Description:FIELD OF INVENTION:
[001] The present disclosure relates to a transition metal oxide supported electrochemical reduction catalyst, and a process for preparation thereof. Particularly, the present invention relates to an efficient electrochemical reduction catalyst and a process of preparation thereof, wherein the electrochemical reduction catalyst is a transition metal oxide supported electrochemical reduction catalyst. The present invention also discloses a simple and a commercially viable process for preparing a transition metal oxide supported electrochemical reduction catalyst and a method for electrochemical reduction CO2 to CO and Isopropyl alcohol.

BACKGROUND OF INVENTION:
[002] The combustion of fossil fuels in activities such as the electricity generation, transportation, and manufacturing produce billions of tons of carbon dioxide annually. Research indicates increasing concentrations of carbon dioxide in the atmosphere may be responsible for altering the Earth's climate, changing the pH of the ocean and other potentially damaging effects. Countries around the world, including India, are seeking ways to mitigate emissions of carbon dioxide. Converting carbon dioxide into economically valuable materials (e.g., fuels and/or industrially useful chemicals/ or commercially valuable products) offers an attractive strategy for mitigating carbon dioxide emissions.

[003] Laboratories around the world have attempted for many years to use electrochemistry and/or photochemistry to convert carbon dioxide to economically valuable products.
However, existing methods for the conversion of carbon dioxide suffer from many limitations, including the stability of systems used in the process, the efficiency of systems, the selectivity of the systems or processes for a desired chemical, the cost of materials used in systems/processes, the ability to control the processes effectively, and the rate at which carbon dioxide is converted. No commercially available solutions for converting carbon dioxide to economically valuable fuels or industrial chemicals currently exist.

[004] Feng Y. et al. in the article titled “Laser-Prepared CuZn Alloy Catalyst for Selective Electrochemical Reduction of CO2 to Ethylene." of Langmuir, 2018, volume 34, issue 45, pages 13544-13549, discloses a copper-zinc alloy catalyst that exhibits excellent selectivity for C2H4 in CO2 electroreduction, with faradaic efficiency of 33.3% at a potential of -1.1 V (vs reversible hydrogen electrode). Accordingly, the alloy electroreduction catalyst requires a higher overpotential i.e. -1.1 V to achieve the faradaic efficiency of 33.3%.

[005] Baek Y. et al. in the article titled “Electrochemical carbon dioxide reduction on copper–zinc alloys: ethanol and ethylene selectivity analysis." of J. Mater. Chem. A, 2022, volume 10, pages 9393-9401, discloses a copper-zinc alloy catalyst that exhibits CO2 electroreduction selectivity for C2H5OH with ∼25% faradaic efficiency at a potential of -0.76 V (vs reversible hydrogen electrode). Accordingly, the alloy electroreduction catalyst requires a higher overpotential i.e. -0.76 V to achieve the faradaic efficiency of ∼25%.

[006] Akihiro Katoh et al in the article titled “Design of Electrocatalyst for CO2 Reduction: V. Effect of the Microcrystalline Structures of Cu‐Sn and Cu‐Zn Alloys on the Electrocatalysis of Reduction." of J. Electrochem. Soc., 2022, volume 141, Issue 8, page 2054, discloses a copper-zinc alloy catalyst that exhibits CO2 electroreduction selectivity for HCOOH, and CO with 20% and 60 % faradaic efficiencies, respectively at a potential of -1.0 V (vs reversible hydrogen electrode). Moreover, the alloy electroreduction catalyst requires a higher overpotential i.e. -1.0 V to achieve the faradaic efficiency of 20%.

[007] Zhang Z.Y. et al in the article titled “Cu-Zn-based alloy/oxide interfaces for enhanced electroreduction of CO2 to C2+ products" of J. Energy Chem., 2023, volume 83, Issue 2023, pages 90-97, discloses a copper-zinc alloy/ Cu-Zn aluminate oxide catalyst that exhibited CO2 electroreduction selectivity for C2+ with an overpotential i.e. -1.15 V.

[008] Su X. et al in the article titled “Hierarchically porous Cu/Zn bimetallic catalysts for highly selective CO2 electroreduction to liquid C2 products" of J App. Cat. B: Environ., 2020, Volume 269, Issue 2020, page 118800, discloses a hierarchically macroporous-mesoporous (HMMP) Cu/Zn alloy catalyst for CO2 electroreduction to C2H5OH with 46.6 % faradaic efficiency, at a potential of -0.8 V (vs reversible hydrogen electrode). Accordingly, the alloy electroreduction catalyst requires a higher overpotential i.e. -0.8 V to achieve the faradaic efficiency of 46.6%.

