Polyoxometalate （n-Bu₄N）₃SVM₁₁O₄₀（M=W/Mo） Synergize With Indium Electrode For Electrocatalytic Reduction Reaction Of CO₂

The conversion of CO₂into various chemicals with added value through electrocatalytic reduction has attracted widespread attention from researchers all over the world.Although some positive results have been achieved so far,electrocatalytic CO₂reduction reaction involving polyoxometalates that have excellent catalytic properties is still in its infancy.And there are various technical problems such as poor stability,high overpotential,and low reduction depth.In this paper,metal indium with higher hydrogen evolution overpotential was selected as the working electrode,and a dual catalytic electrolysis system with metal indium electrode and different polyoxometalates was constructed.Moreover,the evaluation of the catalytic performance of two polyoxometalates in the electrocatalytic reduction of CO₂was analyzed by the reaction products.In this paper,a conventional synthesis method was used to synthesize（n-Bu₄N）₃SVW₁₁O₄₀,which can be used in a non-aqueous electrolyte to cooperate with the In electrode to effectively achieve the targeted transfer of multiple electrons to obtain acetic acid,ethanol and CO.The initial potential of the reaction can be dropped to-0.4 V.And the system achieves the highest total Faraday efficiency of liquid phase products at-0.5 V,which is 75.2%.The electron transfer process of the V center of（n-Bu₄N）₃SVW₁₁O₄₀played a good catalytic role in the reaction.At the same time,the V center made the catalyst surface have higher hydrogen coverage and induced the system to perform multi-electron reduction.Furthmore,W changed the energy band structure of indium electrode by atomic doping,which improved the selectivity and catalytic activity of the reaction system.Another polyoxometalate（n-Bu₄N）₃SVMo₁₁O₄₀synthesized was applied to the research of electrocatalytic CO₂reduction performance.It was found that the addition of（n-Bu₄N）₃SVMo₁₁O₄₀can effectively reduce the initial potential of the reaction to-0.3 V,and the products are CO and ethanol.Among them,the Faraday efficiency of ethanol can reach the maximum at-1.1 V,which is 69.5%.According to the in-situ FT-IR results and related literature,the reaction process was speculated,namely CO₂→^*COOH→^*CO→^*COCH₂→CH₃CH₂OH.In addition,it was found that the oxide film formed by the indium electrode in the air has catalytic activity,while the oxide film formed after participating in electrolysis is inert.The oxygen vacancies formed on the electrode surface provide a guarantee and a platform for the adsorption and reduction of CO₂.Moreover,the Mo element in the polyoxometalate underwent a valence state change,and the electron transfer process may participate in the CO₂reduction reaction process,providing an electron transfer channel for the reaction system.