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.