Study On The Electroreduction Of Nitrogen To Ammonia Preparation Of Non-noble Transition Metal Electrodes By Ampule Method

Ever since Fritz Haber synthesized ammonia with nitrogen and hydrogen in1909,the ammonia industry has been considered the greatest chemical invention of the 20th century.Because of the significance and great challenge of ammonia synthesis reaction,this reaction has been widely concerned and studied in both basic theory research and practical industrial application.At present,the ammonia is synthesized by the Haber-Bosch reaction under high temperature and high pressure conditions,it not only consumes a large amount of energy,but also leads to environmental pollution and greenhouse gas emissions.With the shortage of the earth energy and serious environmental pollution,it is urgent to explore a more efficient and environmentally friendly synthetic ammonia method.It is a more economical and environmentally friendly method of synthesizing ammonia by electrochemical reduction of nitrogen to synthesize NH₃/NH₄⁺,which can occur at room temperature and atmospheric pressure,and greatly saves energy consumption;compared with Haber-Bosch reaction,its equipment is simple and easy to operate,and could greatly save the cost of equipment and operating;The raw materials nitrogen and water have abundant reserves on the earth and they are easy to obtain;Electric energy can be obtained from sustainable energy conversion such as wind and solar energy.By virtue of these advantages,electrochemical NH₃ production has received widespread attention.Here,we use ampoule method to prepare catalytic electrode materials for electrochemical ammonia synthesis.The raw materials of the reaction were loaded into the ampoule bottle,after the ampoule bottle was vacuumed,its opening end is sealed by hot melt and then heated to react to synthesize the required material.The vacuum sealed ampoule bottle eliminates the influence of the environment and makes the precursor reactants fully react.By controlling the mass ratio of the reactants,the product morphology and charge state can be controlled,resulting in electrocatalytic performance.The ampoule method provides a new way for controllable synthesis of electrocatalysts because of its controllability to reaction conditions and environment.Firstly,The stainless-steel-based catalytic electrodes were obtained by a facile one-step sulfurization of stainless-steel foil with sulfurpowder in a vacuum sealed ampoule calcined at high temperature.The surface of the electrode material is rich in defects and sulfur vacancies,as well as the synergy between the crystal planes of FeS₂,which make it have outstanding electrocatalytic performance;Under room temperature and pressure,in the acidic 0.1M Li₂SO₄ electrolyte solution,at-0.2V vs.RHE,the Faraday efficiency is as high as 14.6%,and the yield of NH₃ is 11.5?g h^-1mg^-1Fe;Electrochemical measurements showed that FeS₂ catalytic electrode could effectively inhibit the hydrogen evolution reaction and thus have good selectivity.In addition,due to the presence of Cr in the electrode material,the electrode has long-term stable catalytic performance under acidic electrolyte conditions.Therefore,the FeS₂ electrode based on stainless steel has great potential in the field of electrocatalytic ammonia synthesis.In addition,using the same method,the Zn-based catalytic electrodes were obtained by a facile one-step sulfurization of rich and cheap Zn foil with sulfocarbamide in a vacuum sealed ampoule calcined at high temperature.Through the material characterization,it was found that the electrode material has rich surface defects.Morever,due to the participation of N in the reaction process,the surface of the material has a large number of N vacancies,which enhances the adsorption of N₂ on the electrode surface,so that the catalytic electrode has outstanding electrocatalytic performance.Under room temperature and pressure,in the alkaline 0.1M KOH electrolyte solution,at-0.5V vs.RHE,the Faraday efficiency is 19.067%,and the yield of NH₃ is 3.2?g h^-1cm^-1 at-0.6V vs.RHE.The catalytic electrode can maintain stability only in the alkaline electrolyte solution,and the alkaline conditions also weaken the hydrogen evolution reaction,which is beneficial to the progress of the electrocatalytic ammonia synthesis reaction.