Uncovering the Key Role of the Fermi Level of the Electron Mediator in a Z-Scheme Photocatalyst by Detecting the Charge Transfer Process of WO3-metal-gC3N4 (Metal = Cu, Ag, Au)

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• 作者：Houfen Li ; Hongtao Yu ; Xie Quan ; Shuo Chen ; Yaobin Zhang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：January 27, 2016
• 年：2016
• 卷：8
• 期：3
• 页码：2111-2119
• 全文大小：559K
• ISSN：1944-8252

文摘

Z-scheme photocatalytic system shows superiority in degradation of refractory pollutants and water splitting due to the high redox capacities caused by its unique charge transfer behaviors. As a key component of Z-scheme system, the electron mediator plays an important role in charge carrier migration. According to the energy band theory, we believe the interfacial energy band bendings facilitate the electron transfer via Z-scheme mechanism when the Fermi level of electron mediator is between the Fermi levels of Photosystem II (PS II) and Photosystem I (PS I), whereas charge transfer is inhibited in other cases as energy band barriers would form at the semiconductor-metal interfaces. Here, this inference was verified by the increased hydroxyl radical generation and improved photocurrent on WO₃-Cu-gC₃N₄ (with the desired Fermi level structure), which were not observed on either WO₃-Ag-gC₃N₄ or WO₃-Au-gC₃N₄. Finally, photocatalytic degradation rate of 4-nonylphenol on WO₃-Cu-gC₃N₄ was proved to be as high as 11.6 times than that of WO₃-gC₃N₄, further demonstrating the necessity of a suitable electron mediator in Z-scheme system. This study provides scientific basis for rational construction of Z-scheme photocatalytic system.