Saddle-Shaped Mesoporous Titania with Negative Curvature by Precursor-Induced Deformation Assembly for Efficient...

Mesoporous metal oxides featuring negative-curvature architectures hold promise for photocatalytic energy conversion. However, the construction of mesoporous titania with negative-curvature morphology remains challenging due to rapid hydrolysis and excessive cross-linking. Herein, we report a precursor-induced deformation assembly (PIDA) strategy for the fabrication of saddle-shaped mesoporous TiO2 nanoparticles (saddle-mTiO2). The saddle-mTiO2 nanoparticles possess a uniform size of 80 nm, a high specific surface area (304 m2 g-1), a large pore volume (0.46 cm3 g-1), and a uniform mesopore size (3.0 nm). The Gaussian curvatures of the entire saddle-shaped surface measured via electron tomography are negative, and reach -0.04 nm-2 at the saddle point, and the mean curvatures of the surface are measured as -0.3 to 0.3 nm-1. The curvature of the mesoporous titania can precisely be controlled by regulating the amount of the oily precursor. In situ cryogenic transmission electron microscopy (cryo-TEM) is utilized to capture the formation process of the saddle-shaped mesostructure assembled from composite micelles. The saddle-mTiO2 exhibits excellent photocatalytic hydrogen production performance due to a negative-curvature-induced strengthening of the local surface electric field, with a hydrogen production rate of 7.3 mmol g-1 h-1, which is significantly higher than that of the zero-curvature and positive-curvature surfaces. Overall, our work provides a strategy for the design and synthesis of mesoporous metal oxides with negative-curvature architectures and identifies curvature as a design factor for the structure-performance relationships in mesoporous photocatalytic hydrogen evolution.