NiMo/NiCo₂O₄/NF Composite Catalytic Electrode:Preparation And Application For Electrochemical Water Splitting

Hydrogen production from water electrolysis is an effective way to develop new clean energy resources.Metal/metal compound composite catalyst is a potential bifunctional electrocatalyst for hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）,which can optimize the electronic structure of catalytic active site at the interface through the synergistic effect of two phases at the interface,thus improving the intrinsic activity of the catalyst.In addition,the preparation of self-supported catalytic electrode is also an effective means to improve the activity and stability of electrocatalyst.But for the Ni Mo alloy-based catalysts,it is still challenging to construct appropriate interface to realize robust HER and OER activity improvement.In this study,Ni₅Mo/Ni Co₂O₄ composite catalysts in-situ grown on nickel foam was prepared by hydrothermal-annealing-electrodeposition method for the first time,and the self-supported composite catalytic electrode was applied in electrochemical water splitting.The composite catalytic electrode shows excellent bifunctional activity,with an HER overpotential of 44 m V at 10 m A cm^-2 and an OER overpotential of 305m V at 50 m A cm^-2 in alkaline electrolyte.Besides,it also demonstrates very low HER overpotential（229 m V）and OER overpotential（368 m V）at a large current density(500m A cm^-2).When Ni₅Mo/Ni Co₂O₄/NF is used as anode and cathode for water splitting under alkaline conditions,a stable current density of 10 m A cm^-2 can be achieved at a low cell voltage of 1.54 V and a long-term stability up to 50 hours.It is evidenced that the combination of Ni₅Mo and Ni Co₂O₄ causes electrons transfer from Co²⁺and Co³⁺to Ni⁰ and Mo⁰.The increase of electron density at the Ni⁰ and Mo⁰ active sites leads to weaker hydrogen adsorption on Ni⁰ and Mo⁰,which greatly improves the HER intrinsic activity.The decrease of electron density of Co³⁺active sites enhances its adsorption of oxygenated intermediates,which improves the intrinsic OER activity.