Hierarchical NiO_x nanotube arrays/CoP nanosheets heterostructure enables robust alkaline hydrogen evolution reaction

Rational design of low-cost and high-efficiency electrocatalysts for hydrogen evolution reaction (HER) is critical for scalable and sustainable hydrogen production from economical water-alkali splitting. Herein, density functional theory (DFT) calculations reveal that coupling NiO_x and CoP could effectively boost overall HER kinetics through lowing the H₂O dissociation barrier, accelerating the OH* transfer process, and providing the rapid H* migration kinetics as well as the appropriate H* energetics. Based on these findings, we successfully prepared a three-dimensional (3D) self-supported electrode of ultrathin CoP nanosheets directly grown on the surface-oxidized Ni nanotube arrays via a simple and scalable electrochemical synthesis method. As expected, such a heterostructure electrode exhibits superior alkaline HER performance with low overpotentials of 51 and 164 mV to drive the current densities of 10 and 500 mA cm^-2, respectively, outperforming most of the efficient alkaline HER electrocatalysts.