depositing mono-, bi-, tri- and multi-metallic systems of metals other than Cu, Fe and Ni and for purposes other than electrocatalysts. Brief description of drawings Figure 1 is a graph of a series of pulse cycles; Figure 2 is a graph of cyclic voltammograms (CVs) at various pH levels; Figure 3 is a graph of CVs over various cycle numbers; Figures 4A and 4B show CVs on different conductive substrates and stability of the resulting catalysts; Figure 5 is a graph of CVs of mono-, bi- and tri-metallic systems; Figure 6 shows structural and electronic characterization of CuNiFe catalyst through XRD (Figure 6A), SEM (Figure 6B), Raman spectra (Figure 6C), and XPS (Figures 6D, 6E, 6F and 6G); Figure 7A is a graph of iR uncompensated CV of CuNiFe in 1M KOH in an H-Cell vs NiF (Nickel foam); Figure 7B is a graph of chronopotentiometric analysis at 100 mA / cm2 of CuNiFe and of NiF; Figure 7C is a CV showing the oxidation of the nickel and iron in the CuNiFe nanoparticles, namely Ni(0) to Ni(ll), Fe(l I) to Fe(l 11), and Ni(ll) to N i(l 11) or (IV). Figure 8 compares CuNiFe and lrOx as CVs (Figure 8A) and as chronopotentiometric plots (Figure 8B) Figure 9 graphs stability tests performed on CuNiFe in 1M KOH in an H-cell at applied currents of 100 mA / cm2 (Figure 9A), 200 mA / cm2 (Figure 9B) and 500 mA / cm2 (Figure 9C); Figure 10A is a graph of pH dependent OER activity observed on CuNiFe, signalling non-concerted proton decoupled rate determining step; Figure 10B is a graph of the effect of Cu concentration on the activity of CuNiFe for OER; Figure 11 is a graph of full cell tests of CuNiFe in alkaline electrolysers for alkaline water electrolysis; Figure 12 is a graph of chronopotentiometric analysis of a large-scale anode made according to the invention; Figure 13 shows SEM images at five different points on the surface of the large-scale anode made according to the invention; Figure 14 shows electronic characterization of 1 cm x 1 cm electrodes extracted from the large electrode through CVs (Figure 14A) and through chronopotentiometry (Figure 14B); Figure 15, is TEM image of a CuNiFe film made according to the invention (separated from the conductive substrate for FIB-TEM analysis); Figure 16 is a graph of average size distribution of the deposited nanoparticles calculated from Fiji image analysis using an SEM image; Figure 17 is a Weibull distribution curve for determination of the d50 and d100 particle diameter, with data drawn from the image analysis data from Figure 16. Detailed description The invention provides, in a first aspect, an electrocatalyst comprising a conductive substrate comprising thereon a layer of CuNiFe nanoparticles, wherein the CuNiFe nanoparticles comprise less than 5% Fe. The electrocatalyst may be an electrode. The electrode may be an anode, a cathode, or a bifunctional electrode. For example, the electrocatalyst of the invention may be used as the anode in a water electrolysis process, thereby replacing existing rare and expensive materials that are used in the art for this purpose, such as iridium oxide. Testing has shown that the electrocatalyst of the invention has bifunctionality and can act as both anode and cathode. The conductive substrate may have any suitable form and surface texture underneath the CuNiFe nanoparticulate layer. The conductive substrate may be metallic. The conductive substrate may be a metal foil, such as a tantalum foil. The conductive substrate may be porous, for example a metal foam such as nickel foam (also referred to as NiF or NF). The conformality of the nanoparticulate layer is not significantly affected by the choice of conductive substrate. The layer of CuNiFe nanoparticles may comprise at least 60% Cu, such as at least 70% Cu, such as at least 75% Cu. The layer of CuNiFe nanoparticles may comprise from 0.5 to 5 % Fe, such as from 0.5 to 4 % Fe. The layer of CuNiFe nanoparticles may comprise from 5 to 15 % Ni. The % amount of each element herein is quoted in atomic percentage unless specified differently. Atomic percentage may be determined by X-ray photoemission spectroscopy (XPS). In one example, the XPS data showed a CuNiFe surface to be composed of ~80% Cu, 16% Ni, and 4.7% Fe on NiF and 84% Cu, 13%Ni, and 8% Fe on Titanium foil. The % can be controlled by altering the pH which controls the deposition competition between the participating ions (Cu>Ni>Fe preferred deposition). The layer of CuNiFe nanoparticles comprises less than 5% Fe and may comprise at least 60% Cu and at least 5 % Ni. Optionally, Cu, Ni and Fe and their (oxy) hydroxides together make up 100% of the composition of the layer. The Cu in the CuNiFe nanoparticulate layer may be at least 75% in the form of Cu(0), i.e. metallic copper, preferably at least 85% Cu(0), as determined, for example, by XPS In Figure 6E, for example, the shape of the peak is almost symmetrical indicating the presence of a single oxidation state of copper i.e. Cu(0). References to Cu, Ni and Fe, and to CuNiFe, with respect to the electrocatalyst of the invention include the (oxy)hydroxides of these metals and this trimetallic system. The term “CuNiFe” is used for brevity. Some Fe and Ni on the surface or the layer, when formed in water, may be present in the form oxyhydrides. As indicated above, the Cu may be mostly, if not all, Cu(0), i.e. mostly, if not all, metallic copper. The formation of oxyhydroxides is well documented in literature (e.g. see He, Z., Zhang, J., Gong, Z. et al. Activating lattice oxygen in NiFe-based (oxy)hydroxide for water electrolysis. Nat Commune, 2191 (2022). https: / / doi.org / 10.1038 / s41467-022-29875-4 ; and Yang H, Dong C, Wang H, Qi R, Gong L, Lu Y, He C, Chen S, You B, Liu H, Yao J, Jiang X, Guo X, Xia BY. Constructing nickel-iron oxyhydroxides integrated with iron oxides by microorganism corrosion for oxygen evolution. Proc Natl Acad Sci USA. 2022 May 17;119(20):e2202812119. doi: 10.1073 / pnas.2202812119. Epub 2022 May 9. PMID: 35533282; PMCID: PMC9171921.). When a metal comes in contact with alkaline electrolyte under oxidative potential it forms M-OH followed by transfer of another O forming M-OOH, it has also been identified one of the intermediates in OER. The presence of oxyhydrides can be inferred from the oxidation peaks in CV (see Figure 7A). When the Nickel is oxidized it goes from Ni(ii) to Ni(iv). An additional figure showing the transition can be seen in Figure 7C. There is oxidation of Fe and Ni showing simultaneous formation of oxyhydroxides. The layer of CuNiFe nanoparticles may substantially cover the conductive substrate, or completely cover the conductive substrate. Preferably the CuNiFe nanoparticles form a continuous, unbroken layer on the conductive substrate. The