Ni-based Electrode By Electrodeposition And Catalytic Hydrogen Evolution Property

In order to improve the catalytic performance of Ni-Fe alloy electrodes for hydrogen evolution and the electrolytic stability of Ni-Mo alloy electrodes,Ni-Fe/TiO₂ composite electrode,Ni-Fe porous electrode,Ni-Fe/TiO₂ porous composite electrode and Ni-Mo-C alloy electrodes were prepared by electrodeposition.The surface morphology,composition,surface roughness,coating-substrate adhesion of nickel-based electrodes were analyzed by scanning electron microscopy,energy dispersive spectrometer,laser confocal microscopy and automatic scratch tester.The cathodic polarization curve,electrochemical impedance spectroscopy,cyclic voltammetry,chronoamperomatric current,Tafel curve and rotating disc electrode were used.The hydrogen evolution performance,electrodeposition and hydrogen evolution mechanism of nickel based electrode were studied.The results showed that the catalytic performance of Ni-Fe/TiO₂ composite electrode,Ni-Fe porous electrode and Ni-Fe/TiO₂ porous composite electrode for hydrogen evolution is higher than that of Ni-Fe alloy electrode.The order of hydrogen evolution performance from strong to weak is Ni-Fe/TiO₂ porous composite electrode,Ni-Fe porous electrode,Ni-Fe/TiO₂ composite electrode and Ni-Fe alloy electrode.The hydrogen evolution overpotential of Ni-Fe/TiO₂ porous composite electrode is the lowest than others and the value is 337 mV.Tafel slope is 140 mV·dec^-11 in 1 mol/L NaOH solution at 25℃.The electrochemical adsorption step is the determining step of hydrogen evolution reaction rate.The exchange current density of the reaction is 33 mA/cm² and the apparent activation energy is 27.43 KJ·mol^-1.The reasons for improvement of hydrogen evolution performance of Ni-Fe/TiO₂ porous composite electrode are as follow:the presence of porous structure and composite particles make the specific surface area of electrode increase effectively;The porous structure also has excellent air-evacuation property,which is conducive to desorption of intermediate hydrogen and provides condition for the stable and continuous hydrogen evolution reaction;Ti element of TiO₂nano-particles can form Ti-H hydrogen bond with H atom,which enhances the ability of alloy to adsorb intermediate hydrogen.With the increase of TiO₂ nano-particles in coatings,the adhension between the coating and the matrix increases,and the scratch fracture changes from ductile fracture to brittle fracture.The surface of Ni-Mo-C alloy electrode is mainly composed of large cauliflower-like grains formed by grain clusters.The hydrogen evolution performance of the electrode depends not only on the content of Mo element in the electrode,but also on the surface area of the electrode.The electrolytic stability of Ni-Mo-C alloy electrode is obviously better than that of Ni-Mo alloy electrode,and the catalytic performance of hydrogen evolution is also improved.C element can enhance the desorption ability of H_ads,thus improving the hydrogen evolution performance of the alloy.With the increase of cathode potential,the reaction mechanism changed in turn as follows:Volmer mechanism,Volmer-Heyrovsky mechanism and Volmer-Tafel mechanism.Figure 60;Table 11;Reference 75.