Developing low-cost, highly active and robust electrocatalysts for acidic oxygen evolution reaction (OER) is a critical challenge facing the hydrogen-based energy delivery system. As a cheaper alternative to the benchmark IrO₂, RuO₂ possesses higher OER catalytic activity but suffers from intrinsically low stability arising from Ru dissolution and lattice oxygen overoxidation. Herein, we report a high-vacuum annealing strategy to regulate the oxygen vacancy (O_v) concentration in RuO₂, enabling the controllable modulation of the atomic local coordination structures of RuO₂. At the optimal O_v level, the RuO_2−x-2 catalyst forms stable metallic Ru–Ru bonds while maintaining oxidized Ru–O moieties, achieving an ultralow overpotential of 169 mV at 10 mA·cm⁻² and exceptional stability with 400-hour stable operation in 0.5 M H₂SO₄. Operando X-ray absorption fine structure (XAFS) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) results reveal that the Ru–Ru and adjacent Ru–O sites synergistically activate the oxide pathway mechanism, circumventing the scaling relationship and minimizing the structural distortion during the OER. This work provides not only a facile approach to controllable modulate local structure of RuO₂ but also insights into the synergistic effects between multiple active centers, which would greatly promote the further development of high-performance RuO₂-based OER electrocatalysts.

The sluggish reaction kinetics of alkaline hydrogen oxidation reaction (HOR) is one of the key challenges for anion exchange membrane fuel cells (AEMFCs). To achieve robust alkaline HOR with minimized cost, we developed a single atom-cluster multiscale structure with isolated Pt single atoms anchored on Ru nanoclusters supported on nitrogen-doped carbon nanosheets (Pt1-Ru/NC). The well-defined structure not only provides multiple sites with varied affinity with the intermediates but also enables simultaneous modulation of different sites via interfacial interaction. In addition to weakening Ru–H bond strength, the isolated Pt sites are heavily involved in hydrogen adsorption and synergistically accelerate the Volmer step with the help of Ru sites. Furthermore, this catalyst configuration inhibits the excessive occupancy of oxygen-containing species on Ru sites and facilitates the HOR at elevated potentials. The Pt1-Ru/NC catalyst exhibits superior alkaline HOR performance with extremely high activity and excellent CO-tolerance. An AEMFC with a 0.1 mg·cm_PGM⁻² loading of Pt1-Ru/NC anode catalyst achieves a peak powder density of 1172 mW·cm⁻², which is 2.17 and 1.55 times higher than that of Pt/C and PtRu/C, respectively. This work provides a new catalyst concept to address the sluggish kinetics of electrocatalytic reactions containing multiple intermediates and elemental steps.

Proton exchange membrane water electrolyzer (PEMWE) driven by renewable electricity is a promising technique toward green hydrogen production, but the corrosive environment and high working potential pose severe challenges for developing advanced electrocatalysts for the oxygen evolution reaction (OER). Although Ir-based materials possess relatively balanced activity and stability for the OER, their dissolution behavior cannot be neglected, in particular under high working potentials. In this work, iridium dioxide (IrO₂) nanoparticles (NPs) were anchored on the surface of exfoliated h-boron nitride (BN) nanosheets (NSs) toward the OER reaction in acid media. Highly active Ir(V) species were stabilized by the epitaxial interface between IrO₂ and h-BN, and therefore the IrO₂/BN delivered stable performance at increased working potentials, while the activity of bare IrO₂ NPs without h-BN support decreased rapidly. Also, the smaller lattice spacing of h-BN induced compressive strain for IrO₂, resulting in improved activity. Our results demonstrate the feasibility of stabilizing highly active Ir(V) species for the OER in acid media by constructing robust interface and provide new possibilities toward designing advanced heterostructured electrocatalysts.