IT202000007948A1 - COPPER AND ANTIMONY BASED MATERIAL AND ELECTRODE FOR THE SELECTIVE CONVERSION OF CARBON DIOXIDE TO CARBON MONOXIDE - Google Patents

Description

? COPPER AND ANTIMONY BASED MATERIAL AND ELECTRODE FOR THE SELECTIVE CONVERSION OF CARBON DIOXIDE TO CARBON MONOXIDE?

FIELD OF INVENTION

The present invention refers to a material based on copper and antimony, and to an electrode obtained with this material, useful for the electrochemical reduction of carbon dioxide to carbon monoxide with high efficiency and selectivity.

STATE OF THE TECHNIQUE

The huge emissions of carbon dioxide (CO2), also known as carbon dioxide, from the combustion of fossil fuels, have been recognized as responsible for global climate change. To address this problem, strategies such as the capture and storage of CO2 are being studied, with the aim of slowing or rather stopping the accumulation of CO2 in the atmosphere. The transformation of the captured CO2 into further chemicals, fuels or other,? of fundamental importance to achieve a sustainable carbon cycle and to store energy in the long term. Among the different CO2 transformation technologies, the electrochemical conversion? considered particularly interesting since? can use energy obtained from renewable sources. This technology, while very promising,? of applicability? not immediate due to the high stability? of the CO2 molecule, of the slow kinetics and of the complex mechanisms of the CO2 reduction reaction.

The reduction of CO2 can? take place according to different transfer processes of electrons coupled to protons. The CO2 reduction reactions for the production of compounds containing a single carbon atom and the electrochemical evolution of H2 are listed below as R1-R5, along with their standard potentials:

The values of E <0> are reported in standard conditions (1 atm and 25 ° C) with respect to the reversible hydrogen electrode (RHE) in aqueous media. Unless otherwise specified, in this description all potentials refer to RHE.

Among the numerous products of CO2 reduction, formic acid (HCOOH) and carbon monoxide (CO) are the only economically viable products that have been obtained so far with productivity. relevant. CO? much desired in the industrial sector, since? its mixture with hydrogen (H2), ie the synthetic gas or syngas, can? be converted into hydrocarbons through the Fischer-Tropsch process.

Since? for? are the values of the standard potentials of the above reactions similar, usually the result of the process? a mixture of products, difficult or not easy to use in the industrial sector. Furthermore, the parasitic reaction of hydrogen evolution usually takes place with a higher yield than the reduction of CO2 in aqueous electrolyte.

Therefore, electrode materials are needed that can guarantee a high CO2 conversion efficiency and at the same time a high selectivity. towards a specific reaction product, in particular towards CO; materials of this type are generally known in electrochemistry with the definition of electrocatalysts.

According to experimental and theoretical studies, gold (Au), silver (Ag) and palladium (Pd) are considered the best metallic electrocatalysts for converting CO2 into CO; these metals can not for? be used on an industrial scale for this purpose due to their high cost and availability? reduced.

In addition to the previous materials, the properties have been studied. electrocatalytic, in the reduction of CO2, of metals such as copper (Cu), zinc (Zn), tin (Sn), indium (In) and bismuth (Bi). Cu alone does not have good selectivity? for no product; Does Zn have selectivity? sufficient, but not optimal, for the production of CO; Sn, In and Bi are selective for the production of HCOOH.

In some documents the properties are discussed. as electrocatalysts of compositions other than single metals.

US patent application 2019/0127866 A1 describes an electrocatalyst material for the conversion of CO2 to ethanol, comprising nanoparticles of copper or its alloys supported by nano-sized tips (? Nanospike?) Of carbon doped with nitrogen, boron or phosphorus. The copper alloys indicated as useful by this document are all those of the element with one or more? elements chosen from those of Groups 3-15 of the periodic table. Alloys indicated as preferred are those between copper and an element selected from Ni, Co, Zn, In, Ag and Sn. The electrocatalysts of this document have a selectivity? pi? high due to the electro-reduction of CO2 compared to the evolution of H2 with a high faradic efficiency in the production of ethanol, with a yield in this compound of at least 60% of the mixture; other species, such as carbon monoxide, are therefore produced with a yield not exceeding 40%. In addition to the fact that a mixture of products is still produced, the preparation of the doped carbon nanospikes makes the process not immediate.

