Synthesis And Performance Of Carbon Composite Bismuth-based CO₂ Electroreduction Catalysts

Converting CO₂ into more economic chemicals is one of the important ways to achieve national carbon peak and neutrality targets.CO₂ reduction driven by renewable electricity is not only clean and sustainable,but also has mild operating conditions and diversified products,which has gradually become a research hotspot in this field.However,this technology is now facing tough challenges such as severe competitive hydrogen evolution reaction and low selectivity of specific products.The key to deal with these challenges lies in the development of efficient and low-cost catalysts for electrochemical CO₂reduction.In this paper,main group metals tin and bismuth are selected as the primary active species for they possess high electrochemical activity for CO₂reduction.Meanwhile,they are combined with carbon materials that have good stability,high conductivity and low price to efficiently drive the conversion of CO₂ to value-added formate.The following are the main research contents and results:Carbon coated tin dioxide was prepared via hydrothermal process using low price glucose as carbon source and sodium stannate trihydrate as tin source.After being treated by H₂/Ar gas heat reduction and galvanic replacement,the second metal bismuth was introduced.The effect of the introduction of bismuth and different bimetal composition on materials’morphology and structure were explored,as well as these catalysts’performance of CO₂ electroreduction.The introduction of bismuth metal can further improve the selectivity of CO₂reduction to formate.The selectivity for formate of Sn Bi@C-1:0.5 is about 88%at-1.1 V vs.RHE with a partial current density of-10.57 m A cm^-2 and good stability within 6 h.Through studying the structure-activity relationship of composites,it is speculated that the electronic effect between Sn and Bi sites promotes the CO₂ reduction performance.Using carbon paper after acid treatment as support,nitrogen doped carbon layer coated bismuth oxide nanosheets supported on carbon paper（Bi₂O₃@NC-CP-t,t represents the duration of eletrodeposition）were constructed via three steps including the solvothermal growth,electrodeposition of polypyrrole and calcination in N₂ atmosphere.How electrodeposition time effected their morphology,structure and CO₂ catalytic performance was also studied.The presence of polypyrrole derived carbon layer on the surface can increase the distribution of product formate.Optimized catalyst Bi₂O₃@NC-CP-3（electrodepositing 3 min）exhibits a 90.45%Faradaic efficiency for CO₂-to-formate production with a partial current density of-21.69 m A cm^-2.The integrated electrode Bi₂O₃@NC-CP enables greatly improvement in the catalytic current density.