Spinel/Rock Salt Core/Shell High-Entropy Oxides for Selective CO₂ Hydrogenation

High-entropy oxides (HEOs) exhibit exceptional structural stability through configurational entropy maximization, yet their catalytic activity can be inadvertently constrained by the inherent activity-stability trade-off arising from dynamic site regeneration limitations. Here, we present an entropy recombination strategy that designs a spinel/rock salt core/shell mixed-phase HEO catalyst. This catalyst, featuring a spinel-core entropy modulator, achieves thermodynamic equilibrium via compositional entropy exchange, resulting in an ultra-active thin rock salt shell HEO. The catalyst demonstrates superior mass activity (318 μmol_CO g_cat^-1 s^-1 at 380 °C) and stability in the reverse water gas shift reaction, surpassing Cu-based and even noble metal-based catalysts. The core/shell architecture facilitates a multicomponent surface, oxygen vacancy generation, and Cu exsolution, accelerating the redox pathway's rate-determining step via enhanced hydrogen transport. This work represents a breakthrough in HEO structural engineering, with promising advancements in diverse catalytic applications.