Interparticle double charge transfer mechanism of heterojunction α-Fe2O3/Cu2O mixed oxide catalysts and its visible light photocatalytic activity

Abstract

α-Fe2O3/Cu2O mixed oxide photocatalysts were prepared by one step facile hydrothermal method. During the synthesis, the growth of phase pure and highly crystalline polyhedral Cu2O crystals occurred and simultaneously a heterojunction formed between α-Fe2O3 and Cu2O particles. The optical band gap of bare Cu2O was found to be 1.8eV which was less than the reported values and incorporation of 5wt% α-Fe2O3 further reduced the band gap of Cu2O to 1.75eV, indicating an enhanced absorption of visible light by the binary photocatalysts. More importantly, the loading of α-Fe2O3 on Cu2O augmented the charge carriers separation and transfer at the interface, which was evident by the reduced photoluminescence intensity of α-Fe2O3/Cu2O photocatalysts. The influence of different loading amounts of iron oxide (1–10wt%) on Cu2O was evaluated. Among them, 5wt% α-Fe2O3 loaded Cu2O showed the enhanced photodegradation activity due to the formation of an effective p-n heterojunction and exhibited nearly 30% and 95% increase in the photodegradation rate of methyl orange (MO) compare to bare Cu2O and α-Fe2O3, respectively. The photo generated superoxide radicals were found to be the main reactive species responsible for the degradation of MO. The excellent photodegradation activity of α-Fe2O3/Cu2O photocatalyst is mainly attributed to the enhanced visible light absorption, efficient charge carriers separation and transfer. Based on the experimental results, a double charge transfer mechanism was proposed for the separation and transfer of photogenerated charge carriers in the photocatalysts.