Engineering high‐entropy oxide hollow spheres to overcome the hydrothermal stability trade‐off in <scp>CO</scp> oxidation

Abstract Transition metal oxides, known for excellent redox properties, are widely used in exhaust purification. Doping is a common strategy to enhance redox performance. However, increased oxygen vacancy concentration also promotes water vapor adsorption, leading to a trade‐off between catalytic activity and hydrothermal stability. In this study, a strategy using Ce 0.5 Ni 0.1 Mg 0.1 Fe 0.1 Zn 0.1 Co 0.1 Ox high‐entropy hollow spheres (HEOs‐HS) to overcome the trade‐off between redox activity and hydrothermal stability in transition metal oxide. Synthesized via a glucose‐templated hydrothermal method, the HEOs‐HS catalyst demonstrated exceptional CO oxidation activity in the presence of 4.2 vol% moisture (160 h), and the catalyst exhibited low activation energy (27.84 kJ/mol). Comprehensive characterization revealed that HEOs‐HS possessed a higher concentration of oxygen vacancies; its unique hollow sphere architecture effectively mitigated excessive water adsorption. This protective morphology shielded active sites from direct water interaction. Thus, the synergistic integration of high‐entropy composition and hollow nanostructure successfully inhibited water poisoning, breaking the conventional activity‐stability trade‐off in humid environments.