Electrochemical conversion of carbon dioxide into value-added products

Abstract

The present disclosure provides a method of electrochemical conversion of carbon dioxide (CO2) into value-added products (VAPs) such as ethanol, acetic acid, isoamyl alcohol, isopropanol, metal or ethyl acetates and acetaldehyde. The method of electrochemical conversion of carbon dioxide (CO2) into value-added products (VAPs) utilises a reactor having metallic Copper (Cu) or Cu-alloy symmetric electrodes (cathode and anode), wherein the metallic Cu or Cu-alloy electrodes act as electrocatalyst, and acidified water (H3O +) as electrolyte for generation of H2 gas. The process exhibited a maximum Faradaic Efficiency (FE%) of up to 77.26%, which is an indication of % ethanol and other VAP yield, and Energy Efficiency (EE%) of up to 32.97%.

Description

[0001]TITLE ELECTROCHEMICAL CONVERSION OF CARBON DIOXIDE INTO VALUE-ADDED PRODUCTS CROSS REFERENCE TO RELATED APPLICATIONS The present application is based upon and claims priority to India complete patent application number 202341047481 filed on August 26, 2023, which claims priority to India provisional patent application number 202341047481 filed on July 14, 2023. The entire contents of all are herein incorporated by reference. FIELD: The present disclosure relates to methods of electrochemical conversion of carbon dioxide into value-added products such as ethanol, acetic acid, acetaldehyde, metal acetates, ethyl acetates. DEFINITION: As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise. As used herein, the terms “intermediates”, “organic intermediates”, “cation radical intermediates”, “short-lived cation radical intermediates”, “cation radicals”, “organic cation radicals” may have been used interchangeably, which means the intermediates formed through asymmetric C–C coupling of reaction of asymmetric C-C coupling on the cathode surface of the reactor of the present disclosure. As used herein, the terms “electrochemical reactor” or “reactor” may have been used interchangeably which means the reactor of the present disclosure that electrochemically converts CO2 into VAPs. As used herein, the term “asymmetric C-C coupling” means two CO2molecules undergo C=O bond breaking, where C of one CO2 molecule (C1) gets attached to the electrode (cathode) Cu, and C of another CO2molecule (C2) is attached to Oxygen at one end and to the C1 on the other end leading to formation of short- lived cation radical intermediates of the skeleton Cu−C−C=O with the H bonds to it as below: Cu−C+.H−CH=O .…….. cation radical(1) Cu−CH2−C+.H=O .…..… cation radical(2) Cu−CH2−C+.H2−O ……. cation radical(3) and, further hydrogen bonding to the cation radical(3) results in the formation of the following anions on the electrode (cathode) Cu-surface. Cu−CH3−CH2−O−....….. ethoxide anion on Cu surface Cu−CH3−COO−...…... ethanoate anion on Cu surface BACKGROUND: Global warming has been a major concern, which poses a serious threat to life on the earth in the forms of widespread flooding and extreme weather conditions. While, scientists continue to study global warming and its impact on the earth, and several strategies are being attempted to reduce carbon dioxide emission, the electrochemical reactions of CO2are of specific interest for the synthesis of chemicals and for approaches to decrease global warming. Work has been done looking at synthesizing specialty chemicals such as formate and urea from carbon dioxide. However, a far greater impact on decreasing atmospheric CO2levels might be obtained by converting CO2 into fuels, or in other words synthesising fuels from CO2. In such carbon-based energy cycles, energy from renewable power would be used to synthesize fuels from captured CO2, which, when used, would not release additional CO2to the atmosphere (i.e., ‘‘CO2neutral fuels’’). As such, these processes represent the storage of these energy sources as chemical energy, which allows them to be more widely used, particularly for transportation applications. The main advantages of such carbon-based fuels, vs. storing electricity in batteries or as hydrogen, are the ease of use within existing infrastructures and the higher energy density. Because this involves converting electrical energy to chemical energy, here electrochemistry is an important enabling technology. In one carbon-based energy cycle concept, electrolytic hydrogen would be reacted with CO2to form methanol and water, which, following distillation, yields liquid methanol. Another concept would react electrolytic hydrogen and CO2 to form methane (with condensation of water to shift the equilibrium and achieve good yields). Electro-reduction of CO2to VAPs such as ethanol, acetates that can be used as fuels is practically promising and utilization of the same as renewable electricity and mitigation of CO2emissions, leads to carbon neutrality. The electrochemical reduction of CO2 is a process in which electrical energy is converted to organic chemicals of importance from CO2. Although different organic molecules may be obtained from electrochemical CO2reduction such as formic acid, hydrocarbons (methane, ethane), alcohols (methanol, ethanol, propanol), production of ethanol specifically becomes an important and inevitable process due to the utility of ethanol as alternate fuel to fossil fuel and also as an important organic commodity chemical. Ethanol possesses high energy density and compatibility with present day IC engines and thus can be blended with fossil fuel and used as fuel for automobiles. Ethanol is also a key precursor in the synthesis of various chemical compounds that cater to the medical and food industries. The extensively followed procedure for production of ethanol world- wide is via fermentation of starch rich biomass such as sugarcane, corn, paddy etc. Recently, electrochemical reduction of CO2 to ethanol had become a potentially more effective and sustainable alternative. During the electrochemical reduction of CO2, in the presence of an electrocatalyst, the applied electrical energy converts the C-O bond in CO2 and acidified water (H3O+) to form VAPs with one C (CH4, CH3OH), with two or more C atoms (C2H5OH, C2H6, CH3COOH). Many metal electrocatalysts such as Au, Ag, Sn, and Pb led to the formation of mixed one C products, whereas Cu-based electrocatalysts solely transforms CO2into two or more C products via asymmetric coupling of the adsorbed *CO intermediates on the Cu electrode surface. Out of the many VAPs that can be produced on Cu electrode surface, ethanol is a vital product as it acts as a liquid fuel with high energy density, easy transport, long life storage options as energy storage material etc. To make ethanol as the renewable energy based chemical feedstock, its production with high current density and Faradaic efficiency (FE) employing Cu-based electrocatalysts / electrode becomes significant. The electrochemical reduction of CO2to EtOH and ethylene (C2H4) are electron reduced products, and share the common initial intermediates of *HCCOH. The second intermediate for formation of ethanol is *H2CCHOH which is highly saturated and hence very short-lived. This involves faster reaction between the second intermediate and hydrogen leading to formation of ethanol on a pure Cu electrode surface. The production of ethanol via formation of C–O bond is highly competitive in comparison with the C-H bond and typically results in the 2–3 times less ethanol production in than that of ethane on Cu-electrocatalyst. To increase the ethanol production, re- designing of the Cu electrocatalyst and the electrochemical reactor becomes inevitable. Although, several researches on morphology and facet control, effective occupancy of vacancy, modified electrode or electrocatalysts by dopant engineering, and defects control on the electrodes or electrocatalyst have been reported, the modification of Cu with other CO2-active metals to form Cu based bimetallic is reported to be practically possible. For instance, Cu–Au bimetallic catalysts with enhanced selectivity for electrochemical reduction of CO2 to ethanol, and a synergistic electrocatalytic CO – tandem mechanism on Au, desorbed and migrated to near Cu active sites where C–C coupling resulted in the formation of ethanol. A bimetallic Cu3Ag1 catalyst with electron-deficient Cu sites is reported for enhanced ethanol selectivity by promoting the rate of adsorption of important intermediates in the formation of ethanol. Further, Ag induced strain effects on Cu electrode surfaces is found to enhance the ethanol selectivity and modulates ethanol production by suppressing the Hydrogen Evolution Reaction (HER). In spite of the significant research and development towards the improvement of FE of ethanol production by bimetallic catalysts the production and output efficiency for ethanol from CO2is not at par for practical application (i.e., partial current density > 300 mA cm−2and half-cell cathodic energy efficiencies > 20%). Although the effect of the Cu-based alloys as electrocatalysts on CO2 electro- redcution is not yet clear to explain the high rates of conversion of CO2 to ethanol and thus hinders the design of electrocatalyst and reactor effectively. In a recent research, Cu2O is modified by Ag and the derived CuAg bimetallics (dCu2O / Ag) with precise control on phase, surface morphology and composition for CO2electro-reduction at high current density. Au modified Cu2O resulted in electro- reduction of CO2 to C2H4 and CO, respectively whereas the optimized dCu2O / Ag (2.3%) exhibited an enhanced ethanol production at high applied current density via asymmetric C–C coupling to stabilize reaction intermediates. The FE and EE for ethanol production was obtained as 40.8% and 22.4%, respectively. Thus, to overcome the above-mentioned bottle necks, it becomes clear that there is a need for designing of more efficient electrocatalysts and clear understanding of the mechanism of electro-reduction of CO2 to enhance the ethanol production under commercial current densities and viability. SUMMARY: The present disclosure provides a method of electrochemical conversion of carbon dioxide (CO2) into value-added products (VAPs) such as ethanol, and acetaldehyde. The method of electrochemical conversion of carbon dioxide (CO2) into value-added products (VAPs) utilises an electrochemical reactor having metallic Copper (Cu) or Cu-alloy symmetric electrodes (cathode and anode), wherein the metallic Cu or Cu-alloy electrodes act as electrocatalyst, and acidified water (H3O+) as electrolyte for generation of H2 gas. The process exhibited a maximum Faradaic Efficiency (FE%) of up to 77.26%, which is an indication of % ethanol and other VAP yield, and Energy Efficiency (EE%) of up to 32.97%. