Preparation Of Cu-In And Sn-Bi Catalysts And Their Catalytic Performance For The Electroreduction Of CO₂

CO₂ reduction can directly convert CO₂ into a series of products such as CO and HCOOH.The whole process can be sustainable and pollution-free,which provides a feasible strategy for reducing greenhouse effect.Among them,HCOOH as one of the many products of electrocatalytic reduction,is an excellent hydrogen storage material and can be directly used as fuel or industrial solvent for fuel cells.However,the main problem of CO₂ electroreduction has a series of difficulties such as low product selectivity,high overpotential,low current density and expensive catalysts.In view of the above problems,this paper designed two applicable catalysts and focued on the materials preparation,microstructure and the reaction mechanism of the catalyst.The details are as follows:（1）Use two-steps electrodeposition to prepare catalyst,the copper having dendritic structure is first deposited on copper foam substrate by the hydrogen template method,and then metal indium is electrodeposited by galvanostatic,so that indium having dendritic shape can be obtained.A dendritic Cu-In binary metal electrode was prepared by two-setps electrodeposition,and the relationship between the length of electrodeposited In and electrochemical performance was investigated.When the time of electrodepositing In reaches 30 min,the Cu-In-30 electrode can effectively convert CO₂ into HCOOH.The Faraday efficiency of HCOOH at-0.85 V vs.RHE is 86%,and the partial current density is 42 m A cm^-2,this catalyst can maintain stable performance for 12 hours in liquid phase experiments.However,the In-30 electrode without dendritic structure has a Faraday efficiency only 57%for HCOOH at-0.85 V vs.RHE,and the partial current density is only 5 m A cm^-2.Cyclic voltammetry was used to calculate the electrochemical area（ESA）of the electrode.The ESA of the Cu-In-30 electrode（8.74 cm²）was 3.6 times higher than the In-30electrode（2.42 cm²）.The dendritic structure can greatly increase the specific surface area of the catalyst and expose more active sites.（2）A catalyst with dendritic core-shell structure was prepared by the hydrogen template method on copper foam.The electrodeposition currents were studied on the morphology of the prepared electrode and the performance of electroreducting CO₂.When the current is-4 A cm^-2,the prepared electrode has a dendritic structure and has the best performance for converting CO₂ into HCOOH.The effects of the ratio between Sn²⁺and Bi³⁺ions in the electrolyte on the morphology of the prepared electrode and the ability to convert CO₂ were studied.A series of characterization and electrochemical performance tests showed that when the ratio of Sn²⁺to Bi³⁺ion concentration in the electrolyte was different,the prepared electrodes also have a large difference.When the ratio is 3:1,the catalyst with a dendritic core-shell structure can be formed,and the catalyst exhibits the highest performance for electrochemical CO₂reduction reaction at-1.15 V vs.RHE.The Faraday efficiency of HCOOH can reach95.6%and the partial current density is 178.77 m A cm^-2,which exceeds other reported Bi catalysts.