The article? Achieving highly selective electrocatalytic CO2 reduction by tuning CuO-Sb2O3 nanocomposites ?, Y. Li et al., ACS Sustainable Chem. Eng. 2020, 8, 12, 4948-4954, describes an electrocatalyst material consisting of a mixture of carbon in finely divided form (? Carbon black?) And powders of a mixed oxide of copper (II) (CuO) and antimony (III ) (Sb2O3). The purpose of this study? to identify the best conditions for converting CO2 to CO. The materials of this article are produced by dissolving soluble salts of Cu (II) and Sb (III) in a suspension of carbon black in ethanol, adding a base (KOH) to the suspension and letting the system react for 6 hours at a temperature of 80 ? C obtained with an oil bath; the precipitate obtained is then washed with water and ethanol and finally dried. The mixture of powders so? obtained is then distributed on a carbon paper (? carbon paper?) obtaining electrodes. In the section? Results and discussion? dell? article? confirmed that copper oxide? in the form of CuO (ie copper? in an oxidation state (II)) and that the antimony oxide? in the form of Sb2O3 (i.e. antimony in oxidation state (III)), by means of X-ray diffraction analysis (XRD, Fig. 1.a of the article) which shows the presence of the characteristic peaks of CuO and Sb2O3 , by X-ray photoelectron spectroscopy (XPS, Fig. 1.b) and by Raman spectroscopy (Fig. 1.c). As shown in the article (see figure 3.b), the best results are obtained with the molar ratio Cu: Sb 10: 1, with which faradic yields of approximately 10% for HCOOH, 10% for H2 and 80% are obtained. for CO, while the authors report that as the Sb content increases, the CO yield drops rapidly. The results obtained with the best material of this article are already? interesting, but still not optimal both as CO yield and as selectivity? towards this compound (a mixture of three products is obtained).

Purpose of the present invention? that of overcoming the problems of the known art, and in particular of providing an electrocatalyst material which allows to obtain a yield of CO and a selectivity in the CO2 electrochemical reduction reaction. towards this compound more? high compared to the electrocatalysts of the known art. Another purpose of the invention? to provide a cost-effective process for the large-scale production of this electrocatalyst.

SUMMARY OF THE INVENTION

These objects are achieved with the present invention, which in a first aspect relates to an electrocatalyst material consisting of copper (I) oxide (Cu2O) containing antimony, in which the quantity? of antimony? between 5% and 25.2% by weight.

This material is used in finely divided form to produce electrodes for the electrochemical reduction of CO2, in which said material? combined with an electroconductive material.

In a second aspect, the invention relates to a process for the production of the electrocatalyst material, which includes the following steps:

a) dissolve a copper (II) salt and an antimony (III) salt in a solvent selected from ethanol, ethylene glycol, acetylacetone, diethylamine, ethylenediamine, oleylamine, N, N-dimethylformamide, mixtures of these solvents with each other, with water or with aqueous solutions of D-glucose, hydrazine hydrate, amino acids or sodium carboxymethylcellulose;

b) heat the solution in a microwave oven at a temperature between 180 and 230 ° C for a time between 1 and 10 minutes;

c) separation of the precipitate from the solution and its drying.

