Sub‐Band Assisted Z‐Scheme for Effective Non‐Sacrificial H₂O₂ Photosynthesis

Abstract Photosynthesis of H₂O₂ from earth‐abundant O₂ and H₂O molecules offers an eco‐friendly route for solar‐to‐chemical conversion. The persistent challenge is to tune the photo‐/thermo‐ dynamics of a photocatalyst toward efficient electron–hole separation while maintaining an effective driving force for charge transfer. Such a case is achieved here by way of a synergetic strategy of sub‐band‐assisted Z‐Scheme for effective H₂O₂ photosynthesis via direct O₂ reduction and H₂O oxidation without a sacrificial agent. The optimized SnS₂/g‐C₃N₄ heterojunction shows a high reactivity of 623.0 µmol g⁻¹ h⁻¹ for H₂O₂ production under visible‐light irradiation (λ > 400 nm) in pure water, ≈6 times higher than pristine g‐C₃N₄ (100.5 µmol g⁻¹ h⁻¹). Photodynamic characterizations and theoretical calculations reveal that the enhanced photoactivity is due to a markedly promoted lifetime of trapped active electrons (204.9 ps in the sub‐band and >2.0 ns in a shallow band) and highly improved O₂ activation, as a result of the formation of a suitable sub‐band and catalytic sites along with a low Gibbs‐free energy for charge transfer. Moreover, the Z‐Scheme heterojunction creates and sustains a large driving force for O₂ and H₂O conversion to high value‐added H₂O₂.