Synergistic photocatalysis of Z-scheme type Fe₂O₃/g-C₃N₄ heterojunction coupled with reduced graphene oxide

The rational design of a Z-scheme heterojunction that appropriately connects two semiconductors with different bandgap with matched energies is of great significance for the efficient separation of charge carries and maximum solar-light harvesting. Furthermore, achieving a morphologically controlled, an easily synthesized, and an effective solar-light-driven photocatalyst still presents a significant challenge. Firstly, one-step hydrothermal method was used to facilely synthesize C-Fe₂O₃@rGO by incorporating cubic shape hematite (C-Fe₂O₃) with reduced graphene oxide (rGO). Then, graphitic carbon nitride (g-C₃N₄) was combined with C-Fe₂O₃@rGO via a solvothermal reaction, which resulted in the ternary heterojunction of C-Fe₂O₃@rGO@g-C₃N₄. Under exposer of simulated solar light, the photocatalytic performance of the constructed materials was assessed towards the destruction of methyl orange (MO) organic contaminant. For comparison, C-Fe₂O₃ and C-Fe₂O₃@rGO exhibited a very low photocatalytic activity, with degradation efficiencies of MO dye as 1% and 8%, respectively. In contrast, C-Fe₂O₃@rGO@g-C₃N₄ (5.0 wt.% g-C₃N₄) demonstrated a significantly greater photocatalytic efficiency of ∼40%, due to the formation of a ternary heterojunction. This structure ensures enhanced separation of charge carriers and extended solar-light harvesting. Strikingly, in the existence of a hole scavenger, C-Fe₂O₃@rGO@g-C₃N₄ had a significantly increased photocatalytic efficiency of 93%. The rate constants were 1.6 × 10⁻⁴ and 1.1 × 10⁻³ min⁻¹before and after adding the hole scavenger EDTA-2Na, respectively. This result clearly confirms the successful formation of a Z-scheme nature heterojunction composed of two semiconductors (Fe₂O₃ and g-C₃N₄) and conductive rGO. This synthetic approach can provide a guideline for the rational engineering as well as facile fabrications Z-scheme systems devoid of noble metals for advanced photocatalytic applications.