The research group of Professor Wang Jinlan of Southeast University has made new progress in the study of electrochemical nitrogen fixation mechanism

Recently, the research team of Professor Wang Jinlan of Southeast University has made important progress in the research of electrochemical nitrogen fixation mechanism Its research results were published in Journal of the American Chemical Society (DOI: 10.1021 / JACS 9b09232) with the title of "new mechanism for N2 reduction: the essential role of surface hydraulics" Nitrogen is one of the most important elements in biology Nitrogen is difficult to be used directly because of its high bond energy and very difficult activation At present, Haber Bosch method is widely used in industry to convert the free nitrogen in the air into the combined nitrogen (NH 3) However, this process needs to be carried out under high temperature and pressure, with high energy consumption and a large number of greenhouse gases Electrochemical nitrogen fixation is a new way of ammonia synthesis, which can reduce nitrogen under normal temperature and pressure, so it has attracted much attention However, the current research on the mechanism of electrochemical nitrogen fixation is not comprehensive and has limitations For example, according to the existing reaction mechanism, due to the weak adsorption strength of N2, the activation of N2 is not sufficient, so the electrochemical reduction of N2 on the surface of noble metal catalysts (AU, PD, etc.) needs a high reduction potential to drive However, a series of experimental reports show that Au, Pd and other catalysts can catalyze the electrochemical reduction of N 2 at a very low reduction potential, which leads to a significant difference between the theory and the experiment To solve this problem, Professor Wang Jinlan's research group proposed a new electrochemical nitrogen fixation mechanism, surface hydrogenation mechanism, by using the first principle calculation Different from the conventional mechanism, the first step of the reaction is the adsorption and activation of N2 In the surface hydrogenation mechanism, the reduction of H + is the first step of the reaction, thus forming the surface hydrogenation Under the synergism of surface * H atom and catalyst, N 2 can react with surface * H atom to form * n 2H 2 Intermediate, which is finally reduced to NH 3 In the whole reaction process, surface hydrogenation is the potential determining step, while the reaction of N 2 with H atom to form n 2H 2 is the rate determining step The mechanism can well describe the electrochemical nitrogen fixation process on the surface of noble metal catalyst and solve the difference between theory and experiment In addition, based on this mechanism, the author suggests that the activity of the catalyst can be improved by increasing the concentration of alkali metal ions in the electrolyte solution, which is also consistent with recent experimental reports Therefore, this study can provide a new idea for the research and design of electrochemical nitrogen fixation catalyst The first author of this paper is Ling Chongyi, a postdoctoral, and Professor Wang Jinlan is the corresponding author This work is supported by the national fund for Distinguished Young Scholars, the national key research and development program, and the Postdoctoral Science Foundation.