Engineering grain boundaries in porous Ru/RuO heterogeneous nanosheets for high-efficiency and durable acidic oxygen evolution.

Developing highly efficient Ru-based electrocatalysts for the acidic oxygen evolution reaction (OER) holds pivotal importance in propelling the practical application of proton exchange membrane water electrolysis (PEMWE) technology. However, attaining high activity and remarkable stability simultaneously for acidic OER remains a formidable challenge. Herein, we developed a grain boundaries (GBs) strategy to rationally synthesize a series of porous Ru/RuO nanosheets with adjustable heterojunctions. The Ru/RuO-T with optimal density of heterojunctions demonstrated outstanding acidic OER performance with low overpotential (174 mV@10 mA/cm), small Tafel slope (55.6 mV dec), and high Faradaic efficiency of over 95 % for O gas. In PEMWE testing, the Ru/RuO-T exhibits low cell voltage of 1.59 and 1.73 V to achieve 200 and 500 mA/cm and operates stably for 60 h at 1 A/cm. In situ spectroscopy and electrochemical results disclose that the Ru/RuO-T with optimal grain boundaries are accountable for this active and stable oxygen evolution process via promoting the formation of the OOH intermediate and preventing the over-oxidation of RuO species during catalytic reactions. The work sheds new light on the design of a highly efficient RuO-based electrocatalyst for acidic OER.