| With the development of the industrial revolution,the consumption of fossil fuels has increased dramatically,gradually destroying the carbon cycle.The consequence of this is to cause the greenhouse effect,cause global warming,melting glaciers and other serious ecological and environmental problems,posing a threat to the human living environment.Therefore,using renewable electricity to drive the electrocatalytic carbon dioxide reduction to obtain high-value fuels is a promising strategy.There are many products of electrocatalytic CO2 reduction reaction,mainly CH4、CO、HCOOH、CH3OH、C2H4、C2H5OH,etc.These organic compounds have great value in economic and industrial applications,so they have very great research significance.Among the various reduction products of electrocatalytic carbon dioxide reduction,CO and C2H4 are considered to be very important industrial raw materials.At present,many people have made great efforts to explore high-efficiency electrocatalysts for the reduction and conversion of electrocatalytic carbon dioxide into CO and C2H4 High-performance CO-producing catalysts mostly rely on the use of precious metals such as gold,palladium and silver.Therefore,it is still necessary to explore non-noble metal electrocatalysts with high selection and activity for CO-producing electrocatalytic carbon dioxide reduction.At present,only copper-based materials are the only materials that are expected to increase C2H4 and other C2 products on a large scale.At the same time,in recent years,it has been found that the presence of Cu+in Cu2O is beneficial to carbon dioxide activation and CO intermediate dimerization,so it has better ethylene selectivity than metal copper.However,the selectivity of C2 products such as C2H4is still very low.Therefore,it is also necessary to find a catalyst to improve the performance and activity of electrocatalytic carbon dioxide production C2H4.Due to the problems of low selectivity and poor activity in electrocatalytic carbon dioxide reduction,we will enhance the carbon dioxide adsorption through the doping design of non-noble metals and the adjustment of the composite components to reduce the thermodynamic energy barrier of the reaction and accelerate the reaction kinetics process,so as to improve the performance of electrocatalytic carbon dioxide reduction.The main contents of this paper are as follows:In the first chapter,first introduce the technology of carbon cycle and carbon dioxide reduction,and then introduce the basic theoretical knowledge of electrocatalytic carbon dioxide reduction products,performance parameters,influencing factors,and then introduce the research status and existence of electrocatalytic carbon dioxide reduction materials in detail.The problem.Finally,point out the meaning and research content of the thesis.In the second chapter,B-doped ZnO is mainly studied to improve the performance of CO2 electrochemical reduction for CO production.Firstly,ZnO doped with different mass fractions of B was synthesized,namely 1%B-ZnO,2%B-ZnO and 4%B-ZnO.By testing the performance of electrocatalytic carbon dioxide production of CO,it can be found that the 2%B-ZnO sample with the best CO2 adsorption obtains the best CO2ER high activity and selectivity for CO production,and at RHE-1.0 V the current density is 40 mA cm-2 and FE is 80%.The experimental results prove that the proper doping of B in 2%B-ZnO is beneficial to improve the adsorption and activation of carbon dioxide,and reduces the thermodynamic barrier.It is also proved by Tafel and Nyquist that the doping of B promotes the kinetics.This research proposes a high-performance catalyst aimed at improving adsorption through doping.In the third chapter,Ce-doped ZnO regulates oxygen vacancies to improve the performance of CO2 electrochemical reduction.In our work,ZnO with different concentrations of oxygen vacancy defects was obtained by adjusting the Ce3+doping amount.During the CO2ER performance test,it was found that the performance of the sample was closely related to the concentration of oxygen vacancies in the prepared CexZn1-xO.The experiment found that Ce0.016Zn0.984O,which has the highest oxygen vacancy,obtains the best CO2ER concentration for CO production,and the current density is 24 mA cm-2 and FE is 88%at RHE-1.0 V.Through carbon dioxide isotherm adsorption and TPD tests,it is proved that the high concentration of oxygen vacancies of Ce0.016Zn0.984O is beneficial to increase the adsorption and activation of carbon dioxide,and reduce the thermodynamic barrier,and the Ce doping is proved by Tafel,Mott-Schottky and Nyquist.Regulating the oxygen vacancy of ZnO promotes kinetics.This research proposes a high-performance catalyst for the electrocatalytic reduction of CO2 by adjusting the concentration of oxygen vacancies.In the fourth chapter,the Cu2O/CeO2 composite system enhances the performance of CO2 electrochemical reduction to produce C2H4.The ratio of Cu2O/CeO2 composite system with different mass fractions was synthesized by a simple synthesis method,which were 10%Cu2O/CeO2,20%Cu2O/CeO2,30%Cu2O/CeO2,40%Cu2O/CeO2 and 50%Cu2O/CeO2.By testing the performance of electrocatalytic carbon dioxide to produce C2H4,it is found that the highest performance is 30%Cu2O/CeO2 samples,and the best CO2ER production of C2H4 performance is obtained(at RHE-1.0 V current density 15.6 mA cm-2 and FE C2H4 60%).Through the experimental results,it is found that adjusting the Cu2O/CeO2 composite ratio can improve the adsorption of carbon dioxide by the catalyst,and at the same time play the role of Cu2O in the electrochemical reduction of CO2 to produce C2H4,so 30%Cu2O/CeO2 catalyst can be obtained with the best catalytic performance.Through this research,it is proposed to increase the carbon dioxide adsorption by adjusting the proportion of the composite,so as to obtain a high-performance catalyst.In the fifth chapter,we summarize this paper,and discusses the innovation points,problems and future work prospects of the paper at the same time. |
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