Electronic modulation of Ru active sites <i>via</i> interfacial engineering for efficient overall water splitting

The development of highly efficient and stable bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial to advancing the overall water splitting technology and promoting clean energy systems. This work presents a ruthenium nanoparticle-decorated, iron-doped Ni(OH)₂ heterostructure on nickel foam (Ru-NiFe(OH)₂/NF), synthesized <i>via</i> a one-step corrosion method, which serves as a superior bifunctional electrocatalyst for overall water splitting in alkaline media due to its high activity in both the HER and OER. The Ru-NiFe(OH)₂/NF bifunctional electrocatalyst demonstrates ultra-low overpotentials of 130 mV for HER and 235 mV for OER at 100 mA cm^-2, while maintaining long-term stability for overall water splitting at 100 mA cm^-2, outperforming commercial RuO₂∥Pt/C systems and most previously reported bifunctional electrocatalysts. Experimental observations combined with theoretical calculations reveal that electron transfer between Ru and NiFe(OH)₂ promotes the formation of electron-deficient Ru sites, leading to an upshift of the d-band center toward the Fermi level, which enhances the adsorption capability of reaction intermediates and thus boosts the catalytic activities.