A unique octadecahedron SrTiO3 perovskite oxide with a nano step-shaped facet structure for enhanced photoredox and hydrogen evolution performance

Abstract

As a typical perovskite-type crystal, strontium titanate (SrTiO₃, STO) has remarkable photocatalytic activity and is broadly used in solar-driven overall water splitting. The research on controlling the synthesis of polyhedral STO with different exposures of crystal facets to obtain different optoelectronic properties has been greatly carried out in recent years. However, there are few reports of research on the construction of a nano step-shaped facet structure by the reconstruction of the STO crystal facet at a certain temperature, and the formation mechanism and composition analysis have not been explained clearly. In particular, the influence of crystal surface recombination on the hydrogen production reaction hasn't been thoroughly studied. This work presents the existence of a novel STO with the nano step-shaped facet structure parallel to (100) and (110) facets based on octadecahedron STO by a solid-state reaction, and the formation has been monitored by thermogravimetric analysis and in situ X-ray diffraction. In addition, more importantly, the step-shaped facet structure is rich in Sr, and lacks O and Ti, which is evidenced by EPR and XPS characterization, and it affects the transfer and separation of photo carriers. The complex STO catalysts were prepared by photodeposition of Rh, Cr, and Co to compare the hydrogen production capacity of overall water splitting. The novel step-shaped facet SrTiO₃ has a good deposition effect on the cocatalysts, and the synthesized catalyst can effectively shorten the band gap to 1.92 eV and prolong the photogenerated carriers' lifetime to 3.7356 ns. Consequently, the novel SrTiO₃ sample deposited co-catalysts achieve remarkable activity with the highest H₂ evolution rate of 172.0 μmol h⁻¹, which is 4.6 times higher than that of the original octadecahedron SrTiO₃ prepared by the hydrothermal method. The DFT calculation results prove that the excellent photocatalytic performance is due to the lower work function and effective electron transfer of the SrTiO₃ (100) crystal facet and Sr-rich (110) crystal facet, which is verified by the obvious electron transfer between the CrO₄²⁻ and the two kinds of crystal facets.