Optimal RE (RE = La, Y and Sm) doping conditions and the enhanced mechanism for photocatalytic application of ceria nanorods.

Morphology tuning or additional cations doping is one of the potential and simple methods to enhance the photocatalytic property of ceria, in which rare-earth elements doped ceria nanorods (CeO2-RE NRs) are expected to be a promising photocatalyst with high activity. But the optimal doping conditions including variety and concentration of RE elements are ambiguity, and the contribution of doped RE ions on the enhancement of photocatalytic activity needs to be further concerned either. In this work, we doped La, Y and Sm with a wide range of 0 - 30 % into CeO2 NRs, and investigated the phase, morphology, band gap, oxygen vacancies concentration, PL spectra and photocatalytic activity variation under different doping conditions. All synthesized CeO2-RE NRs own well-shaped nanorod morphology except the 15 and 30 % Y doped samples. The energy band gaps of synthesized samples change slightly, the 10 % of CeO2-RE NRs with the narrowest band gaps own the higher photocatalytic performance. The most outstanding photocatalyst is found as the 10 % Y doped CeO2 NRs with the methylene blue photodegradation ratio of 85.59 % and the rate constant of 0.0134 min-1, which is particularly associated with a significant higher oxygen vacancies concentration and obviously lower recombination rate of photogenerated e-/h+ pairs. The doped RE ions and the promoting oxygen vacancies generation impede the recombination of photogenerated carrier, which is proposed as the main reason to enhance the photocatalytic property of CeO2.