Synthesis Of Ni Fe Layered Double Hydroxides By Nitrogen Modification And Study Of The Electrocatalytic Overall Water Splitting In Alkaline Media

Nowadays,hydrogen energy is favored because of its high energy density,no pollution to the atmosphere by combustion products,and the preparation of water.Therefore,the electrocatalytic hydrolysis of water,including the rates of hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）,has become a research hotspot of widespread concern by researchers.At present,the precious metal materials are mainly applied as the catalysts in the total electrocatalytic hydrolysis of water.But the high price limited its development.Therefore,looking for a kind of catalyst material with low price,excellent catalytic activity and good stability have become the main research problem of scientists.NiFe layered double hydroxide（NiFe LDH）has attracted more attention because of its good OER activity.However,the HER performance of NiFe LDH is pool.Thus researchers tried to study improve the HER performance of NiFe LDH,whereas the OER performance of NiFe LDH was bereft at the same time.Therefore,it is worth studying how to promote the HER performance of NiFe LDH while maintaining the excellent OER performance of NiFe LDH simultaneously.In this work,NiFe LDH has been prepared by one-step hydrothermal method.Nitrogen element was introduced into NiFe LDH by N modification method,and the HER performance of which was improved together with excellent OER properties.N modification the morphology and microstructure of NiFe LDH double hydroxide,the interface between Ni（OH）₂ and Fe OOH and lattice defects.The microstructure existence provides numerous of active sites for the total hydrolysis of water by electrocatalysis.In the meantime,N modification changes the electron distribution on the surface,and the electrons aggregate to Fe,Ni and other elements,which is beneficial to the H*adsorption and the hydrogen formation.The NiFe LDH with different nitrogen modification were investigated for electrochemical performance.The N12-NiFe LDH sample modified by N for 12 h has the best electrocatalytic performance for the complete hydrolysis of water.In 1 M KOH alkaline electrolyte,the HER overpotential of N12-NiFe LDH is 52 m V at 10 m A cm^-2current density and the OER overpotential is 136 m V respectively.The constant current stability performance was good when being tested at 10 m A cm^-2 current density for 18h.After assembling N12-NiFe as the cathode and anode to form an overall water splitting system,the required driving voltage is 1.47 V at 10 m A cm^-2 current density.The stability of N12-NiFe LDH can be maintained for more than 60 hours at 10 m A cm^-2current density.This work provide experimental and theoretical basis for the performance improvement of HER and OER by N modification.