Regulating asymmetric oxygen vacancies in copper-ceria catalysts for achievement of excellent toluene catalytic oxidation

Regulation of oxygen vacancy upon metal oxide catalysts is an effective strategy for improving the catalytic activity in the oxidation of volatile organic compounds. Herein, copper (Cu) ions were introduced into ceria (CeO2) catalysts via the modulation of preparation methods (ball-milling, co-precipitation and sol-gel method) to generate asymmetric oxygen vacancies (AOVs) with varying concentrations at the Cu-CeO2 interface, thereby enhancing the catalytic performance towards toluene. The presence of abundant AOVs promotes the rapid conversion of the redox couples of Ce4+/Ce3+ and Cu+/Cu2+ according to Cu+-OV-Ce3+ ↔ Cu2+-O(ad)2--Ce4+, enhancing the redox property and lattice oxygen mobility of the catalyst synthesized by ball-milling strategy (BM-CuCe). Moreover, the AOVs expedite the backfilling and activation of gaseous oxygen, leading to a transformation of rate-determining steps into the cracking of aromatic rings, significantly improving the catalytic activity towards toluene. The BM-CuCe catalyst, with the highest AOVs concentration, exhibits the excellent catalytic activity, water-resistance capability as well as stability. This work sheds light on the promoting effect of AOVs in the catalytic oxidation of toluene and contributes an attractive strategy for designing highly efficient metal oxide catalysts.