[009] Badawy, I. M. et al in the article titled “Selective electrochemical reduction of CO2 on compositionally variant bimetallic Cu–Zn electrocatalysts derived from scrap brass alloys" of Sci. Rep., 2022, Volume 12, page 13456, discloses a Cu–Zn electrocatalysts for CO2 electroreduction to CO and CHOO- ions with 30.7 % and 21.6 % faradaic efficiency respectively, at a potential of -0.91 V (vs reversible hydrogen electrode). Accordingly, the alloy electroreduction catalyst requires a higher overpotential i.e. -0.91 V to achieve the faradaic efficiency in a range of 21 to 30.7 %.

[0010] Sheng, Z. et al. "Sheet-Like Morphology CuO/Co3O4 Nanocomposites for Enhanced Catalysis in Hydrogenation of CO2 to Methanol." of Nanomaterials 2023, Volume 13, Issue 24, page 3153 discloses introduction of copper onto Co3O4 nanosheets using the ion exchange reverse loading method, which induced certain interactions to form a special Co-Cu interface, which significantly changes the product selectivity of the cobalt-based catalysts. The CuO/Co3O4-IE catalyst exhibits a methanol selectivity of 36.1% in performance evaluation of the CO2 hydrogenation reaction.

[0011] Moreover, the available alloy catalysts of the prior arts even after applying higher overpotential during electroreduction of CO2 have low faradaic efficiencies, in addition the processes of preparation of said electroreduction catalysts are complex.

[0012] Accordingly, there is an urgent need in the art to develop an efficient electroreduction catalyst, along with an easy, and facile yet scalable process for preparation of electroreduction catalyst with improved properties.

[0013] Accordingly, the present invention discloses an efficient transition metal oxide supported electrochemical reduction catalyst, an easy and a commercially scalable process for preparing transition metal oxide supported electrochemical reduction catalyst, and a method for reducing CO2 into CO and isopropanol (or Isopropyl alcohol).

OBJECTIVES OF THE PRESENT INVENTION
[0014] The primary object of the present invention is to provide an efficient transition metal oxide supported electrochemical reduction catalyst.

[0015] Another objective of the present invention is to provide efficient electrochemical reduction catalyst having high Faradaic efficiency at a low energy input.

[0016] Yet another objective of the present invention is to provide an easy and industrially scalable process for preparing a transition metal oxide supported electrochemical reduction catalyst.

[0017] Still another objective of the present invention is to provide an easy, and a commercially scalable method for converting CO2 into CO and isopropanol.

[0018] These and other objective of the present invention will be apparent from the drawings and descriptions herein. Every objective of the invention is attained by at least one embodiment of the present invention.

DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

[0019] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0020] Figure 1 illustrates the X-ray diffraction (XRD) pattern of the synthesized a transition metal oxide supported electrochemical reduction catalyst, along with employed transition metal oxide and the alloy catalyst of the present invention.

[0021] Figure 2 illustrates a scanning electron microscope (SEM) image of a 2.5% Cu-Zn/Co3O4 catalyst of the present invention.

[0022] Figure 3 illustrates a Cyclic voltammetry of 2.5% Cu-Zn/Co3O4 catalyst at 0.6V to -0.5V vs. RHE in Argon and CO2 atmosphere, of the present invention.

[0023] Figure 4: Chronoamperometry of 2.5% Cu-Zn/Co3O4 at -0.5V vs. RHE, of the present invention.

SUMMARY OF THE PRESENT INVENTION
[0024] This summary is provided to introduce a selection of concepts in a simplified manner that is described elaborately in detailed description. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended to determine the scope of the invention.

[0025] In an aspect of the present invention, there is provided an efficient transition metal oxide supported electrochemical reduction catalyst.

[0026] In an aspect of the present invention, there is provided an efficient electrochemical reduction catalyst having high Faradaic efficiency at a low energy input.

[0027] In an aspect of the present invention, there is provided an easy and industrially scalable process for preparing a transition metal oxide supported electrochemical reduction catalyst.

[0028] In an aspect of the present invention, there is provided an easy, and a commercially scalable method for converting CO2 into CO and isopropanol.

[0029] In one of the preferred aspects, the present invention provides transition metal oxide supported electrochemical reduction catalyst comprising: a). 1.0 to 10.0 wt. % of an alloy; and b). 90.0 to 99.0 wt. % of the transition metal oxide.

