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

Abstract

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 SrTiO 3 on Bi 4 Ti 3 O 12 platelets is studied as a new route for the formation of novel nanoheterostructural SrTiO 3 /Bi 4 Ti 3 O 12 platelets at an intermediate stage or (100)-oriented mesocrystalline SrTiO 3 nanoplatelets at the completed stage of the TC reaction. The Bi 4 Ti 3 O 12 platelets act as a source of Ti(OH) 6 2– species and, at the same time, as a substrate for the epitaxial growth of SrTiO 3 . The dissolution of the Bi 4 Ti 3 O 12 platelets proceeds faster from the lateral direction, whereas the epitaxial growth of SrTiO 3 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 Bi 4 Ti 3 O 12 platelet is replaced from the lateral ends toward the interior by SrTiO 3 , 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 SrTiO 3 /Bi 4 Ti 3 O 12 platelets show stable and 15 times higher photocatalytic H 2 production (1265 μmol·g –1 ·h –1 ; solar-to-hydrogen (STH) efficiency = 0.19%) than commercial SrTiO 3 nanopowders (81 μmol·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.

Water Splitting on Multifaceted SrTiO3 Nanocrystals: Calculations of Raman Vibrational Spectrum

“…The increase of the hydrogen production efficiency with STO facet nanoparticles was observed also by Mu [9] and Kržmanc [10]. As a result of recent developments in nanocrystal synthesis, materials with improved charge separation, achieved through heterojunction [10,11], mesocrystallinity [12], porosity [13] or exposed anisotropic facets [9,[14][15][16][17]. The spatial separation of reduction and oxidation active sites can also become an effective method to reduce the recombination of photogenerated charge carriers that, in turn, can improve solar energy conversion efficiency (e.g., [18]).…”

“…However, Nuraje et al consider that virus-templated STO nanowires have improved hydrogen evolution rate characteristics due to smaller particle size (∼5 nm in diameter) that provide a larger surface to volume ratio and the high crystallinity that prevents excited charge recombination at lattice defect sites [8]. The increase of the hydrogen production efficiency with STO facet nanoparticles was observed also by Mu [9] and Kržmanc [10]. As a result of recent developments in nanocrystal synthesis, materials with improved charge separation, achieved through heterojunction [10,11], mesocrystallinity [12], porosity [13] or exposed anisotropic facets [9,[14][15][16][17].…”

Recent Advances in Semiconductor Heterojunctions and Z-Schemes for Photocatalytic Hydrogen Generation

“…Furthermore, 2D structures are mostly reserved to layered semiconductors. Effective synthetic methods need to be developed to produce 2D photocatalysts from non-layered semiconductors, as has been done for SrTiO 3 for example [161].…”

Improved photoredox activity of the 2D Bi4Ti3O12–BiVO4–Bi4V2O10 heterostructure via the piezoelectricity-enhanced charge transfer effect

“…A molten salt method was employed to prepare Bi 4 Ti 3 O 12 nanosheets. 33 According to the component ratio of Bi 4 Ti 3 O 12 , appropriate stoichiometric amounts of Bi 2 O 3 and P25 were vigorously ground for 30 min in a mortar. Then, KCl and NaCl were added to the above mixture in a molar ratio of KCl : NaCl : Bi 4 Ti 3 O 12 = 50 : 50 : 1 as cosolvents to promote Bi 4 Ti 3 O 12 growth.…”