Self-limiting surface leaching stabilizes Ru-based catalysts for acidic water oxidation†

Abstract

Ru-based catalysts are a promising alternative to Ir-based catalysts for the acidic oxygen evolution reaction (OER), but their poor long-term stability remains a significant challenge. Continuous leaching-induced loss of active sites and structural collapse are the primary causes of this instability, severely limiting the practical application of Ru-based catalysts in proton exchange membrane (PEM) electrolyzers. Here, we present a self-limiting surface leaching mechanism that effectively suppresses continuous leaching, thereby significantly prolonging the lifespan of Ru-based catalysts under acidic OER conditions. Specifically, the Ru–Mn solid solution oxide with a hollow shell structure undergoes surface Mn leaching during the initial OER process, resulting in the formation of a Mn-vacancy-rich stable reconstruction layer. This layer effectively inhibits further leaching of both Ru and Mn, thus self-limiting the further degradation of catalysts. As a result, the reconstructed catalyst exhibits an unprecedented durability of up to 2500 h at 10 mA cm⁻² in 0.5 M H₂SO₄. This remarkable stability was also validated in PEM electrolyzers, highlighting its practical applicability. Operando synchrotron characterization combined with theoretical calculations reveals that the formation of Mn vacancies increases the demetallation energy of Ru species, thereby suppressing the continuous leaching and enhancing the long-term stability. This work provides valuable insights for designing highly stable catalysts through a self-limiting leaching mechanism.