[0030] In another the preferred aspect of the present invention, a process for preparing a transition metal oxide supported electrochemical reduction catalyst, the process comprising: a) adding 2 to 5 g of a transition metal salt and 1 to 2 g of urea in 15 ml of water to obtain a reaction mixture; b) combusting the reaction mixture in a furnace at a temperature ranging from 350 to 450℃ for a time period of 15 to 25 minutes, preferably 20 minutes to obtain a combusted reaction mixture; c) calcining the combusted reaction mixture at a temperature ranging from 500 to 700℃ for 8 to 12 hours to obtain a transition metal oxide powder; d) dispersing 0.5 to 2 g of the transition metal oxide powder in 35 to 45 ml, preferably 40 ml of water followed by sonication at 18,000 to 22,000 Hz, preferably 20,000 Hz to obtain a transition metal oxide solution; e) adjusting pH of the transition metal oxide solution to a pH value of 1 (pH =1) by adding an acid followed by adding 5 ml to 20 ml of a ketone with a continuous stirring of 50 to 70 minutes to obtain an acidic transition metal oxide solution having pH value in a range of 1 to 3; f) adding 4 to 6 ml of an aqueous solution of a copper salt and 5 to 7 ml of an aqueous solution of a zinc salt to the acidic transition metal oxide solution followed by dropwise adding 10 to 30 ml of an aldehyde to obtain an acidic mixture; and g) adding 2 to 3 ml of a base to the acidic mixture to obtain a basic mixture and maintaining the temperature of the basic mixture at a temperature of 60°C to 100°C for 6 to 10 hours to obtain the transition metal oxide supported electrochemical reduction catalyst.

[0031] In yet another preferred aspect of the present invention, a method for an electrochemical reduction of carbon dioxide to carbon monoxide and isopropanol, the method characterized in contacting the carbon dioxide with a transition metal oxide supported electrochemical reduction catalyst in an electrochemical cell.

DESCRIPTION OF THE INVENTION:

[0032] The present disclosure addresses the drawbacks of the art and provides an efficient transition metal oxide supported electrochemical reduction catalyst and a method for preparing said transition metal oxide supported electrochemical reduction catalyst. Disclosed method for preparation of said transition metal oxide supported electrochemical reduction catalyst is simple, and industrially viable method. Specifically, the present invention discloses an efficient transition metal oxide supported electrochemical reduction catalyst comprising Cu-Zn alloy dispersed over cobalt oxide. Disclosed catalyst is designed to convert CO2 into more usable and viable forms, aiming to mitigate the anthropogenic carbon cycle. The catalyst effectively converts CO2 into carbon monoxide (CO) and isopropyl alcohol (IPA) with a high Faradaic efficiency at a remarkably low applied potential versus the reversible hydrogen electrode (RHE). Observed performance of the Co3O4 supported Cu-Zn alloy catalyst having Cu-Zn alloy dispersed over cobalt oxide is significantly superior to comparable catalysts, wherein said catalyst demonstrates enhanced efficiency in CO2 reduction at a lower energy input.

[0033] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

[0034] Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.

[0035] It must be noted that as used herein and in the appended claims, the singular forms "a", "and", and "the" include plural referents unless the context dictates otherwise. Thus, for example, reference to "a compound" includes a plurality of such compounds, and reference to "the step" includes reference to one or more steps and equivalents thereof known to those skilled in the art, and so forth.

[0036] The term “some” as used herein is defined as “none, or one, or more than one, or all.” Accordingly, the terms “none,” “one,” “more than one,” “more than one, but not all” or “all” would all fall under the definition of “some.” The term “some embodiments” may refer to no embodiments or to one embodiment or to several embodiments or to all embodiments. Accordingly, the term “some embodiments” is defined as meaning “no embodiment, or one embodiment, or more than one embodiment, or all embodiments.”

[0037] The terminology and structure employed herein is for describing, teaching and illuminating some embodiments and their specific features and elements and does not limit, restrict or reduce the spirit and scope of the claims or their equivalents.

[0038] More specifically, any terms used herein such as but not limited to “includes”, “comprises”, “has”, “consists” and grammatical variants thereof is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. The specification will be understood to also include embodiments which have the transitional phrase “consisting of” or “consisting essentially of” in place of the transitional phrase “comprising.” The transitional phrase “consisting of” excludes any element, step, or ingredient not specified in the claim, except for impurities associated therewith. The transitional phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed disclosure.

[0039] Whether or not a certain feature or element was limited to being used only once, either way it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do NOT preclude there being none of that feature or element, unless otherwise specified by limiting language such as “there NEEDS to be one or more” or “one or more element is REQUIRED.”

[0040] As used herein, the term “about” is used to indicate a degree of variation or tolerance in a numerical or quantitative value. It indicates that the disclosed value is not intended to be strictly limiting, and may vary by plus or minus 5%, without departing from the scope of the invention.

[0041] Unless otherwise defined, all terms, and especially any technical and/or scientific terms, used herein may be taken to have the same meaning as commonly understood by one having an ordinary skill in the art.

[0042] Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements presented in the attached claims. Some embodiments have been described for the purpose of illuminating one or more of the potential ways in which the specific features and/or elements of the attached claims fulfil the requirements of uniqueness, utility and non-obviousness.

[0043] Use of the phrases and/or terms such as but not limited to “a first embodiment,” “a further embodiment,” “an alternate embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or variants thereof do NOT necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or alternatively in the context of more than one embodiment, or further alternatively in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.

[0044] In an aspect of the present invention, there is provided an efficient transition metal oxide supported electrochemical reduction catalyst.