nanoparticles in the layer of CuNiFe nanoparticles may have a mean diameter of from about 50 nm to 200 nm, optionally 100 to about 150 nm, optionally 110 nm to 130 nm, as measured by image analysis of an SEM image, e.g electronic image analysis, e.g. Fiji image analysis (image analysis using Fiji software, which is available open source and an accepted way of determining particle size distributions and mean diameters of particles in the art), of an SEM image The image analysis determines the mean diameter from an SEM image from: the sum of the particle diameters divided by the number of particles. The number of particles in an image used to determine the mean diameter should be at least 10, optionally at least 20, optionally at least 30, optionally at least 50, optionally from 10 to 100, optionally 20 to 50. The nanoparticles in the layer of CuNiFe nanoparticles may have a particle size distribution d50 of from 10 nm to 200 nm, optionally from 50 nm to 150 nm, optionally from 70 nm to 130 nm, optionally from 80 nm to 120 nm, optionally about 100 nm, e.g. as determined from a Weibull graph, generated using, for example, image analysis data from an SEM image, e.g. image analysis data using Fiji software. The nanoparticles in the layer of CuNiFe nanoparticles may have a particle size distribution d100 of from 100 to 300 nm, optionally from 150 to 250 nm, optionally from 180 to 220 nm, optionally from 180 nm to 220 nm, optionally from 190 nm to 210 nm, optionally about 200 nm, e.g. as determined from a Weibull graph, generated using, for example, image analysis data from an SEM image, e.g. image analysis data using Fiji software. The nanoparticles in the layer of CuNiFe nanoparticles may have a particle size distribution d50 of from 10 nm to 200 nm, optionally from 50 nm to 150 nm, optionally from 70 nm to 130 nm, optionally from 80 nm to 120 nm, optionally about 100 nm, e.g. as determined from a Weibull graph, generated using, for example, image analysis data from an SEM image, e.g. image analysis data using Fiji software and a d100 of 300 nm or less, optionally 250 nm or less, optionally 220 nm or less, optionally 210 nm or less, about 200 nm or less. CuNiFe nanoparticles produced using the method described herein have a small particle size distribution, i.e. with low polydispersity, both in terms of size and shape. If a surface has particles of the same size and shape (monodisperse or with very low polydispersity index (PDI)<1) they work as a uniform array producing and behaving similarly which promotes the reaction as no other reaction or pathway of reaction occurs. Compared to known electrocatalysts, the product of the invention has numerous benefits. For example, there is no need to include any rare or expensive elements, whereas the state of the art electrocatalyst for water electrolysis is iridium oxide. Iridium is both rare and expensive relative to Cu, Fe and Ni. Replacing IrOx with the product of the invention may contribute to wider use of water electrolysis and thus the hydrogen economy, since the anode plays a key role in the hydrogen evolution reaction (HER). Similarly, use of the electrocatalyst of the invention, which is comparatively cheap and uses abundant materials, may contribute to carbon circularity by making CO2 reduction a viable process. The invention also provides, in a second aspect, a method for depositing metal on a substrate, the method comprising - providing a three-electrode cell comprising: a working electrode, wherein the working electrode is the substrate on which metal is to be deposited; a counter electrode; a reference electrode; and metal ions in an acidic aqueous solution; subjecting the working electrode to a pulsed current in which each cycle comprises an ON state and an OFF state, wherein the OFF state comprises at least about 0.01 seconds at about zero current in every cycle, thereby depositing the metal on the working electrode. The method may result in nanoparticles comprising the metal being deposited on a conductive substrate (which may be the working electrode). The metal deposited may comprise one, two, three or more, elements from the Periodic Table. The method may be used to deposit any metallic system on a conductive substrate (i.e. the working electrode in the method). The conductive substrate for the second aspect may be as described above in relation to the first aspect. It is particularly useful for manufacturing the electrocatalyst of the first aspect (i.e. in which the metal ions in the method are copper, nickel and iron ions, thereby depositing a CuNiFe nanoparticles on the working electrode or conductive substrate), in which the method enables preparation of stable, scalable and active anodes for alkaline electrolysers; the function of electrocatalysts made in this manner is superior both in half-cell as well as full cell conditions compared to known OER / HER electrode materials. However, other electrocatalysts (i.e. not in accordance with the first aspect) can also be made using the method of the second aspect. The pulsed current of the method controls the shape and homogeneity of the deposited surface. Co-deposition of bimetallic or trimetallic systems (i.e. metals comprising, respectively, two or three metallic elements from the Periodic Table), even multi-metallic systems, is feasible with the inventive method. The different electrode potentials of metal ions in bi-, tri-, or multi-metallic systems may be exploited to control the ultimate composition of the deposited layer of metal ions, by controlling the nature of the pulsed deposition, for example the strength of the applied current. The method may be used deposit nanoparticles comprising the metal (which may, for example, be a bimetallic or trimetallic system) in the form of a layer on a conductive substrate (e.g. the working electrode in the method) and the nanoparticles of metal may have a mean diameter of from about 50 nm to 200 nm, optionally 100 to about 150 nm, optionally 110 nm to 130 nm, as measured by image analysis of an SEM image, e.g electronic image analysis, e.g. Fiji image analysis (image analysis using Fiji software, which is available open source and an accepted way of determining particle size distributions and mean diameters of particles in the art), of an SEM image. The image analysis determines the mean from an SEM image from: the sum of the particle diameters divided by the number of particles. The number of particles in an image used to determine the mean should be at least 10, optionally at least 20, optionally at least 30, optionally at least 50, optionally from 10 to 100, optionally 20 to 50. The method may be used deposit nanoparticles comprising the metal in the form of a layer on a conductive