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Direct Z-Scheme charge transfer in heterostructured MoO3/g-C3N4 photocatalysts and the generation of active radicals in photocatalytic dye degradations

Author:
Xue, Shengyang, Wu, Chunzheng, Pu, Shengyan, Hou, Yaqi, Tong, Tian, Yang, Guang, Qin, Zhaojun, Wang, Zhiming, Bao, Jiming
Source:
Environmental pollution 2019 v.250 pp. 338-345
ISSN:
0269-7491
Subject:
annealing, carbon nitride, dyes, electrochemistry, electron paramagnetic resonance spectroscopy, electrons, free radicals, graphene, hydroxyl radicals, microparticles, mixing, nanosheets, pH, photocatalysis, photocatalysts, rhodamines, semiconductors, superoxide anion, wastewater, water pollution
Abstract:
Photocatalytic degradation is an attractive strategy to purify waste water contaminated by macromolecular organics. Compared with the single-component photocatalysts, heterostructures of different semiconductors have been widely used to improve the photocatalytic performance. In this work, we fabricate a hetero-structured photocatalyst consisting of two-dimensional graphitic carbon nitride (g-C3N4) nanosheets and commercial MoO3 microparticles through a simple mixing and annealing process. The photocatalytic performance was evaluated in various dye degradation reactions, especially Rhodamine (RhB) degradation. The MoO3/g-C3N4 composite shown a significant improvement compared with individual MoO3 or g-C3N4 as well as their physical mixture. By applying electron spin resonance (ESR) spin-trap spectra, radical scavenge experiments and electrochemical analysis, we find that a direct Z-scheme charge transfer between MoO3 and g-C3N4 not only causes an accumulation of electrons in g-C3N4 and holes in MoO3, but also boosts the formation of superoxide radical and hydroxyl radical. The superoxide radical and hole dominate the photocatalytic degradation, while the hydroxyl radical plays a negligible role and its production can be suppressed by lowering the pH value.
Agid:
6366608