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS: Fig. 1 is an illustrative representation of CO2forming C-C asymmetric coupling on Cu electrodes (as electrocatalyst) to form ethanol. Fig. 2 illustrates the eelectrochemical process, electrochemical reactor and reaction for CO2conversion to ethanol and other value-added products (VAPs). Fig. 3 is an illustrative representation of design of the electrochemical reactor to convert CO2to ethanol and VAPs. Fig. 4 illustrates Gas Chromatography (GC) peaks of ethanol, acetaldehyde and acetates identified from the CO2reduction. Fig. 5 illustrates FTIR spectrum of liquid sample from Day 1 and 2 of the Case (i) experiments (after hydrolysis for 10 h and 24 h of completion of the electrocatalytic reduction of CO2 on Cu surface). Fig. 6 illustrates FTIR spectrum of solid sample from Day 1 and 2 of the Case (i) experiments (after hydrolysis for 10 h and 24 h of completion of the electrocatalytic reduction of CO2 on Cu surface) Fig. 7 illustrates UV-Vis spectrum of liquid sample from Day 1 and 2 of the Case (i) experiments (after hydrolysis for 10 h and 24 h of completion of the electrocatalytic reduction of CO2 on Cu surface). Fig. 8 illustrates UV-Vis spectrum of the solid sample from Day 1 and 2 of the Case (i) experiments (after hydrolysis for 10 h and 24 h of completion of the electrocatalytic reduction of CO2 on Cu surface). Fig. 9 illustrates GC peaks of ethanol identified from the CO2reduction for case (ii) without initiator and industrial CO2 as the source at a flow rate of 150ml / min with purity of 99.3%. Fig. 10 illustrates FTIR spectrum of liquid sample from Day 1 and 2 of the Case (ii) experiments (after hydrolysis for 10 hrs and 24 hrs of completion of the electrocatalytic reduction of CO2 on Cu surface) Fig. 11 illustrates UV-Vis spectrum of the liquid sample from the Case (ii) experiments (after hydrolysis for 10 h and 24 h of completion of the electrocatalytic reduction of CO2at a flow rate of 150ml / min on Cu surface) Fig. 12 illustrates GC peaks of ethanol identified from the CO2 reduction for case (iii) without initiator and industrial CO2as the source at a flow rate of 500ml / min with purity of 99.3%. Fig.13 illustrates FTIR spectrum of liquid sample from the Case (iii) experiments (after hydrolysis for 10 hrs and 24 hrs of completion of the electrocatalytic reduction of CO2 on Cu surface). Fig. 14 illustrates UV-Vis spectrum of the liquid sample from the Case (iii) experiments (after hydrolysis for 10 h and 24 h of completion of the electrocatalytic reduction of CO2at a flow rate of 500ml / min on Cu surface) Fig. 15 illustrates GC peaks of ethanol and isoamyl alcohol identified from the CO2reduction for case (iv) with initiator and industrial CO2as the source with purity of 99.3%. Fig. 16 illustrates FTIR spectrum of liquid sample from the Case (iv) experiments (after hydrolysis for 10 hrs and 24 hrs of completion of the electrocatalytic reduction of CO2 on Cu surface). Fig. 17 illustrates FTIR spectrum of solid sample from the case (iv) experiments (after hydrolysis for 10 hrs and 24 hrs of completion of the electrocatalytic reduction of CO2 on Cu surface). Fig. 18 illustrates UV-Vis spectrum of the liquid sample from the Case (iv) experiments (after hydrolysis for 10 h and 24 h of completion of the electrocatalytic reduction of CO2at a flow rate of 150ml / min with initiator on Cu surface). DETAILED DESCRIPTION: The preferred embodiments of the present disclosure will be described in detail with the following disclosure and examples. The foregoing general description and the following detailed description are provided to illustrate only some embodiments of the present disclosure and not to limit the scope of the present disclosure. The disclosure is capable of other embodiments and can be carried out or practiced in various other ways. Unless otherwise specified, all the technical and scientific terms used herein have the same meaning as is generally understood by a person skilled in the art pertaining to the present disclosure. Headings are used solely for organizational purposes, and are not intended to limit the disclosure in any way. The use of the singular includes the plural unless specifically stated otherwise. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well. The use of “or” means “and / or” unless stated otherwise. As used herein, the terms “comprises” and / or “comprising” specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Furthermore, to the extent that the terms “includes,” “having,” “has,” “with,” “composed,” “comprised” or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” As used herein, ranges and amounts can be expressed as “about” a particular value or range. “About” is intended to also include the exact amount. Hence “about 5 percent” means “about 5 percent” and also “5 percent.” “About” means within typical experimental error for the application or purpose intended. It is to be understood that wherein a numerical range is recited, it includes all values within that range, and all narrower ranges within that range, whether specifically recited or not. Reference throughout this specification to “one embodiment,” “an embodiment,” “one example,” or “an example” means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present disclosure. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” “one example,” or “an example” in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combinations and / or sub-combinations in one or more embodiments or examples. In addition, it should be appreciated that if any figures are provided herewith, they are for explanation purposes to persons ordinarily skilled in the art and that the drawings of them are not necessarily drawn to scale. In this specification, certain aspects of one embodiment include process steps and / or operations and / or instructions described herein for illustrative purposes in a particular order and / or grouping. However, the particular order and / or grouping shown and discussed herein are illustrative only and not limiting. Those of skill in the art will recognise that other orders and / or grouping of the process steps and / or operations and / or instructions are possible and, in some embodiments, one or more of the process steps and / or operations and / or instructions discussed above can be combined and / or deleted. In addition, portions of one or more of the process steps and / or operations and / or instructions can be re-grouped as portions of one or more other of the process steps and / or operations and / or instructions discussed herein. Consequently, the particular order and / or grouping of the process steps and / or operations and / or instructions discussed herein do not limit the scope of the disclosure. The present disclosure provides a method of electrochemical conversion of carbon dioxide (CO2) into value-added products (VAPs) such as ethanol, acetic acid, ethyl acetate, metal ethanoates and acetaldehyde. The method of electrochemical conversion of carbon dioxide (CO2) into value- added products (VAPs) utilises an electrochemical reactor having metallic Copper (Cu) or Cu-alloy symmetric electrodes (cathode and anode), wherein the metallic Cu or Cu-alloy electrodes act as electrocatalyst, and acidified water (H3O+) as electrolyte for generation of H2gas. The process exhibited a maximum Faradaic Efficiency (FE%) of up to 77.26%, which is an indication of % ethanol and other VAP yield, and Energy Efficiency (EE%) of up to 32.97%. The method of electrochemical conversion of carbon dioxide (CO2) into value- added products (VAPs) includes: − adding deionised water to an electrochemical reactor vessel and dipping a metallic Cu or Cu-alloy cathode, and a metallic Cu or Cu-alloy anode in the deionised water; − placing a magnetic stirrer in the reactor vessel; − purging CO2into the deionised water in the reactor vessel from an external CO2 source; − applying current density to the cathode and anode through an external power source; and − adding a concentrated acid to the deionised water in the reactor vessel with constant stirring to form a reaction solution, which produces H2 gas in-situ from the acidified water on the cathode surface, wherein the applied current density initiates the reaction of asymmetric C-C coupling on the cathode surface forming short-lived cation radical intermediates, wherein the short-lived cation radical intermediates react among themselves, or the short-lived cation radical intermediates react with the in-situ produced H2 gas, or both, forming organic acid anions and alkoxides; wherein, on the anode, dissolution of Cu occurs forming Cu2+ions; wherein, the organic acid anions and alkoxides react with the Cu2+ions formed at the anode forming metallorganic complexes; wherein, the metallorganic complexes are left for hydrolysis for about 12 h at 35oto 45oC to form the value-added products (VAP), wherein ethanol is the major VAP. The Cu-alloy for the electrodes can be selected from Cu / CuO, Cu / Ag, Cu / Ti, Cu / Pt, and Cu / Pd, wherein the dopant i.e., CuO, Ag, Ti, Pt, and Pd is present in an amount of less than or equal to 2.5% by weight of the alloy. When the dopant in the Cu-alloy electrodes is either Ag, Pt, or Pd, the yield of VAP increases by 5% in comparison to metallic Cu electrodes. An external current of 1 to 5 A was applied to the Cu electrodes in a voltage range of 1 to 5 V, which facilitates the formed H2 and CO2 gases to react with each other on the Cu electrode surface. This reaction of the H2and CO2gases form intermediates, wherein the intermediates are organic cation radicals such as CHO- CHO*, *COH2-CHO, CH3-CHO*, CH3-CH2-O* lead to formation of ethanol and other VAPs as depicted in Fig.1. In an embodiment of the disclosure, the Cu or Cu-alloy electrodes are dipped in an initiator solution (in water) and concentrated acid is added, which forms both H2 gas and CO2 gas in-situ. As described in the disclosure, in different embodiments, the CO2required for the electrochemical process can either be supplied from an external CO2 source, or the CO2can be generated in-situ through use of initiators, or both CO2supplied from an external source, as well as initiator generated CO2 can be utilised. However, H2 gas is generated in-situ in all the embodiments to have the process economical. The acidified water is the source for H2. When initiator is used, Mg2+ions from the initiator also reacts with the organic acid anions and alkoxides to form metallorganic complexes. The materials employed for the experiments of the present disclosure are procured from SRL chemicals and are of analytical grade. The chemicals are used without further purification. Industrial CO2 based experiments at flow rates of 150 ml / min and 500 ml / min were conducted in a distillery plant at Nagpur with 99.3% purity of CO2. Initiator for CO2 in-situ source The initiator is a metal carbonate preferably selected from Na2CO3, K2CO3, CaCO3,and MgCO3, wherein the metal carbonate is mixed with 40-45% by weight of Magnesium Oxide (MgO) to facilitate the metallorganic complex formation with the intermediates of the C-C asymmetric coupling on electrode surface (leading to hydrolysis and ethanol formation with high specificity and selectivity). The organic intermediates act as ligands to co-ordinate with Cu2+and Mg2+ions. Mg2+ions are generated via addition of inorganic acids such as HCl, H2SO4, HNO3 to the initiator solution forming ionic salts of the anions with Mg2+ions and release hydrogen (H2), carbon dioxide (CO2) and oxygen gas in the process as depicted via the equations below: 0.6 MgCO3+ 0.4 MgO +2 HCl ^ MgCl2+ 0.6 CO2+ H2+ ½ O20.6 MgCO3 + 2 + 0.6 CO2 + H2 + ½ O2 0.6 MgCO3+ 0.4 MgO + H2SO4^ MgSO4+ 0.6 CO2+ H2+ ½ O2For every mole of carbonate and MgO, 0.6 moles of CO2and one mole of H2are generated in the solution. This initiates formation of C-C asymmetric bond on the Cu electrode surface and further reduction of the same via the generated H2gas. Further reduction of the intermediates by hydrogen gas leads to formation of organometallic complexes on the Cu surface due to coordination with Cu2+ions (dissolution of Cu by applied potential and current) and the precipitate falls into solution with progress in the reaction time as shown in Fig.2. Reaction parameters for CO2 to ethanol and other VAPs formation The Cu or Cu-alloy electrocatalyst are fabricated in the form of a plate and 5*10 cm2of the same is immersed in the reaction solution. After adding acid to initiator and generation in-house CO2 and H2 (and also with external supply of CO2 from cylinders or storage tanks), voltage of 1 to 3 V is applied to the system to stabilize the applied current density up to 5 A (high current density of 50 mA / cm2). The reaction completes in the span of 3 to 5h depending on the amount of CO2is taken as the source to get converted to ethanol and VAPs. The flow rate of CO2is fixed at 150ml / min and 500 ml / min. CO2 is purged into the reaction solution till the completion of the conversion. The completion of the reaction is identified by the disappearance of any vigorous reaction on the Cu surface. Brown or black coloured precipitate is formed on the Cu surface which dissolutes to the solution as the reaction progresses. The reaction mixture changes its appearance from milky white to colourless (upon addition of acid) to blue solution after completion of the reaction. Experimental procedure: As shown in Fig. 2 and 3, the electrochemical reactor is a lab scale prototype made of Borosil glass with applied current and voltage. The Cu electrodes act as both anode and cathode and is designed in the form of a slab with rectangular handle. The handle of the electrode