Investigation of the kinetics and mechanism of Z-scheme Ag3PO4/WO3 p–n junction photocatalysts with enhanced removal efficiency for RhB

Abstract

Semiconductor-based photocatalysis attracts wide attention owing to its ability to directly utilize solar energy for the production of solar fuels. In particular, the construction of Z-scheme heterojunctions is demonstrated to benefit the photocatalytic performance because of the separation and transfer of the photogenerated charge carriers and well-preserved strong redox ability. In this work, a series of Z-scheme Ag₃PO₄/WO₃ p–n junction photocatalysts were prepared employing a facile impregnation method. The photocatalysts (Ag₃PO₄/WO₃ p–n junction) presented enhanced photo-degradation efficiency; for example, with AW-45, 99.9% degradation could be obtained for RhB (30 ppm) on irradiation (λ > 420 nm, 350 W xenon lamp) for 7 min, which is a great improvement compared with the individual constituents. The degradation rate for AW-45 was 27 times higher than that of a commercial powder (P25). The apparent kinetic rate of catalytic degradation was obtained according to the results from the degradation process. The mechanism for electron transfer between Ag₃PO₄ and WO₃ was also investigated. The reduction and oxidation processes concentrated on the CB (conducting band) of Ag₃PO₄ and the VB (valence band) of WO₃, resulting in promoting the mechanism for photocatalytic degradation in the Z-scheme Ag₃PO₄/WO₃ p–n junction photocatalysts.