Grain-boundary-proximal hydroxyl defects in Pt-regulated inverse spinel high-entropy oxide enabling efficient CO2 photoreduction

Achieving efficient photocatalytic performance for high-entropy oxides (HEOs) continues to pose significant challenge, primarily attributed to their intrinsically limited charge carrier mobility and sluggish surface reaction kinetics resulting from heterogeneous defect distributions. Herein, the new Pt-regulated inverse spinel HEOs with honeycomb-like architecture are developed employing a facile sol-gel technique. The doping of trace amounts of Pt in the octahedral B voids of the high-entropy (FeZnAlCoMn) 3 O 4 can enables electronic structure optimization and regulates the grain-boundary-proximal hydroxyl defects, thereby improving CO 2 adsorption/activation capabilities, charge transfer and separation efficiency, and surface reaction kinetics. As a result, the optimal high-entropy 1.6%Pt-(FeZnAlCoMn) 3 O 4 achieves 3.41 times average CO evolution rate of (FeZnAlCoMn) 3 O 4 and stable operations for 4 cycles in the photocatalytic CO 2 reduction. This contribution provides novel insights into the targeted design and regulation of high-entropy oxides (HEOs) for efficient photocatalytic CO 2 reduction, thereby establishing a new paradigm for grain boundary defect engineering that can be extended to other application fields. A new Pt-regulated inverse spinel high-entropy oxide (FeZnAlCoMn) 3 O 4 catalyst is developed, in which the doping of trace amounts of Pt in the octahedral B voids enables electronic structure optimization and regulates the grain-boundary-proximal hydroxyl defects, thereby significantly improving CO 2 reduction performance. • Pt-regulated inverse spinel HEOs with honeycomb-like architecture are developed. • Doping of Pt in the octahedral B voids enables electronic structure optimization . • Grain-boundary-proximal hydroxyl defects improve CO 2 adsorption/activation. • Charge separation efficiency and surface reaction kinetics are enhanced. • Pt-(FeZnAlCoMn) 3 O 4 achieves significantly improved CO 2 reduction performance.