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)
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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通过检测WO3-金属-gC(3)N(4)（金属= Cu、Ag、Au）的电荷转移过程揭示Z型光催化剂中电子介体费米能级的关键作用
DOI：
10.1021/acsami.5b10613
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发表时间：
2016-01-27
影响因子：
9.5
通讯作者：
Zhang, Yaobin
中科院分区：
文献类型：
--
作者：
Li, Houfen;Yu, Hongtao;Zhang, Yaobin
Z型光催化体系因其独特的电荷转移行为而具有较高的氧化还原能力，在降解难降解污染物和分解水方面显示出优越性。电子介体作为Z-体系的关键组分，在载流子迁移过程中起着重要的作用。根据能带理论，我们认为当电子介体的费米能级介于光系统II（PS II）和光系统I（PS I）的费米能级之间时，界面能带弯曲通过Z-模式机制促进电子转移，而在其它情况下，由于电子介体-金属界面处会形成能带势垒，电荷转移受到抑制。在此，通过在WO 3-Cu-gC（3）N（4）（具有期望的费米能级结构）上增加的羟基自由基产生和改善的光电流验证了该推断，这在WO 3-Ag-gC（3）N（4）或WO 3-Cu-gC（3）N（4）上均未观察到。最后，对壬基酚的光催化降解率在WO 3-Cu-gC（3）N（4）上达到了WO 3-gC（3）N（4）的11.6倍，进一步证明了在Z-体系中需要合适的电子介体。该研究为Z型光催化体系的合理构建提供了科学依据。
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-gC(3)N(4) (with the desired Fermi level structure), which were not observed on either WO3-Ag-gC(3)N(4) or WO3-Cu-gC(3)N(4). Finally, photocatalytic degradation rate of 4-nonylphenoI on WO3-Cu-gC(3)N(4) was proved to be as high as 11.6 times than that of WO3-gC(3)N(4), 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.