Tuning Oxygen Vacancies of the Co3O4 Catalyst through an Ethanol-Assisted Hydrothermal Method for Low-Temperature CO Oxidation

Co3O4 is considered to be the most promising catalyst for CO oxidation due to its superior activity and low cost. Oxygen vacancies can improve the low-temperature catalytic activity due to their ability to activate oxygen. In this work, Co3O4-xET samples with different oxygen vacancies are synthesized through an ethanol-assisted hydrothermal method and applied to low-temperature CO oxidation. The catalytic activity and stability of the Co3O4 catalyst could be significantly improved with the increase of ethanol concentration and display a "volcanic" curve. The Co3O4-50ET catalyst displays the best catalytic performance with the complete oxidation of CO at 110 °C and excellent stability. With Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), O2 temperature-programmed desorption (TPD), in situ diffuse reflectance infrared spectroscopy (DRIFTS), and other characterization methods, the relationship between surface oxygen vacancies and catalytic properties is studied. It can be found that the ethanol reduction process could promote the redox performance and oxygen migration ability and increase the oxygen vacancies of the Co3O4 catalyst.