MOF-derived (MoS2, γ-Fe2O3)/graphene Z-scheme photocatalysts with excellent activity for oxygen evolution under visible light irradiation

Constructing Z-scheme heterojunctions is considered as an effective strategy to obtain catalysts of high efficiency in electron-hole separation in photocatalysis. Unfortunately, suitable heterojunctions are difficult to fabricate because the direct interaction between two semiconductors may lead to unpredictable negative effects such as electron scattering or electron trapping due to the existence of defects which causes the formation of new substances. Furthermore, the van der Waals contact between two semiconductors also results in bad electron diffusion. In this work, a MOF-derived carbon material as a Z-scheme photocatalyst was synthesized via one-step thermal treatment of MoS2 dots @Fe-MOF (MIL-101). Under visible light irradiation, the well-constructed Z-scheme (MoS2, gamma-Fe2O3)/graphene photocatalyst shows 2-fold photocatalytic oxygen evolution activity (4400 mu mol g(-1) h(-1)) compared to that of gamma-Fe2O3/graphene (2053 mu mol g(-1) h(-1)). Based on ultraviolet photoelectron spectrometry (UPS), Mott-Schottky plot, photocurrent and photoluminescence spectroscopy (PL) results, the photo-induced electrons from the conduction band of gamma-Fe2O3 could transport quickly to the valence band of MoS(2)via highly conductive graphene as an electron transport channel, which could significantly enhance the electron-hole separation efficiency as well as photocatalytic performance.