Breaking the activity-stability trade-off in acidic oxygen evolution reaction via steering charge-compensation mechanisms in RuO2

Abstract

The practical application of RuO2 catalysts for the acidic oxygen evolution reaction (OER) is severely hampered by their inherent trade-off between activity and stability. To address this fundamental challenge, we herein report a strategy that employs alkaline earth metal ions (Ae2+=Mg2+, Ca2+, Sr2+ and Ba2+) as chemical probes to deliberately steer the intrinsic charge-compensation mechanisms within the RuO2 lattice. We demonstrate that Ae2+ doping effectively shifts the dominant charge-balance pathway from an oxygen-vacancy compensation mechanism towards a cation charge compensation mechanism. This strategic shift simultaneously increases the population of active high-valent Ru species while suppressing the formation of structurally detrimental oxygen vacancies, thereby breaking the conventional activity-stability dichotomy. As a result, the optimized Sr-RuO2 catalyst exhibits exceptional performance, achieving an ultralow overpotential of 199 mV at 10 mA cm-2 and remarkable durability for 200 hours at 1 A cm-2 in a practical proton exchange membrane water electrolyzer (PEMWE). Through a combination of operando spectroscopy and electrochemical analysis, we directly correlate the enhanced cation charge compensation with the promotion of the lattice oxygen mechanism (LOM), which is identified as the origin of the accelerated kinetics. This work provides profound mechanistic insights into the governing role of charge-compensation principles in electrocatalysis and establishes a universal design paradigm for advanced acidic OER catalysts.