Interstitial charge transfer pathways in a TiO2/CdIn2S4 heterojunction photocatalyst for direct conversion of sunlight into fuel

Abstract

Herein, a TiO₂/CdIn₂S₄ nanoheterostructure photocatalyst was fabricated by a single step low temperature precipitation method. The interesting hierarchical nanostructure was obtained by in situ decoration of TiO₂ nanoparticles on the surface of thin sheets of CdIn₂S₄ micro-flowers, which improves the light absorption capacity. The synergistic interaction between CdIn₂S₄ and TiO₂ matrices leads to alteration in the electronic band structure of TiO₂ and creates the energy levels between the conduction and valence bands. The successful formation of a ‘type II’ heterojunction in TiO₂/CdIn₂S₄ nanoheterostructures leads to a significant improvement in photocatalytic H₂ production from water (7.86 mmol h⁻¹ g⁻¹) under direct sunlight, which is ∼5.5 times higher than that of bare TiO₂ and ∼2 times higher than that of bare CdIn₂S₄. The suppressed rate of photoinduced charge carrier recombination due to the enhanced interstitial charge transfer mechanism through various radiative and non-radiative pathways arising from the intimate contact between both the semiconductors leads to this improved photocatalytic performance. The appropriate selection of components endows the resultant nanoheterostructure photocatalyst with the best of both worlds. This work provides a simplistic low temperature, commercially scalable and energy efficient synthetic approach for construction of a hierarchical TiO₂/CdIn₂S₄ nanoheterostructure with superior catalytic ability and potential for application in direct conversion of solar energy into fuel and related fields.