The Studies On Ag,Au Doped Cu₂O Catalysts For Electrocatalytic Reduction Of CO₂ To C₂ Products

Fossil fuels have been immoderately consumed since the Industrial Revolution,while the concentration of CO2 in the atmosphere is inevitably increasing,along with the severe climate change.Nowadays,reducing the concentration of carbon dioxide in the atmosphere has become a worldwide concern for mankind to solve.Using clean energy as an energy source to convert carbon dioxide into high-value chemicals through electrocatalytic carbon dioxide reduction reaction is an ideal way to solve the problem of carbon dioxide.Copper is currently the only metal catalyst that can deeply reduce CO2 to multi-carbon alcohols and hydrocarbons.However,the selectivity of a single product of copper-based catalysts is not high,and it faces competition from hydrogen evolution reactions,which limits its application.In response to these problems,introducing another metal on the basis of the copper-based catalysts to form tandem catalysts is an effective way to improve the selectivity of multi-carbon products.The tandem catalysts can convert CO2 to CO on the introduced metal,and then reduce CO to multi-carbon products on the copper-based catalysts.Based on cuprous oxide catalysts,this paper introduces Ag and Au into Cu2O to form tandem catalysts,and aims achieve highly selective electrocatalytic reduction of carbon dioxide to C2 products.The main contents of the paper are as follows:1.Cu2O nanocubes were prepared by chemical method and phase separated Cu2O-Ag tandem catalysts were prepared by a simple replacement reaction and tested for electrocatalytic CO2 reduction.Compared with the original Cu2O nanocubes,the Cu2O-Ag tandem catalysts reach a maximum C2 products Faradaic efficiency of 72.85%at-1.18 V(vs RHE)with the partial current density of 243.32 mA·cm-2,involving 27.23%ethylene,30.60%ethanol and 15.02%acetate.The Faradaic efficiency of acetate is three times higher than that of Cu2O at the same potential.The experimental results show that the introduction of Ag enhances the reducing activity of CO and the yield of C2 products is also improved.The density functional theory calculation results show that the high concentration of CO on the surface of Cu can help to reduce the energy barrier of C-C coupling reaction and promote the formation of C2 products.CO is the important intermediate for C-C coupling reaction in electrocatalytic carbon dioxide reduction reaction to C2 products.The introduction of Ag boosts the concentration of CO in the catalytic process,which endows Cu2O with excellent ability of electrocatalytic CO2 to C2 products.This work provides a simple and reasonable way to prepare copper-based catalysts with high selectivity and activity for C2 products.2.Macro Cu2O nanospheres were prepared by chemical method and surface-modified Au/Cu2O tandem catalysts with different molar ratios of Au on carbon paper were prepared by simple impregnation method and tested for electrocatalytic CO2 reduction.The experimental results show that the performance of the Au/Cu2O catalysts is significantly better than that of Cu2O.At-1.28 V(vs RHE),the Faradaic efficiency of the C2H4 of Au/Cu2O-2 is 10.61%,which is almost twice than that of Cu2O.In the entire test range,the ethanol Faradaic efficiency of Au/Cu2O-2 is maintained at about 4%,which is higher than the optimal ethanol yield of Cu2O.At the same time,the hydrogen evolution reaction competition reaction is significantly reduced,and the overall current density of the catalytic reaction is increased.This study provides a new idea for macro preparation of nano-sized Cu2O tandem catalysts.