substrate and the nanoparticles of metal may have a particle size distribution d50 of from 10 nm to 200 nm, optionally from 50 nm to 150 nm, optionally from 70 nm to 130 nm, optionally from 80 nm to 120 nm, optionally about 100 nm, e.g. as determined from a Weibull graph, generated using, for example, image analysis data of an SEM image, e.g. image analysis data using Fiji software. The nanoparticles of the metal may have a particle size distribution d100 of from 100 to 300 nm, optionally from 150 to 250 nm, optionally from 180 to 220 nm, optionally from 180 nm to 220 nm, optionally from 190 nm to 210 nm, optionally about 200 nm, as determined by image analysis of an SEM image. d100=200nm, e.g. as determined from a Weibull graph, generated using, for example, image analysis data from an SEM image, e.g. image analysis data using Fiji software. The method may be used deposit nanoparticles comprising the metal in the form of a layer on a conductive substrate (e.g. the working electrode in the method) and the nanoparticles of metal may have a particle size distribution d50 of from 10 nm to 200 nm, optionally from 50 nm to 150 nm, optionally from 70 nm to 130 nm, optionally from 80 nm to 120 nm, optionally about 100 nm, e.g. as determined from a Weibull graph, generated using, for example, image analysis data from an SEM image, e.g. image analysis data using Fiji software and a d100 of 300 nm or less, optionally 250 nm or less, optionally 220 nm or less, optionally 210 nm or less, about 200 nm or less. With the inventive method, a conformal layer may be deposited on the working electrode (conductive substrate). The conformal layer has few or no gaps and is highly regular. Microscopy reveals an absence of undesirable structures such as dendrites or “nanoflowers", see for example the SEM in Figures 6B and 13 and the TEM in Figure 15. The microscopy images also demonstrate that the microstructure is substantially homogeneous; Figure 13 further demonstrates that the surface is regular across random sample areas of a deposited metal layer. The conformal layer does not come off with sonication, which is a problem with deposited metal layers in some prior art methods. The TEM image in Figure 15 shows a CuNiFe layer made by acidic aqueous pulsed deposition. The deposited trimetallic layer was stripped away from the substrate to facilitate TEM analysis. The TEM images illustrate the homogeneous, nanoparticulate nature of the deposited surface. The pulsed current used in the method may be applied for a minimum of 5 cycles, optionally a minimum of 10 cycles, optionally a minimum of 20 cycles, optionally a minimum of 30 cycles, optionally a minimum or 40 cycles, optionally a minimum of 50 cycles, preferably a minimum of 100 cycles. A “cycle” is defined herein as a combination of a single “ON” state of the pulsed current and an “OFF” state. The pulsed current may be applied for up to 400 cycles, for example up to 350 cycles. In some embodiments, the pulsed current is applied for about 300 cycles. The pulsed current is preferably applied for just sufficient cycles such that all active deposition sites on the conductive substrate are occupied. If the pulsed current is applied for less time then active deposition sites on the conductive substrate remain unoccupied, and activity will not be as high as a substrate on which all active deposition sites have been occupied by the deposited nanoparticles. If the pulsed current is continued for many more cycles than required for occupation of all active deposition sites on the conductive substrate, the electrocatalyst exhibits no greater performance (for example for OER or HER), but attracts excess metal to the surface layer, which wastes material. The current density of the ON state of the pulsed current may be at least about -2 mA / cm2, such as at least about -5 mA / cm2, such as at least about -10 mA / cm2, such as at least about -20 mA / cm2, such as at least about -50 mA / cm2. The current density of the ON state of the pulsed current may up to about -500 mA / cm2, such as up to about -400 mA / cm2, such as up to about -300 mA / cm2, such as up to about -200 mA / cm2, such as up to about -150 mA / cm2, such as up to about -130 mA / cm2. In the present case, “at least” and “up to” refers to the magnitude of the current density. For electrodeposition, the current density is negative. In some embodiments, the current density of the ON state is from about -5 mA / cm2 to about -500 mA / cm2, such as from about -10 mA / cm2 to about -300 mA / cm2, such as about -10 mA / cm2 to about -200 mA / cm2, such as about -50 mA / cm2 to about -150 mA / cm2, such as from about -70 mA / cm2 to about -130 mA / cm2. The ON state may have a length of from about 0.1 to 1.0 seconds per cycle, preferably from about 0.2 to 0.8 seconds per cycle. The OFF state may have a length of from about 0.01 to about 0.1 seconds per cycle, preferably from about 0.02 to about 0.08 seconds per cycle. The ratio of duration of the ON state to the OFF state may be from about 5:1 to about 15:1. Although the pulse is described as ON and OFF, the OFF state need not be exactly zero. A low applied current would fulfil the function of allowing restoration of concentration of the metal ions in solution in the proximity of the working electrode (conductive substrate). The term “about zero” means a current at or near zero that facilitates this recuperation of concentration near the working electrode. In some embodiments, the applied current is at zero during the OFF state. The pH of the acidic aqueous solution may be at about 6.5 or less, preferably 6 or less, such as from about 0.5 to about 6, such as from about 1 to about 3. The acidity of the solution may be selected depending on the desired stoichiometry of the end product for bi- and multi-metallic systems, since the pH affects the competition between different metal ions. The temperature and pressure at which the method is conducted may be ambient. Ambient conditions, also referred to as SATP or standard temperature and pressure, which may be taken to be about 1 atm and about 20 to 25 °C In some embodiments, the method is conducted at a temperature (temperature of the acidic aqueous solution) of from about 5 °C to about 90 °C, such as from about 10 °C to about 60 °C, such as from about 10 °C to about 50 °C, optionally from about 10 °C to about 30 °C, optionally from about 15 °C to about 30 °C. Providing metal ions in an acidic aqueous solution may comprise providing two or more different metal ions, thereby depositing a bimetallic or multi-metallic system, which may be a trimetallic system. In some embodiments the method provides three different elements of metal ions in solution, each of which is