A Study On Transition-metal Based Catalysts For The Electrochemical Reduction Of Carbon Dioxide

Since the industrial revolution,the energy crisis and environmental issues caused by the excessive consumption of the fossil fuels have been the problems that human beings must solve.Owing to the simple reaction device,the friendly environmental reaction process,and the high energy utilization,it is a promising way to convert CO₂ to useful fuels through the method of the electrochemical reduction.However,the sluggish kinetic process and complex reaction routes of the CO₂ electroreduction reaction largely limit the conversion efficiency and products selectivity.Herein,the key of the CO₂ electroreduction reaction is to farbticate catalysts with high activation and selectivity.The main catalysts applied for the CO₂ electroreduction are metal-based catalysts,including metals,metal oxides,and metal chalcogenides.Owing to the high overpotential and competition with hydrogen evolution reaction,single metal catalysts not exhibit high performance and energy utilization toward the CO₂ electroreduction.However,the catalytic activity and product selectivity of the single metal catalysts could be largely enhanced through the approach of bimetallic compounds and partially oxidation.We prepared bimetallic and partially oxidized metal catalysts based on the above ideas,and the details are as follow.（1）Firstly,through the method of electrodepositing electrochemical treatment,Cu₂Cd/Cd/Cu catalyst was prepared.The catalyst shows CO conversion faradaic efficiency of 84%with a current density of 8 mA cm^-22 at-1.0 V vs.RHE in CO₂-saturated0.1 M KHCO₃ solution.And the activity of the catalyst could sustain more than 13 h toward CO₂ reduction.Detailed investigation has revealed that the electrocatalytic capability of this catalyst can attributed to the boundary between Cd and Cu that could provide sufficient active sites for the CO₂ reduction and the formation of Cu₂Cd alloy that could optimize the binding energy between the catalyst and the intermediate.It is anticipated that this research may provide new sights for the preparation of the bimetallic catalysts and enhancement of the catalytic performance.（2）Partially oxidized Co powder was synthesized through a hydrothermal method,and electrochemical tests and products analysis demonstrate that CoO@Co exhibits higher current density and faradaic efficiency of formate than pure cobalt or cobalt oxide.It could be ascribed that the interface between metal and metal oxide could provide numerous active sites for the CO₂ reduction.The CoO@Co/C composite exhibits higher current density than CoO@Co,and the potential for the catalyst reacting with CO₂ absorbed directly is lower than that for the catalyst reacting with CO₂ in solution.It indicates the catalyst owns higher catalytic activity after the process of composite.