Rh,Sb-codoped SrTiO3 cubic nanoparticles encapsulated by ZnIn2S4 nanosheets for efficient visible-light-driven hydrogen evolution

Abstract

Strontium titanate (SrTiO₃) is a typical kind of titanate photocatalyst for solar-driven hydrogen production, but its sunlight absorption is confined to the ultraviolet region. Indium zinc sulfide (ZnIn₂S₄) materials can respond to visible light, yet suffer from the rapid recombination of photogenerated charge carriers. In this study, a Rh,Sb-codoped SrTiO₃@ZnIn₂S₄ heterojunction photocatalyst was synthesized by encapsulating the surface of Rh,Sb-SrTiO₃ cubic nanoparticles with ZnIn₂S₄ nanosheets. Rh and Sb ions were applied to regulate the band structure of SrTiO₃, making it responsive to visible light. Constructing a heterojunction could promote the separation of photogenerated charge carriers for SrTiO₃ and ZnIn₂S₄. The characterization results of ultraviolet–visible, X-ray photoelectron spectroscopy, and electrochemical analyses demonstrated that the difference in the work function between Rh,Sb-SrTiO₃ and ZnIn₂S₄ formed an interfacial electric field. It facilitated the separation and migration of photogenerated charge carriers, thereby enhancing the photocatalytic hydrogen evolution activity. The visible-light-driven hydrogen evolution activity of ZnIn₂S₄ was unaffected by pure SrTiO₃, but significantly enhanced by Rh,Sb-SrTiO₃. The optimal Rh,Sb-SrTiO₃@ZnIn₂S₄ photocatalyst provided a hydrogen evolution rate of about 107.63 μmol h⁻¹ under visible light (λ ≥ 420 nm), which was 4.6 times that of pristine ZnIn₂S₄.