Preparation Of Carbon Film Supported Metal Compounds And Their Electrocatalytic Nitrogen Fixation Performance

Ammonia is one of the most important chemicals because it has a wide range of applications in fertilizer production and energy transportation.The production of ammonia mainly relies on the traditional high-temperature and high-pressure Haber-Bosch process,which has large energy consumption and prominent environmental problems.In recent years,in order to achieve the green production of ammonia,electrocatalytic nitrogen fixation has emerged due to its environmentally friendly,cost-effective,and sustainable characteristics.However,ammonia production by electrocatalysts is far from practical applications.Searching for high-efficient,durable and cost-saving catalysts for electrochemical nitrogen reduction reaction（NRR）is a central issue in the development of N₂ fixation.This feasible energy conversion technology is of great significance for future practical applications.In this paper,through the strategies of element doping,introduction of carrier and nanalization,a new type of transition metal base compound nanomaterials was optimized and designed.The phase composition and morphology characteristics of the materials were characterized by a series of testing techniques,and their electrocatalytic properties were studied.Constructing high-efficient and cost-saving catalysts for electrochemical nitrogen reduction reaction（NRR）under ambient conditions is of great significance,but quite challenging.Herein,a series of foam-like composites comprised of small RhP_xnanoparticles（NPs）and N,P co-doped carbon（NPC）framework are first reported as novel high-efficiency NRR electrocatalysts.Interestingly,the electronic structure and catalytic behavior of RhP_x are modified by altering the contents of P in composites.Density function theory（DFT）calculations prove that the introduction of P into the rhodium lattice can dramatically reduce the catalytic reaction barrier and facilitate the intermediate process of catalytic reaction.Meanwhile,embedding RhP_x with adjustable phosphorus content on the NPC substrate can give the complex more active sites,excellent electrical conductivity,and enhanced stability.Compared with most of the reported materials,this new catalyst possesses high ammonia（NH₃）yield rate of 37.6μg h^-1 mg^-1_cat.and Faraday efficiency（FE）of 7.64%,as well as good selectivity and superior stability in acid conditions.This work provides a theoretical basis and practical scheme for the wide application of other robust transition metal phosphides electrocatalysts in NRR.Although molybdenum-dependent nitrogenases and molecular complexes can effectively electrochemically reduce N₂ to NH₃ under environmental conditions,developing molybdenum-based nanocatalysts for high-performance electrochemical nitrogen fixation remains a key challenge.Here,we report a transition metal phosphide composite material Mo₂N@NC as a high-efficiency electrocatalyst.In an acidic medium,the NH₃ yield of Mo₂N@NC at-0.3 V is 70.47μg h^-1 mg^-1_cat.,and the Faraday efficiency is 8.32%.At the same time,it has high selectivity and good electrochemical stability.This work not only provides us with an attractive earth-abundant catalyst material for electrochemical reduction of N₂ to NH₃,but also opens up a new approach for the rational design of three-dimensional porous nanostructures of transition metal nitride as highly active electrocatalysts for nitrogen fixation.