deposited on the working electrode. The metal or metals of the metal ions may be or comprise transition metals. The metal ions may comprise one or more of Cu, Ni, Fe, Co, Mn, Zn, Mo, Ti, V, W. For example, the metal ions may comprise Ni and Co; Zn and Co; Ni and Fe; Co and Fe; Mo and Ni; Mo, Ni and Co; Ni and V; Mo and V; Mo and Ti; Co and Mo; W and Mo; Ti and V; Wand Ti; or combinations of Cu, Ni and Fe. The metal ions may comprise Cu, Ni or Fe alone; Cu and Ni; Cu and Fe; Ni and Fe; or Cu, Ni and Fe. The method of the invention may therefore be used to deposit a nanoparticulate layer of Cu, of CuNi, of CuFe, of NiFe, or of CuNiFe; these products may be useful as electrocatalysts. The catalysts, e.g. NiFe catalysts, may also be useful for other reactions, including, but not limited to catalysts in Fischer Tropsch reactions. In the method, equimolar or substantially equimolar amounts of two or more different metal ions may be provided at the start of the process. Due to the competitive deposition between metal ion types in systems involving two or more different metals, some ions may remain in solution at the end of the process; the excess ions may be recycled for use in a subsequent deposition process. In some embodiments, the start of the process provides Cu, Fe and Ni ions in an equimolar amount; excess Fe and Ni ions may be recycled for a subsequent deposition process. In some embodiments, the ions provided are Cu, Fe and Ni. In the deposited layer, the Cu may be mostly Cu(0), i.e. mostly metallic copper. There may be only few hydroxides and oxides of Cu, because Fe has a lower electrochemical potential and is largely oxidized in favour of Cu to become Fe(lll+) whilst Cu can mostly remain as Cu(0). The working electrode may comprise any suitably conducting material, for example, a metal, an alloy of metals, and / or carbon. The electrode may comprise a transition metal for example, a transition metal selected from any of groups 9 to 11 of the Periodic Table. The electrode may comprise a metal selected from, but not limited to, rhenium, iridium, palladium, platinum, nickel, copper, indium, rubidium, silver and gold. The electrode may be a gold macroelectrode. If the electrode comprises carbon, the carbon may be selected from edge plane pyrolytic graphite, basal plane pyrolytic graphite, a glassy carbon, boron doped diamond, highly ordered pyrolytic graphite, carbon powder and carbon nanotubes. The working electrode may be porous or have a cellular structure. The working electrode may be metallic, optionally a metal foil or a metal foam, optionally Ti foil, Ni foil, Ni mesh or Ni foam (also abbreviated to NiF). A metallic foam is a metallic material having cellular structure. The metal foam is preferably an open celled foam. In some embodiments, the working electrode is NiF and the metal ions are Cu, Fe and Ni ions. The method of the invention achieves a similar microstructure for a particular deposited metallic nanoparticulate layer regardless of the composition or roughness of the working electrode (the conductive substrate); the length of the OFF state may be adjusted to account for an adjustment of diffusion required for different materials used for the working electrode. The microstructure of the deposited metal layer may vary depending on the metallic system involved. For example, a single metallic system of Cu will exhibit larger particle size than a CuNiFe trimetallic system, because Cu nanoparticles tend to grow quickly in an acidic system. However, no dendrimers, nanoflowers or other undesirable microstructures were observed when single, bi- and tri- metallic systems were tested and a nanoparticulate conformal layer was formed in all cases using the method of the invention. As shown in the examples, the method of the invention can be scaled economically without loss of desirable properties such as catalyst function. In testing, the electrocatalysts made according to the method of the invention exhibited high stability and endurance under large current densities. Particularly relevant for scalability and 5 improved environmental outcomes are the relatively mild reaction conditions for the method of the invention. No binder is required; no harsh additives are required; the method can be conducted at ambient temperature and pressure; the precursors are simple (a slightly acidic solution and abundant transition metal ions can be used); standard equipment can be used, for example a simple glass vessel; and the method 10 can be concluded in five minutes. Accordingly, the present invention provides the use of an electrocatalyst as described herein or substrate having the metal(s) deposited thereon as described herein as the anode and / or cathode in a process for alkaline water electrolysis. 15 Accordingly, the present invention provides the use of the electrocatalyst as described herein or substrate having the metal(s) deposited thereon as described herein as the anode and / or cathode in a process for CO2 reduction. Examples Preparation of electrodes and materials synthesis: An electrodeposition method was optimised for different deposition parameters to deposit a conformal, highly active, and stable ternary metal system based on Cu, Ni, and Fe. A conventional 3-electrode cell was used with nickel foam as working electrode, platinum electrode as counter and Ag / AgCI as reference electrode for the process. An aqueous bath containing 5 mM each of CuCl2.2H2O, FeCl3.6H2O, and NiNo3.6H2O and 30 mM H2SO4 was used as the deposition solution without addition of any other surfactants, binders, or additives at standard ambient temperature and pressure. A pulsed current method was used over a constant deposition to allow growth of homogenous, oriented, and unique microstructured thin film. The deposition time, deposition pH was optimised to create a thin film rich in copper (>79%) which contributes to higher surface area while maintaining an impurity level (<5%) Iron concentration. It is established that lower concentration of iron along with nickel and copper accelerates the reaction kinetics. The impurity level approach applied was optimised for the deposition time and pH of solution. In a representative deposition process, the inventors applied a pulse of-100 mA / cm2 for an ON cycle of 0.5 seconds followed by an OFF pulse of 0 mA / cm2 for 0.05 seconds. The pair of pulses were repeated for 300 times, making total deposition time of 165 seconds. The catalyst obtained constitutes Cu, Ni, and Fe (oxy)hydroxides hence referred as CuNiFe for short. The deposition method is simple, one pot, works at standard temperature and pressure and can be used to formulate mono / bi / ternary metal system for electrocatalysis or thin films of any