TiO(2) nanocrystals with tunable bulk/surface defects were synthesized and characterized with TEM, XRD, BET, positron annihilation, and photocurrent measurements. The effect of defects on photocatalytic activity was studied. It was found for the first time that decreasing the relative concentration ratio of bulk defects to surface defects in TiO(2) nanocrystals could significantly improve the separation efficiency of photogenerated electrons and holes, thus significantly enhancing the photocatalytic efficiency.

The mesoporous nanorod-like ceria with high BET surface area of 121 m2/g is prepared by a facile method, microwave-assisted hydrolysis of Ce(NO3)3·6H2O in presence of urea. As compared to bulk ceria, its absorption edge significantly shifts to the visible region with a band gap of as low as 2.75 eV due to the presence of Ce3+. A novel strategy of significantly improving its photocatalytic efficiency is developed by coupling oxygen ion conduction to photocatalysis in the mesoporous nanorod-like ceria, in which UV–visible photons and thermal energy from a Hg lamp were integrated. Under such photothermocatalytic oxidation conditions, the mesoporous nanorod-like ceria exhibits much higher photothermocatalytic activity for the gas-phase minerlization of organic contaminants than corresponding alone thermocatalytic and photocatalytic activity and good photothermocatalytic stability. The significantly enhanced mobility of oxygen ions with increasing temperature raised by thermal energy from the Hg lamp greatly improves the separation efficiency of photogenerated electrons and holes by UV–vis photons in the mesoporous nanorod-like ceria. Moreover, the hole-trapped lattice oxygen ion generated by UV–vis irradiation is more active than the lattice oxygen ion for benzene oxidation. These beneficial effects promote catalytic efficiency for gas-phase purification of organic contaminants such as benzene, hexane, and actone.

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