Copper-Based Composite Catalysts For Electrochemical CO₂ Reduction Reaction

The large-scale use of fossil fuels increases the concentration of carbon dioxide（CO₂）in the atmosphere and exacerbates the greenhouse effect.As a non-toxic carbon resource,CO₂ can be transformed into valuable compounds and reduce the concentration of CO₂ in the atmosphere.Electrochemical CO₂ reduction reaction has attracted the attention of researchers due to its simple and controllable reaction process and the production of valuable compounds.Among the metal catalysts for electrochemical CO₂ reduction reaction,only copper（Cu）can obtain a variety of products in large quantities,but the variety of products leads to the low selectivity of Cu to a single product.In this thesis,the Cu-based composite catalyst was prepared to improve the selectivity of Cu to a single product.The copper-selenium composite catalyst and the copper-oxygen composite catalyst were prepared by electrodeposition.Compared with the copper-oxygen composite catalyst,the copper-selenium composite catalyst reduces the Faradaic efficiency of CO₂ reduction of gas phase products and improves the selectivity of liquid phase products.The formic acid Faradaic efficiency of the copper-selenium composite catalyst was 47.6%,and the current density did not decrease after 39000 seconds of testing.The addition of selenium element increases the oxygen vacancy and electrochemical active surface area,and increasing the oxygen vacancy is beneficial to improve CO₂ adsorption.Copper nitrogen-doped carbon catalyst and copper-carbon catalyst were prepared by reducing copper on different carbon supports.Compared with copper-carbon,copper nitrogen-doped carbon reduces the onset potential of the ethylene product,reduces the hydrogen evolution reaction activity,and improves the Faradaic efficiency of the ethylene product.The ethylene Faradaic efficiency of copper nitrogen-doped carbon was 29.3%,and the current density did not decrease after 18000 seconds of testing.Copper nitrogen-doped carbon catalyst and copper nitrogen-doped porous carbon catalyst were prepared by reducing copper on different carbon supports.Compared with copper nitrogen-doped carbon,copper nitrogen-doped porous carbon has higher selectivity for methane products,its methane Faradaic efficiency is 28%,and the current density has not decreased after6000 seconds of testing.By comparing the Faradaic efficiency of gas phase products of different catalysts,the results show that the ratio of inorganic salt to adenine and the amount of Cu used will affect the selectivity of the catalyst product.