SrTiO3/Bi4Ti3O12 Nanoheterostructural Platelets Synthesized by Topotactic Epitaxy as Effective Noble-Metal-Free Photocatalysts for pH-Neutral Hydrogen Evolution

Low-temperature hydrothermal epitaxial growth and topochemical conversion (TC) reactions offer unexploited possibilities for the morphological engineering of heterostructural and non-equilibrium shape (photo)catalyst particles. The hydrothermal epitaxial growth of SrTiO3 on Bi4Ti3O12 platelets is studied as a new route for the formation of novel nanoheterostructural SrTiO3/Bi4Ti3O12 platelets at an intermediate stage or (100)-oriented mesocrystalline SrTiO3 nanoplatelets at the completed stage of the TC reaction. The Bi4Ti3O12 platelets act as a source of Ti(OH)(6)(2-) species and, at the same time, as a substrate for the epitaxial growth of SrTiO3. The dissolution of the Bi4Ti3O12 platelets proceeds faster from the lateral direction, whereas the epitaxial growth of SrTiO3 occurs on both bismuth-oxide-terminated basal surface planes of the Bi(4)Ti(3)O(12 )platelets. In the progress of the TC reaction, the Bi4Ti3O12 platelet is replaced from the lateral ends toward the interior by SrTiO3, while Bi(4)Ti(3)O(12 )is preserved in the core of the heterostructural platelet. Without any support from noble-metal doping or cocatalysts, the SrTiO3/Bi(4)Ti(3)O(12 )platelets show stable and 15 times higher photocatalytic H-2 production (1265 mu mol.g(-1).h(-1); solar-to-hydrogen (STH) efficiency = 0.19%) than commercial SrTiO3 nanopowders (81 mu mol.g(-1).h(-1); STH = 0.012%) in pH-neutral water/methanol solutions. A plausible Z scheme is proposed to describe the charge-transfer mechanism during the photocatalysis.

Automated summary

The hydrothermal epitaxial growth of SrTiO3 on Bi4Ti3O12 platelets enables the formation of novel nanoheterostructural SrTiO3/Bi4Ti3O12 platelets. During the topochemical conversion reaction, the Bi4Ti3O12 platelets are gradually replaced by SrTiO3, resulting in a stable and efficient photocatalyst without noble-metal doping or cocatalysts.