Zhang Yawen / Yan Chunhua group of Peking University and their collaborators have made a breakthrough in the field of electrocatalytic synthesis of ammonia at room temperature and atmospheric pressure

The synthetic ammonia industry plays an important role in the development of national economy and society At present, the global ammonia output has exceeded 100 million tons every year, most of which are used in agricultural production to solve the problem of food and clothing, and other parts are used as important industrial raw materials In addition, ammonia has the advantages of high hydrogen content (mass ratio up to 17.6%) and easy liquefaction, which is expected to become an important clean hydrogen storage and energy storage material with broad application prospects However, because nitrogen molecules are very stable and difficult to activate, the synthesis of ammonia under mild conditions is difficult to proceed rapidly The widely used Haber Bosch method in industry adopts high temperature and high pressure (300-500 ℃, 100-200 High purity hydrogen and nitrogen react on the surface of iron-based catalyst to generate ammonia under severe conditions, such as atmospheric pressure Both the energy and hydrogen come from fossil fuel (such as methane, etc.), showing the disadvantages of high energy consumption, high fossil fuel consumption and high carbon dioxide emission The synthetic ammonia industry consumes 3 – 5% of the global methane and 1 – 2% of the global energy supply every year, and produces 1.6% of the carbon dioxide emissions It is an urgent scientific challenge to find a suitable green alternative to achieve high efficiency, low energy consumption and low emission of synthetic ammonia under mild conditions Electrocatalytic reduction of nitrogen provides a new way of sustainable ammonia synthesis The reaction can be carried out under normal temperature and pressure, using a large number of easily available water and nitrogen (air) as reaction raw materials, and using the electric energy generated by sustainable energy (solar energy, wind energy, etc.) as energy source, the "zero emission" synthetic ammonia can be realized Therefore, whether as a potential alternative to the traditional Haber Bosch method or as an important part of the new clean energy system, the electrochemical synthesis of ammonia technology has great development potential and broad application prospects However, the electrochemical synthesis of ammonia technology is still facing major challenges, and its development is seriously restricted by the very low selectivity and activity of existing catalysts If the technology is to be applied, the selectivity and activity of the catalyst must be greatly improved at the same time However, the existing research experience and theory show that the catalyst generally faces a serious "selectivity activity" dilemma The catalysts with high theoretical activity usually lead to severe side reaction of hydrogen evolution, thus showing low reaction selectivity; while the catalysts with high selectivity may have too strong adsorption of nitrogen, resulting in the product difficult to desorb, showing too low reaction activity Therefore, in order to make progress in electrocatalytic ammonia synthesis and greatly improve the selectivity and activity of catalysts, it is necessary to break through the existing theory and develop new catalysts and catalytic systems Zhang Yawen / Yan Chunhua research group of Peking University, Yin Anxiang research group of Beijing University of science and technology, and Si Rui research group of Shanghai synchrotron radiation light source have made pioneering use of non noble metal catalyst (bismuth nano catalyst) and alkali metal (potassium ion) Co catalyst The synergism between them can enhance the adsorption and activation of nitrogen molecules on the catalyst surface, and inhibit the side reaction of hydrogen evolution, so as to break through the existing limit and greatly improve the selectivity and reaction rate of electrocatalytic synthesis of ammonia Under normal temperature and pressure (25 ℃, 1 atmospheric pressure), high selectivity and high rate ammonia production can be realized from water and nitrogen The results are higher than those reported so far, which provides a possibility for the electrochemical synthesis of ammonia It is worth mentioning that the catalytic system has wide applicability It is not only limited to bismuth catalyst, but also suitable for a series of commonly used catalysts (such as Pt, Au, etc.) In addition, the catalytic system can also significantly enhance the electrocatalytic reduction of carbon dioxide with important energy and environmental significance This study provides a new way to use sustainable energy and high efficiency to synthesize ammonia under mild conditions The research results were published in nature catalyst (DOI: 10.1038 / s41929-019-0241-7) under the title of "promoting nitrogen electronic reduction to ammonia with bismithanocrystals and potassium locations in water" Figure 1 Bi-k + catalytic system to achieve high-efficiency electrochemical synthesis of ammonia: theoretical simulation, reaction model and catalytic performance (source: nature Catalysis) This research is supported by national key research and development plan, National Natural Science Foundation, Beijing University of technology, Peking University high performance computing platform, etc The collaborators of this study include Hu Changwen group and Wang Bo group of Beijing University of technology, who are greatly assisted by Sun Wei, researcher of Peking University, Wang Guoxiong, researcher of Dalian Institute of chemical and physical sciences, Chinese Academy of Sciences, and Zhou Zhiyou, Professor of Xiamen University Yin Anxiang, Professor Zhang Yawen, Professor Yan Chunhua and researcher of Shanghai Synchrotron Radiation Source Department of Beijing University of science and technology are the co correspondents of the work The first co authors are Hao Yuchen, Ph.D candidate of Beijing University of science and technology, and Guo Yu, Ph.D candidate of Peking University.