Hangil Lee

Controlling the number of oxygen vacancies ( V o s) in metal‐oxide nanoparticles (MO NPs; TiO 2 , SnO 2 , and CeO 2 ) using Li‐ions has been shown to endow MO NPs with improved photocatalytic and electrocatalytic properties. Increasing the number of V o s in nanostructures provides a foundation for efficient multi‐use catalyst designs that facilitate biomass oxidation reactions and improve electrocatalytic activity. Herein, the trends in the properties of MO‐based catalysts are investigated with varying amounts of V o s achieved by Li‐ion deposition. The controlled introduction of V o s into MO NPs tunes the band structures and surface chemistry, leading to enhanced activities of the NPs as photocatalysts for the selective oxidation of 2,5‐hydroxymethylfurfural and as electrocatalysts for acidic hydrogen evolution. It is believed that Li‐ion deposition in the MO matrix provides a novel approach for optimizing oxide‐based catalyst defect engineering, thereby enabling more efficient biomass conversion and water splitting. These findings contribute significantly to the field of multi‐purpose catalysis and are expected to inspire new catalyst designs for a more sustainable future. The results provide a pathway for the facile and efficient engineering of surface defect structures on catalytic metal oxide NPs toward designing high‐performance photocatalysts.