Preparation And Reduction Performance Of Bismuth-based Electrocatalysts

Energy and environment are two important issues facing the sustainable development of human society.Among them,excessive greenhouse gas（CO₂）produced by fossil fuel combustion in industry,agricultural activities,and various other human activities is seriously affecting people’s daily life.Specifically,the excessive emission of carbon dioxide,a greenhouse gas,has caused problems such as global warming,extreme weather,acidification of seawater,and aggravation of land drought.The treatment of excess carbon dioxide gas,especially the resource development and utilization technology has always been concerned and pursued by people.At present,the use of carbon dioxide is mostly concentrated in oil field flooding or in the synthesis of some chemicals,such as urea.How to convert carbon dioxide into more valuable chemicals or fuels is an important problem to be solved to solve the increasingly severe global energy crisis and environmental pollution.The efficiency and product selectivity of electrocatalytic carbon dioxide conversion are closely related to the structure of the catalyst.In this paper,simple hydrothermal and solvothermal methods were used to prepare nanorod-shaped and sheet-shaped bismuth sulfide,bismuth sulfide/bismuth oxycarbonate heterojunction composites with different morphologies and structures by adjusting the experimental parameters such as bismuth source and temperature..Through the characterization of morphology and structure and related electrochemical performance tests in the H-type electrolytic cell that has passed the air tightness test,the differences in the performance of bismuth-based materials with different morphologies and structures as electrocatalysts in reducing carbon dioxide are explored.its reason.The specific related experiments are as follows:First,a simple solvothermal method was used to prepare traditional nanorod-shaped bismuth sulfide materials and two-dimensional nano-sheet-shaped bismuth sulfide materials by adjusting different solvent environments,temperatures,and bismuth sources.The morphology and structure of the two structures were characterized.Through the nitrogen adsorption and desorption test,the specific surface area of the nano-sheet-shaped bismuth sulfide material is 90.2 m²/g,which is 2.25 times that of the nano-rod-shaped bismuth sulfide material.The pore size of bismuth sulfide materials is mostly concentrated between 2-50 nm,which belongs to mesoporous materials.Therefore,compared with nanorod-like bismuth sulfide,the nanosheet-shaped bismuth sulfide material has a larger surface area,which can expose more active sites.Subsequent electrochemical tests also proved that,compared with the traditional nanorod-shaped bismuth sulfide material,the nano-flaky bismuth sulfide material has a higher current density at the same voltage;the faradaic efficiency of electrochemical reduction of carbon dioxide to formic acid is also higher.In addition,after the current stability test under the constant voltage condition of-1.45 V（vs.Ag/Ag Cl）for 3 h,the nanosheet-like bismuth sulfide can still maintain good structural and performance stability.Therefore,it is a feasible way to improve the performance of electrocatalytic carbon dioxide reduction by adjusting the morphology and structure of bismuth-based electrocatalysts.Electrochemical reduction of carbon dioxide technology under a certain range of voltage,the current density of its transformation into a specific product needs to be greater than 300 m A cm^-2 for a long time,good stability,Faraday efficiency greater than80%and good stability,in the industry to be applicable.Compared with the traditional nano-rod structure,the bismuth sulfide material with nano-sheet structure has better electrocatalytic performance,but its current density is still far below the required standard for practical use.In the field of photocatalysis,heterostructure materials have excellent electron transport rate and abundant active sites due to their unique structural advantages.Therefore,in order to improve the conductivity of bismuth-based materials,inspired by the structural advantages of heterostructure materials in the field of photocatalytic applications,we adopted a simple solvothermal method,by adjusting different solvent environments,temperatures and bismuth sources,etc.,to prepare Bismuth sulfide/bismuth oxycarbonate heterojunction composite material was obtained,and then through XRD,SEM,TEM and TEM-EDS structural characterization,it was tested for nitrogen adsorption and desorption.The specific surface area of this heterostructure composite material is 93.4 m²/g,in the electrochemical test,the current density of the material at the same voltage is also higher than that of the nanosheet-shaped bismuth sulfide material,and its current density is-1.45 V（vs.Ag/Ag Cl）The density is close to 20 m A cm^-2.After 3 h of current stability test,the material also performed well.Based on this,we analyzed that by adjusting the morphology and structure of bismuth-based materials,we prepared nano-sheet-shaped bismuth-based materials and composite bismuth-skeleton materials,which increased the adsorption of carbon dioxide and the transport rate of electrons,thereby improving the electron transfer rate of bismuth-based catalysts.The performance of chemical reduction of carbon dioxide is a feasible new route.