Effect of Morphology-Dependent Oxygen Vacancies of CeO₂ on the Catalytic Oxidation of Toluene

Catalytic oxidation is regarded as an effective, economical, and practical approach to remove volatile organic compounds such as important air pollutants. CeO₂ catalysts with different morphologies exhibit different oxygen vacancies content, which plays a vital role in oxidation reaction. Herein, three distinct morphologies of CeO₂ i.e., shuttle (CeO₂ (S)), nanorod (CeO₂ (R)), and nanoparticle (CeO₂ (P)), were successfully fabricated by the SEM and TEM results, and investigated for toluene catalytic oxidation. The various characterizations showed that the CeO₂ (S) catalyst exhibited a larger surface area along with higher surface oxygen vacancies in contrast to CeO₂ (R) and CeO₂ (P), which is responsible for its excellent toluene catalytic oxidation. The 90% toluene conversion temperature at 225 °C over CeO₂ (S) was less than that over CeO₂ (R) (283 °C) and CeO₂ (P) (360 °C). In addition, CeO₂ (S) showed a greater reaction rate (14.37 × 10⁻² μmol∙g⁻¹∙s⁻¹), TOF_ov (4.8 × 10⁻⁴∙s⁻¹) at 190 °C and lower activation energy value (67.4 kJ/mol). Furthermore, the CeO₂ (S) also displayed good recyclability, long-term activity stability, and good tolerance to water. As a result, CeO₂ (S) is considered a good candidate to remove toluene.