Facet-selected oxygen-deficient ruthenium oxide for acidic oxygen evolution catalysis

Proton exchange membrane water electrolysis enables sustainable hydrogen production, where ruthenium dioxide catalysts are highly active for the oxygen evolution reaction but suffer from degradation associated with the lattice oxygen oxidation mechanism. Conventional stabilization strategies mainly focus on heteroatom doping, but often diminish intrinsic Ru active sites. Here, we propose a Ru-intrinsic and defect-inheritance strategy that does not rely on doping and yields a reconstructed RuO₂ with surface oxygen-deficiency on preferentially exposed (101) facet (od-RuO₂). These facet-selected oxygen-deficient Ru sites strengthen the hybridization of Ru t_2g orbitals and π-donor oxygen ligands, shifting and broadening the t_2g^* states towards the Fermi level, thereby facilitating OOH bond formation through the adsorbate evolution mechanism dominated pathway. Herein, od-RuO₂ achieves an overpotential of 161 mV at 10 mA cm^-2 and operates for over 3000 hours, and also sustains membrane electrolyser operation, demonstrating its potential for durable acidic oxygen evolution catalysis.