Single-crystal SrTiO3 hollow sphere with ultrathin shell for efficient photocatalytic water splitting
Hollow nanostructures with highly accessible surfaces and short charge-transport distances are pivotal for photo(electro)chemical reactions. Perovskite-type SrTiO3 (STO) is a promising photocatalyst for solar water splitting, yet the synthesis of uniform hollow single crystals with well-defined shells remains challenging due to the cubic symmetry and thermodynamic instability of curved surfaces. Here, we report the controllable synthesis of single-crystal STO hollow spheres with ultrathin shells (UTSS-STO) via a simple etching method. Selective etching of low-crystallinity interiors within mesoporous STO single crystals (MS-STO) yields hollow spherical shells and 2D sheet-like single crystals. The resulting UTSS-STO exhibits a 2.5-fold enhancement in photocatalytic hydrogen evolution compared to MS-STO. This improvement is attributed to the ultrathin porous shell, which shortens charge transport lengths and provides abundant active sites, as well as interlayer stress and an optimized electronic band structure that facilitate charge separation. HAADF-STEM and EDS mapping confirm uniform distribution of Rh/Cr2O3 cocatalysts on both inner and outer surfaces of the shell. This work demonstrates the advantage of hollow spherical shells for STO photocatalysts and offers insights into the fabrication of uniform hollow single crystals for efficient solar energy conversion.