acts as the current collector that is connected to the power source (PS). The dimensions of the slab of each Cu electrode is 15cm*20cm*0.5cm (length*breadth*thickness). Approximately, 5cm*10cm*0.5cm dimension of each electrode that is exposed to the reaction solution. As both the sides of the electrodes are exposed, the dimension of the electrode involved in the reaction would be 2*(5cm*10cm*0.5cm). The power source (from Won-a-Tech, Korea) with 12 V and 10 A capacity of voltage and current is applied, which is the required voltage and current to the reaction solution via Cu electrodes. The power source is provided with software interface to acquire the dynamic data of the voltage (V) and Current (I) during the course of the reaction. As shown in Fig. 2, two inlets provided on the cap of the reactor are the provisions to pass CO2 (along with in-situ prepared through initiator-based reaction, as industrial gas, as distillery CO2or as Flue gas) and H2gas into the reaction medium for continuous supply of the gases and its conversion on the electrode surface. The rate of flow of the CO2 and H2 gases are between 150 ml / min to 500 ml / min. The copper electrodes are connected to the power source via cables (one terminal acts as anode, and the other acts as cathode). The power source is set at the upper voltage of 3V and current up to 5A for the reaction to proceed. Vigorous dissolution of anodic copper electrode occurs with simultaneous reduction of CO2 by H2gas on the cathodic copper. The intermediate cation radicals are short lived and combine with H2 resulting in formation of ethoxide and ethanoate anions, that coordinate with the dissolute Cu2+ions to form metallorganic compounds. In addition, any free ethoxide or ethanoate anion that goes into the solution where they coordinate with Mg2+ions from the initiator and forms metallorganic compounds. The reaction is allowed to continue for 3 to 5 hours depending upon the flow rate of CO2. After the completion of the reaction, the reaction solution is replaced in an air tight container and placed at 35oto 45oC overnight to allow hydrolysis of the metallorganic compounds into ethanol, acetic acid or metal acetates. The other by-products formed are isoamyl alcohol (a secondary alcohol) and negligible amounts of acetaldehyde (via any incomplete reduction of CO2). The major products and the minor products are identified by Gas Chromatography (GC), Fourier Transform InfraRed spectroscopy (FTIR), Ultra Violet-Visible spectroscopy (UV-Vis), to understand the metallorganic compounds formed in the reaction that leads to the formation of ethanol as major product on allowing to hydrolyse overnight at elevated temperatures of 35oto 45oC. Examples: The present disclosure will now be explained in further detail by the following examples. These examples are illustrative of certain embodiments of the disclosure without limiting the scope of the present disclosure. The following electrocatalytic reduction experiments of CO2 on Cu electrode surface is carried out. (i) Initiator as CO2 source and acidified water (concentrated acid added to the metal carbonate and MgO initiator solution) as electrolyte, (ii) Industrial CO2as source with flow rate of 150ml / min and acidified water as electrolyte, (iii) Industrial CO2as source with flow rate of 500ml / min and acidified water as electrolyte, (iv) Industrial CO2with a flow rate of 150ml / min combined with initiator as CO2source, and acidified water as electrolyte, (v) Industrial CO2with a flow rate of 500ml / min combined with initiator as CO2source, and acidified water as electrolyte. The reaction time for all the reactions varied from 3 and 5 h, with high current density to accelerate the reaction and also to achieve specificity and selectivity of the products formed especially ethanol. The process achieves CO2–to–ethanol conversion under high current operation with partial current density of 0.5 to 1 Acm−2at 1 to 3V vs reversible hydrogen electrode and showed high and significant conversion efficiency. The ethanol produced are analysed and confirmed by GC, FITR, UV-Vis techniques. Example 1: (Case i) Initiator as CO2 source and acidified water as electrolyte 60% MgCO3+ 40% MgO was employed as initiator to be the CO2source. Acidified deionised water (Concentrated acid added to the initiator solution) as the electrolyte. On adding acid to the initiator solution, H2gas is generated with formation of inorganic Mg salts of the acid. The H2 gas generated reacts with CO2 on Cu surface forming intermediate cation radicals as depicted in Fig. 1. The cation radicals are short-lived and resulted in taking up H2further forming ethanoxide and ethanoate anions which combine with the Cu2+ions from the dissolution of anode and Mg2+ions formed in the solution from the reaction of initiator and acid resulting in Metallorganic compounds of Copper and or Magnesium ethanoate or ethoxide. Here the organic anions formed by the asymmetric C-C coupling on the cathodic Cu surface acts as the ligands to coordinate with the metal ions. The reaction is continued at an applied voltage of 1 to 3 V and current density of 50 mA / cm2for 3h. The reaction solution turned from milky white to colourless to blue to indicate the completion of the reaction. Alcohol especially ethanol shows blue colour in acidic medium. Thus, when the solution turns blue, the reaction is stopped and the reaction solution along with the metallorganic complexes formed on Cu surface is left overnight at 35oto 45oC to undergo hydrolysis and form ethanol as major product with minor products such as isoamyl alcohol, acetic acid, acetaldehyde so on and so forth. The yield of the reaction is obtained from the FE and EE of the process based on the electrochemical reaction as described below: 0.6 MgCO3+ 0.4 MgO + 2H++ 2e- ^ 0.6 CO2+ Mg2++ H2+ ½ O2↑ two moles of CO2 one cation radical(1) is obtained) C2H2O.++ ½H2 + e ^ C2H3O.+(H3C-C.+=O cation radical(2) formation leading to breaking of one C=C bond, formation of one C-H bond) C2H3O.++ ½H2+ e ^ C2H4O.+(H3C-C.+-OH cation radical(3) formation leading to breaking of one C=O bond, formation of one O-H bond) C2H4O.++ ½H2+ e ^ C2H5O- (formation of ethoxide anion on Cu surface) Cu ^ Cu2++ 2e + + 6e ^ [Cu(C2H5O)6]2+Xn-metallorganic complex (octahedral where Xn-is inorganic anions such as Cl-, NO3-, SO42-and n varies from 1 to 2 depending on the acid utilized. Additional reaction happening in the solution due to the presence of Mg2+ions when the mother solution is left overnight at 35o-45oC are as below [Cu(C2H5O)6]2++ 2Mg2++ 4H++ O2 + 4e- ^ Mg(C2H5O)2 + CuO + MgO + Overall reaction of the process involves 10 electrons to complete the formation of ethanol via electrocatalytic reduction. Thus, the Faradaic efficiency (FE%) is calculated for case (i) is where n is the number of moles of the product formed, e is the number of electrons transferred in the electrochemical reaction, F is Faraday’s constant (96500 C / mol), Q the charge is represented via Q = I*t here I is the current applied in Amps to the system and t is the reaction time in hours. Faradaic efficiency for case (i) is calculated as follows: Case i: n = 4, e = 10, I is 5 A, t = 3h Q = 15Ah; hence of CO2 to ethanol with respect to SHE and is the reduction potential of the reaction versus SHE. In case (i), the is 1.28V and that of is 3V, so the EE is obtained as 30.53%. Evaluation: Example 1 (Case i): Gas Chromatography (GC) Analysis of the Products from Case (i) The confirmation of the formation of products of reduction of CO2 into value added products (VAPs) such as ethanol, acetates, acetaldehyde etc. is carried out by GC. Fig. 4 and Table 1 demonstrate the products formed and the % yield of them. Table 1 The percentage yield of different major and minor products obtained by electrochemical reduction of CO2 S. Species Peak Retention Area Yield of products = No position Time under [product]*100 / [CO2]*[H+] in ppm (mins) the peak 1. Ethanol 2.78 10 70 70% 2. Acetaldehyde 3.01 10 7 7% 3. Acetates 4.25 10 20 20% 4. Methanol 3.43 10 3 3% From Fig. 4 and Table 1, it is clear that the major product formed in Case (i) is ethanol with 70% yield. The yield % of ethanol from GC analysis agrees satisfactorily with the FE% calculated from the electrochemical experiment and equations. The minor products formed are acetaldehyde with 7% yield, Acetic acid or acetate with 20% yield, methanol up to 3%. Thus, the GC analysis of the products support the asymmetric C-C coupling route (as shown in Fig. 1) of ethanol formation as the major specific product from electrocatalytic reduction of CO2on copper surface. FTIR analysis of the liquid and the solid samples from Case (i) The FTIR analysis of liquid and solid samples from the electrochemical reactor after hydrolysis overnight at 35o-45oC is carried out and the results are analysed in this section. Fig 5 and Tab1e 2 depict the FTIR spectrum in the wavenumber range of 500 to 4500 cm-1and their corresponding functional group identification for the liquid samples. Table 2 FTIR peaks and functional groups identified in the liquid sample of Case (i) S. Wave number Functional group identified Remarks No (cm-1) 1. 1639.19 The stretching vibration mode The alkane stretching of C-H in CH3-CH2-; vibrations may be from absorption of alkane bonds methyl and ethyl groups present in ethanol and methanol 2. 3248-3340 Absorption peak of hydroxyl AreaO-H / AreaC-H = group, alcoholic in nature; 0.11 / 0.063 = 1.75 Symmetric stretching mode of O-H bonds From Fig. 4 and Table 2, it can be inferred that two peaks are obtained for the liquid samples collected from case (i) experiments after 10 h and 24 h of completion of the reaction. Both the samples show overlapping peaks at 1639.19 cm-1and 3248-3340 cm-1. The former peak at 1639.19 cm-1is a sharp one and corresponds to the stretching vibration mode of C-H in CH3-CH2- and absorption of alkane bonds. The alkane stretching vibrations may be attributed to the methyl and ethyl groups present in ethanol and methanol formed as major and minor product in the case (i). The latter broad peak in the wavenumber range of 3248- 3340 cm-1represents absorption peak of hydroxyl group, alcoholic in nature via the symmetric stretching mode of O-H bonds. Fig. 6 and Tab1e 3 depict the FTIR spectrum in the wavenumber range of 500 to 4500 cm-1and their corresponding functional group identification for the solid samples. Table 3 FTIR peaks and functional groups identified in the solid sample of Case (i) S. Wave number Functional group Remarks No (cm-1) identified 1. 1635.34 The stretching The alkane stretching vibrations vibration mode of involving C-H stretching modes C-H in CH3-CH2-; The C=O group is contributed absorption of either from the carboxylic moiety alkane bonds or ketonic moiety The stretching and The intensity is less indicating bending vibrations lower concentration of C=O of C=O 2. 3248-3550 Absorption peak of Presence of O- moiety from the hydroxyl group, hydroxyl terminal of the alcoholic in nature compound Symmetric stretching mode of O-H bonds 3. 1420-1483 The symmetric The presence of COO- is stretching confirmed by the peaks at 1635 vibrations of C-O and 1420-1483 cm-1, hence the bond solid is an organic acid salt of Cu 4. 1015.34 Asymmetric Confirmation of COO- moiety bending of C-O bond 5. 