Atomic-Level Platinum Filling into Ni-Vacancies of Dual-Deficient NiO for Boosting Electrocatalytic Hydrogen Evolution

Developing low-cost and high-efficiency catalysts for sustainable hydrogen production through electrocatalytic hydrogen evolution reaction (HER) is crucial yet remains challenging. Here, a strategy is proposed to fill Ni-vacancy (Ni_v) sites of dual-deficient NiO (D-NiO-Pt) deliberately created by Ar plasma with homogeneously distributed Pt atoms driven by oxygen vacancies (O_v). The incorporated Pt atoms filling the Ni_v reduce the formation energy to increase crystal stability, and subsequently combine with additional O_v to tune the electronic structure of the surrounding Ni sites. Thus, a more ideal hydrogen adsorption free energy (ΔG_H*) closer to 0 of Ni sites and Pt sites can be achieved. As a result, the D-NiO-Pt electrode achieves superior mass activity of ≈1600 mA mg⁻¹ (normalized by platinum) and nearly negligible loss of activity during long-term operation, which is much better than as-prepared Pt-containing NiO catalysts without plasma treatment. A low overpotential of 20 mV is required for the D-NiO-Pt at 10 mA cm⁻² in alkaline HER, outperforming that of the commercial Pt/C. In addition, the universal access to the other Ni-based compounds including nickel phosphide (Ni₂P), nickel sulfide (Ni_0.96S), and nickel selenide (NiSe₂) is also demonstrated by employing a vacancy-driven Pt filling mechanism.