Sub‐10 Nanometer Anatase–Brookite Biphasic TiO 2 Nanoparticles Deposited on Wrinkled Nanosilica for Photocatalytic Carbon Dioxide Reduction

In this work, mesoporous silica nanoparticles with centrally radial open pore channels were synthesized, followed by the uniform deposition of small‐sized (5–10 nm) anatase–brookite biphasic TiO 2 semiconductor nanoparticles with varying loadings. The mesoporous silica framework effectively promotes homogeneous dispersion of the TiO 2 nanoparticles and suppresses their aggregation. Comprehensive structural and optical characterizations were performed using UV–vis spectroscopy, powder X‐ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and high‐resolution transmission electron microscopy (HRTEM). The results confirm the coexistence of anatase and brookite phases uniformly distributed over the mesoporous silica support. The optimized mesoporous silica‐supported anatase–brookite biphasic TiO 2 photocatalyst exhibited superior photocatalytic CO 2 reduction performance in pure water, yielding 23.8 µmol g −1 of CO and 1.54 µmol g −1 of CH 4 without the use of any sacrificial agent or cocatalyst. The synergistic coexistence of anatase and brookite phases within a single particle enhances charge separation through faster electron trapping across the S‐scheme heterojunction interface and lower electron/hole pair recombination, which is believed to be responsible for the significantly improved CO 2 reduction activity.