434 – 837 Symmetric and Confirmation of formation of CU asymmetric ethanoate or copper (II) acetate stretching and monohydrate bending vibrations of Cu-COO- functional moiety From Fig. 6 and Table 3, five peaks were identified for solid product samples from case (i) experiments after 10 and 24 h of completion of the reaction. Fig. 6 clearly indicates that the intensity of the peaks of the solid samples reduces significantly after 24 h of the completion of the reaction in comparison with 10 h samples. This observation is attributed to the hydrolysis of the metallorganic complexes and release of ethanol into the liquid medium and solid samples get converted to metal oxides, acetates etc. The first peak at 1635.34 cm-1 depicts the stretching vibration mode of C-H in CH3-CH2- of ethanol and CH3of methanol caused by the absorption of alkane bonds and the stretching and bending vibrations of C=O bonds in the aldehyde or esters. The alkane stretching vibrations involving C-H stretching modes, the C=O group is contributed either from the carboxylic moiety or aldehyde moiety. As the intensity of the peak is less the concentration of C=O group is lower in the sample. The second broad peak in the range of 3248-3550 cm-1is caused by the absorption of hydroxyl group, alcoholic in nature via the symmetric stretching mode of O-H bonds. The third broad peak in the range of 1420-1483 cm-1represents the symmetric stretching vibrations of C-O bond. This confirms the presence of COO- and hence the solid is an organic acid salt of Cu / Mg. Fourth peak at 1015.34 cm-1 indicates the asymmetric bending mode of C-O bonds confirming the presence of COO- moiety in the solid sample. Fifth broad peak in the range of 434 to 837 cm-1 is due to the asymmetric and symmetric stretching vibrations of Cu-COO- moiety demonstrating the presence of copper acetate monohydrate or copper ethanoate in the solid sample. Thus, Fig. 6 and Table 3 supports the formation of acetates as one of the products in the electrocatalytic reduction of CO2on copper surface. UV-Vis analysis of the liquid and the solid samples from Case (i) The UV-Vis analysis of liquid and solid samples from the electrochemical reactor after hydrolysis overnight at 35o-45oC is carried out and the results are analysed in this section. Fig. 7 and Tab1e 4 depict the UV-Vis spectrum in the wavelength range of 190 to 800 nm and their corresponding electronic transition identification for the liquid samples. Table 4 UV-Vis peaks and electronic transitions identified in the liquid sample of Case (i) S. Wavelength Electronic Remarks No (nm) transitions 1. 197 (Day 1 andn-σ* transitionnon-bonding electrons to anti- 2) bonding sigma (s) orbital 2. 278 (Day 1 andpi-pi* transitionThe lone pair of electrons on 2) the carboxyl oxygen gets involved in the transition Fig. 7 and Table 4 exhibit two peaks at the wavelength of 197 and 278 nm. The inset in the Fig 7 is the expanded view of the peaks within the wavelength range of 190 to 390 nm. The first peak at 197 nm is the characteristic ethanol peak and is caused by n- σ* transition of non-bonding electrons from OH group to the anti- bonding sigma orbital. The second peak at 278 nm is the impurity peak caused by pi-pi* transition where the pi-electrons of the C=O functional group is involved in the transition. Thus, supporting the formation of ethanol as major product with aldehyde and acetates as minor products during the CO2reduction by electrocatalytic process. Fig. 8 and Tab1e 5 depict the UV-Vis spectrum in the wavelength range of 190 to 800 nm and their corresponding electronic transition identification for the solid samples. Table 5 UV-Vis peaks and electronic transitions identified in the liquid sample of Case (i) S. Wavelength Electronic Remarks No (nm) transitions 1. 192 (Day 1&2) singlet Cu-O bonds Solid deposited transitions d–d transitions of Cu2+ions were on Cu considered to be the origin of the visible band and near-UV band σ–σ* transitions of the Cu–O bonds Strongly allowed transition The peaks at visible and NIR are absent (other singlet and triplet) because of the water adsorption on the octahedral sites (diagonal axis) Fig. 8 and Table 5 shows only one peak at 192 nm indicating the presence of CH3CH2O- anions. The Cu-O or Mg-O bonds involving d-d transitions and the strongly allowed σ–σ* transitions are not observed due to the water molecules coordinated along the diagonal axis of the Cu-ethoxide metallorganic compound as seen from the structure provided in the inset of Fig.8. Example 2: (Case ii) Industrial CO2 as source with flow rate of 150ml / min and acidified water as electrolyte In the case (ii), experiments were conducted employing the industrial CO2 as source without addition of initiator. Acidified deionised water as the electrolyte. On adding acid to the water, H2 gas is generated. The H2 gas generated reacts with CO2 on Cu surface forming cation radicals as depicted in Fig. 1. The cation radicals are short lived and resulted in taking up H2further forming ethanoxide and ethanoate anions which combine with the Cu2+ions from the dissolution of anode resulting in Metallorganic compounds such as Copper ethanoate or ethoxide. Here the organic anions formed by the asymmetric C-C coupling on the cathodic Cu surface acts as the ligands to coordinate with the metal ions. The reaction is continued at an applied voltage of 1 to 3 V and current density of 100 mA / cm2for 5h. The reaction solution turned from colourless to blue to indicate the completion of the reaction. Alcohol especially ethanol shows blue colour in acidic medium. Thus when the solution turns blue, the reaction is stopped and the reaction solution along with the metallorganic complexes formed on Cu surface is left overnight at 35oto 45oC to undergo hydrolysis and form ethanol as major product with minor products such as isoamyl alcohol, acetic acid, acetaldehyde so on and so forth. The yield of the reaction is obtained from the FE and EE of the process based on the electrochemical reaction as described below: 2CO2+ H2+ e ^ C2H2O+.+ 1½O2↑ two moles of CO2 one cation radical(1) is obtained) C2H2O.++ ½H2 + e ^ C2H3O.+(H3C-C.+=O cation radical(2) formation leading to breaking of one C=C bond, formation of one C-H bond) C2H3O.++ ½H2 + e ^ C2H4O.+(H3C-C.+-OH cation radical(3) formation leading to breaking of one C=O bond, formation of one O-H bond) C2H4O.++ ½H2 + e ^ C2H5O- (formation of ethoxide anion on Cu surface) Cu ^ Cu2++ 2e + 6e ^ [Cu(C2H5O)6]2+Xn-metallorganic complex (octahedral complexes) where Xn-is inorganic anions such as Cl-, NO3-, SO42-and n varies from 1 to 2 depending on the acid utilized. Additional reaction happening in the solution when the mother solution is left overnight at 35o-45oC are as below: [Cu(C2H5O)6]2++ 6H++ ½ O2+ 2e- ^ CuO + 6C2H5OH Overall reaction of the process involves 10 electrons to complete the formation of ethanol via electrocatalytic reduction. Thus the Faradaic efficiency (FE%) is calculated for case (i) is is the number of moles of the product formed, e is the number of electrons transferred in the electrochemical reaction, F is Faraday’s constant (96500 C / mol), Q the charge is represented via Q = I*t here I is the current applied in Amps to the system and t is the reaction time in hours. Faradaic efficiency for case (i) is calculated as follows: Case ii: n = 6, e = 10, I is 5 A, t = 5h Q = 25Ah; hence 1C = 2.78 *10-4Ah; therefore So, the ethanol yield from Case (ii) is 64.39% The Energy Efficiency (EE%) is given as where is the standard reduction potential of CO2 to ethanol with respect to SHE and is the reduction potential of the reaction versus SHE. In case (ii), the is 1.28V and that of is 3V, so the EE is obtained as 27.47%. Evaluation: Example 2 (Case ii): Gas Chromatography (GC) Analysis of the Products from Case (ii) From Fig. 9, it is clear that the major product formed in Case (ii) is ethanol with 100% purity. The yield % of ethanol from GC analysis agrees satisfactorily with the FE% calculated from the electrochemical experiment and equations. No minor products are formed case (ii) as no initiator had been utilized. Thus, the GC analysis of the products support the asymmetric C-C coupling route (as shown in Fig. 1) of ethanol formation as the major specific product from electrocatalytic reduction of CO2 on copper surface. FTIR analysis of the liquid and the solid samples from Case (ii) The FTIR analysis of liquid samples from the electrochemical reactor after hydrolysis overnight at 35o-45oC is carried out and the results are analysed in this section. Fig.10 and Tab1e 6 depicts the FTIR spectrum in the wavenumber range of 500 to 4500 cm-1and their corresponding functional group identification for the liquid samples. Table 6 FTIR peaks and functional groups identified in the liquid sample of Case (ii) S. Wave number Functional group identified Remarks No (cm-1) 1. 1100 The symmetric stretching of C-O bond of primary and C-O bond secondary alcohol 1. 1640 The stretching vibration mode The alkane stretching of C-H in CH3-CH2-; vibrations may be from absorption of alkane bonds methyl and ethyl groups present in ethanol and methanol 2. 3250-3400 Absorption peak of hydroxyl AreaO-H / AreaC-H = group, alcoholic in nature; 0.08 / 0.063 = 1.27 Symmetric stretching mode of O-H bonds From Fig. 10 and Table 6, it can be inferred that three peaks are obtained for the liquid samples collected from case (ii) experiments after 10 h and 24 h of completion of the reaction. The samples show overlapping peaks at 1100, 1640 and 3250-3400 cm-1. The first sharp peak at 1100 cm-1corresponds to the stretching vibration mode of C-O bond of primary as well as secondary alcohol. As GC shows high purity of ethanol produced, the peak is mainly due to ethanol the primary alcohol. The second sharp peak at 1640 cm-1depicts the stretching vibration modes of C-H in CH3-CH2- and absorption of alkane bonds. The alkane stretching vibrations may be attributed to the methyl and ethyl groups present in ethanol formed in the case (ii). The third broad peak in the wavenumber range of 3250-3400 cm-1represents absorption peak of hydroxyl group, alcoholic in nature via the symmetric stretching mode of O-H bonds. From the literature (https: / / doi.org / 10.1021 / ed400824g) it had been observed that the area ratio of O- H to C-H peaks is ≤ 1.27, the yield of ethanol is less than 70%. Thus, FTIR analysis of the liquid samples also support the FE% and yield of ethanol from the experiments carried out in case (ii). Case (ii) experiment involves pure industrial CO2as source at a flow rate of 150 ml / min without addition of initiator, the solid precipitate formed on the Cu electrode surface is mostly CuO and Cu acetates. UV-Vis analysis of liquid samples of case (ii) experiments The UV-Vis analysis of liquid samples from the electrochemical reactor after hydrolysis overnight at 35o-45oC is carried out and the results are analysed in this section. Fig. 11 and Tab1e 7 depict the UV-Vis spectrum in the wavelength range of 190 to 800 nm and their corresponding electronic transition identification for the liquid samples. Single peak at 196 nm indicates the presence of ethanol as major product from case (ii) experiments and also supports highest purity of the ethanol formed. Table 7 UV-Vis peaks and electronic transitions identified in the liquid sample of Case (i) S. Wavelength Electronic Remarks No (nm) transitions 1. 196n-σ* transitionnon-bonding electrons to anti- bonding sigma (s) orbital Example 3: (Case iii) Industrial CO2 as source with flow rate of 500ml / min and acidified water as electrolyte In the case (iii), experiments were conducted employing the industrial CO2as source at a flow rate of 500ml / min without addition of initiator. Acidified deionised water as the electrolyte. On adding acid to the water, H2 gas is generated. The H2 gas generated reacts with CO2 on Cu surface forming cation radicals as depicted in Fig. 1. The cation radicals are short lived and resulted in taking up H2 further forming ethanoxide and ethanoate anions which combine with the Cu2+ions from the dissolution of anode resulting in Metallorganic compounds such as Copper ethanoate or ethoxide. Here the organic anions formed by the asymmetric C-C coupling on the cathodic Cu surface acts as the ligands to coordinate with the metal ions. The reaction is continued at an applied voltage of 1 to 5 V and current density of 100 mA / cm2for 5h. The reaction solution turned from colourless to blue to indicate the completion of the reaction. Alcohol especially ethanol shows blue colour in acidic medium. Thus, when the solution turns blue, the reaction is stopped and the reaction solution along with the metallorganic complexes formed on Cu surface is left overnight at 35oto 45oC to undergo hydrolysis and form ethanol as major product with minor products such as isoamyl alcohol, acetic acid, acetaldehyde so on and so forth. The yield of the reaction is obtained from the FE and EE of the process based on the electrochemical reaction as described below: 2CO2+ H2+ e ^ C2H2O+.+ 1½O2↑ C.+=C=O cation radical for two moles of CO2one cation radical(1) is C2H2O.