[0045] In an aspect of the present invention, there is provided an efficient electrochemical reduction catalyst having high Faradaic efficiency at a low energy input.

[0046] In an aspect of the present invention, there is provided an easy and industrially scalable process for preparing a transition metal oxide supported electrochemical reduction catalyst.

[0047] In an aspect of the present invention, there is provided an easy, and a commercially scalable method for converting CO2 into CO and isopropanol.

[0048] In one of the preferred aspects, the present invention provides transition metal oxide supported electrochemical reduction catalyst comprising: a) 1.0 to 10.0 wt. % of an alloy; and b) 90.0 to 99.0 wt. % of the transition metal oxide.

[0049] In an aspect of the present invention, the alloy is Cu-Zn alloy comprising copper and zinc in a weight ratio of 1:1.

[0050] In another aspect of the present invention, the electrochemical reduction catalyst has a Faradaic efficiency of 50 to 60 %, at an applied potential of -0.3 V to -0.7 V, preferably -0.5 V.

[0051] In an aspect of the present invention, the applied potential is a potential applied to the electrode comprising electrochemical reduction catalyst against a reversible hydrogen electrode (RHE) in an electrochemical cell.

[0052] In yet another aspect of the present invention, the electrochemical reduction catalyst has a CO2 (carbon dioxide) to CO (carbon monoxide) and CO2 (carbon dioxide) to CH3CH(OH)CH3 (isopropyl alcohol) conversion efficacies in a range of 40 to 46 %, and 10 to 16 %, respectively.

[0053] In still another aspect of the present invention, the transition metal oxide supported electrochemical reduction catalyst is Co3O4 supported Cu-Zn alloy catalyst comprising 2.5 wt. % of a Cu-Zn alloy, wherein the Co3O4 supported Cu-Zn alloy catalyst has a Faradaic efficiency of 56.3 %, and a CO2 (carbon dioxide) to CO (carbon monoxide) and CO2 to CH3CH(OH)CH3 (isopropyl alcohol) conversion efficacies 42.8 %, and 13.5 %, respectively.

[0054] In another aspect of the present invention, the transition metal oxide supported electrochemical reduction catalyst is Co3O4 supported Cu-Zn alloy catalyst comprising 2.5 wt. % of a Cu-Zn alloy, wherein the Co3O4 supported Cu-Zn alloy catalyst has a Faradaic efficiency of 56.3 %, at an applied potential of -0.5 V.

[0055] In another preferred aspect of the present invention, a process for preparing a transition metal oxide supported electrochemical reduction catalyst, the process comprising: a) adding 2 to 5 g of a transition metal salt and 1 to 2 g of urea in 15 ml of water to obtain a reaction mixture; b) combusting the reaction mixture in a furnace at a temperature ranging from 350 to 450 ℃ for a time period of 15 to 25 minutes, preferably 20 minutes to obtain a combusted reaction mixture; c) calcining the combusted reaction mixture at a temperature of 500 to 700 ℃ for 8 to 12 hours to obtain a transition metal oxide powder; d) dispersing 0.5 to 2 g of the transition metal oxide powder in 35 to 45 ml, preferably 40 ml of water followed by sonication at 18,000 to 22,000 Hz, preferably 20,000 Hz to obtain a transition metal oxide solution; e) adjusting pH of the transition metal oxide solution to a pH value of 1 (pH =1) by adding an acid followed by adding 5 to 20 ml of a ketone with a continuous stirring for 50 to 70 minutes to obtain an acidic transition metal oxide solution having pH value in a range of 1 to 3; f) adding 4 to 6 ml of an aqueous solution of a copper salt and 5 to 7 ml of an aqueous solution of a zinc salt to the acidic transition metal oxide solution followed by dropwise adding 10 ml to 30 ml of an aldehyde to obtain an acidic mixture; and g) adding 2 to 3 ml of a base to the acidic mixture to obtain a basic mixture followed by maintaining temperature of the basic mixture at a temperature ranging 60°C to 100°C for 6 to 10 hours to obtain the transition metal oxide supported electrochemical reduction catalyst.

[0056] In an aspect of the present invention, the aqueous solution of the copper salt comprises 0.01 to 0.1 g of the copper salt.

[0057] In an aspect of the present invention, the aqueous solution of the zinc salt comprises 0.01 to 0.1 g of the zinc salt.

