Delocalized Electronic Buffering at Pd/High-Entropy Oxide Interfaces Enables Water-Tolerant Methane Oxidation

Abstract Developing Pd-based catalysts for methane oxidation that combine low-temperature activity with strong water tolerance remains a major challenge for emission control applications. Herein, we introduce a high-entropy architecture into Co3O4-based spinel supports to regulate Pd-support interfacial interactions. The resulting high-entropy support (HE-Co-Sp) forms a hybridized and electronically delocalized Co–O–M (M = multiple cations) network, providing dynamic electron-buffering capability. This electronic framework promotes rapid replenishment of reactive oxygen species at Pd sites, thereby enhancing low-temperature methane oxidation activity. Concurrently, interfacial electronic coupling induces electron transfer from the support to Pd, as evidenced by XANES, EXAFS, and Pd 3d XPS measurements, leading to a moderated Pd electronic state and suppressed H2O adsorption. As a result, Pd/HE-Co-Sp exhibits markedly improved stability under wet methane oxidation under highly O2-rich conditions compared with Pd/θ-Al2O3, Pd/Co3O4, and Pd/MnCo2O4. These findings establish high-entropy-induced electronic delocalization as an effective strategy for designing water-tolerant methane oxidation catalysts.