Fabrication of Z-Scheme WO 3 /KNbO 3 Photocatalyst with Enhanced Separation of Charge Carriers
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doi: 10.1007/s40242-020-9106-5
Article
Fabrication of Z-Scheme WO3/KNbO3 Photocatalyst with Enhanced Separation of Charge Carriers ZHENG Xiuzhen1, HAN Huijuan1, YE Xiangju3, MENG Sugang1,2*, ZHAO Shuangshuang1, WANG Xiangxiang1 and CHEN Shifu1* 1. College of Chemistry and Materials Science, Huaibei Normal University, Huaibei 235000, P. R. China; 2. State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350116, P. R. China; 3. College of Chemistry and Material Engineering, Anhui Science and Technology University, Fengyang 233100, P. R. China Abstract Z-Scheme photocatalysts as a research focus perform strong redox capability and high photocatalytic performance. WO3/KNbO3 photocatalysts were fabricated by ball milling method, and performed higher photocatalytic activity in liquid degradation(rhodamine B, methylene blue and bisphenol A), compared with WO 3 or KNbO3 monomer. This is due to that Z-scheme heterojunction is formed between WO3 and KNbO3, and the holes photoexcited in valence band of KNbO 3 are quickly combined with the electrons in conduction band of WO 3. The electrons accumulated in conduction band of KNbO 3 show high reducibility, thereby reducing O 2 to •O2−, and the holes in valence band of WO3 show high oxidative to oxidize H 2O to •OH, respectively. Furthermore, it is proved by means of electron spin resonance(ESR) spectra, terephthalic acid photoluminescence probing technique(TA-PL), and UV-Vis absorption spectra of nitroblue tetrazolium. This work indicates that the fabrication of Z-scheme structure can improve the photocatalytic activity by efficiently separating the photogenerated electrons and holes in the photocatalytic reaction system, which is helpful to deeply understand the migration mechanism of photoexcited carrier(band-band transfer and Z-scheme transfer) in heterojunction photocatalysts. Keywords WO3/KNbO3; Z-Scheme; Photogenerated electron and hole; Photocatalytic degradation; Active species
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Introduction
Organic pollution caused by urban industrialization is now a common environmental problem, and many technologies have been developed to deal with this issue. Photocatalytic technology is an efficient, inexpensive and environmentally friendly method to protect the environment[1—4]. In the past few decades, various semiconductor photocatalysts, such as metal oxides[5—7], nitrides[8—10] and sulfides[11—13], have been studied to improve the photocatalytic activity. However, they are limited by the rapid recombination of photoinduced electronhole pairs, preventing their widespread application. To overcome this difficulty, researches in recent years have focused on the preparation of composite catalytic materials with various heterostructures[14,15], and the formation of heterojunctions through band-gap matching recombination can effectively improve the charge carrier transfer and separation[16,17]. At present, heterojunction composite photocatalysts have been widely prepared. Scientists have even dedicated themselves to
studying the reason why t
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