Facile fabrication of direct solid-state Z-scheme g-C3N4/Fe2O3 heterojunction: a cost-effective photocatalyst with high efficiency for the degradation of aqueous organic pollutants

Abstract

Graphitic carbon nitride (g-C₃N₄) is a low cost photocatalyst for the visible light-driven degradation of aqueous organic pollutants. Nevertheless, the fast recombination of electron–hole pairs significantly inhibits its photocatalytic activity. Consequently, we report a novel strategy in which the low cost α-Fe₂O₃ photocatalyst is in situ introduced to accelerate the photogenerated charge separation of g-C₃N₄ based on a Z-scheme mechanism. Under the irradiation of visible light, the photocatalytic activity significantly improved on coupling g-C₃N₄ and α-Fe₂O₃, and a peak Rhodamine B (RhB) degradation efficiency of over 99% were observed. This value is significantly higher than that over pure g-C₃N₄ (ca. 67%) and α-Fe₂O₃ (ca. 6%). Additionally, the as-prepared g-C₃N₄/Fe₂O₃ exhibits highly stable photocatalytic activity. The loading of α-Fe₂O₃ on the g-C₃N₄ surface results in the formation of a direct solid-state Z-scheme structure. The improved separation of electron–hole pairs and strong redox ability of the charge carriers are responsible for the improved photocatalytic activity of g-C₃N₄/Fe₂O₃. Finally, the h⁺ and ˙O₂⁻ radicals are confirmed as the major oxidation species and a possible photocatalytic mechanism is proposed in the g-C₃N₄/Fe₂O₃ reaction system. This work is of significance to promote the large-scale application of g-C₃N₄-based photocatalysts in water purification.