BRIEF DESCRIPTION OF THE FIGURES

The invention will come described in detail below with reference to the figures, in which:

- Fig. 1 shows photomicrographs obtained with a scanning electron field effect microscope (FESEM) of various materials of the invention and three comparison materials;

- Fig.2 shows the results of X-ray diffraction (XRD) of powder samples of materials of the invention having different composition and three comparison materials;

- Fig. 3 shows spectra obtained by X-ray photoelectron spectroscopy (XPS) for Cu and Sb on a sample of the invention;

- Fig. 4 is a schematic view of an electrolytic cell used to carry out the CO2 reduction tests reported in the section of the Examples;

- Fig. 5 shows representative graphs of the faradic efficiency in the conversion from CO2 to CO obtained with a material of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The inventors have found that copper (I) oxide (Cu2O, cuprous oxide) containing antimony in quantities? between 5 and 25.2% by weight, when used to produce an electrode, it allows to obtain the electrochemical reduction of CO2 to CO with values pi? high faradic efficiency and selectivity? compared to known materials. The compounds of the invention allow these results to be obtained by using copper and antimony, which are cheap and widely available components.

A material similar to that of the present invention? described in the article? Optimal synthesis of antimony-doped cuprous oxides for photoelectrochemical applications ?, Dae Yun et al., Thin Solid Films 671 (2019) 120-126. This document ? for? directed to the study of the influence of Sb concentration on the properties? structural, electrical and photoelectrochemical of cuprous oxide thin films for the purpose of photoelectrochemical cleavage of water; moreover, this study reports materials in which the quantity? of Sb reaches a maximum of up to 1% by moles, and indicates as the preferred material for the aforementioned purpose Cu2O doped with 0.75% molar of Sb.

The materials of the invention will be generally indicated in the following with the notation Cu2O / Sb, independently of the specific composition.

The Cu2O / Sb materials of the invention have an Sb content of between 5.2 and 25.2% by weight; materials with an Sb content of between 17.2 and 20.1% by weight are preferred.

The materials of the invention are obtained and used in the form of powders. The morphology of these powders? uniform and homogeneous at least up to the Sb concentration of 25.2%. Fig. 1 shows images obtained with a scanning field effect electron microscope (FESEM) of samples of the invention with increasing Sb content (Figs. From 1 (b) to 1 (g)) and, for comparison, of three samples produced following the same method as the samples of the invention but containing only copper (Fig. 1 (a)), only antimony (Fig. 1 (i)), and a sample containing a quantity of of antimony greater than 25.2% (equal to 36%; Fig. 1 (h)); in particular, the quantity? % by weight of Sb in the samples of the invention prepared as described in Example 1, determined by chemical analysis,? the following:

- Fig. 1 (b): 5.2;

- Fig. 1 (c): 9.4;

- Fig. 1 (d): 13.6;

- Fig. 1 (e): 17.2;

- Fig. 1 (f): 20.1;

- Fig. 1 (g): 25.2.

As can be seen in the images, the materials of the invention with an Sb content up to 25.2% by weight have a similar morphology to each other, and consist of powders in the form of essentially spherical particles with a very narrow dimensional distribution (all particles are about 5 µm in size), composed of tightly packed nanoparticles. For concentrations higher than 25.2%, Sb-rich particles and the formation of an isolated phase consisting of crystalline Sb2O3 are observed (octahedral particles in Fig. 1 (h), to be compared with the image of pure antimony oxide in Fig. . 1 (i)). Analysis of energy dispersive X-ray spectroscopy (EDX) indicates that Sb? uniformly distributed in the samples object of the invention.

The XRD analysis confirms that the material? essentially cuprous oxide. Fig. 2 shows, from top to bottom, the diffractograms respectively for the sample containing only copper, for the samples with increasing antimony concentration, and for the sample containing only antimony. As can be seen in the figure, in the samples of the invention up to the Sb content of 25.2% by weight there are only peaks attributable to the Cu2O phase (with decreasing intensity as the Sb content increases); in the sample with an Sb content of 36.0% by weight, on the other hand, peaks attributable to the Sb2O3 phase appear, albeit with low intensity.

