Interfacial Hydrogen-Bonding Network and Active-Site Electronic Structure Modulation via Indium Doping in RuO ₂ for Efficient and Durable OER

The challenged stability of iridium-free metal oxides in proton exchange membrane (PEM) water electrolyzers has always posed challenges that hinder the development of hydrogen energy production by water splitting. To overcome this challenge, we strategically incorporated p-block indium (In) to ruthenium oxides (RuO 2 ) to mitigate the easy loss of active Ru sites. In-doped RuO 2 required an overpotential as low as 174 mV at 10 mA/cm 2 and maintained sustainable electrolysis for 600 h at 100 mA/cm 2 . Fourier transform infrared and X-ray photoelectron spectroscopy results surprisingly demonstrate that In dopants in RuO 2 facilitate surface hydroxylation, which lowers the water dissociation step energy barrier prior to the oxygen evolution reaction (OER) and can also increase the electron density of Ru to avoid the formation of high-valence oxides, which threaten the structural stability of the catalyst. This work presents the critical role of surface hydroxylation and reports an efficient In doping strategy to improve the activity and stability of Ru-based catalysts, thereby establishing a foundation for low-cost and highly efficient hydrogen production.