Acid-etched spinel CoMn2O4 with highly active surface lattice oxygen species for significant improvement of catalytic performance of VOCs oxidation

The strategy of acid-etching was applied to improve the catalytic activity of spinel CoMn2O4, and 0.06 M (acid etching concentration) catalyst exhibited a nearly 16-fold increase in toluene reaction rate at 210 °C compared with pristine catalyst. The crystal, nanosphere and mesoporous structures of 0.06 M catalyst were not damaged significantly. And importantly, the presence of rich oxygen vacancies weakened the metal-oxygen bond strength and improved the mobility of surface lattice oxygen species to enhance the catalytic performance. The active surface lattice oxygen reacted directly with toluene over 0.06 M catalyst, which was significantly different with that the bulk lattice oxygen had to migrate to the surface for toluene oxidation over the pristine catalyst. Meanwhile, the formation and consumption rates of intermediates were significantly accelerated over 0.06 M catalyst with abundant oxygen vacancies. This work provides vital experimental proof for understanding the relationship between the oxygen vacancies and lattice oxygen species participating in toluene oxidation.