[0058] In an aspect of the present invention, the transition metal salt is selected from cobalt nitrate trihydrate, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulphate heptahydrate and a combination thereof, wherein the copper salt is selected from copper nitrate trihydrate, copper chloride dihydrate, copper sulphate pentahydrate, and a combination thereof, wherein the zinc salt is selected from zinc nitrate hexahydrate, zinc chloride dihydrate, zinc sulphate heptahydrate and a combination thereof, wherein preferably the transition metal oxide is cobalt oxide (Co3O4), wherein the aldehyde is selected from formaldehyde (HCHO), glyoxal (OCHCHO), and glutaral (CH2)3(CHO)2 and a combination thereof, wherein the ketone is acetone, wherein the acid is selected from nitric acid (HNO3), hydrochloric acid (HCl), acetic acid (CH3COOH) and a combination thereof, wherein the base is selected from potassium hydroxide (KOH), sodium hydroxide (NaOH) and a combination thereof, wherein the transition metal oxide supported electrochemical reduction catalyst comprises 1.0 to 10.0 wt. % of an alloy; and 90.0 to 99.0 wt. % of the transition metal oxide, wherein the electrochemical reduction catalyst has a Faradaic efficiency of 50 to 60 %, at an applied potential of -0.3 V to -0.7 V, preferably -0.5 V in the electrochemical reduction, and wherein the transition metal oxide supported electrochemical reduction catalyst of step g) is washed 2 to 5 times with distilled water, and then dried in a hot air oven at a temperature of 60℃ to 75℃, preferably at 70℃.

[0059] In another preferred aspect of the present invention, a method for an electrochemical reduction of carbon dioxide to carbon monoxide and isopropanol, the method characterized in contacting the carbon dioxide with a transition metal oxide supported electrochemical reduction catalyst in an electrochemical cell.

[0060] In still another aspect of the present invention, the transition metal oxide supported electrochemical reduction catalyst comprising: a) 1.0 to 10.0 wt. % of an alloy; and b) 90.0 to 99.0 wt. % of the transition metal oxide, wherein the alloy catalyst has a Faradaic efficiency of 50 to 60 %, at an applied potential of -0.3 V to -0.7 V, preferably at -0.5 V.

[0061] In yet another aspect of the present invention, the transition metal oxide supported alloy catalyst is Co3O4 supported Cu-Zn alloy catalyst comprising 2.5 wt. % of a Cu-Zn alloy, wherein the Co3O4 supported Cu-Zn alloy catalyst has a Faradaic efficiency of 56.3 %, at an applied potential of -0.5 V in the electrochemical cell, wherein the Co3O4 supported Cu-Zn alloy catalyst has a CO2 (carbon dioxide) to CO (carbon monoxide) and CO2 (carbon dioxide) to CH3CH(OH)CH3 (isopropyl alcohol) conversion efficacies 42.8 %, and 13.5 %, respectively.

[0062] In an aspect of the present invention, the applied potential is a potential applied to the electrode comprising electrochemical reduction catalyst against a reversible hydrogen electrode (RHE) in an electrochemical cell.

EXAMPLES:

[0063] The present disclosure is further illustrated by reference to the following examples which is for illustrative purpose only and does not limit the scope of the disclosure in any way. These examples are not intended to be inclusive of all aspects of the subject matter disclosed herein, but rather to illustrate representative features, methods, compositions, and results. These examples are not intended to exclude equivalents and variations of the present disclosure, which are apparent to one skilled in the art.

Example 1: Preparing of the Transition Metal Oxide Supported Electrochemical Reduction Catalyst:

[0064] The support oxide (Co3O4) was prepared using a solution combustion method. In this method, the precursor cobalt nitrate trihydrate (5 g) was treated with fuel urea (1.715g) in 15 ml water. Then, the reaction mixture was kept inside a muffle furnace for a time period of 20 minutes to undergo the process of combustion at 400℃, followed by the calcination. The powder resulting after 10 hours of calcination was then cooled down and characterized by XRD (Figure 1). For preparing 2.5 % Cu-Zn alloy dispersed over Co3O4, formaldehyde reduction method was used. 1g of the obtained transition metal oxide (support oxide (Co3O4)) was first dispersed in 40 ml water and subjected to ultrasonic treatment at a frequency 20,000 hz. Subsequently 0.5 to1 ml nitric acid was added to adjust the pH in acidic range (at pH = 1), followed by addition of 10 ml acetone.

[0065] After stirring the mixture for 1 hour, 4 to 6 ml of copper nitrate trihydrate aqueous solution (comprising 0.01 to 0.1 g of the copper nitrate trihydrate) and 5 to 7 ml zinc nitrate hexahydrate aqueous solution (comprising 0.01 to 0.1 g of the zinc nitrate hexahydrate) were introduced, and 20 ml formaldehyde was added dropwise. 2 to 3 ml of a base selected from KOH, NaOH, and a combination thereof was then added to the bring the pH in basic range (at a pH of 10). The solution was maintained at 80°C for 8 hours under controlled stirring. Afterwards, the precipitate was collected, washed multiple times (2-5 times) with distilled water, and dried in a hot air oven.

[0066] In an exemplary embodiment of the present invention, various transition metal oxide supported electrochemical reduction catalysts i.e. Co3O4 supported Cu-Zn alloy catalyst comprising Cu-Zn alloy dispersed over Co3O4 [Cu-Zn/Co3O4], were prepared by altering the weight percentage of the Cu-Zn alloy from 1 to 10 weight %.