dimension needed without loss of surficial or structural properties. The pulse cycle is shown in Figure 1. pH of electrolytic bath A series of electrolytic baths consisting of 5 mM each of Cu (II), Ni (II), and Fe (III) ions and H2SO4 concentration ranging from 20-40 mM were made (CuNiFe_20mM, CuNiFe_30mM, CuNiFe_32mM, CuNiFe_40mM). The ON pulses of-100mA / cm2for0.5 s followed by OFF pulses for 0.5 s were applied for 300 cycles of ON and OFF pulses. The deposition process resulted in formation of thin films in each case and were tested for water oxidation in H-cell. Figure 2 graphs cyclic voltammograms in 1M KOH in H-cell using 3-electrode system. Lower concentrations of H2SO4 cause less competition between Cu (II) and Fe (III) ions resulting in Ni and Fe rich films. At higher sulphuric acid concentrations Cu deposition predominates, as indicated in the area under oxidation peak in CV (CuNiFe_40mMH2SO4). From the activity plots, solution containing 32mM H2SO4 (40 pL725 mL) performed best, and this catalyst and process parameters were chosen for further analysis. Deposition time A conformal, compact, homogenous microstructure of the catalyst plays a vital role in intrinsic activity and long-term stability. To exert better control over the thickness, growth, and orientation of deposited film, the inventors tested different number of deposition cycles (100, 200, 300, 350 cycles). Figure 3 shows the oxygen evolution activity on the deposited samples, an optimum thickness with a desirable conformal microstructure achieved with 300 cycles of deposition showed highest activity in a H-cell. The graph of Figure 3 shows cyclic voltammograms in 1M KOH in H-cell using a 3-electrode system. At lower deposition times the material loading is less and hence less activity, the possible reason for lower activity might be less surface area as demonstrated by respective area under oxidation peak (least in 100 cycles, increases up to 300 cycles then reduces again). The sample deposited with 32mM H2SO4 and for 300 cycles showed best activated and a unique microstructure. The pH of the electrolytic bath was sufficient to deposited oriented copper rich thin fil. In the inventive method, iron deposition is restricted in favour of copper; this competition leads to deposition of copper rich films with impurity level of Fe concentration. The nickel concentration is also lowered but not as much as the lowered level of iron. Conductive substrate The inventive deposition process can be used to deposit controlled microstructures by a slight tweak or as such on most conductive substrates. The process creates a regulated mass flow of depositing ions such that thin film ends with a compact microstructure. The inventors tested the inventive deposition process on metal foil (maintains a planar flow) and a porous film (non-planar flow and associated diffusion) for the generality. Figures 4A and 4B show the comparison of OER activities of CuNiFe deposited on Ti metal foil and nickel foam (NiF). The cyclic voltammograms (CVs) show that CuNiFe is deposited in both cases are highly active. The higher current observed in CuNiFe is mostly because of porous substrate which enhances surface area. Demonstration of similar activities on metal or porous substrates indicates the activity for OER on CuNiFe is mostly intrinsic and not merely a surface area enhancement. The activity is a synergism between the three metal ions creating dispersed active sites that are stabilised and hence offer high turnover numbers. The stability comparison at 100 mA / cm2 also corroborates the intrinsic nature of the activity as they are stable on both foils with slightly different overpotentials. The stability on both substrates also confirms the strong adhesion between substrates and catalyst made from the special deposition parameters. Figures 4A and 4B illustrate cyclic voltammograms in 1M KOH in H-cell using 3-electrode system on CuNiFe@Ti and CuNiFe@NiF. Although the activity for OER is better on NiF substrate there is higher activity of the material on Ti foil, which suggests high intrinsic activity of CuNiFe. The catalyst was stable on both NiF as well as Ti. Metallic system The inventive process was used with similar electrolytic solution to deposit mono-, bi-, and tri-metal systems (Cu, CuNi, CuFe, NiFe, CuNiFe). The process was able to deposit thin films for all metals. This gives an insight into the general and broader applicability of the deposition process for a controlled compact microstructure. Figure 5 shows the OER activity on the deposited mono-, bi-, and tri-metallic systems on NiF by using the same deposition process. The graph illustrates cyclic voltammograms in 1M KOH in H-cell using 3-electrode system on Cu, CuNi, CuFe, NiFe, CuNiFe and demonstrates that the order of activities is mono-< bi-<tri-metallic system. The order indicates the synergistic cooperation between different metal centres for OER. CuNi, and CuFe activity order also provides insights into the need of control over solution pH to enrich catalyst with copper while limiting the co-deposition of Ni and Fe. The films show lesser activity than NiFe film but higher than Cu. The process can be tailored with slight modification for other metal systems consisting of single to polymetallic ions. Product characterization Inventive CuNiFe thin films on nickel foam substrate were thoroughly characterized for structural and catalytic properties. X-ray diffraction (XRD) analysis (Figure 6A) shows the formation of CuNiFe mixed oxides. The peaks corresponding to NiFe-oxides and Copper oxide are found at 30.4 ° and 38.6°’ respectively. The scanning electron microscopy (SEM) image (Figure 6B) shows a conformal layer of CuNife nanoparticles. The presence of a compact, conformal microstructure imparts higher resistance towards leaching or corroding oxidation to the film, exhibiting high activity and stability. EDX mapping showed the distribution of elements across the thin film. Elemental distribution shows high percentage of Cu and Ni, copper from deposition and Ni from being present on surface and substrate but shows less percentage of Fe throughout the surface proving that iron is present at impurity levels to boost the OER activity. Lower concentration of oxygen suggests presence of metallic core which enhances the conductivity and thus better charge transfer. Raman spectra (Figure 6C) confirm the formation of CuNiFe. Peaks were observed for Ni-O, O-Cu-O, Fe-0 peaks from 200-800 cm-1. X-ray photoemission spectroscopy (XPS) (Figures 6D to 6G) was used to probe further the electronic structure. The XPS spectra for Fe (III) showed that iron is present mostly in +2 oxidation state, presence of small iron concentration in nickel foam is also seen as listed in its commercial properties. From the XPS spectra, concentration of iron in pure nickel foam is >8% while it is less than 5% in CuNiFe film. The elemental scan of copper showed that copper is mostly in metallic state with very low concentration of oxides. This also confirms catalyst film being at conductive metallic core enhancing charge transfer. The elemental scan of Ni in nickel foam and CuNiFe@NiF showed presence of Ni (II) in both with a slight shift towards higher binding energies indicating presence of some Ni2Oa along with Ni (OH)2. Similar shifts were found in the elemental scan of O1s, indicating shift from Ni (OH)2 to Ni2O3 and NiOOH. Electrochemical measurements All electrochemical measurements were recorded in a H-cell with alkaline exchange membrane unless stated otherwise. 