Boosting Acidic Oxygen Evolution Electrocatalysis by Engineering the Interfacial Water at the Electrified RuO 2 -Electrolyte Interface

Rational engineering of the catalyst-electrolyte interface where the electrochemical processes occur to facilitate the proton transfer kinetics is crucial in various electrochemical reactions. Here, we show that the long-term stability of acidic oxygen evolution reaction (OER) catalyzed by RuO 2 can be significantly promoted by engineering the interfacial water structure through interstitial boron (B) insertion (B-RuO 2 ). Experimental results including in situ attenuated total reflectance-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), local pH monitoring, and ab initio molecular dynamics (AIMD) simulations demonstrate that the insertion of boron atoms into the RuO 2 lattice could facilitate the diffusion of protons across the interface by enhancing the connectivity of hydrogen-bond networks, thereby suppressing the continuous oxidative collapse of Ru. Moreover, the interstitial boron insertion could induce interfacial water reorientation and move nonbonding oxygen (O NB ) away from Fermi level (E f ), resulting in decreased O NB and suppressed nucleophilic attack by interfacial H 2 O on O NB, further preventing structural corrosion caused by lattice oxygen loss. Consequently, the obtained B-RuO 2 shows remarkable long-term operational stability, demonstrating over 1000 h of continuous operation at 10 mA cm –2 . When applied in a practical proton exchange membrane water electrolyzer (PEMWE), it achieves a high current density of 3.0 A cm –2 at a voltage of 1.752 V and maintains stable performance at 4 A cm –2 for 200 h. This work provides a novel strategy for regulating the proton diffusion kinetics through engineering the interfacial water structure to promote acidic OER performance.