Example 2: Characterization of the Transition Metal Oxide Supported Electrochemical Reduction Catalyst:

[0067] The synthesized transition metal oxide supported electrochemical reduction catalyst are characterized by X-ray diffraction (P-XRD), and Field Emission Scanning Electron Microscopy (FESEM).

X-ray diffraction:
[0068] The X-ray diffraction (XRD) pattern of transition metal oxide supported electrochemical reduction catalyst synthesized in the present invention is presented in Figure 1. The diffraction peaks for Co3O4 are observed at 18.94°, 31.26°, 36.84°, 38.56°, 44.82°, 55.64°, 59.34°, and 65.24°, corresponding to the (111), (220), (311), (400), (422), (511), and (440) planes, respectively. These peaks align well with the characteristic pattern of the cubic phase of Co3O4. Whereas for Cu-Zn alloy the diffraction peaks observed at 36.39°, 42.39°, 43.29°, 50.40°, 61.38° and 74.01° corresponding to (101) (111) (110), (200) α, (200) β and (220) planes respectively. All the composition follows the peak arrangement for Co3O4 as the limitation of p-XRD does not allow to detect the fine dispersion of the nanoparticles over the oxide surfaces.

Field Emission Scanning Electron Microscopy (FESEM):
[0069] The FESEM is used to characterize topographic details of the surface of the of transition metal oxide supported electrochemical reduction catalyst synthesized in the present invention. Figure 3 illustrates Scanning Electron Microscopy images of the transition metal oxide supported electrochemical reduction catalyst i.e. Co3O4 supported Cu-Zn alloy catalyst comprising 2.5 weight % of the Cu-Zn alloy (or 2.5 % Cu-Zn/Co3O4 catalyst) of the present invention.

Example 3: Conversion of Carbon Dioxide to Carbon Monoxide and Isopropanol

[0070] Synthesized Co3O4 supported Cu-Zn alloy catalyst having Cu-Zn alloy dispersed over cobalt oxide, was employed for an electrochemical reduction of CO2, wherein the catalyst efficiently converts CO2 into carbon monoxide (CO) and isopropyl alcohol (IPA) with a high Faradaic efficiency of 56.3% at a remarkably low applied potential of -0.5 V versus the reversible hydrogen electrode (RHE) in an electrochemical cell. The performance of the catalyst was found significantly superior to comparable catalysts of the prior arts, wherein the enhanced efficiency of the synthesized Co3O4 supported Cu-Zn alloy catalyst significantly enabled the catalyst for electroreduction of CO2 at a lower energy input.
The overall reaction of the conversion is given below:
CO2 + ne- CO (43%) + CH3CH(OH)CH3 (13.5%) + Resistive losses
[0071] The Cyclic voltammetry (CV) of the electrochemical reduction catalyst comprising electrochemical cell were performed in two distinct environments: first, in an argon atmosphere to eliminate contaminants and dissolved oxygen from the system, and second, in a CO2-saturated environment to activate the catalyst and prepare it for the subsequent electrochemical reactions. The current density was higher in the CO2 environment than in the Argon atmosphere. The electrochemical measurements were performed at three discrete potentials, 0.6V to -0.5V, -0.6V and -0.7 V vs. RHE.

[0072] Chronoamperometry was performed to observe the stability of the system at -0.5 V. The chronoamperometry graph in Figure 4 illustrates trend of the current density changes over a period of 1800 seconds during the experiment. At the starting point, a sharp negative peak around -7 mA/cm2 in Figure 4 reflects an immediate activation of the electrode surface and the rapid onset of reduction reactions. Almost immediately after, the current quickly moves toward 0 mA/cm2, indicating that the system is stabilizing, likely due to the formation of the electrical double layer and the quick consumption of easily accessible CO2 at the electrode interface. Following this initial phase, the current begins to decrease more gradually and consistently over time, eventually levelling off around -1 mA/cm2. This slow decline suggests the system has reached a steady state, where the reduction of CO2 continues at a more stable and controlled rate.

[0073] After performing chronoamperometry the gas and liquid analysis was performed in gas chromatography to analyse the product formation. In gas analysis, the major product formed was carbon monoxide (CO), and in liquid analysis the product was Isopropyl.

[0074] In an exemplary embodiment of the present invention, all transition metal oxide supported electrochemical reduction catalysts having different weight percentage of the Cu-Zn alloy were evaluated for their efficacies, the results are tabulated in Table 1.

