Laser Construction Of Heterogeneous Structures To Regulate The Activity Of Electrocatalytic Reduction Of Carbon Dioxide

Since the Industrial Revolution,the massive use of fossil fuels has produced excessive carbon dioxide（CO₂）,which has significantly enhanced the greenhouse effect,led to the deterioration of climate and environment,and threatened the sustainable development of human society.Electrocatalytic reduction of CO₂ to high value-added chemicals is one of the efficient ways to use CO₂.However,CO₂ is an inert molecule with stable structure.The activation energy of CO₂ reduction reaction is high,and the process involves multiple steps such as adsorption,activation and hydrogenation,which is easy to produce byproducts.Therefore,it is difficult to efficiently convert CO₂ into specific compounds.To solve this problem,it is very important to design and develop efficient electrocatalysts.Construction of bimetallic oxide/alloy heterojunction catalysts is a recognized and effective method to improve catalyst performance by integrating the advantages of different metals.Heterostructural interfaces can achieve synergistic catalytic effects by regulating electron transfer,geometric structure and chemical reactions,thereby reducing the reaction barrier of key reaction intermediates and promoting formic acid formation.Based on the above reasons,this paper carries out research in the following two aspects.（1）At present,copper-tin alloy catalysts have shown the capability to reduce CO₂ to formic acid or formate.However,their poor adsorption and activation capacities for CO₂ molecules,as well as the sluggish kinetics in water dissociation and*H supply restrict the proton-coupled electron transfer processes in electrocatalytic CO₂RR to produce formic acid.In order to solve the above problems and achieve efficient catalytic CO₂RR,the ultra-small Sn O₂/Cu₆Sn₅/Cu O nanocatalysts with superscalar phase boundaries are designed by laser sputtering.The introduction of Sn O₂ enhances the adsorption and activation of CO₂,while Cu O promotes H₂O decomposition and provides abundant*H intermediates,resulting in tandem catalytic sites on the Sn O₂/Cu₆Sn₅/Cu O composite catalysts and thus leading to excellent CO₂RR activity and high selectivity to formic acid.In the H-type cell,the Faradic efficiency of formic acid(FE_HCOOH)produced by Sn O₂/Cu₆Sn₅/Cu O reaches 90.13%,and the current density reaches25.2 m A cm^-2 at-0.95 V vs.RHE.In a flow cell,FE_HCOOH could reach 95.64%at-0.95 V vs.RHE with a current density of 70 m A cm^-2.In order to clarify the enhancement mechanism of Sn O₂/Cu₆Sn₅/Cu O for the production of formic acid from CO₂RR,the coordination environment and electronic structure of Cu₆Sn₅/oxides are analyzed by X-ray photoelectron spectroscopy（XPS）and X-ray absorption fine structure spectroscopy（XAFS）.It is confirmed that the electron transfer between Cu and Sn promotes the chemisorption of CO₂.The results of CO₂-temperature programmed desorption（CO₂-TPD）,in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy（ATR-SEIRAS）and kinetic isotope effect（KIE）experiments confirm that the multiphase boundary constructed by introducing oxides is beneficial to the activation of CO₂ and the supply of*H,which improves the CO₂RR activity and formic acid selectivity of the catalyst.（2）In this paper,Bi/Cu Bi₂O₄ heterojunction nanocatalyst is constructed by laser sputtering for the problems of low selectivity,poor activity and poor stability of Bi-based catalysts.The introduction of Cu into the Bi-based catalyst can regulate the electronic structure of the catalyst and the binding energy of the reaction intermediates at the active site,thus promoting the formation of formic acid.Compared with pure Bi catalysts,bimetallic oxide-derived Bi-based heterojunction catalysts（Bi/Cu Bi₂O₄）showed higher formic acid product activity and selectivity.In the H-type electrolytic cell,the FE_HCOOH of Bi catalyst is 72.32%at-0.95 V vs.RHE,and the current density is 15.65 m A cm^-2.Bi/Cu Bi₂O₄ heterojunction catalyst shows higher formic acid selectivity(FE_HCOOH=96.03%)and higher current density(20.8 m A cm^-2).Moreover,FE_HCOOH can be maintained at more than 90%within 30 h in the CO₂RR process of Bi/Cu Bi₂O₄,which proves that the performance of the catalyst remains stable for a long time.The above properties indicate that this heterojunction interface,as the active phase of the bimetallic catalyst,provides an effective active site for CO₂RR,resulting in higher CO₂RR activity and formic acid selectivity.