++ ½H2 + e ^ C2H3O.+(H3C-C.+=O cation radical(2) formation leading to breaking of one C=C bond, formation of one C-H bond) C2H3O.++ ½H2 + e ^ C2H4O.+(H3C-C.+-OH cation radical(3) formation leading to breaking of one C=O bond, formation of one O-H bond) C2H4O.++ ½H2 + e ^ C2H5O- (formation of ethoxide anion on Cu surface) Cu ^ Cu2++ 2e + 6e ^ [Cu(C2H5O)6]2+Xn-metallorganic complex (octahedral complexes) where Xn-is inorganic anions such as Cl-, NO3-, SO42-and n varies from 1 to 2 depending on the acid utilized. Additional reaction happening in the solution when the mother solution is left overnight at 35o-45oC are as below: [Cu(C2H5O)6]2++ 6H++ ½ O2+ 2e- ^ CuO + 6C2H5OH Overall reaction of the process involves 10 electrons to complete the formation of ethanol via electrocatalytic reduction. Thus, the Faradaic efficiency (FE%) is calculated for case (iii) is n is the number of moles of the product formed, e is the number of electrons transferred in the electrochemical reaction, F is Faraday’s constant (96500 C / mol), Q the charge is represented via Q = I*t here I is the current applied in Amps to the system and t is the reaction time in hours. Faradaic efficiency for case (i) is calculated as follows: Case iii: n = 6, e = 10, I is 4.5 A, t = 5h Q = 22.5Ah; hence 1C = 2.78 *10-4Ah; therefore So, the ethanol yield from Case (iii) is 71.54% The Energy Efficiency (EE%) is given as where is the standard of CO2to ethanol with respect to SHE and is the reduction potential of the reaction versus SHE. In case (iii), the is 1.28V and that of is 3V, so the EE is obtained as 30.52%. Evaluation: Example 3 (Case iii): Gas Chromatography (GC) Analysis of the Products from Case (iii) From Fig.12, it is clear that the major product formed in Case (iii) is ethanol with 100% purity. The yield % of ethanol from GC analysis agrees satisfactorily with the FE% calculated from the electrochemical experiment and equations. No minor products are formed case (iii) as no initiator had been utilized. Thus, the GC analysis of the products support the asymmetric C-C coupling route (as shown in Fig. 1) of ethanol formation as the major specific product from electrocatalytic reduction of CO2 on copper surface. FTIR analysis of the liquid and the solid samples from Case (iii) The FTIR analysis of liquid samples from the electrochemical reactor after hydrolysis overnight at 35o-45oC is carried out and the results are analysed in this section. Fig.13 and Tab1e 8 depicts the FTIR spectrum in the wavenumber range of 500 to 4500 cm-1and their corresponding functional group identification for the liquid samples. Table 8 FTIR peaks and functional groups identified in the liquid sample of Case (iii) S. Wave number Functional group identified Remarks No (cm-1) 1. 1100 The symmetric stretching of C-O bond of primary and C-O bond secondary alcohol 1. 1640 The stretching vibration mode The alkane stretching of C-H in CH3-CH2-; vibrations may be from absorption of alkane bonds methyl and ethyl groups present in ethanol and methanol 2. 3250-3400 Absorption peak of hydroxyl AreaO-H / AreaC-H = group, alcoholic in nature; 0.1 / 0.063 = 1.59 Symmetric stretching mode of O-H bonds From Fig. 13 and Table 8, it can be inferred that three peaks are obtained for the liquid samples collected from case (iii) experiments after 10 h and 24 h of completion of the reaction. The samples show overlapping peaks at 1100, 1640 and 3250-3400 cm-1. The first sharp peak at 1100 cm-1corresponds to the stretching vibration mode of C-O bond of primary as well as secondary alcohol. As GC shows high purity of ethanol produced, the peak is mainly due to ethanol the primary alcohol. The second sharp peak at 1640 cm-1depicts the stretching vibration modes of C-H in CH3-CH2- and absorption of alkane bonds. The alkane stretching vibrations may be attributed to the methyl and ethyl groups present in ethanol formed in the case (iii). The third broad peak in the wavenumber range of 3250-3400 cm-1represents absorption peak of hydroxyl group, alcoholic in nature via the symmetric stretching mode of O-H bonds. From the literature (https: / / doi.org / 10.1021 / ed400824g) it had been observed that the area ratio of O- H to C-H peaks is ≤ 1.59, the yield of ethanol is less than 75%. Thus, FTIR analysis of the liquid samples also support the FE% and yield of ethanol from the experiments carried out in case (iii). Case (iii) experiment involves pure industrial CO2as source at a flow rate of 500 ml / min without addition of initiator, the solid precipitate formed on the Cu electrode surface is mostly CuO and Cu acetates. UV-Vis analysis of liquid samples of case (iii) experiments The UV-Vis analysis of liquid samples from the electrochemical reactor after hydrolysis overnight at 35o-45oC is carried out and the results are analysed in this section. Fig. 14 and Tab1e 9 depict the UV-Vis spectrum in the wavelength range of 190 to 800 nm and their corresponding electronic transition identification for the liquid samples. Sharp peak at 191 nm indicates the presence of ethanol as major product from case (iii) experiments. A hump at 198 nm indicates ethanol bonded to metal ion as ethoxide anion. A broad peak at higher wavelength of 275 nm indicates impurities or unhydrolysed Cu based metallorgnanic complexes dispersed in the solution leading to a singlet d-d* transitions in UV-Vis spectra. Table 9 UV-Vis peaks and electronic transitions identified in the liquid sample of Case (iii) S. Wavelength Electronic Remarks No (nm) transitions 1. 191n-σ* transitionnon-bonding electrons to anti- bonding sigma (s) orbital 2. 198n-σ* transitionnon-bonding electrons to anti- bonding sigma (s) orbital, may be secondary alcohol 3. 275 Singlet transition Presence of Cu-ethoxide or Cu- acetate complexes leading to d-d* transitions Thus, FTIR and UV-Vis spectra of the liquid sample from case (iii) experiments although indicate good yield of ethanol from CO2electroreduction on Cu surface, it also provides proof of presence of secondary or other primary alcohol such as isopropanol or isoamyl alcohol, unhydrolysed metallorganic complexes of Cu such as Cu-ethoxide or Cu-ethanoate in the solution. Hence, the yield of ethanol is less than 75% as calculated via the FE% from electrochemical data. Example 4: (Case iv) Industrial CO2 with a flow rate of 150ml / min combined with initiator as CO2 source, and acidified water as electrolyte In the case (iv), experiments were conducted employing the industrial CO2as source at a flow rate of 150ml / min with addition of initiator in acidified deionised water as the electrolyte. On adding acid to the initiator, CO2and H2gas is generated along with the formation of salt of the inorganic acid. The H2 gas generated reacts with CO2from initiator and from the industrial outlet, on Cu surface forming cation radicals as depicted in Fig 1. The cation radicals are short- lived and resulted in taking up H2 further forming ethanoxide and ethanoate anions which combine with the Cu2+ions from the dissolution of anode and Mg2+ions in the solution resulting in metallorganic compounds such as Copper and / or magnesium ethanoate or ethoxide. Here the organic anions formed by the asymmetric C-C coupling on the cathodic Cu surface acts as the ligands to coordinate with the metal ions. The reaction is continued at an applied voltage of 1 to 5 V and current density of 75 mA / cm2for 5h. The reaction solution turned from milky white to colourless to blue to indicate the completion of the reaction. Alcohol especially ethanol shows blue colour in acidic medium. Thus, when the solution turns blue, the reaction is stopped and the reaction solution along with the metallorganic complexes formed on Cu surface as well as in the solution (Mg based metallorganic complexes) is left overnight at 35oto 45oC to undergo hydrolysis and form ethanol as major product with minor products such as isoamyl alcohol, acetic acid, acetaldehyde so on and so forth. The yield of the reaction is obtained from the FE and EE of the process based on the electrochemical reaction as described below: 0.6 MgCO3 + 0.4 MgO + 2H++ 2e- ^ 0.6 CO2 + Mg2++ H2 + ½ O2 ↑ ^ two moles of CO2one cation radical(1) is obtained) C2H2O.++ ½H2+ e ^ C2H3O.+(H3C-C.+=O cation radical(2) formation leading to breaking of one C=C bond, formation of one C-H bond) C2H3O.++ ½H2+ e ^ C2H4O.+(H3C-C.+-OH cation radical(3) formation leading to breaking of one C=O bond, formation of one O-H bond) C2H4O.++ ½H2+ e ^ C2H5O- (formation of ethoxide anion on Cu surface) Cu ^ Cu2++ 2e + 6e ^ [Cu(C2H5O)6]2+Xn-metallorganic complex (octahedral complexes) where Xn-is inorganic anions such as Cl-, NO3-, SO42-and n varies from 1 to 2 depending on the acid utilized. Additional reaction happening in the solution due to the presence of Mg2+ions when the mother solution is left overnight at 35o-45oC are as below [Cu(C2H5O)6]2++ 2Mg2++ 4H++ O2 + 4e- ^ Mg(C2H5O)2 + CuO + MgO + Overall reaction of the process involves 18 electrons to complete the formation of ethanol via electrocatalytic reduction. Thus, the Faradaic efficiency (FE%) is calculated for case (iv) is is the number of moles of the product formed, e is the number of transferred in the electrochemical reaction, F is Faraday’s constant (96500 C / mol), Q the charge is represented via Q = I*t here I is the current applied in Amps to the system and t is the reaction time in hours. Faradaic efficiency for case (i) is calculated as follows: Case iv: n = 4, e = 10, I is 3.5 A, t = 5h Q = 17.5Ah; hence 1C = 2.78 *10-4Ah; therefore So, the ethanol yield from Case (iv) is 61.32% The Energy Efficiency (EE%) is given as where is the standard of CO2 to ethanol with respect to SHE is the reduction potential of the reaction versus SHE. In case (iv), the is 1.28V and that of is 3V, so the EE is obtained as 26.16%. Evaluation: Example 4 (Case iv): Gas Chromatography (GC) Analysis of the Products from Case (iv) From Fig. 15, it is clear that the major product formed in Case (iv) is ethanol (3.645 ppm) with isoamyl alcohol (2.465ppm) as by-product. The yield % of ethanol from GC analysis agrees satisfactorily with the FE% calculated from the electrochemical experiment and equations. Isoamyl alcohol as minor products are formed in case (iv) as initiator had been utilized. Thus, the GC analysis of the products support the asymmetric C-C coupling route (as shown in Fig. 1) of ethanol formation as the major specific product from electrocatalytic reduction of CO2 on copper surface. The FTIR analysis of liquid samples from the electrochemical reactor after hydrolysis overnight at 35o-45oC is carried out and the results are analysed in this section. Fig. 16 and Tab1e 10 depict the FTIR spectrum in the wavenumber range of 500 to 4500 cm-1and their corresponding functional group identification for the liquid samples. Table 10 FTIR peaks and functional groups identified in the liquid sample of Case (iii) S. Wave number Functional group identified Remarks No (cm-1) 1. 1100 The symmetric stretching of C-O bond of primary and C-O bond secondary alcohol 1. 1640 The stretching vibration mode The alkane stretching of C-H in CH3-CH2-; vibrations may be from absorption of alkane bonds methyl and ethyl groups present in ethanol and methanol 2. 