Enhanced photocatalytic performance of TiO2-SiO2 composites: The role of structural defects and optimal composition

TiO 2 -SiO 2 composites with varying molar ratios were synthesized and systematically evaluated for the photocatalytic degradation of methylene blue (MB) under UV irradiation. X-ray diffraction and spectroscopic analyses revealed that the incorporation of amorphous SiO 2 reduced TiO 2 crystallinity, suppressed rutile phase formation, and promoted the generation of structural defects, particularly non-bridging oxygen species. Among the investigated compositions, the TiO 2 -SiO 2 1:1 composite exhibited the highest defect density and the smallest crystallite size, indicating enhanced interfacial interaction and surface reactivity. Photocatalytic experiments demonstrated that the TiO 2 -SiO 2 1:1 composite achieved approximately 90% MB degradation within 160 min, significantly outperforming pure TiO 2 and other TiO 2 -SiO 2 ratios. The corresponding apparent kinetic rate constant reached 0.0134 min −1 , which is nearly four times higher than that of pure TiO 2 (0.0034 min −1 ), confirming the decisive role of defect-rich structures in accelerating photocatalytic reactions. The enhanced performance is attributed to the synergistic effects of optimized crystallinity, defect generation, and increased surface hydroxylation induced by SiO 2 incorporation. These findings provide clear evidence that compositional control–driven defect engineering is a key strategy for improving the photocatalytic efficiency of TiO 2 -SiO 2 composites for organic wastewater treatment.