Circumventing the Linear Scaling Limitation in Oxygen Evolution by Metal-Site Proton-Acceptor-Assisted Deprotonation

Oxygen evolution reaction electrocatalysts following the adsorbate evolution mechanism (AEM) exhibit exceptional structural stability, but the activity is inherently constrained by the linear scaling relationship associated with single-metal sites. Here, we propose a metal-site proton-acceptor-assisted deprotonation AEM (MP-AEM) by incorporating Pd into RuO₂ as secondary metal-site proton acceptors to activate a novel proton-transfer pathway. Theoretical calculations and operando characterizations confirm that Pd-RuO₂ generates new intermediates, reducing the rate-determining energy barrier by 0.41 eV. Moreover, Pd proton acceptor lowers the O─H bond dissociation barrier and optimizes the hydrogen-bond network, thereby accelerating the deprotonation kinetics. Furthermore, reduced Ru valence and weakened Ru─O covalency inhibit Ru oxidative dissolution and the lattice-oxygen-mediated mechanism. The Pd-RuO₂ applied in proton exchange membrane water electrolyzers (PEMWEs) requires only 1.55 V @ 1 A cm^-2 and shows 15-fold higher stability than pure RuO₂. This work establishes an innovative pathway and insight for designing highly efficient PEMWEs catalysts.