Construction of Bi₂S₃/TiO₂/MoS₂ S-Scheme Heterostructure with a Switchable Charge Migration Pathway for Selective CO₂ Reduction

Switching between the redox potential of an appropriate semiconductor heterostructure could show critical applications in selective CO₂ reduction. Designing a semiconductor photocatalyst with a wavelength-dependent response is an effective strategy for regulating the direction of electron flow and tuning the redox potential. Herein, the switching mechanism between two charge migration pathways and redox potentials in a Bi₂S₃/TiO₂/MoS₂ heterostructure by regulating the light wavelength is achieved. In situ irradiated X-ray photoelectron spectroscopy (ISI-XPS), electron spin resonance (ESR), photoluminescence (PL), and experimental scavenger analyses prove that the charge transport follows the S-scheme approach under UV–vis–NIR irradiation and the heterojunction approach under vis–NIR irradiation, confirming the switchable feature of the Bi₂S₃/TiO₂/MoS₂ heterostructure. This switchable feature leads to the reduction of CO₂ molecules to CH₃OH and C₂H₅OH under UV–vis–NIR irradiation, while CH₄ and CO are produced under Vis–NIR irradiation. Interestingly, the apparent quantum efficiency of the optimal composite at λ = 600 nm is 4.23%. This research work presents an opportunity to develop photocatalysts with switchable charge transport and selective CO₂ reduction.