Table 1: Faradic Efficacies and CO2 conversion efficacy of the Electrochemical Catalysts
Wt. % of Cu-Zn alloy in Co3O4 supported Cu-Zn alloy catalyst Applied Potential CO2 to CO conversion efficacy CO2 to IPA
conversion efficacy Faradaic efficiency
1 wt. % -0.5 V vs. RHE 18.6 % 20 % 38.6%
2.5 wt. % -0.5 V vs. RHE 42.8 % 13.5 % 56.3 %
5 wt. % -0.5 V vs. RHE 2.0 % 0.4 % 2.4 %
10 wt. % -0.5 V vs. RHE 1.06 % 0.14 % 0.45%

[0075] Out of the tested electrochemical catalysts, the transition metal oxide supported electrochemical reduction catalyst comprising 2.5% Cu-Zn/Co3O4 provided the best results with a Faradic efficacy of 56.3%, with CO2 (carbon dioxide) to CO (carbon monoxide) and CH3CH(OH)CH3 (isopropyl alcohol) conversion efficacies of 42.8 % and 13.5 %, respectively.
Figure 3 illustrates a cyclic voltammetry of 2.5% Cu-Zn/Co3O4 catalyst at 0.6V to -0.5V vs. RHE in Argon and CO2 atmosphere, of the present invention.
[0076] The efficacy of the transition metal oxide supported electrochemical reduction catalyst of the present invention was compared with the available Cu-Zn alloy catalysts of the arts. The advantageous characteristics of the electrochemical reduction catalyst of the subject invention are illustrated in Table 2.

Table 2: A Comparison of Efficacy of the Catalyst of the art with the electrochemical reduction catalyst of the Present Invention
S.no Catalyst Overpotential Products and
Faradaic efficiency Limitations
1 Cu-Zn alloy -1.1V vs. RHE C2H4 =33.1% High overpotential and low FE1
2 Cu-Zn alloy -0.7V vs. RHE C2H5OH =⁓25%, and C2H4=Not known High overpotential and low FE2
3 Cu-Zn alloy -1V vs. RHE HCOOH=20% and CO= 60% High overpotential and low FE3
4 Cu-Zn alloy/Cu-Zn aluminate oxide -1.15 V vs. RHE C2+ products=88.5% High overpotential and formation of mixed alcohols, difficult to separate4
5 Cu-Zn alloy -0.8V vs. RHE C2H5OH=46.6% High overpotential and low FE5
6 Cu-Zn alloy -0.91V vs. RHE CO =30.7% and CHOO-=21.6% High overpotential and low FE6
7 CuZn/Co3O4 -0.5V vs. RHE CO = 43% and CH3CH(OH)CH3=20.5% Low overpotential and high FE
(Present Invention)
Reference: 1 Feng Y. et al. 2018. Langmuir, 34, 13544−13549; 2 Baek Y. et al. 2022. J. Mater. Chem. A, 10, 9393; 3Akihiro Katoh et al 1994. J. Electrochem. Soc. 141 2054; 4Zhang Z.Y. et al. 2023. J. Energy Chem.,83, 2023, 90-97; 5Su X. et al., 2020. Applied Catalysis B: Envir.,269, 2020, 118800; and 6 Badawy, I. M. et al., 2022. Sci Rep 12, 13456.

[0077] Advantage of the present invention over existing solutions:

a. The transition metal oxide supported electrochemical reduction catalyst of the present invention has lower overpotential (low energy input).

b. The transition metal oxide supported electrochemical reduction catalyst of the present invention has a high Faradaic efficiency (Ratio of Converted electrons/total input electrons).

c. The process for preparation of the transition metal oxide supported electrochemical reduction catalyst of the present invention is an easy, an economic, a less energy intensive and an industrially viable process.

d. The obtained reaction products (CO, IPA) has its own advantage, as CO serves as a crucial feedstock and an integral part in many manufacturing processes and chemical industries, food industries, etc, and Isopropyl alcohol is a versatile solvent used in many manufacturing and pharmaceutical industries. , Claims:1. A transition metal oxide supported electrochemical reduction catalyst comprising:
a) 1.0 to 10.0 wt. % of an alloy; and
b) 90.0 to 99.0 wt. % of the transition metal oxide.
2. The transition metal oxide supported electrochemical reduction catalyst as claimed in claim 1, wherein the alloy is Cu-Zn alloy comprising copper and zinc in a weight ratio of 1:1.

3. The transition metal oxide supported electrochemical reduction catalyst as claimed in claim 1, wherein the electrochemical reduction catalyst has a Faradaic efficiency of 50 to 60 %, at an applied potential of -0.3 V to -0.7 V, preferably -0.5 V.

4. The transition metal oxide supported electrochemical reduction catalyst as claimed in claim 1, wherein the electrochemical reduction catalyst has a CO2 (carbon dioxide) to CO (carbon monoxide) and CO2 (carbon dioxide) to CH3CH(OH)CH3 (isopropyl alcohol) conversion efficacies in a range of 40 to 46 %, and 10 to 16 %, respectively.

