Surface Modification Of Metal Oxides For Electrocatalytic Reduction Of Nitrogen

The serious environmental pollution caused by the massive consumption of fossil energy threatens our lives.Therefore,sustainable development has become the mainstream direction of human survival and development in the 21st century.Ammonia is an indispensable raw material for chemical production.At present,industrial synthetic ammonia still relies on the century-old Haber-Bosch method,but this technology consumes a lot of fossil energy and emits a lot of greenhouse gases.Therefore,exploring efficient,mild,and sustainable ammonia synthesis technology is of great significance to scientific research and industrial applications.Recently,electrochemical nitrogen fixation catalytic technology has further converted electrical energy generated by renewable energy sources(such as solar energy and nuclear energy)into chemical energy,and has attracted attention because of its advantages of mild reaction,controllable reaction conditions,and simple operation.The important part of the electrochemical catalysis process is the electrochemical reduction reaction.However,the high bond energy of N≡N(941 kJ mol-1)and the high energy gap(10.82 eV)make it difficult for nitrogen to activate at room temperature.In addition,electrocatalysts are more prone to hydrogen evolution(HER)reactions in aqueous electrolytes.Therefore,the development of high-efficiency electrocatalysts for the synthesis of ammonia is currently the most urgent key issue to be solved.At present,transition metal oxides have the advantages of being cheap,easy to obtain,and high in activity,and are widely used in industrial catalysts,which has attracted widespread attention.In electrocatalytic reactions,transition metal oxides also exhibit good chemical stability,but they are still limited by the problem of low activity.In view of the problems of transition metal oxides,the transition metal oxides are combined with heteroatoms,and their surface structure and composition are adjusted to achieve the goal of improving the electrocatalytic performance of transition metal oxides.The research content is as follows:W18O49 was selected as the catalytic substrate,and the heteroatoms with better nitrogen fixation activity were screened for modification.Mo-doped W18O49 was prepared by hydrothermal method.By doping with Mo atoms,the nitrogen electrocatalytic reduction performance of W18O49 can be significantly improved.The results show that under neutral conditions,the catalytic performance of Mo-doped modification is increased by about 2 times,the Faraday efficiency after modification reaches 12.1%(the Faraday efficiency of W18O49 is 5.8%)and the ammonia production is 5.3 μg h-1 mgcat.-1(The ammonia production of W18O49 is 2.6 μg h-1 mgcat.-1).The test results show that Mo doping introduces a large number of oxygen defects,increases the adsorption and activation of N2,and inhibits HER,thereby promoting the conversion efficiency of N2.