Long-lived photogenerated charge carriers of 001-facet-exposed TiO2 with enhanced thermal stability as an efficient photocatalyst

摘要

The thermal stability of the (001) facet-exposed nanocrystalline TiO2 with high photocatalytic activity is often neglected although it is generally needed to be subjected to certain high-temperature treatment for applications. Herein, it is found that the (0 01) facet exposure percentage of nanocrystalline anatase TiO2 could be decreased from 71 % to 25% when the thermal treatment temperature is raised from 100 to 500 °C. Interestingly, its thermal stability is greatly enhanced after phosphate modification, even slightly changed for the 001-facet-exposed percentage (67%) after thermal treatment at 650 °C. It is suggested for the first time that the enhanced thermal stability mainly depends on the modified phosphate groups with high thermal stability binding strongly to the exposed 001 facet of TiO2. More important, it is confirmed that the enhanced thermal stability greatly prolongs lifetime and promotes separation of photogenerated charge carriers of 001-facet-exposed TiO2 mainly by means of time-resolved surface photovoltage responses, leading to the obviously improved photocatalytic activity for degrading liquid-phase phenol and gas-phase acetaldehyde. This is attributed to the synergetic effects of high-percentage 001 -facet exposure, high anatase crystallinity, and strong ability to adsorb O2.