Facilitating Hot Electron Injection from Graphene to Semiconductor by Rectifying Contact for Vis-NIR-Driven H₂ O₂...

Solar-driven production of hydrogen peroxide (H₂ O₂ ), as an important industrial chemical oxidant with an extensive range of applications, from oxygen reduction is a sustainable alternative to mainstream anthraquinone oxidation and direct hydrogenation of dioxygen methods. The efficiency of solar to hydrogen peroxide over semiconductor-based photocatalysts is still largely limited by the narrow light absorption to visible light. Here, the authors proposed and demonstrate the proof-of-concept application of light-generated hot electrons in a graphene/semiconductor (exemplified with widely used TiO₂ ) dyad to largely extend visible light spectra up to 800 nm for efficient H₂ O₂ production. The well-designed graphene/semiconductor heterojunction has a rectifying interface with a zero barrier for the hot electron injection, largely boosting excited hot electrons with an average lifetime of ≈0.5 ps into charge carriers with a long fluorescent lifetime (4.0 ns) for subsequent H₂ O₂ production. The optimized dyadic photocatalyst can provide an H₂ O₂ yield of 0.67 mm g^-1  h^-1 under visible light irradiation (λ ≥ 400 nm), which is 20 times of the state-of-the-art noble-metal-free titanium oxide-based photocatalyst, and even achieves an H₂ O₂ yield of 0.14 mm g^-1  h^-1 upon photoexcitation by near-infrared-region light (≈800 nm).