1M KOH was used as electrolyte, platinum mesh as counter electrodes and Hg / HgO as reference electrode. The electrochemical polarization curves are reported as such without any iR correction to indicate the maximum voltage needed for the cell operation. Figure 7A is an iR uncompensated voltammetry of CuNiFe in 1M KOH in an H-Cell vs NiF and shows the activity towards OER on NiF and CuNiFe@NiF. The overpotential for 25mA / cm2 shifted by -140 mV towards negative from NiF to CuNiFe implying higher activity of the catalyst. The deposited CuNiFe@NiF was also compared with commercially available IrO-GDE for OER in alkaline solutions. The inventors also tested the activity and stability of CuNiFe vs NiF. Figure 7B shows the stability chronopotentiometry graphs at 100mA / cm2. CuNiFe shows less overpotential as well as higher stability over NiF confirming its better OER performance in alkaline media. IrOx is used as a commercially available anode in alkaline electrolysers. The inventors used IrOx deposited on gas diffusion layer (GDL) to test the viability of CuNiFe@NiF catalyst as anode in 1M KOH solutions. Figure 8A shows the CV curves on CuNiFe and commercially-available lrOx, in 1M KOH. In a H-cell CuNiFe is a better anode for oxygen evolution than lrOx. Figure 8B shows the chronopotentiometric plots in similar experimental conditions and shows higher stability at 100 mA / cm2 for CuNiFe compared to IrOx. On an average 1cm2, CuNiFe anode needs 800mV less overpotential than a system with IrOx as anode. Figures 9A-C are graphs of stability tests performed on CuNiFe at (a) 100, (b) 200, and (c) 500 mA / cm2 applied currents in 1M KOH in an H-cell. The data is iR uncorrected and measured in a H-cell. The stability of CuNiFe@NiF was unprecedented as the system was stable at 100, 200, and 500 mA / cm2. Figure 9A shows stability of CuNiFe at 100mA / cm2 in a H-cell. The catalyst was stable for more than 500 hours at 100mA / cm2 applied current. The catalyst was stable for 200mA / cm2 for more than 300 hours (Figure 9B) and did not degrade even at 500mA / cm2 for measurement time of 24 hours (Figure 9C). The high activity of the CuNiFe catalyst can be ascribed to the synergistic interaction between the metal ions. Figure 5 confirms the cooperative interaction between the metal ions, from the activity trend observed, mono-<bi-<tri-metallic system. It is endorsed widely in research that tri-metallic systems function better for water oxidation reaction. Few of the reasons for higher activity in ternary systems can be accredited to rich conductive metal core (in these examples: copper), highly active impurity level iron and nickel sites and stabilising copper oxide outer layer. Furthermore, CV tests under different pH were recorded (Figure 10A) to probe the mechanistic details. The CV polarization curves shows pH dependent activities indicated there is probably a chemical proton transfer decoupled rather than a concerted proton coupled electron transfer rate determining step. Incorporation of copper in FeNi system imparts higher surface area to the catalyst resulting in higher OER activity. Copper also influences the OER mechanism making it a bulk intrinsic activity. Figure 10B shows the effect of Cu concentration on the activity of the CuNiFe catalysts. The concentration of Fe and Ni was constant at 5mM each. At low concentration of copper, CuNiFe shows lesser activity and an associated smaller area under the oxidation peak. At higher concentration, the surface area is high, and activity is higher but with higher overpotentials and corrosion more readily than at optimum concentration of copper (5mM). Evaluation as an electrode in an alkaline electrolyser full=cell setup The fabricated CuNiFe@NiF based thin film was used in a 2-electrode, full cell setup at standard and ambient temperature and pressure conditions for alkaline water electrolysis (AEMWE). Figure 11 shows the cell potential with different electrode combinations. When Pt was used as cathode and commercially available lrOx-GDE as anode, the cell potential needed to maintain current of -100mA / cm2 was -4.5 V and continuously increased with high rate. However, when the lrOx-GDE anode was replaced with CuNiFe, a lowering of cell potential was observed, from -4.75V to -3.75V. In addition, rate of degradation is far less than in Pt||lrO-GDE couple. This demonstrates the superiority of deposited CuNiFe as anode in alkaline water electrolyser. The inventors also tested the bifunctionality of the deposited CuNiFe films. A chronopotentiometric test at 100mA / cm2 using CuNiFe both as anode and cathode was done in 1M KOH solution at standard temperature and pressure (SATP). The overall cell potential is almost equal to the one with Pt as cathode. The unique feature of the cell thus constructed is the stability of the couple over >30 hours of operation. This further confirms the intrinsic high activity of fabricated CuNiFe for charge transfer for a redox reaction. As can be seen in Figure 11, the comparative full cell tests using Pt cathodes and anodes either commercially available or inventive CiNiFe shows that the inventive CuNiFe performs better than IrO. The couple made of CuNiFe as both cathode and anode showed promising activity and stability as equal to Pt used as cathode. Larger scale testing The developed electrodeposition process is a single step, one pot synthesis technique that can be used to fabricate any dimension anode in minutes without any complications. To test the process for scalability a 45 cm2 electrode was cut from activated NiF substrate. The electrode was placed in a simple beaker with a Pt anode and Ag / AgCI reference electrode. The electrolytic bath solution was similar to that described in the examples above. After operation of 300 cycles of ON and OFF current pulses (165 seconds), a thin film of CuNiFe was deposited on the substrate. The electrode was tested