5. The transition metal oxide supported electrochemical reduction catalyst as claimed in claim 1, wherein the transition metal oxide supported electrochemical reduction catalyst is Co3O4 supported Cu-Zn alloy catalyst comprising 2.5 wt. % of a Cu-Zn alloy, wherein the Co3O4 supported Cu-Zn alloy catalyst has a Faradaic efficiency of 56.3 %, and a CO2 (carbon dioxide) to CO (carbon monoxide) and CO2 (carbon dioxide) to CH3CH(OH)CH3 (isopropyl alcohol) conversion efficacies 42.8 %, and 13.5 %, respectively.

6. A process for preparing a transition metal oxide supported electrochemical reduction catalyst, the process comprising:
a) adding 2 to 5 g of a transition metal salt and 1 to 2 g of urea in 15 ml of water to obtain a reaction mixture;
b) combusting the reaction mixture in a furnace at a temperature ranging from 350 to 450℃, for a time period of 15 to 25 minutes, preferably 20 minutes to obtain a combusted reaction mixture;
c) calcining the combusted reaction mixture at a temperature ranging from 500 to 700 ℃ for 8 to 12 hours to obtain a transition metal oxide powder;
d) dispersing 0.5 to 2 g of the transition metal oxide powder in 35 to 45 ml, preferably 40 ml of water followed by sonication at 18,000 to 22,000 Hz, preferably 20,000 Hz to obtain a transition metal oxide solution;
e) adjusting pH of the transition metal oxide solution to a pH value of 1 (pH =1) by adding an acid followed by adding 5 to 20 ml of a ketone with a stirring for 50 to 70 minutes to obtain an acidic transition metal oxide solution having pH value in a range of 1 to 3;
f) adding 4 to 6 ml of an aqueous solution of a copper salt and 5 to 7 ml of an aqueous solution of a zinc salt to the acidic transition metal oxide solution followed by dropwise adding 10 ml to 30 ml of an aldehyde to obtain an acidic mixture; and
g) adding 2 to 3 ml of a base to the acidic mixture to obtain a basic mixture followed by maintaining temperature of the basic mixture at a temperature ranging 60°C to 100°C for 6 to 10 hours to obtain the transition metal oxide supported electrochemical reduction catalyst.

7. The process as claimed in claim 6, wherein the transition metal salt is selected from cobalt nitrate trihydrate, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulphate heptahydrate and a combination thereof, wherein the copper salt is selected from copper nitrate trihydrate, copper chloride dihydrate, copper sulphate pentahydrate, and a combination thereof, wherein the zinc salt is selected from zinc nitrate hexahydrate, zinc chloride dihydrate, zinc sulphate heptahydrate and a combination thereof, wherein preferably the transition metal oxide is cobalt oxide (Co3O4), wherein the aldehyde is selected from formaldehyde (HCHO), glyoxal (OCHCHO), glutaral (CH₂)₃(CHO)₂) and a combination thereof, wherein the ketone is acetone, wherein the acid is selected from nitric acid (HNO3), hydrochloric acid (HCl), acetic acid (CH3COOH) and a combination thereof, wherein the base is selected from potassium hydroxide (KOH), sodium hydroxide (NaOH) and a combination thereof, wherein the transition metal oxide supported electrochemical reduction catalyst comprises 1.0 to 10.0 wt. % of an alloy; and 90.0 to 99.0 wt. % of the transition metal oxide, wherein the electrochemical reduction catalyst has a Faradaic efficiency of 50 to 60 %, at an applied potential of -0.3 V to -0.7 V, preferably -0.5 V in the electrochemical reduction, and wherein the transition metal oxide supported electrochemical reduction catalyst of step g) is washed 2 to 5 times with distilled water, and then dried in a hot air oven at a temperature of 60℃ to 75℃, preferably 70 ℃.

8. A method for an electrochemical reduction of carbon dioxide to carbon monoxide and isopropanol, the method characterized in contacting the carbon dioxide with a transition metal oxide supported electrochemical reduction catalyst in an electrochemical cell.

9. The method as claimed in claim 8, wherein the transition metal oxide supported electrochemical reduction catalyst comprises 1.0 to 10.0 wt. % of an alloy; and 90.0 to 99.0 wt. % of the transition metal oxide, and wherein the alloy catalyst has a Faradaic efficiency of 50 to 60 %, at an applied potential of -0.3 V to -0.7 V, preferably -0.5 V in the electrochemical cell.

10. The method as claimed in claim 8, wherein the transition metal oxide supported electrochemical reduction catalyst is Co3O4 supported Cu-Zn alloy catalyst comprising 2.5 wt. % of a Cu-Zn alloy, wherein the Co3O4 supported Cu-Zn alloy catalyst has a Faradaic efficiency of 56.3 % at an applied potential of -0.5 V, and has a CO2 (carbon dioxide) to CO (carbon monoxide) and CO2 (carbon dioxide) to CH3CH(OH)CH3 (isopropyl alcohol) conversion efficacies 42.8 %, and 13.5 %, respectively.