Study On The Electrochemical Nitrogen Reduction Reaction By In₂O₃ And Doped Carbon

Ammonia is the most basic raw material in industrial and agricultural production,and it is also an excellent hydrogen carrier.The high levels of energy consumption and high pollution of traditional ammonia synthesis methods limit its further development.The research on green ammonia synthesis pathway with less energy consumption has been the direction of researchers.In recent years,scholars have conducted a large number of studies on electrochemistry nitrogen reduction,but these studies still have deficiencies such as high cost,low reaction production rate,low Faraday efficiency and HER competition.Electrochemistry reduction is one of the most environmentally friendly methods in NH₃ production,which is carried out at room temperature and atmospheric pressure with renewable power supply.Compared with the traditional Harber-Bosch method,Electrochemistry reduction method has the advantages of mild reaction conditions and low energy consumption.Therefore,it is a challenge to achieve the sustainable conversion of N₂ to NH₃ under mild conditions and develop low-cost electrochemistry with high chemical activity and selectivity.Non-noble metal oxides and heteroatom-doped materials have certain catalytic properties,and have attracted wide attention worldwide due to their low cost,high catalytic efficiency and excellent stability.This work focuses on the synthesis of In₂O₃and doped carbon-based materials and their electrocatalytic reduction activity,selectivity and reaction mechanism for N_2.The structure and composition of the obtained materials were analyzed,and the basic properties such as catalyst surface configuration,adsorption sites,electronic properties and nitrogen reduction mechanism were discussed.In addition,the electrocatalytic reduction reaction of ionic liquids as electrolytes was studied.The main work is divided into the following three parts.1.Indium oxide materials with different structures were prepared by the reaction of urea and indium chloride after washing and drying.The material was characterized by SEM,TEM,BET,XRD and XPS,and the physical characteristics such as structure and element distribution of the material were studied.The electrochemical performance,catalytic activity and stability of In₂O₃ materials were studied by cyclic voltammetry（CV）,linear voltammetry（LSV）,ammonia production rate and Faraday efficiency.In 0.1M HCl solution at room temperature and atmospheric pressure,In₂O₃as a catalyst for the reduction of nitrogen to NH₃yield up to 6.42μg·h^-1m L^-1,Faraday efficiency of 6.8%.The reaction mechanism of N₂ on In₂O₃ surface was investigated by in situ infrared spectroscopy.The characterization shows the evolution of nitrogen on active sites in the material,which is of great significance to reveal how oxygen vacancies affect the electrocatalytic reduction of ammonia by nitrogen.2.Exploring the mechanism of nitrogen reduction reaction,it is found that ionic liquids as electrolytes have the advantages of high solubility,nonvolatile and good stability of N₂.Imidazole ionic liquids with different structures were synthesized as electrolytes for electrochemical catalytic reactions.Indium trioxide under optimal conditions was used as electrocatalyst to explore the effect of electrolyte on electrocatalytic nitrogen reduction reaction at room temperature and atmospheric pressure.Increasing the solubility of gaseous reactants in electrocatalytic reduction of ammonia also avoids the main side reaction in electrolyte-hydrogen evolution reaction.The experimental results and theoretical calculations show that compared with in 0.1M HCl solution,the NH₃ yield in BMIM[BF₄]/PC electrolyte can reach 13.46μg·h^-1m L^-1,and the Faraday efficiency is 11.48%,and the ammonia yield increases by 78.8%.Faraday efficiency increased by 68.9%。3.Effect of atomic doping on the reduction of ammonia by N₂ electrocatalysis was studied by preparing N,S co-doped carbon materials with polythioamide as precursor.The structure and heteroatom distribution of the material were characterized by a series of tests,and the calculation of ammonia production rate and Faraday efficiency was studied from the aspects of catalytic activity and stability of NSC materials.Structural characterization and pore size analysis of this carbon material are mesoporous materials with large specific surface area.These characteristics are used for the electrocatalytic reduction of nitrogen to NH₃ in hydrochloric acid aqueous solution at normal temperature and pressure,which is conducive to the exposure of electrocatalytic activity sites and the transfer of reaction substances.This has a good reference significance for the future design of new efficient NRR electrocatalysts.