as an anode in a large alkaline electrolyser. The electrode has retained the desirable catalytic properties and was stable for 24 hours of measurement at an applied current of 4.5 A in 1M KOH solution. The overpotential at 100mA / cm2 was <400 mV same as observed in lab scale electrodes (1cm2). Figure 12 shows the activity and stability of the large-scale electrode; in particular, Figure 12 is a chronopotentiometric analysis of the anode at 4.5 ampere current in which the electrode shows only 1.4 V overpotential for a current of 4.5 ampere. The activity analysis confirms the scalability of the optimised process without losing any performance on going from small to large. This opens avenues for using this deposition process for industry relevant large surface area electrodes. In a comprehensive empirical investigation designed to substantiate the efficacy of the deposition technique for conformal active electrodes, a sizable electrode measuring 5 cm x 5 cm was partitioned into five distinct sections, from each of which discrete 1 cm x 1 cm small electrodes were extracted. Each 1 cm x 1 cm electrode, obtained from the extraction process, underwent individual testing for microstructure and electrochemical activity within a 1M KOH solution contained within an H-cell. From the SEM analysis it is obvious the microstructure is similar on each selected point from the large electrode. Figure 13 shows the SEM images collected at the different points. The microstructure at various points is similar, confirming the homogeneity of film and applicability of the deposition process for depositing any desirable electrode dimensions. The recorded cyclic voltammograms (CVs) displayed in Figure 14A exhibit no marginal distinctions in onset potentials and a negligible difference in total extractable current at the maximum applied potential across various points. Figure 14B (chronopotentiometric graphs) illustrates the steady-state activity at applied currents from 25-500mA / cm2, the trend confirms the conformity of the surface and retained high activity and stability of the scaled-up electrode. In both measurements the faradaic response is similar in each case. The similarity stems from similar surface properties and intrinsic properties of the deposited film, which is very important for any surface assited catalytic reaction. The similar area under peak in CVs suggest the similar amount of active catalyst indicating controlled mass transport of depositing ions at each point on the electrode. These measurements demonstrate a uniform and conformal surface on the large electrode with consistent homogeneity and activity which makes it ready to be exploited for commercial purposes. Figure 16 shows a plot of the size distribution of the deposited CuNiFe nanoparticles, calculated from Fiji image analysis using an SEM image. From Gausian fitting, the mean diameter of the CuNiFe nanoparticles was determined to be 123.14 nm. The data was further used to generate Weibull distribution (as shown in Figure 17) to determine d50 and d100 for the CuNiFe nanoparticles. D50 is about 100 nm; D100 is about 200 nm (in other words, there are no CuNiFe particles having a diameter larger than about 200 nm). References mentioned herein or otherwise useful for background: 1. Song, F. et al. An Unconventional Iron Nickel Catalyst for the Oxygen Evolution Reaction. ACS Cent Sei 5, 558-568 (2019). 2. Zhang, P. et al. Dendritic core-shell nickel-iron-copper metal / metal oxide electrode for efficient electrocatalytic water oxidation. Nature Communications 2018 9:1 9, 1-10 (2018). 3. Abdollahi, M., Al Sbei, S., Rosenbaum, M. A. &Harnisch, F. The oxygen dilemma: The challenge of the anode reaction for microbial electrosynthesis from CO2. Front Microbiol 13, 947550 (2022). 4. Chen, F. Y., Wu, Z. Y., Adler, Z. &Wang, H. Stability challenges of electrocatalytic oxygen evolution reaction: From mechanistic understanding to reactor design. Joule 5, 1704-1731 (2021). 5. Guide - Circular Carbon Economy, https: / / www.cceguide.org / guide / . 6. Mikunda, T. et al. Carbon capture and storage and the sustainable development goals. International Journal of Greenhouse Gas Control 108, 103318 (2021). 7. Vass, A., Kormanyos, A., Koszo, Z., Endrodi, B. &Janaky, C. Anode Catalysts in CO2 Electrolysis: Challenges and Untapped Opportunities. ACS Catal 12, 1037-1051 (2022). 8. Torrero, J. et al. High Performance and Durable Anode with 10-Fold Reduction of Iridium Loading for Proton Exchange Membrane Water Electrolysis. Adv Energy Mater 13, 2204169(2023). 9. Hall, D. E. Alkaline Water Electrolysis Anode Materials. J Electrochem Soc 132, 41C-48C (1985). 10. Angeles-Olvera, Z. et al. Nickel-Based Electrocatalysts for Water Electrolysis. Energies 2022, Vol. 15, Page 1609 15, 1609 (2022). 11. Ali Akbari, M. S., Bagheri, R., Song, Z. &Najafpour, M. M. Oxygen-evolution reaction by nickel / nickel oxide interface in the presence of ferrate(VI). Scientific Reports 2020 10:110, 1-11 (2020). 12. Zhang, D. et al. Effect of the valence state of initial iron source on oxygen evolution activity of Fe-doped Ni-MOF. Chemical Papers 74, 2775-2784 (2020). 13. Spanos, I., Masa, J., Zeradjanin, A. &Schldgl, R. The Effect of Iron Impurities on Transition Metal Catalysts for the Oxygen Evolution Reaction in Alkaline Environment: Activity Mediators or Active Sites? Catal Letters 151, 1843-1856 (2021). 14. Roberts, M. W. &Smart, R. S. C. The defect structure of nickel oxide surfaces as revealed by photoelectron spectroscopy. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases 80, 2957-2968 (1984). 15. Koshtyal, Y. et al. Atomic Layer Deposition of NiO to Produce Active Material for Thin-Film Lithium-Ion Batteries. Coatings 2019, Vol. 9, Page 301 9, 301 (2019). 16. Wang, H. et al. Copper doping-induced high-valence nickel-iron-based electrocatalyst toward enhanced and durable oxygen evolution reaction. Chern Catalysis 3, 100552 (2023). 17. Jung, H. Y., Park, J. H., Ro, J. C. &Suh, S. J. Fabrication of Trimetallic Fe-Co-Ni Electrocatalysts for Highly Efficient Oxygen Evolution Reaction. ACS Omega 7, 45636-45641 (2022). 18. Devi, H. R. et al. Trimetallic oxide-hydroxide porous nanosheets for efficient water oxidation. Chemical Engineering Journal 435, 135019 (2022). 19. Li, X. et al. Exceptional oxygen evolution reactivities on CaCoO3 and SrCoO3. Sci Adv 5, (2019). 20. Giordano, L. et al. pH dependence of OER activity of oxides: Current and future perspectives. Catal Today 262, 2-10 (2016). 21. Zhang, P. et al. Dendritic core-shell nickel-iron-copper metal / metal oxide electrode for efficient electrocatalytic water oxidation. Nature Communications 2018 9:1 9, 1-10 (2018). 22. CN115094469A 23. CN110773171A 24. CN112553650A

