Engineering Cobalt Oxide with Coexisting Cobalt Defects and Oxygen Vacancies for Enhanced Catalytic Oxidation of Toluene

Most research studies reported that oxygen vacancies on transition metal oxides are crucial for improving the catalytic oxidation activities. However, few studies investigated the coexistence effect of metal defects and oxygen vacancies on the performances and mechanisms of catalysts. Herein, we present a facile approach for synthesizing a Co3–xO4–y catalyst with both cobalt defects and oxygen vacancies simultaneously, exhibiting significant thermo-/photothermo-catalytic performance for toluene oxidation (300 ppm, GHSV = 72,000 mL g–1 h–1) with over 90% toluene conversion in 10 min of light illumination (with a corresponding light-to-heat conversion temperature of ∼180 °C). Furthermore, the synchrotron radiation X-ray absorption spectroscopy, O2 temperature-programmed desorption, and density functional theory calculations demonstrate that cobalt defects are conducive to the formation of oxygen vacancies. In situ DRIFTS studies reveal that the as-formed surface-reactive oxygen species can be replenished continuously during the reaction progress, and the coexisting oxygen vacancies can accelerate the conversion of intermediates, thereby promoting the toluene degradation.