Uniform nanorhombic α-Fe2O3 on g-C3N4 nanosheet: 2D/2D lattice matched S-scheme heterojunction towards efficient styrene oxidation and H2 evolution

Abstract

The design and modification of heterojunction photocatalysts to enhance efficient interfacial charge transfer and superior photocatalytic performance are fundamental objectives in the field of solar-light-driven energy conversion and production. This study presents a novel S-scheme heterojunction which features lattice-matched morphological hetero-nanostructures, composing of two-dimensional (2D) graphitic carbon nitride (CN) loaded with uniformly distributed and size-consistent 2D nano-rhombohedral α-Fe₂O₃ (Fe₂O₃ NR/CN). The directional charge transfer in the lattice-matched S-scheme heterojunction was confirmed using a combination of in situ irradiated X-ray photoelectron spectroscopy, metal deposition experiments, electron paramagnetic resonance, and density functional theory calculations. The optimized heterojunction demonstrates exceptional photocatalytic activity, achieving a hydrogen generation rate that surpasses those of g-C₃N₄ and α-Fe₂O₃ alone by factors of 2.1 and 7, respectively. Additionally, this heterojunction exhibits an excellent styrene conversion rate of 94.1 % and a styrene epoxidation selectivity of 95.3 % under light irradiation at 80 °C using tert-butyl hydroperoxide (TBHP) as the oxidant. The incorporation of uniformly distributed nano-rhombohedral α-Fe₂O₃ particles with g-C₃N₄ successfully constructs an unobstructed interfacial pathway to form the lattice-matched S-scheme heterojunction, enabling efficient separation of photogenerated carriers. This unique structure provides a valuable reference for dual-functional photocatalytic reactions.