Application Of Heteroatom Modified Transition Metal Nitride In Electrolyzed Water

With the rapid growth of the world's population,the demand for energy in modern society is growing dramatically.Fossil energy is the main source of energy for human beings.However,the fossil energy is unsustainable owing to he limited reserves and the corresponding consumption associated environmental pollution.Therefore,it is crucial to find a new type of renewable clean energy.Hydrogen is widely considered to be a promising alternative because of its high calorific value,low or no pollution,and rich sources.Among the various methods for hydrogen preparation,electrocatalytic water splitting has attracted a lot of attention since it can obtain pure hydrogen and does not emit other toxic and harmful gases.The electrolyzed water process requires catalyst due to factors such as high thermodynamic barrier and slow kinetics.Till now,the most efficient catalysts are noble metals such as platinum,rhodium and ruthenium compounds,which are expensive and cannot be applied in a large-scale industrial production.Therefore,preparation of catalysts based on an abundant transition metal with low cost becomes one of the research hotspots.The main research contents of this paper are as follows:?1?Ni-modified FeWN₂ bimetal nitride:Ni-FeWN₂ nanosheets were prepared by hydrothermal method and high temperature ammonia nitriding.The thickness of the nanosheet is about 10 nm,and the nanosheets are connected to each other to form a three-dimensional structure.When oxygen is evolved in 0.1 M KOH,the overpotential of Ni-FeWN₂ at a current density of 10 mA cm^-2 is 340mV,which is smaller than pure FeWN₂ without Ni modification?380 mV?and the commercial IrO₂?360 mV?.During chronoamperometric measurement,Ni-FeWN₂ shows good stability in the catalytic OER reaction.After 8 h test,it maintains 83%activity,which is superior to commercial IrO₂?70%?in the same conditions.?2?The precursor of nickel hydroxide nanosheets was synthesized by hydrothermal method,and different amounts of Pt were loaded by solution impregnation method and then the precursor was nitrided with ammonia gas at different temperatures.A series of Pt-modified nickel nitrides:1.5Pt@Ni₃N-360,1.5Pt@Ni₃N-400,0.75Pt@Ni₃N-360,Ni₃N-360 were finally obtained and employed as bifunctional electrocatalysts for water splitting in alkaline solution.Among them,the overpotential to achieve the oxygen evolution current density of 10 mA cm^-2 on 1.5Pt@Ni₃N-360 is only 285 mV,much smaller than that on commercial IrO₂ of 360 mV.The more active sites,larger electrochemical active area and the synergistic effect of Pt with Ni₃N are the main reasons for the excellent OER performance of 1.5Pt@Ni₃N-360.For cathodic hydrogen evolution reaction?HER?,the prepared 1.5Pt@Ni₃N-360 also exhibits excellent ctivity in 1 M KOH.the overpotential at the current density of 10 mA cm^-2 is only 70 mV,better than that of the state-of-art 20%Pt/C?72 mV?.By using a lower Pt loading amount on Ni₃N,a bifunctional electrocatalyst with excellent OER and HER performance under alkaline conditions can be realized.