Reconstruction Of Nanoporous Copper-based Compounds And Electrocatalytic Performance For CO₂ Reduction Research

In modern industrial society,with the continuous consumption of fossil fuels,the energy crisis is becoming more and more prominent.At the same time,t he excessive emission of greenhouse gases such as carbon dioxide（CO ₂）has also caused a series of environmental problems.The novel idea to solve the above two problems is to imitate plant photosynthesis to convert excess CO₂ in the air into usable fuels.At present,many studies have applied chemical,biological,photochemical,electrochemical,and other methods to achieve the above transformation.Among them,the electrochemical conversion method has obvious advantages because of its mild reaction enviro nment and controllable conversion conditions,but the performance of electrocatalytic carbon dioxide reduction reaction（CO₂RR）is usually restricted by catalysts.Therefore,the research on catalysts with high selectivity,high current density,and high s tability remains a key challenge.Cu is the only catalyst proved to be able to electro chemically convert CO₂ into rich hydrocarbons and alcohols in aqueous solution,but the selectivity and activity of pure copper are very poor.Modifying the surface of co pper or combining it with other elements is an effective way to improve selectivity.In addition,the structure and composition of Cu-based catalysts often evolve under actual reaction conditions.Therefore,revealing the actual active substances of cataly sts is of great significance for understanding the structure-activity relationship and constructing novel CO₂RR catalysts.In view of the above problems,based on the principle of the alloy phase diagram,combined with arc melting,spinning technology,and selective etching method,nanoporous Cu_2-xSe and Cu₂S compounds were prepared in this project.The electrocatalytic CO₂RR properties of two nanoporous compounds were investigated.The reconstruction dynamics of the catalyst surface under CO₂RR was revealed and the kinetic mechanism of CO₂RR was clarified.The main contents are as follows:1.The precursor ribbons composed of Cu and Cu₂Se was prepared by arc melting and melting-spinning technology,and the Cu phase was removed by chemical corrosion to obtain the nanoporous Cu_2-xSe compound catalyst.The catalyst shows excellent methanol selectivity in CO₂RR.The Faraday efficiency of methanol on-0.5V vs.RHE is～58%,with the stability for about 70 h,which is better than nanoporous Cu（～10%）.In situ spectroscopic characterization revealed the forma tion process of nanoporous Cu_2-xSe surface reconstructed into Cu（Se-5%）@Cu_2-xSe in the process of electrocatalytic reduction.Density functional theory calculation shows that the Se modified Cu active phase reconstructed on the surface of nanoporous Cu_2-xSe can promote the charge transfer and*COOH adsorption process,significantly reduce the energy barrier formed by the key intermediate*CHO in the process of carbon dioxide electroreduction,and accelerate the kinetic process of CO₂RR to methanol.2.The precursor ribbons were prepared by arc melting and spinning technology,which was composed of Cu and Cu_1.8S two phases.The Cu phase was removed by chemical corrosion to obtain the nanoporous Cu₂S compound catalyst.The catalyst shows excellent formic acid selectivity in CO₂RR.In the wide voltage range of-0.7～-1.1 V vs.RHE,the Faraday efficiency of formic acid can be maintained at about 80%,and the stability of 91 h can be achieved.It is superior to the catalytic efficiency of most ccopper-based catalysts for formic acid.The excellent performance of the catalyst is attributed to the fact that sulfur doping promot es the formation of*OCO and*OCHO intermediates,thus promoting the formation of formic acid.In conclusion,nanoporous Cu_2-xSe compounds and Cu₂S compounds were successfully prepared by arc melting,spinning and selective etching.They were applied to electrocatalytic carbon dioxide reduction and showed excellent catalytic performance.Copper selenium compounds solve the problem of low selectivity of CO₂RR methanol.Copper sulfur compounds solve the problem of high selectivity and narrow voltage range.This is of great significance for the industrial application of electrocatalytic reduction of carbon dioxide.