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Investigation of Electron Behavior in Nano‐TiO 2 Photocatalysis by Using In Situ Open‐Circuit Voltage and Photoconductivity Measurements
Author(s) -
Liu Baoshun,
Wang Xuelei,
Wen Liping,
Zhao Xiujian
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201300243
Subject(s) - photocatalysis , materials science , methanol , electron , photochemistry , fermi level , photoconductivity , chemistry , analytical chemistry (journal) , atomic physics , optoelectronics , catalysis , physics , organic chemistry , quantum mechanics
The in situ open‐circuit voltages ( V oc ) and the in situ photoconductivities have been measured to study electron behavior in photocatalysis and its effect on the photocatalytic oxidation of methanol. It was observed that electron injection to the conduction band (CB) of TiO 2 under light illumination during photocatalysis includes two sources: from the valence band (VB) of TiO 2 and from the methanol molecule. The electron injection from methanol to TiO 2 is slower than that directly from the VB, which indicates that the adsorption mode of methanol on the TiO 2 surface can change between dark and illuminated states. The electron injection from methanol to the CB of TiO 2 leads to the upshift of the Fermi level of electrons in TiO 2 , which is the thermodynamic driving force of photocatalytic oxidation. It was also found that the charge state of nano‐TiO 2 is continuously changing during photocatalysis as electrons are injected from methanol to TiO 2 . Combined with the apparent Langmuir–Hinshelwood kinetic model, the relation between photocatalytic kinetics and electrons in the TiO 2 CB was developed and verified experimentally. The photocatalytic rate constant is the variation of the Fermi level with time, based on which a new method was developed to calculate the photocatalytic kinetic rate constant by monitoring the change of V oc with time during photocatalysis.