Wu Zhizhou, Li Liuyang, Zhou Xuedong, Parkin Ivan P, Zhao Xiujian, Liu Baoshun
State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan City, Hubei Province, China.
Department of Chemistry, Materials Chemistry Centre, University College London, London, WC1H 0AJ, UK.
Phys Chem Chem Phys. 2022 Mar 2;24(9):5618-5626. doi: 10.1039/d1cp04941k.
Pristine TiO materials are mainly used as photocatalysts under super-bandgap light illumination. The sub-bandgap (SBG) photocatalytic response has seldom been investigated and the mechanism of action remains unclear. In the current research, we firstly study the SBG light electronic transition of pristine P25 TiO by means of diffusion reflectance and (photo)conductance measurements under finely controllable conditions. It is revealed that the SBG light can promote valence band (VB) electrons to the exponentially-distributed gap states of the TiO, which can then be thermally activated to the CB states. A hole in the VB and an electron in the CB can be generated by the synergism of a SBG photon and heat. It is also seen that the photoinduced electrons can transfer to O through the CB states, and that the holes can be captured by isopropanol molecules. As a result, isopropanol dehydrogenation can occur over pristine TiO under SBG light illumination. It is seen that the photocatalytic activity increases with temperature and the energy of the SBG photons, in agreement with the light-heat synergistic electric transition the exponential gap states. The present research reveals a mechanism for the SBG light photocatalytic response of pristine TiO materials, which is important in designing highly-active visible light active photocatalysts.
纯净的二氧化钛材料主要用作超带隙光照射下的光催化剂。亚带隙（SBG）光催化响应很少被研究，其作用机制仍不清楚。在当前研究中，我们首先通过在精细可控条件下的漫反射和（光）电导测量来研究纯净P25二氧化钛的亚带隙光电子跃迁。结果表明，亚带隙光可将价带（VB）电子激发到二氧化钛的指数分布带隙态，然后这些电子可被热激活到导带（CB）态。一个亚带隙光子和热的协同作用可在价带产生一个空穴，在导带产生一个电子。还可以看到，光生电子可通过导带态转移到氧，空穴可被异丙醇分子捕获。因此，在亚带隙光照射下，纯净的二氧化钛上可发生异丙醇脱氢反应。可以看出，光催化活性随温度和亚带隙光子能量的增加而增加，这与光热协同电子跃迁到指数带隙态一致。本研究揭示了纯净二氧化钛材料亚带隙光催化响应的机制，这对设计高活性可见光活性光催化剂具有重要意义。