The composition ? also confirmed by high resolution (HR) XPS spectroscopy. Figure 3 shows the typical spectra of the sample containing 17.2% by weight of Sb. From the XPS measurement (Fig. 3a) it appears that antimony? present in the sample in the form of Sb <3+> ions, as evidenced by the intense peaks related to Sb 3d5 / 2 and Sb 3d3 / 2 centered respectively at 530.06 eV and 539.45 eV. Fig.3b instead shows the region of the XPS spectrum corresponding to the Cu 2p doublet; since? the Cu 2p peak? difficult to deconvolve due to the overlap of numerous peaks, the Auger CuLMM region is also acquired (inset in Figure 3b). The kinetic energy of the peak? 916.8 eV, which corresponds to Cu <+>. Auger parameter changed? approximately 1848.8 eV, correlated to an average oxidation state of Cu (I). ? so it is clear that copper? present in samples in the form of Cu <+> ion.

Since the electrocatalyst materials of the invention are in themselves? poor electrical conductors, for the production of electrodes for CO2 reduction are used in combination with conductive materials. Preferably, the conductive material? in turn in the form of powders or other finely divided form. For this purpose, a carbon-based material is generally used, thanks to its low activity. catalytic, for example carbon black, graphite, graphenes, carbon nanotubes or mixtures thereof; your favorite conductor material? carbon black. The electrocatalyst material of the invention and the conductive material are used in weight ratios ranging from 9: 1 to 19: 1. For the production of the electrode, the mixture between the electrocatalyst material of the invention and the conductive material is distributed on a support, which can? to be in turn conductor or not. Examples of preferred substrates are conductive carbon paper, conductive carbon cloth and metal mesh. The stabilization of the powder mixture on the support can? be obtained with ionomers, that is? conductive polymers for ions, which form a containing and conductive film on the powders.

In its second aspect, the invention relates to a process for the production of the electrocatalyst material, which consists of the steps a) to c) mentioned above.

Step a) consists in dissolving a copper (II) salt and an antimony (III) salt in a solvent chosen from ethanol, ethylene glycol, acetylacetone, diethylamine, ethylenediamine, oleylamine, N, N-dimethylformamide, mixtures of these solvents with each other, with water or with aqueous solutions of D-glucose, hydrazine hydrate, amino acids and sodium carboxymethylcellulose. The salts more? suitable for the purposes of the invention are acetates, sulphates and nitrates of both metals.

The solution cos? formed is heated in a microwave oven, inside a sealed container of suitable material (eg Teflon) at a temperature between 180 and 230 ° C for a time between 1 and 10 minutes. In addition to causing the reaction of the metal salts to form the final material, the heating in microwaves in the presence of the solvents mentioned determines the reduction of the Cu <2+> ion of the starting copper salt to the Cu <+> ion present in the Cu2O oxide . In the case of ethylene glycol, the glycol functions both as a solvent and as a reducing agent and the increase in temperature can? increase its capacity? reducing agent. Normally a temperature between 180? C and 230? C? suitable for the formation of Cu <+> from Cu <2+> in the indicated solution.

Finally, the precipitate formed in microwave heating is separated from the liquid phase, for example by filtration or centrifugation, washed with ethanol, and dried, for example by an oven treatment at a temperature between 50 and 100 ° C under vacuum or in an atmosphere. inert.

The process of the invention differs from that of the article by Li et al. previously mentioned for the use of microwave heating instead of traditional heating, which as said determines the reduction of the Cu <2+> ion of the starting copper salt and the formation of the Cu2O phase.

The invention will come further described in the experimental section below. Materials, instrumentation and methods

The following precursors were used in the preparation of the samples:

- copper (II) acetate, Cu (OAc) 2? xH2O (Sigma-Aldrich, catalog no. 66923-66-8 degree of hydration, ~ 1), purity 98%;

- antimony (III) acetate, Sb (OAc) 3, (Sigma-Aldrich, catalog no. 6923-52-0), purity 99.99%;

- ethylene glycol (Sigma-Aldrich, catalog no. 107-21-1), purity 99.8%;

- Nafion's solution <? > 117 (Sigma-Aldrich, catalog no. 31175-20-9; Nafion is a registered trademark of E. I. du Pont de Nemours and Company), purity: ~ 5% in a mixture of lower aliphatic alcohols and water.