3250-3400 Absorption peak of hydroxyl AreaO-H / AreaC-H= group, alcoholic in nature; 0.1 / 0.063 = 1.59 Symmetric stretching mode of O-H bonds As shown in Fig.16 and Table 10, three prominent peaks are noticed in the FTIR spectrum of the liquid samples. A broad high intense peak around 3300 cm-1attributed to the absorption peak of hydroxyl group, alcoholic in nature and due to the symmetric stretching mode of O-H bonds. A sharp moderate intense peak at 1640 cm-1representing the stretching vibration mode of C-H in CH3-CH2-; absorption of alkane bonds. A sharp less intense peak around 1100 cm-1depicts the C-O symmetric stretching of secondary alcohol or esters. As the liquid samples show only these three peaks, the products present in the liquid samples are ethanol, isopropanol or isoamyl alcohol, acetoacetate ester in different proportions. The intensity ratio of peak @ 3300 cm-1and peak @ 1640 cm-1demonstrates the yield of ethanol in the liquid sample. In the present scenario, the intensity ratio becomes approximately 60%. The amount of ethanol present is ~60% whereas the rest of the composition is constituted by secondary alcohol such as isopropanol or isoamyl alcohol and esters like aceto acetates. Based on the vapour pressure and volatility of the secondary alcohol and aceto acetate ester, they can be evaporated and condensed to get pure ethanol from the mixture. Fig. 17 depicts the FTIR spectrum of solid products formed from experiments of case (iv). From Fig.17, we can see six peaks in FTIR spectrum. Peak 1: A broad peak around 3600 to 3800 cm-1and associated by a shoulder peak at 3500 cm-1. The 3600-3700 cm-1peak is attributed to O-H symmetric stretching peak with intermolecular bonding such as hydrogen bonding or covalent bonding with metal ions like Cu2+and Mg2+. This indicates the presence of alkoxide anions in the system. Peak 2: A shoulder peak at 3500 cm-1is caused by O-H stretching mode of vibration that is not intermolecular bonded (free O-H group). This shoulder peak indicates presence of additional O-H group that is free in the system. Thus, from Peaks 1 & 2 we infer presence of alkoxide and alcohol groups in the solid sample. Peak 3: A sharp less intense peak around 1820 to 1850 cm-1accounts for strong hydrous C=O symmetric stretching vibration in the samples. Although the intensity of the peak varies for the First distillate deposit sample, the brown precipitate and the deposits on Cu electrode showed overlapping very less intense and sharp peak. This behavior indicates that upon distillation, the precipitate becomes anhydrous and hence is sharp whereas the as obtained precipitate is hydrous in nature. Thus, peak 3 demonstrates presence of carboxyl, keto or ester group in the solid samples. Peak 4: Peak around 1300 to 1350 cm-1corresponds to C-O stretching of ester (aliphatic and aromatic). In the present scenario, as there are no aromatic compounds involved in the source or possibility in the products, aliphatic ester presence is accounted for this peak. The presence of split peak indicates the intermolecular bonded ester group (acetoacetate ligands bonded to Cu2+or Mg2+ions). Peak 5: Peak around 820 to 850 cm-1is caused due to the presence of C=C bending vibrational mode in the solid product, this contributes to the secondary alcohol formation in the liquid sample on hydrolysis and further hydrogenation. Peak 6: Very less intense but sharp peak around 650 to 700 cm-1, is due to the presence of C=C bending mode of vibration. Here the alkene group is disubstituted and in cis configuration. This is the confirmation for formation of secondary alcohol in liquid sample via hydrolysis and hydrogenation. The presence of cis configuration confirms formation of isopropanol as one of the products in liquid phase. In addition to the six peaks explained above, extra two small but prominent peaks are noticed for solid deposit obtained in the round bottom flask after first distillation of the stock solution from experiment of case (iv). The two peaks at 947 and 1086 cm-1are due to C-H bending vibrations with 1,2,4 trisubstituted C atom, C-O stretching mode of aliphatic ether. Thus, from the FTIR spectrum of liquid and solid samples obtained from Experiments of case (iv) conducted with CO2from the industrial plant and initiator as the source formed products such as ethanol (major), isopropanol (minor), acetoacetate ester (minor) in liquid phase and Cu or Mg alkoxides or acetoacetate esters in solid phase. UV-Vis analysis of liquid samples of case (iv) experiments The UV-Vis analysis of liquid samples from the electrochemical reactor after hydrolysis overnight at 35o-45oC is carried out and the results are analysed in this section. Fig. 18 and Tab1e 11 depict the UV-Vis spectrum in the wavelength range of 190 to 800 nm and their corresponding electronic transition identification for the liquid samples. Sharp peak at 192 nm indicates the presence of ethanol as major product from case (iv) experiments. A hump at 198 nm indicates ethanol bonded to metal ion as ethoxide anion. Table 11 UV-Vis peaks and electronic transitions identified in the liquid sample of Case (iv) S. Wavelength Electronic Remarks No (nm) transitions 1. 192n-σ* transitionnon-bonding electrons to anti- bonding sigma (s) orbital 2. 198n-σ* transitionnon-bonding electrons to anti- bonding sigma (s) orbital, may be secondary alcohol Thus, FTIR and UV-Vis spectra of the liquid sample from case (iv) experiments although indicate good yield of ethanol from CO2 electroreduction on Cu surface, it also provides proof of presence of secondary or other primary alcohol such as isopropanol or isoamyl alcohol, in the solution. Hence, the yield of ethanol is less than 75% as calculated via the FE% from electrochemical data. Example 5: (Case v) Industrial CO2 with a flow rate of 500ml / min combined with initiator as CO2 source, and acidified water as electrolyte In the case (v), experiments were conducted employing the industrial CO2 as source at a flow rate of 500ml / min with addition of initiator in acidified deionised water as the electrolyte. On adding acid to the initiator, CO2 and H2 gas is generated along with the formation of salt of the inorganic acid. The H2gas generated reacts with CO2 from initiator and from the industrial outlet, on Cu surface forming cation radicals as depicted in Fig 1. The cation radicals are short- lived and resulted in taking up H2 further forming ethanoxide and ethanoate anions which combine with the Cu2+ions from the dissolution of anode and Mg2+ions in the solution resulting in metallorganic compounds such as Copper and / or magnesium ethanoate or ethoxide. Here the organic anions formed by the asymmetric C-C coupling on the cathodic Cu surface acts as the ligands to coordinate with the metal ions. The reaction is continued at an applied voltage of 1 to 5 V and current density of 75 mA / cm2for 5h. The reaction solution turned from milky white to colourless to blue to indicate the completion of the reaction. Alcohol especially ethanol shows blue colour in acidic medium. Thus, when the solution turns blue, the reaction is stopped and the reaction solution along with the metallorganic complexes formed on Cu surface as well as in the solution (Mg based metallorganic complexes) is left overnight at 35oto 45oC to undergo hydrolysis and form ethanol as major product with minor products such as isoamyl alcohol, acetic acid, acetaldehyde so on and so forth. The yield of the reaction is obtained from the FE and EE of the process based on the electrochemical reaction as described below: 0.6 MgCO3+ 0.4 MgO + 2H++ 2e- ^ 0.6 CO2+ Mg2++ H2+ ½ O2↑ ^ two moles of CO2 one cation radical(1) is obtained) C2H2O.++ ½H2 + e ^ C2H3O.+(H3C-C.+=O cation radical(2) formation leading to breaking of one C=C bond, formation of one C-H bond) C2H3O.++ ½H2 + e ^ C2H4O.+(H3C-C.+-OH cation radical(3) formation leading to breaking of one C=O bond, formation of one O-H bond) C2H4O.++ ½H2 + e ^ C2H5O- (formation of ethoxide anion on Cu surface) Cu ^ Cu2++ 2e + 6e ^ [Cu(C2H5O)6]2+Xn-metallorganic complex (octahedral complexes) where Xn-is inorganic anions such as Cl-, NO3-, SO42-and n varies from 1 to 2 depending on the acid utilized. Additional reaction happening in the solution due to the presence of Mg2+ions when the mother solution is left overnight at 35o-45oC are as below. [Cu(C2H5O)6]2++ 2Mg2++ 4H++ O2+ 4e- ^ Mg(C2H5O)2+ CuO + MgO + Overall reaction of the process involves 18 electrons to complete the formation of ethanol via electrocatalytic reduction. Thus, the Faradaic efficiency (FE%) is calculated for case (v) is is the number of moles of the product formed, e is the number of electrons transferred in the electrochemical reaction, F is Faraday’s constant (96500 C / mol), Q the charge is represented via Q = I*t here I is the current applied in Amps to the system and t is the reaction time in hours. Faradaic efficiency for case (i) is calculated as follows: Case v: n = 4, e = 18, I is 5 A, t = 5h Q = 25Ah; hence 1C = 2.78 *10-4Ah; therefore So, the ethanol yield from Case (v) is 77.26% The Energy Efficiency (EE%) is given as where is the standard reduction potential of CO2 to ethanol with respect to SHE is the reduction potential of the reaction versus SHE. in case (v), the is 1.28V and that of is 3V, so the EE is obtained as 32.97%. Evaluation: Example 5 (Case v): The products analysed from the liquid and solid samples of Case (v) experiments were identical to that of case (iv). The increased flow rate of the industrial CO2had improved the yield of ethanol in the reaction medium. Table 12 provides the comprehensive chart of the major and minor products formed from the electrochemical reduction of CO2to ethanol on copper surface via five different experiments conducted. Table 12 provides the comprehensive chart of the products formed in experiments case (i) to (v) Initiator Rate of Amount Major Minor products Example # as CO2 External of H2 product (Case #) source CO2 purged generated Yes No 100 ml Ethanol Methanol, Example 1 External Acetaldehyde (Case i) CO2 metallorganic complexes No 150ml / min 100 ml Ethanol Isopropanol, esters Example 2 and negligible (Case ii) amount of ether Example 3 No 500 ml / min 250 ml Ethanol Isoamyl alcohol, (Case iii) esters and ethers Yes 150ml / min 100 ml Ethanol Secondary alcohols, metallorganic Example 4 complexes, metal- (Case iv) ethoxides, metal- ethanoates Yes 500 ml / min 250 ml Ethanol Isoamyl alcohol, Secondary alcohols, Example 5 metallorganic (Case v) complexes, metal- ethoxides, metal- ethanoates Table 13 summarises the Faradaic efficiency (FE) and Energy efficiency (EE) of all the examples 1 to 5. Table 13 Initiat Rate of Example # or as External Faradaic efficiency Energy efficiency (Case #) CO2 CO2 (FE) (EE) source purged No Example 1(Case i)YesExternal 71.54% 30.53% CO2Example 2 150ml / m(Case ii)Noin64.39% 27.47%Example 3 500(Case iii)Noml / min71.54% 30.52%Example 4 150ml / m(Case iv)Yesin61.32% 26.16%Example 5 500(Case v)Yesml / min77. 26% 32.97%Advantages: The method of conversion of CO2 to VAPs of the present disclosure has the following non-limiting advantages. − The source of carbon (from CO2) is free of cost or negligible cost − Cu electrodes or Cu alloy electrodes as electrocatalyst employed is an earth abundant material and hence highly cost effective − Recycling of the electrode and electrocatalyst is highly feasible and facile making the process highly closed loop − Completely renewables driven – zero waste concept with 5R compliance − Flow type electrochemical reactor design leads to high selectivity and yield of production of VAPs − Excellent Faradaic efficiency (FE) of the process, leading to good yield of ethanol, thus highly economical − Carbon credits due to CO2reduction − Mitigation of CO2content in the atmosphere at lower cost and involving production of useful fuels. − To process tonnes of CO2 per day, continuous flow electrochemical reactor can be designed with ease and hence scaling up and mass production is highly feasible − Less chemical intensive process, easy design and operation − Ethanol produced is a vital fuel to automobile industries, essential precursor to medicinal and food industry, the demand is high, − Use within existing infrastructures and the higher energy density, − Cu and Cu-alloy electrodes possess high hydrogen overvoltage and negligible CO adsorption. − Even when the CO2 from the external CO2 source has impurities such as NOx, or SOx gases (such as when flue gas is the external CO2source), the VAP yield remains unaffected. − Consistent batch yield, with minimum or negligible batch variation. Applications: The method of conversion of CO2 to VAPs of the present disclosure has the following non-limiting industrial applications. − Production of VAPs such as ethanol, acetaldehyde, isoamyl alcohol, isopropanol, methanol, secondary alcohols, esters, ethers, metal- ethanoates, metal-ethoxides, metallorganic complexes. Although the present disclosure is described in terms of certain preferred embodiments, it is to be understood that they have been presented by way of example, and not limitation. Thus, the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

