Preparation Of Bismuth Based Catalysts And Its Electrochemical Reduction Performance Of CO₂

Since the reform and opening up,China’s industrialization process has been significantly accelerated.Energy shortage and environmental pollution have become two major problems to be solved in our country,which makes people pay more attention to the importance of sustainable development.In recent years,the concentration of CO₂in the environment continues to rise,and the greenhouse effect has caused great damage to the ecological environment.Therefore,it is important to study the technology of the CO₂control in the Times.Electrochemical reduction of carbon dioxide can produce chemical products with high added value,which is favored by people.The electrochemical reduction of CO₂is considered to be the most promising CO₂resource utilization method due to the advantages of moderate reaction conditions,easy to access the raw materials,easy to apply in large-scale,etc.This method uses renewable solar energy,wind power to generate electricity,which can not only reduce the CO₂concentration in the environment,but also relieve the pressure of resource shortage.However,electrochemical reduction of CO₂also has some defects,such as low selectivity of target products and poor stability of electrode materials.Therefore,it is necessary to design and develop efficient and stable catalysts.In this paper,Bi-based catalytic materials with low price,easy to access,non-poisonous and mainly producing formate were used as the main research object.New catalytic materials with different morphologies,high selectivity and high catalytic activity were synthesized by hydrothermal method,and analyzed by a series of characterization methods,with the expect to improve the current density and Faradaic efficiency.The main conclusions of the paper are as follows:（1）The Bi/MCNOs electrode catalyst was prepared by hydrothermal method.The micro-morphology and phase composition of Bi/MCNOs and Bi were characterized by means of SEM,XRD,XPS,etc.The activity,specific surface area and reaction mechanism of the catalyst for electrochemical reduction of CO₂were analyzed by LSV and ECSA.It is found that the electrode loaded with MCNOS has a small nano-spherical structure.Compared with the Bi electrode,the specific surface area of the Bi/MCNOs is larger and the electrical conductivity is better.In the same test conditions,the activity of Bi/MCNOs electrode for CO₂reduction to formate is higher.At-1.6V vs.Ag/Ag Cl,the Faraday efficiency of Bi/MCNOS electrode can reach 91.2%,the current density can reach 25m A·cm^-2,and its electrochemical activity showed no significant attenuation within electrolysis for 23h,indicating good electrocatalytic stabilities.The reaction had the best catalysis and stability when the concentration of HCO₃^-was 0.5mol/L,the reduction potential was-1.6V vs.Ag/Ag Cl,the temperature was 10℃and the amount of catalyst was 10mg.（2）Bi nanowire electrode and Bi nanoflake electrode catalyst were successfully synthesized by hydrothermal method with using different experimental raw material.SEM,XRD,XPS and other test methods were used to characterize and analyze the phase composition and micro-morphology of the catalysts,through the LSV and ECSA test,specific surface area and reaction mechanism can be analyzed.The results show that the microstructure of the materials has a great influence on the performance of electrochemical reduction of CO₂to formate.Bi nanowire electrode has larger specific surface and higher electrochemical active surface,which enhances the ability of CO₂adsorption and helps it improve the electrocatalytic activity of electrochemical reduction of CO₂.At-1.6V vs.Ag/Ag Cl,the Faraday efficiency of Bi nanowire electrode and Bi nanoflake electrode reached90.1%and 80.9%separately.The current density of Bi nanowire electrode was 30m A·cm^-2,and the current density of Bi nanoflake electrode was 26m A·cm^-2.After continuous electrolysis for 23h,the Faraday efficiency of Bi nanowire electrode and Bi nanoflake electrode did not decrease significantly,showing good stability.