Electrocatalytic Reduction Of CO₂ Based On Tin Oxide And Indium Oxide Catalysts

With the rapid development of industry and technology,the demand of energy is increasing day by day.As fossil fuels(eg.coal,oil and natural gas)are consumed in large quantities,the concentration of CO2 in the atmosphere rises sharply,causing ecological and environmental problems.Thus,electrochemical carbon dioxide reduction reaction(CO2RR)to high value chemicals seem to be a promising way to relieve this attracting lbut challenging issue.However,CO2RR still faces intractable problems,such as high overpotential,unsatisfactory activity,and poor selectivity and stability.Therefore,the emphasis of CO2RR research is understanding the mechanism of reaction and developing high efficient and stability catalysts.In this thesis,taking Tin and Indium oxide nanomaterials as the research objects,we endeavored to explore structure-dependent catalytic properties of SnO2 nanocrystal and to develop efficient and stable catalysts.The main research progress is summarized as follows:1.Understanding the structure-performance relationship of catalysts in the electroreduction of carbon dioxide is crucial for achieving high efficient CO2RR.Herein,we took SnO2 nanocrystals with well-defiend surface structure as model catalysts to explore surface structure-dependent electrocatalytic reduction of CO2.We found that the catalytic performance of SnO2 catalysts was closely related to the formation of stable catalytic interface during the electrocatalytic process of CO2RR.For ocatahedral SnO2 nanocrystals enclosed with {111} facets(Oct-{111}),a stable and effective Sn/SnOx catalytic interface was constructed during CO2RR.Due to the maximum electrochemical area and catalytic interface area,the Oct-{111} catalyst exhibited the best CO2RR activity among the measured samples.We concluded that the catalytic activities of crystal facets were in the sequence:{111}>{110}>{221}.2.Developing efficient and stable electrocatalysts has always been the focus of research on CO2 electroreduction reaction.Indium Tin oxide(ITO)compsite catalysts was grown on carbon nanotubes by co-precipitation metod.By adjusting the In/Sn ratio,ITO/CNT composite catalysts with different phase structures can be obtained.Among them,rhombohedral In2SnO5/CNT catalysts exhibited the best CO2RR activities,very high Faradaic efficiency of C1 products(including HCOOH and CO)>95%can be achieved at a wide potential range from-0.7 V to-1.0 V vs.RHE.The electrocatalysts also exhibits excellent long-term stability(98 h at-0.7 V vs.RHE).It was demonstrated by electrochemical surface area(ECSA)and electrochemical impedance testing(EIS)that In2SnO5/CNT has higher electrochemical active area and smaller interfacial charge-transfer resistance than In2O3/CNT,which leads,In2Sn05/CNT showing better CO2 reduction activity.