CLAIMS 1. A method of electrochemical conversion of carbon dioxide (CO2) into value- added products (VAP) comprising: − adding deionised water to an electrochemical reactor vessel and dipping a metallic Cu or Cu-alloy cathode, and a metallic Cu or Cu-alloy anode in the deionised water; − placing a magnetic stirrer in the reactor vessel; − purging CO2into the deionised water in the reactor vessel from an external CO2 source; − applying current density to the cathode and anode through an external power source, wherein the power source set at voltage of 1V to 3V and current up to 5A; and − adding a concentrated acid such as HCl, H2SO4, HNO3 to the deionised water in the reactor vessel with constant stirring, which produces H2 gas in-situ from the acidified water on the cathode surface, wherein the applied current density initiates the reaction of asymmetric C- C coupling of CO2 molecules on the cathode surface forming short-lived cation radical intermediates, wherein the short-lived cation radical intermediates react among themselves, or the short-lived cation radical intermediates react with the in-situ produced H2gas, or react with both, forming organic acid anions and alkoxides; wherein, on the anode, dissolution of Cu occurs forming Cu2+ions; wherein, the organic acid anions and alkoxides react with the Cu2+ions formed at the anode forming metallorganic complexes, wherein the metallorganic complexes are left for hydrolysis for about 12 hours at 35oC to 45oC to form the value-added products (VAP), wherein ethanol is the major VAP.

