Balancing Ru–O bond covalency and strength via atomic Ta doping for robust acidic oxygen evolution

Abstract

Ruthenium dioxide electrocatalysts hold promise for achieving high oxygen evolution reaction activity in proton exchange membrane water electrolysers (PEMWEs). However, the control of their stability remains extremely challenging due to their easy oxidation and dissolution during electrochemical reactions. Herein, we address these challenges by constructing atomically dispersed Ta–O–Ru asymmetric local motifs for an efficient and stable OER process via a simple molten salt-assisted method. The optimized candidate (RuO_x–10Ta) exhibits a low overpotential of 189 mV and high durability exceeding 700 hours at 10 mA cm⁻², boasting a six-fold longer lifespan than commercial RuO₂. In situ characterizations and DFT calculations reveal that in this asymmetric configuration, high-valent Ta dopants downshift the O 2p and Ru 4d band centres, thereby moderating the Ru–O covalency to facilitate water dissociation and intermediate transformation. Meanwhile, this Ta–O–Ru motif with a robust Ta–O bond acts as an electron and structural buffer that suppresses lattice oxygen loss and Ru overoxidation, enhancing the overall catalyst stability. When integrated into a PEMWE device as an anode catalyst, it achieved a low cell voltage of 1.639 V at 1 A cm⁻² and sustained stable operation for over 200 hours at 200 mA cm⁻². These findings highlight the potential of asymmetric coordination engineering as a generalizable strategy for developing robust and efficient OER catalysts under harsh acidic conditions.