Abstract:

Artificial photosynthesis is an appealing approach for generating hydrogen peroxide (H₂O₂) from H₂O and O₂ with solar energy as the sole energy input. However, the current catalyst systems commonly face challenges such as the limited optical absorption, poor electron-hole pair separation efficiency, and restricted surface reactivity, which hinders the overall photoactivity. Here, we immobilize cubic-phase ultrathin In₄SnS₈ nanosheets (E_g = 2.16 eV) with thickness of 5–10 nm on the surface of few-layer Ti₃C₂ to develop a sandwich-like hierarchical structure of Ti₃C₂/In₄SnS₈ nanohybrid via in situ hydrothermal strategy. The enlarged interfacial area and close contact between Ti₃C₂ and In₄SnS₈ benefit for carrier transportation among nanohybrids. Characterization through X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) corroborates the successful construction of Ti₃C₂/In₄SnS₈ nanostructures. Band structures investigation including valence band maximum and Mott-Schottky plots reveals the formation of Schottky junction in this 2D/2D heterostructure, that favors for ultrafast charge carrier separation and transportation from In₄SnS₈ to Ti₃C₂ and preventing the electrons backflow from Ti₃C₂ to In₄SnS₈. Photoluminescene analysis and photo/electrochemical measurements prove that the combination of Ti₃C₂ and In₄SnS₈ accelerates the transportation of photoexcited electron-hole pairs and efficiently suppresses charge carrier recombination. Unsurprisingly, 7 wt% Ti₃C₂/In₄SnS₈ catalysts exhibit the highest visible-light-driven photoreactivity with H₂O₂ production rates of 1.998 µmol∙L⁻¹∙min^‒1 that is 2.2 times larger than that of single In₄SnS₈. Additionally, Ti₃C₂/In₄SnS₈ demonstrates a multifunctional capability in Cr(Ⅵ) reduction with the greatest reaction rates of 19.8 × 10⁻³ min^‒1 that is almost 4-fold larger than that of individual semiconductor. Moreover, the nanohybrids exhibit excellent photostability after 5 cycles testing in both reaction systems. The morphology, crystal structure and composition for Ti₃C₂/In₄SnS₈ remain unaltered after photoreaction. A comprehensive analysis including trapping agents and atmosphere experiments as well as electron paramagnetic resonance demonstrates that the H₂O₂ evolution pathway consists of two channels: a two-step successive 1e^‒ oxygen reduction reaction and a one-step 2e^‒ water oxidation reaction. This work may provide a viable protocol for designing efficient and multifunctional photocatalytic systems for solar-to-chemical energy conversion.

Key words: Ti₃C₂, In₄SnS₈, Photocatalysis, H₂O₂ production, Cr(Ⅵ) reduction