Superhydrophilic/Superaerophobic Hierarchical NiP2@MoO2/Co(Ni)MoO4 Core–Shell Array Electrocatalysts for Efficient Hydrogen Production at Large Current Densities

Rationally constructing low-cost, high-efficiency, and durable electrocatalysts toward the hydrogen evolution reaction at large current densities is imperative for water splitting, especially for large-scale industrial applications. Herein, a hierarchical core-shell NiP2@MoO2/Co(Ni)MoO4 cuboid array electrode with superhydrophilic/superaerophobic properties is successfully fabricated and the formation mechanism of the core-shell structure is systematically investigated. Through an in situ partially converted gas-solid reaction during the phosphating process, Ni and Co elements are leached and rearranged to form NiP2 particles and amorphous CoO as the shell layer and the inner undecomposed Co(Ni)MoO4 crystals serve as the core layer. Because of its seamless core-shell structure and superhydrophilicity/superaerophobicity of hierarchical cuboid arrays, NiP2@MoO2/Co(Ni)MoO4 exhibits superior HER activity in 1 M KOH with only an overpotential of 297 mV to deliver 1000 mA cm-2 and can work steadily for 650 h at 200 mA cm-2. Remarkably, when coupled with NiFe LDH for overall water splitting, it can drive an AA battery with an ultralow cell voltage of 1.49 V to deliver 10 mA cm-2. This work sheds new light on designing large-current-density efficient HER electrocatalysts for large-scale industrial applications.