Effect Of LaNi₅ On Microstructure And Hydrogen Evolution Reaction Of Ni-Cr-Fe Porous Electrode Materials

With the exhaustion of fossil fuels,hydrogen energy as a new secondary energy has attracted much concern.One of the most used technologies for the electrolytic hydrogen production is alkaline water electrolysis.However,due to high energy requirements in most industrial electrolysis,electrolytic water technology cannot be developed on a large scale.Pt,Pd and their alloys have very low hydrogen evolution overpotential and good electroanalytical hydrogen stability.But these alloys are very expensive,thus limiting their applications.Therefore,it is of great significance to find low cost electrode materials with good hydrogen evolution performance.Ni-based porous cathode materials have been widely studied due to their low overpotential and excellent performance of electrocatalytic hydrogen evolution.The purpose of this paper is to explore the hydrogen evolution properties of Ni-Cr-Fe porous electrode materials.At the same time,study on the addition of LaNi₅ and the difference of LaNi₅ content in the porous material,in order to obtain high activity and stability of the hydrogen evolution catalytic electrode.The Ni-Cr-Fe and Ni-Cr-Fe-LaNi₅ porous electrode materials were fabricated by powder metallurgy.The phase,surface morphology and microstructure of the electrode materials were characterized by X-Ray Diffraction?XRD?,Scanning Electron Mircosope?SEM?,Electron Back-Scanning?ed?Diffraction?BSED?.The electrocatalytic hydrogen evolution performance of the electrode materials was tested by cyclic voltammetry,linear cathode polarization,electrochemical alternating impedance.The research work mainly achieved the following results:The Ni-Cr-Fe porous electrode materials has abundant pores.The porosity is up to 39.96%,and gas permeability is 120 m³m^-2h^-1kPa^-1.The electrode material was mainly composed by?Ni,Cr,Fe?solid solution and Cr when the sintering temperature was 850?.Part of Cr elemental spread into Ni,formation of solid solution?Ni,Cr?when the sintering temperature was 950?.The Ni₇₀Cr₂₀Fe₁₀0 electrodes sintered at850?exhibits the best activity on HER with a low Tafel slope(b=–183.63 mV dec^-1).The electricity analytical control step of electrode is electrochemical hydrogen reaction,and the exchange current density is 2.26×10^-4A.cm^-2.After the addition of rare earth alloy LaNi₅,the pore structure parameters of porous electrode materials were slightly increased.The pattern indicates that the prepared Ni-Cr-Fe-LaNi₅ porous material has a very similar crystal structure to that of Ni-Cr-Fe alloy.The microstructure of electrodes were characterized and the results showed that the Ni-Cr-Fe-LaNi₅ porous electrode materials consists of three parts,?Ni,Cr,Fe?solid solution,Cr elemental and LaNi₅ when the sintering temperature was850?.When the sintering temperature rises to 950?,a small amount?Ni,Cr?solid solution formation,and LaNi₅ phase as an independent phase exists in Ni-Cr-Fe-LaNi₅porous alloy.Increased the surface roughness of the Ni-Cr-Fe-LaNi₅ electrode.Different contents of rare earth alloy LaNi₅ were added to the Ni-Cr-Fe porous electrode materials.It can be seen from the cathode polarization curve that the electrode with rare earth LaNi₅ has better electrocatalytic activity.When the content of LaNi₅ was 8%,the Tafel slope of the electrode was-162.57mV dec^-1,the exchange current density was 8.73×10^-44 A.cm^-2,and the electrocatalytic hydrogen evolution performance was the best.Moreover,the cathode current density of the electrode material remained stable after 24000s,and the current density remained stable after 6hours.SEM images shows that the surface morphology unchanged after a long time of electrolysis,which reveals a good stability of the electrocatalytic performance of the electrode.