High‐Entropy Stabilization of Lattice‐Oxygen‐Activated RuO ₂ for Robust Proton Exchange Membrane Water Electrolysis

ABSTRACT RuO 2 is the most promising anodic oxygen evolution reaction catalyst for use in proton exchange membrane water electrolysers (PEMWE) due to following the lattice oxygen oxidation mechanism (LOM) pathway. However, the excessive participation of lattice oxygen leads to structural collapse and the leaching of Ru at high oxidation potentials, causing a sharp decrease in stability. To enhance its stability while maintaining a highly active LOM pathway, we develop highly entropic RuO 2 ((VCrMnNiRu)O 2 ) with an entropic stabilization effect. (VCrMnNiRu)O 2 not only displays a low overpotential of 216 mV at 10 mA cm −2 and high mass activity of 199.706 A g Ru −1 at 250 mV overpotential in 0.5 m H 2 SO 4 , but also the Pt/C||(VCrMnNiRu)O 2 electrode pairs deliver good stability with 1500 h of continuous operation at 500 mA cm −2 in PEMWE. A combination of advanced in situ spectroscopic techniques and density functional theory calculations confirms that the high‐entropy effect can inhibit the overoxidation of Ru and Ru leaching.