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Ag as Cocatalyst and Electron-Hole Medium in CeO2 QDs/Ag/Ag2Se Z-scheme Heterojunction Enhanced the Photo-Electrocatalytic Properties of the Photoelectrode

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College of Science, Donghua University, Shanghai 201620, China
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Department of Physics, Department of Materials Science and Engineering, and Department of Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong 999077, China
*
Authors to whom correspondence should be addressed.
Nanomaterials 2020, 10(2), 253; https://doi.org/10.3390/nano10020253
Received: 9 January 2020 / Revised: 25 January 2020 / Accepted: 27 January 2020 / Published: 31 January 2020
(This article belongs to the Section Energy and Catalysis)
A recyclable photoelectrode with high degradation capability for organic pollutants is crucial for environmental protection and, in this work, a novel CeO2 quantum dot (QDs)/Ag2Se Z-scheme photoelectrode boasting increased visible light absorption and fast separation and transfer of photo-induced carriers is prepared and demonstrated. A higher voltage increases the photocurrent and 95.8% of tetracycline (TC) is degraded by 10% CeO2 QDs/Ag2Se in 75 minutes. The degradation rate is superior to that achieved by photocatalysis (92.3% of TC in 90 min) or electrocatalysis (27.7% of TC in 90 min). Oxygen vacancies on the CeO2 QDs advance the separation and transfer of photogenerated carriers at the interfacial region. Free radical capture tests demonstrate that •O2, •OH, and h+ are the principal active substances and, by also considering the bandgaps of CeO2 QDs and Ag2Se, the photocatalytic mechanism of CeO2 QDs/Ag2Se abides by the Z-scheme rather than the traditional heterojunction scheme. A small amount of metallic Ag formed in the photocatalysis process can form a high-speed charge transfer nano channel, which can greatly inhibit the photogenerated carrier recombination, improve the photocatalytic performance, and help form a steady Z-scheme photocatalysis system. This study would lay a foundation for the design of a Z-scheme solar photocatalytic system. View Full-Text
Keywords: CeO2 quantum dots; Ag2Se nanoflowers; Z-scheme; cocatalyst; photo-electrocatalysis CeO2 quantum dots; Ag2Se nanoflowers; Z-scheme; cocatalyst; photo-electrocatalysis
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MDPI and ACS Style

Li, L.; Feng, H.; Wei, X.; Jiang, K.; Xue, S.; Chu, P.K. Ag as Cocatalyst and Electron-Hole Medium in CeO2 QDs/Ag/Ag2Se Z-scheme Heterojunction Enhanced the Photo-Electrocatalytic Properties of the Photoelectrode. Nanomaterials 2020, 10, 253.

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