The chemical composition analyzes of the samples were performed by inductively coupled plasma optical emission spectroscopy (ICP-OES, iCAP 7600 DUO instrument, Thermo Fisher Scientific); any analysis? was performed by dissolving 5.0 mg of the sample in 10.0 ml of an aqueous solution with 10% aqua regia.

Electron microscope images and energy dispersion X-ray spectroscopy (EDX) analyzes were obtained with a FESEM Supra 40 (Zeiss) equipped with a detector (Oxford Instruments Si (Li)) for X-ray spectroscopy analyzes X energy dispersive (EDX).

The phase composition of each sample? was determined by X-ray diffraction (XRD) with a diffractometer (PANalytical X? Pert Pro equipped with an X? Celerator detector) that uses Cu K? (? = 1.54178?) Generated at 40 kV and 30 mA. Were XRD diffractograms recorded in field 2? 25-80? with a step (2?) of 0.017? and a counting time of 0.45 seconds.

The high resolution (HR) XPS analyzes were performed with a PHI 5000 VersaProbe (Physical Electronics) instrument using monochromatic Al K radiation? (1486.6 CE).

The analyzes of the gaseous products derived from CO2 electro-reduction were carried out in real time with an INFICON Fusion <? > equipped with two channels with a 10 m Rt-Molsieve 5A column and an 8 m Rt-Q-Bond column, respectively, and conductivity micro detectors. thermal (micro-TCD).

EXAMPLE 1

This example refers to the synthesis of the materials of the invention.

Seven samples of materials of the invention with different Sb content were prepared using copper acetate and antimony as precursors, used in the quantities. reported in Table 1. The samples of the invention are indicated as A-G. For comparison, they were produced in the same way? described below is also a sample starting from copper acetate only (sample indicated as? Cu? in the table), a sample starting from antimony acetate only (sample? Sb?), and a sample of mixed composition Cu / Sb not of the invention (sample? NI?). The last column of the table shows the values of Sb content in each of the samples of the invention, obtained with ICP-OES analysis (the data for the Cu and Sb samples is not reported because of course in these two cases the analysis for the determination of the percentage content of Sb has not been carried out).

Table 1

The quantities of indicated precursors were dissolved in 40 ml of ethylene glycol and 5 ml of bidistilled H2O (resistivity about 18 M ?? cm). Any solution? it was then transferred to a Teflon container (volume 100 mL). The Teflon container? been sealed, placed in a microwave oven (Milestone, STARTSynth, segment HPR-1000-10S with temperature and pressure control), heated to 220 ° C and then maintained at this temperature by feeding the oven with a maximum power of 900 W for a total irradiation time of 2 minutes. After cooling to room temperature, the product in suspension in each container? was separated by centrifugation and washed twice with bidistilled H2O and then once with ethanol. Any sample of dust? it was finally vacuum dried at 60 ° C overnight.

In addition to the ICP-OES analysis, the samples of the invention were examined with scanning electron microscopy and EDX analysis to determine the morphology (also for the Cu and Sb samples) and the distribution of antimony, with X-ray diffraction for determine the crystal structure (also for Cu and Sb samples) and by XPS to determine the oxidation state of Cu and Sb; the results of the three analyzes have been previously discussed with reference to Figures 1, 2 and 3 respectively.

EXAMPLE 2

This example refers to the production of electrodes for the electrochemical reduction of CO2 with the materials of the invention (samples A-F) and with the three comparison materials (samples Cu, Sb and NI).

Any electrode? was prepared by mixing 10 mg of sample A-F, Cu, Sb or NI, 1 mg of carbon black from acetylene, 90? l of Nafion solution <? > 117 and 320? L of isopropanol. Any blend? was sonicated for 30 minutes until a uniform suspension was obtained. Any suspension? it was then used to coat a carbon paper covered with a gas permeable layer (GDL; SIGRACET 28BC, SGL Technologies); the geometric surface of each electrode was 1.5 cm <2>. The electrode obtained? been dried at 60 ° C overnight to evaporate the solvents. The loading of the electrocatalyst on each electrode? state of about 3.0 mg cm <-2>. The electrodes cos? obtained are indicated below with the abbreviations Ex, in which the subscript x corresponds to the sample A-F, Cu, Sb or NI used for its production.

