Engineering robust oxygen vacancies towards efficient toluene purification: coupling crystal facets with Mn–Ce solid solution

Abstract

Introducing oxygen vacancy defects into catalysts is considered an effective method for enhancing their functionality, although there is still room for improvement. This study proposes a novel atmospheric pressure strategy that effectively coupled the crystal surface effect with the solid solution structure, producing CeMn catalysts with abundant defects and outstanding toluene purification properties. Comprehensive characterization shows that the abundant MnCe solid solution formed in the 3Ce1Mn catalysts significantly increased the concentration of oxygen vacancies, leading to an increase in reactive oxygen species and enhanced oxygen mobility. In addition, the highly active crystalline facets (200) exposed by 3Ce1Mn are integrated with the solid solution structure to optimize electron transfer across Ce–Mn, increase the number of active centers, and improve low-temperature reducibility, resulting in a 3Ce1Mn catalyst with excellent catalytic performance (T₉₀ = 195 °C), outstanding stability, and good water resistance (60 h and 10 vol%). Theoretical calculations using the DFT method also demonstrate a beneficial impact of the oxygen defect structure in 3Ce1Mn on the adsorption and activation of toluene and oxygen molecules. In situ DRIFTS studies demonstrated that the decomposition pathway of 3Ce1Mn to toluene is optimized, proceeding via toluene → benzyl alcohol → benzaldehyde → benzoic acid → maleic anhydride → CO₂ and H₂O, in which the accumulation of these intermediates is extremely low. The present study presents a novel approach for designing catalysts with defect structures involving the solid-solution structure and crystalline facets.