The Property Study Of Water Electrolysis And Nitrogen Reduction Reaction On Transition Metal Cobalt Based Nanomaterials

Due to the energy shortage and environmental pollution caused by excessive consumption of fossil energy,it is urgent to develop clean and sustainable energy.Hydrogen energy is considered as the"ultimate energy"of human society due to its abundance,high combustion value and no pollution.In addition,ammonia not only is an importance chemical source,but also is regarded as excellent fuel and energy carrier.Nowadays,industrial production of hydrogen and ammonia mainly derive from fossil fuels,thus promoting energy shortage and environmental pollution.In order to resolve these problems,the development of electrocatalytic technology to produce hydrogen and ammonia is a promising strategy.The water electrolysis and electrochemical ammonia synthesis are two competitive reactions,so the electrocatalyst is the critical factor to affect their performances.Transition metal based nanomaterials have received intensive attention for the water electrolysis and electrochemical ammonia synthesis due to their unique physicochemical properties,low cost and abundant reserves.In this thesis,we tailor the composition,size and morphology of the transition metal based nanomaterials to investigate their effect on the catalytic performance for water electrolysis and electrochemical ammonia synthesis.The main research contents and results of this thesis are as follows:?1?We first synthesize the Ni-Co-OH nanowires on the carbon cloth by hydrothermal reaction urea as reducing agent and hexadecyltrimethylazanium bromide as surfactant,followed by sulfidation treatment.The obtained Nihollow nanotube arrays are used as template for in situ grown of zeolitic imidazolate frameworks?ZIFs?,which are finally carbonized to obtain the ZIF-derived carbon coated on Ninanotubes with porous and hollow structure.The catalyst has well-developed porosity,hollow structure and a large number of ultrafine Ni Co nanoparticles,which can provide convenient channels and sufficient active sites for water electrolysis.Therefore,the catalyst exhibited excellent performance for hydrogen evolution reaction and oxygen evolution reaction with overpotentials of 81m V and 280 m V at current density of 10 m A·cm^-2 under alkaline conditions,respectively.This method employs nanoarray as self-sacrificial template for the synthesis of ZIF derived carbon composites,which provides an effective strategy for water electrolysis with high performance and stability.?2?We report a simple and efficient one-pot method to synthesize two-dimensional leaf-like zeolitic imidazolate frameworks?Zn,Co-ZIF?using cobalt nitrate hexahydrate,zinc nitrate hexahydrate and 2-methylimidazole as precursors.After high-temperature anneal under N2 and phosphation treatment,the Co P decorated nitrogen-doped carbon nanosheet composite?Co P-N-CNSs?is obtained.In addition,the composition and morphology of the Co P-N-CNSs can be tailored by changing the ratio of precursors and reaction time.For the electrocatalytic nitrogen reduction reaction,the Co P-N-CNSs show high ammonia yield(12.4?g·h^-1·mg^-1_cat.),moderate Faraday efficiency?5.4%?and excellent stability.This work provides an effective method for the preparation of highly active catalysts for electrochemical ammonia synthesis.