Study On Surface Modification Of Transition Metal Oxides To Enhance The Performance Of Electrocatalytic CO₂ Reduction

The massive accumulation of carbon dioxide（CO₂）in the atmosphere caused by the burning and irreversible consumption of fossil fuels is a vital cause of rapidly increasing global climate change.Electrochemical CO₂ reduction（ECR）,which can use the electricity generated from renewable energy sources,stands out among the various conversion methods.ECR relies on highly efficient electrocatalysts to convert CO₂ into value-added products to achieve a sustainable carbon cycle and alleviate the energy and environmental crisis.Transition metal oxides have attracted attention because of effective ECR active sites and numerous preparation methods,rich sources,conducive to regulation and other advantages,but there are still poor activity,low current density and other problems about it.In this thesis,we try to improve the ECR performance of catalysts through surface modification of transition metal oxides,such as the double-doping strategy and interface construction.Specific research results are as follows:（1）F-Pb-CuO catalyst was synthesized by a simple hydrothermal method using a double-doping strategy for highly efficient and selective ECR to ethylene（C₂H₄）.The successful synthesis of F-Pb-CuO catalyst was demonstrated by the characterization of XRD,XPS,Raman and TEM.The Faraday efficiency（FE）of the F-Pb-CuO catalyst is 58.4%for the C₂H₄ in H-type electrolytic cell（-1.15 V vs.RHE）and 77%for the C₂₊products（mainly C₂H₄）in the flow cell and the corresponding current density can reach-600 m A cm^-2.Experimental results and theoretical calculations manifested that the introduction of Pb lowers the barrier of generating *COOH,which is conducive to generating more *CO,while the introduction of F is conducive to enhancing the adsorption of *CO and reducing the barrier of C-C coupling.The two synergistic actions in different steps of the reaction path improve the ECR performance of the catalyst and promote the generation of C2H4.（2）The CuO/CB（carbon black）composite catalyst was prepared by simple ultrasonic treatment.The composition of the Cd O/CB catalyst was determined by XRD and XPS,and the TEM showed a cubic structure and a clear interface between Cd O and CB.With the introduction of carbon black,there is a certain increase in current density due to its conductivity,unexpectedly it also promoted the efficient generation of CO through ECR.The total ECR FE（including CO and HCOOH）of Cd O/CB catalyst is 92.7%,and the FECO is 87.4% in H-type electrolytic cell,in contrast to that of pure Cd O with numbers of 69.5% and 62.4%,respectively,and the current density and ECR performance of Cd O/CB catalyst can maintain stable within 10 h under the same conditions.The results show that the excellent ECR performance of Cd O/CB composite catalyst is due to the interface between Cd O and CB and the high contact area.