This study compares two spinel-type high-entropy oxides under reverse water–gas shift conditions, highlighting redox behavior implications.
High-entropy oxides (HEOs) offer tunable redox chemistry and thermal stability for catalytic applications. Here, we compare two spinel-type HEOs, MnFeCoNiCuOx and MnCoNiCuZnOx, with similar configurational entropy but different redox behaviors under reverse water–gas shift (RWGS) conditions. Only MnFeCoNiCuOx exhibits reversible exsolution and reincorporation of Fe/Co/Ni/Cu alloy nanoparticles (NPs) during H2–CO2 cycling, as confirmed by in situ X-ray absorption spectroscopy and wavelet-transformation. This dynamic restructuring correlates with higher concentrations of oxygen vacancy and exsolved Fe/Co/Ni/Cu alloy NPs, resulting in higher RWGS activity above 400 °C. In contrast, redox-inert Zn2+ in MnCoNiCuZnOx suppresses lattice flexibility and alloy formation. These findings underscore that redox-active cations, rather than entropy alone, govern the regenerative behavior and catalytic performance in HEO systems.
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Chou et al. (2025) studied this question.
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