Length effect of ceria nanorod on its oxygen vacancy formation and photocatalytic property

Ceria nanorods (NRs) with an average length of 23, 73, 115, 131, and 192 nm were synthesized separately by a facile hydrothermal method and then were roasted at 600 degrees C in air, 50% H-2, and pure H-2 to generate various concentrations of surface oxygen vacancies (OVs). OVs concentration in ceria lattice is firstly increasing and then trends to decrease with the rising of ceria NRs length, while the band gap of ceria NRs expands with length increasing and slightly widens with the elevation of surface OVs concentration. Separation efficiency of photo-excited electrons/holes (e(-)/h(+)) and photodegradation ratio of methylene blue (MB) with ceria NRs elevate firstly and then decrease with the length increasing, while the generated OVs promote the photocatalytic activity of ceria. The ceria NRs with an average length of 115 nm and calcined in hydrogen show a better photocatalytic activity with the MB degradation ratio of 86.32%.