Photocatalytic reduction of CO2 using a high-entropy fluorite oxide

Global economic and technological advancements have led to a significant surge in CO 2 emissions, posing severe environmental challenges. This study explores the photocatalytic reduction of CO 2 using a high-entropy fluorite oxide (HEFO), (Ce 0.2 Zr 0.2 Ti 0.2 Sn 0.2 Ca 0.2 )O 2-δ , synthesized via solid-state reactions. XRD, SEM, and XPS analyses confirmed a single-phase fluorite structure and revealed excellent light absorption (250–400 nm) with a 2.6 eV bandgap. Photocatalytic CO 2 reduction experiments demonstrated the superior performance of fine particles (72 % CO 2 conversion, 12.01 μmol h −1  g −1 methane generation, 61.2 % selectivity) compared to that of coarse one. This enhanced activity was attributed to a higher oxygen vacancy concentration, which optimized the surface electronic structure, increased the number of active sites, and improved CO 2 adsorption and activation. This study highlights the potential of HEFOs for renewable fuel production via CO 2 photoreduction.