Chinese Journal of Catalysis ›› 2016, Vol. 37 ›› Issue (12): 2059-2068.DOI: 10.1016/S1872-2067(16)62574-3

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Time-resolved photoluminescence of anatase/rutile TiO2 phase junction revealing charge separation dynamics

Xiuli Wang, Shuai Shen, Zhaochi Feng, Can Li   

  1. State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
  • Received:2016-09-12 Revised:2016-10-15 Online:2016-12-27 Published:2016-12-27
  • Contact: Can Li
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21203185, 21373209) and the National Basic Research Program of China (2014CB239400).

Abstract:

Junctions are an important structure that allows charge separation in solar cells and photocatalysts. Here, we studied the charge transfer at an anatase/rutile TiO2 phase junction using time-resolved photoluminescence spectroscopy. Visible (~500 nm) and near-infrared (NIR,~830 nm) emissions were monitored to give insight into the photoinduced charges of anatase and rutile in the junction, respectively. New fast photoluminescence decay components appeared in the visible emission of rutile-phase dominated TiO2 and in the NIR emission of many mixed phase TiO2 samples. The fast decays confirmed that the charge separation occurred at the phase junction. The visible emission intensity from the mixed phase TiO2 increased, revealing that charge transfer from rutile to anatase was the main pathway. The charge separation slowed the microsecond time scale photoluminescence decay rate for charge carriers in both anatase and rutile. However, the millisecond decay of the charge carriers in anatase TiO2 was accelerated, while there was almost no change in the charge carrier dynamics of rutile TiO2. Thus, charge separation at the anatase/rutile phase junction caused an increase in the charge carrier concentration on a microsecond time scale, because of slower electron-hole recombination. The enhanced photocatalytic activity previously observed at anatase/rutile phase junctions is likely caused by the improved charge carrier dynamics we report here. These findings may contribute to the development of improved photocatalytic materials.

Key words: Titanium dioxide (TiO2), Anatase/rutile phase junction, Charge separation, Charge recombination, Time-resolved photoluminescence