Claims

1. An electrocatalyst comprising a conductive substrate comprising thereon a layer of CuNiFe nanoparticles, wherein the CuNiFe nanoparticles comprise less than 5 at.% Fe.

2. The electrocatalyst of claim 1, wherein the electrocatalyst is an electrode.

3. The electrocatalyst of claim 1 or claim 2, wherein the conductive substrate is a metal foil, such as a Ta foil.

4. The electrocatalyst of claim 1 or claim 2, wherein the conductive substrate is a metal foam, such as a Ni foam.

5. The electrocatalyst of any one of the preceding claims, wherein the layer of CuNiFe nanoparticles comprises at least 60 at.% Cu, preferably at least 70 at.% Cu.

6. The electrocatalyst of any one of the preceding claims, wherein the layer of CuNiFe nanoparticles substantially or completely covers the conductive substrate.

7. The electrocatalyst of any one of the preceding claims, wherein the CuNiFe nanoparticles have a mean diameter of from about 100 nm to about 150 nm, as measured by image analysis of an SEM image.

8. A method for depositing metal on a substrate, the method comprising: providing a three-electrode cell comprising: a working electrode, wherein the working electrode is a substrate on which metal is to be deposited; a counter electrode; a reference electrode; and metal ions in an acidic aqueous solution;subjecting the working electrode to a pulsed current in which each cycle comprises an ON state and an OFF state, wherein the OFF state comprises at least about 0.01 seconds at about zero current in every cycle, thereby depositing the metal on the working electrode.

9. The method of claim 8, wherein the pulsed current is applied for a minimum of 50 cycles, preferably a minimum of 100 cycles.

10. The method of claim 8 or claim 9, wherein the pulsed current is applied for a maximum of 400 cycles, preferably a maximum of 350 cycles.

11. The method of any one of claims 8 to 10, wherein the current density of the ON state of the pulsed current is from about -50 to about -150 mA / cm2.

12. The method of any one of claims 8 to 11, wherein the ON state has a length of from about 0.1 to 1.0 seconds per cycle, preferably from about 0.2 to 0.8 seconds per cycle.

13. The method of any one of claims 8 to 12, wherein the OFF state has a length of from about 0.01 to about 0.1 seconds per cycle, preferably from about 0.02 to about 0.08 seconds per cycle.

14. The method of any one of claims 8 to 13, wherein the ratio of duration of the ON state to the OFF state is from about 5:1 to about 15:1.

15. The method of any one of claims 8 to 14, wherein the pH of the acidic aqueous solution is from about 0.5 to about 6.5.

16. The method of any one of claims 8 to 15, wherein the temperature and pressure are ambient temperature and pressure.

17. The method of any one of claims 8 to 16, wherein two or more different metal ions are provided in the acidic aqueous solution, thereby depositing a bimetallic or multi-metallic system.

18. The method of any one of claims 8 to 17, wherein the metal ions are transition metals.

19. The method of any one of claims 8 to 18, wherein the metal ions comprise Cu, Ni and Fe ions.

20. The method of any one of claims 8 to 19, wherein equimolar amounts of two or more different metal ions are provided in the acidic aqueous solution at the start of the method.

21. A substrate having deposited there on a metal, the metal having been deposited according to the method of any one of claims 8 to 20.

22. Use of the electrocatalyst of any one of claim 1 to 7 or the substrate of claim 21 as the anode and / or cathode in a process for alkaline water electrolysis.5 23. Use of the electrocatalyst of any one of claims 1 to 7 or the substrate of claim21 as the anode and / or cathode in a process for CO2 reduction.

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