Preparation Of Tin-based Bimetallic Oxide Nanomaterials And Study On Electrocatalytic Reduction Of Carbon Dioxide

With the rapid increase in global consumption of fossil fuels,the energy crisis and climate problems are becoming increasingly severe.Electrocatalytic reduction of carbon dioxide（CO₂RR）is an effective means to solve the above problems.CO₂RR can not only achieve fixed emission reduction of CO₂,but also convert it into high economic value products such as HCOOH,CO,CH₃OH,etc.However,there are still some problems in the application of this technology,such as large reaction potential,low current utilization rate and poor catalytic selectivity.Therefore,the development of new catalysts with high catalytic activity,better selectivity and stability is the key to the application of CO₂RR.In recent years,metal composite materials have been widely used to construct CO₂RR catalysts.Among them,tin-based composite catalysts have attracted the attention of researchers due to their rich raw materials,easy preparation,and good catalytic activity.In this thesis,tin-based metal oxide nanotubes were prepared by electrospinning and used in the study of CO₂RR in aqueous solutions.（1）Electrostatic spinning was used to synthesize nanofibers rich in tin-cobalt metal precursors,and then calcined in a 500°C air atmosphere for 2 h to prepare tin-cobalt composite metal oxide nanomaterials（Sn Co-MSN）.Through FESEM,TEM and EDX characterization,it was found that Sn Co-MSN has a composite structure with nanorods loaded on the outer wall of nanotubes.By adjusting the raw material synthesis ratio,the influence of element content on the structure was clarified.BET test shows that Sn Co-MSN has good specific surface area(20.8 m² g^-1)and pore volume(92.9 cm³ g^-1).Electrochemical test results show that the Sn Co-MSN composite structure can expose more catalytically active sites,which helps to improve the catalytic performance of CO₂RR.Combined with XPS,XRD and other characterization,the effect of metal oxide valence on catalytic activity was further analyzed.In addition,through experimental comparison with tin oxide nanomaterials（Sn-MSN）and cobalt oxide nanomaterials（Co-MSN）,it was found that the synergistic effect of tin-cobalt bimetals can significantly improve the catalytic performance of CO₂RR at-0.9 V vs.RHE Under the potential of RHE,the Faraday efficiency of electroreduction to CO can reach 94.4%.（2）Electrostatic spinning was used to synthesize nanofibers rich in tin-copper metal precursors,and then calcined and oxidized in an air atmosphere to prepare tin-copper composite metal oxide nanomaterials（Sn Cu-MSN）.Characterized by FESEM,TEM and EDX,the results show that Sn Cu-MSN has a composite structure of nanotube arrays loaded with nanorod arrays.By adjusting the calcination temperature,the effect of temperature on the structure of the catalyst material was explored,and the synthesis mechanism of the bimetal oxide composite nanomaterial was determined.Compared with the experiments of tin oxide nanomaterials（Sn-MSN）and copper oxide nanomaterials（Cu-MSN）,it was found that copper loading has a better effect on the catalytic selectivity of tin-based oxide nanomaterials.At a potential of-0.9 V vs.RHE,the Faraday efficiency of Sn Cu-MSN electroreduction to prepare HCOOH can reach 95.1%,which is an increase of 23%compared with Sn-MSN.Combining XPS and XRD characterization,the structure shows that Cu⁺in Sn Cu-MSN material has a better promotion effect on the catalytic performance of CO₂RR.Combined with LSV,CV,ECSA,I-T and other electrochemical tests,it is shown that the composite structure of Sn Cu-MSN provides more catalytic interfaces and helps to improve the catalytic activity.