2. The method of electrochemical conversion as claimed in claim 1, wherein when the symmetric electrodes are Cu-alloy electrodes, the Cu-alloy is selected from Cu / CuO, Cu / Ag, Cu / Ti, Cu / Pt, or Cu / Pd, wherein the dopant CuO, Ag, Ti, Pt, or Pd is present in an amount of less than or equal to 2.5% by weight of the Cu-alloy composition.

3. The method of electrochemical conversion as claimed in claim 1, wherein the Faradaic efficiency (FE) is 64.39% when CO2 is purged at 150ml / min, and 71.54% when CO2 is purged at 500ml / min; and the Energy efficiency (EE) is 27.47% when CO2is purged at 150ml / min, and 30.52% when CO2is purged at 500ml / min.

4. The method of electrochemical conversion as claimed in claim 1, wherein the VAP produced includes ethanol, acetaldehyde, isoamyl alcohol, isopropanol, methanol, secondary alcohols, esters, ethers, metal-ethanoates, metal- ethoxides, metallorganic complexes.

5. A method of electrochemical conversion of carbon dioxide (CO2) into value- added products (VAPs) comprising: − adding deionised water to an electrochemical reactor vessel and dipping a metallic Cu or Cu-alloy cathode, and a metallic Cu or Cu-alloy anode in the deionised water; − placing a magnetic stirrer in the reactor vessel; − adding an initiator mixture of a metal carbonate and Magnesium oxide (MgO) to the deionised water in the reactor vessel to form an initiator solution; − applying current density to the cathode and anode through an external power source, wherein the power source set at voltage of 1V to 3V and current up to 5A; and − adding a concentrated acid such as HCl, H2SO4, HNO3 to the initiator solution in the reactor vessel with constant stirring, which produces H2gasin-situ from the acidified water on the cathode surface, and produces CO2 gas in-situ through the reaction of initiator carbonates and the acid; and wherein the applied current density initiates the reaction of asymmetric C- C coupling of CO2molecules on the cathode surface forming short-lived cation radical intermediates, wherein the short-lived cation radical intermediates react among themselves, or the short-lived cation radical intermediates react with the in-situ produced H2 gas, or react with both, forming organic acid anions and alkoxides; wherein, on the anode, dissolution of Cu occurs forming Cu2+ions; wherein, the organic acid anions and alkoxides react with the Cu2+ions formed at the anode forming metallorganic complexes, wherein the metallorganic complexes are left for hydrolysis for about 12 hours at 35oC to 45oC to form the value-added products (VAP), wherein ethanol is the major VAP.

6. The method of electrochemical conversion as claimed in claim 5, wherein when the symmetric electrodes are Cu-alloy electrodes, the Cu-alloy is selected from Cu / CuO, Cu / Ag, Cu / Ti, Cu / Pt, or Cu / Pd, wherein the dopant CuO, Ag, Ti, Pt, or Pd is present in an amount of less than or equal to 2.5% by weight of the Cu-alloy composition.

7. The method of electrochemical conversion as claimed in claim 5, wherein the initiator mixture includes a metal carbonate selected from Na2CO3, K2CO3, CaCO3, and MgCO3, and Magnesium Oxide (MgO), wherein the ratio of the metal carbonate to MgO is 6 : 4 to 5.5 : 4.

5.

8. The method of electrochemical conversion as claimed in claim 5, wherein the Faradaic efficiency (FE) is up to 71.54%; and the Energy efficiency (EE) is up to 30.53%.

9. The method of electrochemical conversion as claimed in claim 5, wherein the VAP produced includes ethanol, acetaldehyde, isoamyl alcohol, isopropanol, methanol, secondary alcohols, esters, ethers, metal-ethanoates, metal- ethoxides, metallorganic complexes.

10. A method of electrochemical conversion of carbon dioxide (CO2) into value- added products (VAPs) comprising: − adding deionised water to an electrochemical reactor vessel and dipping a metallic Cu or Cu-alloy cathode, and a metallic Cu or Cu-alloy anode in the deionised water; − placing a magnetic stirrer in the reactor vessel; − adding an initiator mixture of a metal carbonate and Magnesium oxide (MgO) to the deionised water in the reactor vessel to form an initiator solution; − purging CO2 into the initiator solution from an external CO2 source; − applying current density to the cathode and anode through an external power source, wherein the power source set at voltage of 1V to 3V and current up to 5A; and − adding a concentrated acid such as HCl, H2SO4, HNO3to the initiator solution in the reactor vessel with constant stirring, which produces H2gas in-situ from the acidified water on the cathode surface, and produces CO2 gas in-situ through the reaction of initiator carbonates and the acid; and wherein the applied current density initiates the reaction of asymmetric C- C coupling of CO2 molecules on the cathode surface forming short-lived cation radical intermediates, wherein the short-lived cation radical intermediates react among themselves, or the short-lived cation radical intermediates react with the in-situ produced H2 gas, or react with both, forming organic acid anions and alkoxides; wherein, on the anode, dissolution of Cu occurs forming Cu2+ions;wherein, the organic acid anions and alkoxides react with the Cu2+ions formed at the anode forming metallorganic complexes, wherein the metallorganic complexes are left for hydrolysis for about 12 hours at 35oC to 45oC to form the value-added products (VAP), wherein ethanol is the major VAP.

11. The method of electrochemical conversion as claimed in claim 10, wherein when the symmetric electrodes are Cu-alloy electrodes, the Cu-alloy is selected from Cu / CuO, Cu / Ag, Cu / Ti, Cu / Pt, or Cu / Pd, wherein the dopant CuO, Ag, Ti, Pt, or Pd is present in an amount of less than or equal to 2.5% by weight of the Cu-alloy composition.

12. The method of electrochemical conversion as claimed in claim 10, wherein the initiator mixture includes a metal carbonate selected from Na2CO3, K2CO3, CaCO3,and MgCO3, and Magnesium Oxide (MgO), wherein the ratio of the metal carbonate to MgO is 6 : 4 to 5.5 : 4.

5.

13. The method of electrochemical conversion as claimed in claim 10, wherein the Faradaic efficiency (FE) is 61.32% when CO2is purged at 150ml / min, and 77. 26% when CO2is purged at 500ml / min; and the Energy efficiency (EE) is 26.16% when CO2 is purged at 150ml / min, and 32.97% when CO2 is purged at 500ml / min.

14. The method of electrochemical conversion as claimed in claim 10, wherein the VAP produced includes ethanol, acetaldehyde, isoamyl alcohol, isopropanol, methanol, secondary alcohols, esters, ethers, metal-ethanoates, metal- ethoxides, metallorganic complexes.

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