EXAMPLE 3

This example refers to the measurement of the CO2 reduction efficiency of the electrodes prepared in the previous Example.

The electrochemical measurements were carried out with a cell having the configuration shown in Fig. 4; the cell as a whole, 10,? shown in the figure enclosed by a discontinuous line. As shown in the figure, the cell? with two compartments separated by an ion exchange membrane 11 (membrane Nafion <?> N117, Sigma-Aldrich), and adopts a three-electrode configuration. Each compartment has a total volume of 10ml and contains 7ml of electrolyte, and thus 3ml of headspace. The reference electrode, 12,? an Ag / AgCl electrode (1 mm, LF-1 leak-free) which is inserted into the cathode compartment. The counter electrode, 13,? a sheet of Pt (Goodfellow, 99.95%). The working electrode, that is? that of the invention,? indicated in the figure as element 14. How electrolyte solution? An aqueous solution of 0.1 M KHCO3 was used. In this configuration, the gaseous CO2 is fed into both half-cells from the lower part of the two compartments, while the mixture of products on which the results are evaluated? removed from the cathode compartment (right in the figure); most of this mixture is sent to the separation and purification stage (made with methods known in the sector and not described in this text), while a fraction of the mixture? sent for analysis. Chronoamperometric measurements were performed using a CHI760D electrochemical workstation (CH Instruments, Inc., USA). The gas phase products were analyzed in real time with a micro gas chromatograph (? GC). The input of the? GC instrument was connected to the cathode side of the electrochemical cell through a GENIE filter, to remove moisture. from the gas before it enters the analysis instrument (? GC). During the chronoamperometric measurements, the electrolytes on both sides of the anode and cathode were static, while? a constant CO2 flow rate of 15 ml / min was maintained to saturate the cathode electrolyte and to bring the gaseous products to the? GC. The tests were performed at different potentials between -0.79 V and -0.99 V. The potential? corrected by compensating for the drop in ohmic potential, of which 85% by the instrument (iR compensation).

The selectivity? ? described by the faradic efficiency (FE), which? the relationship between the quantity? of charge (coulomb, C) required to produce a certain amount? of a product and the total charge consumed in the reaction time, and d? expressed by the following relationship:

FE (%) = nNF / Q x 100

where n ? the number of electrons transferred in the faradic process (for the reduction of CO2 to CO and H2, n? 2 as shown in the reactions R1 and R5 above), N are the moles of a product generated in a specific reaction period, F? the faradic constant (96485.33 C / mol) and Q? the total charge in a specific reaction period.

The results of the two-value tests are shown in Table 2.

Table 2

As can be seen from the results of the tests, the ESb electrode does not produce CO for either of the two potentials. The Cu electrode has poor selectivity for CO, with FECO values below 10%. The comparison electrode ENI shows poor selectivity values? towards CO, probably why? formed by a mixture containing only a quantity? reduced active material together with a completely inactive material (antimony oxide). The EA-EF electrodes of the invention, on the other hand, have a high selectivity. towards CO, with FECO higher than 80% for all materials A-F at -0.79 V. Among these materials, in particular, D and E show excellent selectivity values? for CO, equal to at least 90% to both potentials.

EXAMPLE 4

This example refers to the CO2 reduction measurement with an electrode of the invention at various potentials.

The ED electrode, which gave the best results in Example 3,? been tested at five different potential values between -0.69 V and -1.09 V. In each test? The evolution of CO and H2 over time was assessed during tests lasting between one and two hours.

