One-Step Controllable Synthesis of Catalytic Ni₄Mo/MoO_x/Cu Nanointerfaces for Highly Efficient Water Reduction

Currently, in addition to the electroactive non-noble metal water-splitting electrocatalysts, a scalable synthetic route and simple activity enhancement strategy is also urgently needed. In particular, the well-controlled synthesis of the well-recognized metal–metal nanointer face in a single step remains a key challenge. Here, the synthesis of Cu-supported Ni₄Mo nanodots on MoO_x nanosheets (Ni₄Mo/MoO_x) with controllable Ni₄Mo particle size and d-band structure is reported via a facile one-step electrodeposition process. Density functional theory (DFT) calculations reveal that the active open-shell effect from Ni-3d-band optimizes the electronic configuration. The Cu-substrate enables the surface Ni–Mo alloy dots to be more electron-rich, forming a local connected electron-rich network, which boosts the charge transfer for effective binding of O-related species and proton–electron charge exchange in the hydrogen evolution reaction. The Cu-supported Ni₄Mo/MoO_x shows an ultralow overpotential of 16 mV at a current density of 10 mA cm⁻² in 1 m KOH, demonstrating the smallest overpotential, at loadings as low as 0.27 mg cm⁻², among all non-noble metal catalysts reported to date. Moreover, an overpotential of 105 mV allows it to achieve a current density of 250 mA cm⁻² in 70 °C 30% KOH, a remarkable performance for alkaline hydrogen evolution with competitive potential for applications.