Electrochemical Reduction Of CO₂ On Indium Electrode In SiW₁₁Mn Or SiW₉V₃ Environment

The reduction of CO₂ to various valuable chemicals and fuels by electrocatalysis has attracted worldwide attention.In the study of electrocatalytic reduction of CO₂,although some achievements have been made,it still faces technical problems such as high overpotential,low selectivity,and difficulty in producing highly selective C₂₊products with higher commercial value.In this paper,metal indium with high hydrogen evolution overpotential was selected as the cathode working electrode,the heteropoly acid catholyte and metal indium were selected to build the electrocatalytic CO₂ reduction system.The catalytic performance of heteropoly acid in electrocatalytic reduction of CO₂ was investigated by evaluating the CO₂ electrocatalytic reduction products.In this paper,Keggin-type heteropoly acid SiW₁₁Mn was prepared by conventional synthesis method.In the electrocatalytic system constructed of heteropoly acid catholyte and indium,the products of electrocatalytic reduction of CO₂ are formate and acetate.The effect of heteropoly acid SiW₁₁Mn concentration on the catalytic efficiency of electrocatalytic reduction of CO₂ was investigated.Finally,2 mM SiW₁₁Mn-0.1 M Na₂SO₄ was selected as the electrolyte system parameter of this experiment.Electrochemical tests showed that the addition of heteropolyacid SiW₁₁Mn effectively reduced the initial overpotential of the reaction to-0.8 V.The Faraday efficiency of the product reached the highest at-1.0 V,the Faraday efficiency for the production of acetate was 72.1%,and the Faraday efficiency for the production of formate was 6.1%.It was found that in the electrocatalytic reduction of CO₂,the W element in the heteropoly acid SiW₁₁Mn enters the material structure of indium oxide in a doped manner.Electrochemical tests showed that the electron transfer process of Mn center of heteropoly acid SiW₁₁Mn may participate in the reduction reaction of CO₂ and play a catalytic role.The catalytic performance of another heteropoly acid SiW₉V₃ for electrocatalytic reduction of CO₂ was investigated in an electrolyte system of 2 mM SiW₉V₃-0.1 M Na₂SO₄.Electrochemical tests showed that the addition of heteropoly acid SiW₉V₃ effectively reduced the initial overpotential of the reaction to-1.0 V.The Faraday efficiency of the product reached the highest at-1.15 V,the Faraday efficiency for the production of acetate was 96.5%,and the Faraday efficiency for the production of formate was 2.4%.The indium electrode was pretreated by plasma cleaning method,the results show that the difference in the indium treatment method has no particularly significant effect on the Faraday efficiency of the product,indicating that the source of carbon in the formate and acetate products is the reduction of CO₂ and not from the organic solvent used in the chemical cleaning process.It was found that the V center of heteropoly acid SiW₉V₃ undergoes valence change during CO₂ electrocatalytic reduction,and its electron transfer process may participate in the reduction reaction of CO₂ and thus play a catalytic role.The W element in the heteropoly acid enteres the material structure of the indium oxide in a doped manner,changing the energy band structure,effectively reduces the overpotential of the reaction and efficiently converts CO₂ into acetate.