Significant photocatalytic performance enhancement of TiO2 by CeO2 atomic layer deposition.

Different cycles (10-80) of CeO2 were coated on TiO2 nanoparticles by atomic layer deposition (ALD) using tris(i-propylcyclopentadienyl)cerium and de-ionized water as precursors at 250 °C in a fluidized bed reactor. X-ray diffraction analysis showed that TiO2 kept anatase structure after CeO2 ALD. With an increase in the number of ALD coating cycles, both photoluminescence intensity and band gap of the samples continuously decreased. The photocatalytic activity was evaluated based on the degradation of methylene blue (MB) solution under UV light. The photocatalysis experiment demonstrated that 40 cycles of CeO2 deposited TiO2 sample (40Ce/TiO2) showed the highest photocatalytic activity and had a more than three-fold activity enhancement over uncoated TiO2 for the degradation of MB. The enhanced photocatalytic activity was attributed to the fact that CeO2 played a role as e-/h+ pair trap centers and consequently reduced e-/h+ pair recombination rate.