Ultrasmall Strained RuO₂ as a Highly Efficient Electrocatalyst for Acidic Oxygen Evolution Reaction

The development of noniridium electrocatalysts toward acidic oxygen evolution reaction (OER) is essential for designing efficient proton-exchange-membrane water electrolyzers (PEMWEs) for hydrogen production. Ruthenium oxide has long been expected as a promising candidate but still suffers from inadequate durability. Here we deploy a strain engineering strategy to improve the OER performance. Density functional theory calculations demonstrate that introducing tensile strain into the RuO₂ lattice can concurrently optimize the adsorption behavior and enhance the structural stability. Experimentally, we successfully synthesized tensile-strained RuO₂ nanoparticles via a graphene oxide confinement method. This catalyst exhibits a low-record overpotential of 136 mV and a high durability over 160 h at 10 mA cm^-2 in acidic media. When integrated into a PEMWE device, an exceptional water splitting performance is achieved with a large current density of 3.45 A cm^-2 at 1.8 V and a long-term operation at 0.2 A cm^-2 for 120 h, suggesting its potential for practical applications.