Dependence of crystal facets and ceria modification on toluene oxidation for Co3O4 catalyst

Co3O4-based catalysts have exhibited significant potential in the catalytic elimination of volatile organic compounds (VOCs). Given that crystal planes play a crucial role in the oxidation of VOCs, it is essential to consider crystal facet engineering during catalyst development. In this study, a CeO2/Co3O4 catalyst was developed for oxidizing toluene, with specific emphasis on the preferentially exposed crystal facets of Co3O4 and CeO2 modification. A 5%CeO2 doped Co3O4 catalyst with preferentially exposed (1 1 1) crystallographic planes exhibited an excellent activity, achieving a high toluene conversion rate of 90% at 223 degrees C with an activation energy (Ea) of 64.55 kJ/mol under a weight hourly space velocity (WHSV) of 30,000 mL & sdot;g- 1 & sdot;h- 1 and 1000 ppm toluene injection. Moreover, the catalyst showed a durable stability in the presence of 2 vol% vapour or under a high WHSV of 60,000 mL & sdot;g- 1 & sdot;h- 1. All characterizations suggested that the catalytic performance of Co3O4 was significantly dependent on the exposed crystal facets. The enhanced interaction between CeO2 and Co3O4(111) led to the generation of more active sites and/or species, including chemical active oxygens, Co3+ and Ce3+. All of these contributed to superior oxidation capability and versatile reducibility for activating oxygen and oxidizing toluene. Additionally, the transformation of benzoic acid to maleic anhydride was enhanced after loading 5%CeO2 onto Co3O4(111), leading to complete degradation of toluene. Therefore, the study highlights the significance of Co3O4 crystal facets during developing the novel Co3O4-based catalysts for VOCs oxidation.