Engineering asymmetric oxygen vacancies in binary manganese oxides: A strategic approach to boost catalytic oxidation of toluene

In this paper, the effect of asymmetric oxygen vacancies (AOv) on the catalytic oxidation of toluene in Ce, Sm and Y doped binary manganese-based catalysts was investigated. Structural characterization revealed that the introduction of Ce, Sm and Y can effectively generate special AOv, and different types of AOv can improve the catalytic activity and selectivity of the catalyst for toluene oxidation. The AOv formed due to the different ionic radii and electronegativity of the dopants exhibit asymmetric ligand active sites. Among the elements involved, Ce ions, because of their distinct electronegativity, have a stronger tendency to attract oxygen ions within the Mn-O-Ce structure. This interaction weakens the Mn-O bond strength, thereby facilitating the redox reaction of toluene. The activity results showed that the CeMn catalyst doped by Ce had stronger toluene oxidation activity and stability, with the Turnover frequency (TOF) activity of 22.14 x 10- 6 & sdot;s- 1, which is 7.69 times higher compared with the TOF of the pristine delta-Mn. The CeMn catalyst maintained stable catalytic performance during 48 h of continuous testing. In situ DRIFTS demonstrates that the cleavage of benzoic acid during the reaction is the rate-controlling step of the reaction. This work provides insights into the role of AOv in catalytic oxidation and contributes to the rational design of efficient catalysts for environmental applications.