Understanding the High Photocatalytic Activity of (B, Ag)-Codoped TiO2 under Solar-Light Irradiation with XPS, Solid-State NMR, and DFT Calculations
Understanding the High Photocatalytic Activity of (B, Ag)-Codoped TiO2 under Solar-Light Irradiation with XPS, Solid-State NMR, and DFT Calculations
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利用 XPS、固态 NMR 和 DFT 计算了解太阳光照射下 (B, Ag) 共掺杂 TiO2 的高光催化活性
DOI：
10.1021/ja312205c
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发表时间：
2013-01-30
影响因子：
15
通讯作者：
Deng, Feng
中科院分区：
文献类型：
--
作者：
Feng, Ningdong;Wang, Qiang;Deng, Feng
用XPS和B-11固体核磁共振谱结合密度泛函理论(DFT)研究了(B，Ag)共掺杂的TiO2光催化剂在太阳光照射下活性异常高的原因。XPS实验结果表明，部分掺杂的Ag(Ag3+)离子被注入到(B，Ag)共掺杂的二氧化钛晶格中，并靠近间隙B(B-Int)位，形成了[B-Int-O-Ag]结构单元。利用原位XPS实验跟踪了B和Ag掺杂在UV-Vis辐照过程中化学态的变化。研究发现，在光照过程中，[B-Int-O-Ag]单元可以俘获(B，Ag)共掺的TiO2光诱导电子形成独特的中间结构，这是原位XPS光谱中观察到的Bis和Ag3d峰发生光致位移的原因。包括B-11三量子和双量子幻角旋转(MAS)在内的固体核磁共振实验表明，催化剂中存在多达6种不同的硼物种，只有三配位的间隙硼(T*)物种与取代银物种密切相关，导致形成[T*-O-Ag]结构单元。此外，DFT计算表明，[T*-O-Ag]结构单元负责捕获光生电子，延长了光生载流子的寿命，最终导致光催化活性的显著提高。所有这些史无前例的发现对于理解B和Ag掺杂剂在二氧化钛介导光催化反应中的作用及其协同效应具有重要意义。
The origin of the exceptionally high activity of (B, Ag)-codoped TiO2 catalysts under solar-light irradiation has been investigated by XPS and B-11 solid-state NMR spectroscopy in conjunction with density functional theory (DFT) calculations. XPS experimental results demonstrated that a portion of the dopant Ag (Ag3+) ions were implanted into the crystalline lattice of (B, Ag)-codoped TiO2 and were in close proximity to the interstitial B (B-int) sites, forming [B-int-O-Ag] structural units. In situ XPS experiments were employed to follow the evolution of the chemical states of the B and Ag dopants during UV-vis irradiation. It was found that the [B-int-O-Ag] units could trap the photoinduced electron to form a unique intermediate structure in the (B, Ag)-codoped TiO2 during the irradiation, which is responsible for the photoinduced shifts of the B Is and Ag 3d peaks observed in the in situ XPS spectra. Solid-state NMR experiments including B-11 triple-quantum and double-quantum magic angle spinning (MAS) NMR revealed that up to six different boron species were present in the catalysts and only the tricoordinated interstitial boron (T*) species was in close proximity to the substitutional Ag species, leading to formation of [T*-O-Ag] structural units. Furthermore, as demonstrated by DFT calculations, the [T*-O-Ag] structural units were responsible for trapping the photoinduced electrons, which prolongs the life of the photoinduced charge carriers and eventually leads to a remarkable enhancement in the photocatalytic activity. All these unprecedented findings are expected to be crucial for understanding the roles of B and Ag dopants and their synergistic effect in numerous titania-mediated photocatalytic reactions.