The results of these tests are shown graphically in Fig. 5. In detail, Figures 5 (a) to 5 (e) report tests carried out at the following potentials: 5 (a) -0.69 V; 5 (b) -0.79 V; 5 (c) -0.89 V; 5 (d) -0.99 V; 5 (e) -1.09 V. The tests at -0.79 V and -0.99 are the same whose results are already? been reported in the previous example. The results of these tests are summarized in a synthetic form in the graph of Fig. 5 (f), which shows the faradic efficiency values for CO and H2, detected when the reduction process? arrived at full capacity, to all potential assessed.

As can be seen in the graphs, in each test c ?? an initial settling time between about 10 minutes (test at -0.99 V) and 20 minutes; there? ? attributed to the stabilization of the electrode and the filling of the headspace of the electrochemical cell and the tubes between the cell and the? GC. Then, the FE values stabilize, indicating the stable performance of the electrode. The ED electrode shows excellent performance in the conversion of CO2 into CO (FECO> 80%) in the whole range of potentials explored, with values up to 90-92% at potentials from -0.79 V to -1.09 V At potential pi? negative (<-1.09 V), the FECO falls below 90%. FEH2 values remain low (? 9%) from -0.69 V to -1.09 V. No other products in the gas phase were detected besides CO and H2. Liquid products (e.g., HCOOH) have not been quantified, but can you? believe that they are present in quantity? very modest or negligible, since? the total faradic efficiency for CO and H2 measured in all tests? around 100%.

COMMENT ON THE RESULTS

As demonstrated in the tests described above, the electrocatalyst materials of the invention catalyze the electrochemical reduction of CO2 with high selectivity. towards CO. The materials of the invention then offer further advantages.

First, antimony and copper, and their compounds used as precursors in the process of the invention, are cheap materials; the production of these materials? furthermore simple and easily scalable on an industrial level, also why? does not use toxic or harmful products; the invention therefore offers a technically valid and competitive alternative to the use of metals such as Au, Ag and Pd.

Since? the materials of the invention are in powder form, they can be used in reactors with various configurations such as gas diffusion electrode (GDE) and different sizes.

Claims (11)

CLAIMS 1. Electrocatalyst material consisting of copper (I) oxide (Cu2O) containing antimony, in which the quantity? of antimony? between 5% and 25.2% by weight. 2. Electrocatalyst material according to claim 1, wherein the quantity? of antimony? between 17.2% and 20.1% by weight. 3. Electrode consisting of powder of an electrocatalyst material of any one of claims 1 or 2 and a conductive material deposited on a support, in a weight ratio between electrocatalyst material and conductive material comprised between 9: 1 and 19: 1. 4. Electrode according to claim 3, wherein the conductive material? in powder form. 5. Electrode according to any one of claims 3 or 4 wherein the conductive material? carbon based. 6. Electrode according to claim 5, wherein the conductive material? chosen from carbon black, graphite, graphenes, carbon nanotubes or their mixtures. 7. Electrode according to any one of claims 3 to 6 wherein the support? chosen from conductive carbon paper, conductive carbon cloth and metal mesh. Electrode according to any one of claims 3 to 7, wherein the powder of the electrocatalyst material and optionally of the conductive material are stabilized on the support with an ionomer. 9. Process for producing the electrocatalyst material of any one of claims 1 or 2, which includes the following steps: a) dissolve a copper (II) salt and an antimony (III) salt in a solvent selected from ethanol, ethylene glycol, acetylacetone, diethylamine, ethylenediamine, oleylamine, N, N-dimethylformamide, mixtures of these solvents with each other, with water or with aqueous solutions of D-glucose, hydrazine hydrate, amino acids or sodium carboxymethylcellulose; b) heat the solution in a microwave oven at a temperature between 180 and 230 ° C for a time between 1 and 10 minutes; c) separation of the precipitate from the solution and its drying. 10. Process according to claim 9, wherein the copper (II) salt? chosen from acetate, sulfate and nitrate, and the antimony (III) salt? chosen from acetate, sulphate and nitrate. Method for the selective electrochemical reduction of CO2 to CO, which comprises the use of an electrode of any one of claims 3 to 8 at a potential between -0.69 V and -1.09 V.