Defect-engineered In2O3-x hierarchical nanoflowers for enhanced photocatalytic formaldehyde removal under UV light

The development of efficient photocatalysts for indoor air purification remains a significant challenge. In this study, oxygen-deficient indium oxide nanoflowers (In 2 O 3-x NFs) were synthesized via an acetic acid and P123-assisted template method followed by H 2 calcination. The as-prepared In 2 O 3-x NFs possess a hierarchical nanoflower-like morphology with a significantly enlarged specific surface area, which provides abundant active sites for enhanced adsorption of formaldehyde molecules. Moreover, the introduced oxygen defects effectively narrow the bandgap, extending the light absorption into the visible region, and serve as traps to promote the separation and migration of photogenerated charge carriers. As a result, the optimized In 2 O 3-x NFs exhibit remarkably improved photocatalytic activity for gaseous formaldehyde degradation under UV irradiation. After 2 h of illumination, the degradation efficiency achieved by In 2 O 3-x NFs is approximately 2 times and 4.5 times higher than those of pure In 2 O 3 NFs and In 2 O 3 nanoparticles (NPs), respectively. This work offers a feasible defect-engineering strategy for designing high-performance metal oxide photocatalysts toward volatile organic compound removal.