High-entropy RuO catalyst with dual-site oxide path for durable acidic oxygen evolution reaction.

Developing durable acidic oxygen evolution reaction catalysts is critical for industrial proton exchange membrane water electrolyzers. We incorporate high-entropy atoms (Co, Ni, Cu, Mn, Sm) into RuO (RuO-HEAE) via annealing, achieving remarkably high stability (>1500 h at 100 mA cm). In situ differential electrochemical mass spectrometry and operando Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy reveal RuO-HEAE follows a dual-site oxide path mechanism instead of the conventional adsorbate evolution mechanism. Quantitative Fourier-transformed extended X-ray absorption fine structure fitting and density functional theory calculations show this mechanistic shift stems from an elongated Ru-M distance in second coordination shell of RuO-HEAE, enabling direct O-O coupling. This OPM-type catalyst delivers ~1500 h of stable operation at 1 A cm and 50 °C, demonstrating superior durability versus most reported RuO-based catalysts. This work provides fundamental insights for designing highly stable proton exchange membrane water electrolysis.