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A light-heat synergism in the sub-bandgap photocatalytic response of pristine TiO2: a study of in situ diffusion reflectance and conductance

Wu, Zhizhou; Li, Liuyang; Zhou, Xuedong; Parkin, Ivan P; Zhao, Xiujian; Liu, Baoshun; (2022) A light-heat synergism in the sub-bandgap photocatalytic response of pristine TiO2: a study of in situ diffusion reflectance and conductance. Physical Chemistry Chemical Physics , 24 (9) pp. 5618-5626. 10.1039/d1cp04941k. Green open access

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Abstract

Pristine TiO2 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 TiO2 by means of in situ 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 TiO2, 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 O2 through the CB states, and that the holes can be captured by isopropanol molecules. As a result, isopropanol dehydrogenation can occur over pristine TiO2 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 via the exponential gap states. The present research reveals a mechanism for the SBG light photocatalytic response of pristine TiO2 materials, which is important in designing highly-active visible light active photocatalysts.

Type: Article
Title: A light-heat synergism in the sub-bandgap photocatalytic response of pristine TiO2: a study of in situ diffusion reflectance and conductance
Location: England
Open access status: An open access version is available from UCL Discovery
DOI: 10.1039/d1cp04941k
Publisher version: https://doi.org/10.1039/D1CP04941K
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10146524
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