Fabrication Of Nickel-Based Self-Supporting Electrodes For Hydrogen Evolution

Hydrogen is considered an essential part for the energy architecture of future world,and the production of"green hydrogen"using renewable energy has received extensive research interest.Nickel（Ni）,by virtue of its low cost,high conductivity and good stability for hydrogen evolution reaction（HER）under alkaline conditions,has been widely studied as a cathode material for industrial electrolytic water splitting.However,the HER kinetics over metallic nickel are rather sluggish,and the rate of reactant and gas diffusion is low,resulting in high overpotentials at high current densities.In addition,the powder catalysts prepared also suffer from issues such as low loading,weak adhesion to the substrate,and poor stability under high current densities.In this study,the self-supporting electrodes with ordered nanostructures were prepared on the surface of nickel foam（NF）,which displays enhancing the electrocatalytic activity and stability for hydrogen evolution.The main research contents are as follows:1.Preparation of Ni/MoO_2-x/NF self-supported electrode and its performance of HER.Ni/MoO_2-x/NF self-supported electrode was prepared using a two-step method involving high-temperature pyrolysis and hydrogen reduction.Scanning electron microscopy（SEM）and high-resolution transmission electron microscopy（HRTEM）revealed that the uniform nanoarray of MoO_2-xnanosheets was grown on the surface of the substrate,and MoO_2-xnanosheets with small nanoparticles Ni was grown on the surface of the substrate.The perpendicular nanoarray on the electrode surface provides more active sites,which is beneficial to efficient mass transfer and gas evolution.The Ni/MoO_2-x/NF catalyst displays a high HER activity,small overpotentials(11 and 134 m V at a current density of 10 m A cm^-2and 500 m A cm^-2)in 1 M KOH electrolyte,respectively.The Tafel slope is 33 m V dec^-1.The catalyst showed excellent stability with no decline during 200 h operation at a current density of 200 m A cm^-2.In-situ Raman spectroscopy revealed that oxygen-deficient MoO_2-xpromotes water molecule adsorption and dissociation,while small Ni particles facilitates gas evolution.The synergistic effect of both components significantly enhances the HER activity and stability.This work provides a feasible strategy for the rational design of cathodic catalysts for hydrogen evolution in water electrolysis.2.Preparation of NiCoP/NF self-supporting electrode and its performance for HER.NiCoP arrays were grown on the surface of Ni foam using a one-step cathodic electrochemical deposition method.SEM revealed that spherical NiCoP particles were uniformly dispersed on the surface of the nickel foam,and energy-dispersive X-ray spectroscopy（EDS）confirmed the uniform distribution of Ni,Co and P elements.The overpotentials were 56 m V and 184 m V at current densities of 10 m A cm^-2and 500m A cm^-2in 1 M KOH,respectively.The Tafel slope is 45 m V dec^-1.The long-term stability was assessed for 100 h at 400 m A cm^-2,and the results indicate an excellent stability for HER.The overall water splitting activity was tested in 1.0 m KOH using NiFe-LDH/NF anode.The catalyst showed a high activity with a cell voltage of 1.73V to reach the current density of 500 m A cm^-2.It displayed a good stability for 25 h.This work showed that the addition of Co and P not only optimized the electronic structure of the catalyst,but also modulated the microstructure of the catalyst,thus significantly improving the HER performance of the NiCoP/NF self-supporting electrode.This method provides a feasible strategy for the preparation of low-cost and high-activity catalysts.