Enhancement effects of surface and bulk oxygen vacancies on the photocatalytic properties of ceria

Abstract

Ceria is a widely known photocatalyst, to clearly understand the effects of oxygen vacancies (OVs) distribution on photocatalytic performance of ceria, surface and bulk OVs have been introduced in ceria nanorods and nanopolyhedrons. According to H2-TPR, XPS, Raman, and EPR results, P-800 (ceria nanopolyhedrons calcined at 800 °C) and R-800 (ceria nanorods calcined at 800 °C) had surface and bulk OVs and a larger OV concentration than P-500 (ceria nanopolyhedrons calcined at 500 °C) and R-500 (ceria nanorods calcined at 500 °C) which just had surface OVs, respectively. The former showed a clearly enhanced photocatalytic activity toward methylene blue (MB) and tetracycline (TC) degradation compared with the latter. After introducing surface and bulk OVs, the generated defect states in Ce 4f, metallization of ceria, and lower energy shifted density of states (DOS) co-promoted the separation of photo-excited e−/h+, which may mainly contribute to the enhancement of photocatalytic performance of P-800 and R-800. R-800 had the major active species of ·O2−/h+ to photodegrade TC, which was different from R-500 of e−/h+, due to the more negative ECB and more absorbed O2 for R-800. The synergistic effects of surface and bulk OVs were more significant for ceria nanorods than nanopolyhedrons, which may be due to the exposed facet of (110).