Spontaneous Ruthenium Doping in Hierarchical Flower-like Ni2P/NiO Heterostructure Nanosheets for Superb Alkaline Hydrogen Evolution

Abstract Developing efficient alkaline hydrogen evolution reaction (HER) electrocatalysts remain a critical challenge for the realization of large-scale hydrogen production from water splitting, while the high energy barrier of the Volmer-step considerably impedes the catalytic activity in water-alkali electrolyzers. Herein, a novel Ru-doped hierarchical flower-like Ni2P/NiO heterostructure nanosheets vertically aligned on Ni foam substrates (Ru-Ni2P/NiO/NF HNSs) electrocatalyst is synthesized by a top-down strategy to achieve a top-level performance of HER in alkaline media. Benefitting from electronic reconfiguration, hierarchical flower-like nanosheet structure, and abundant heterogeneous interfaces, the as-obtained Ru-Ni2P/NiO/NF HNSs require an ultralow onset overpotential of 0 mV, a minimum overpotential of 12 mV and 112 mV to afford 10 mA cm–2 and 1000 mA cm–2, respectively, and a Tafel slope of 22.6 mV decade–1. Further X-ray photoelectron spectroscopy analysis combined with density functional theory calculations reveal the charge density redistribution, where electron accumulation on Ru favors the optimization of H2O absorption energies and the reduced energy barrier of the Volmer step, whereas the coupling effect of Ni2P/NiO heterogeneous interfaces is responsible for accelerating the Tafel step activity, synergistically resulting in accelerating alkaline HER kinetics. These findings reveal the significance of the rational combination of noble metal doping and heterostructure engineering toward the rational design and preparing of highly efficient electrocatalysts for the HER and beyond.