Combined experimental and theoretical study of o-xylene elimination on Fe-Mn oxides catalysts

What is the role of interface in the catalytic elimination of multi-carbon air pollutants?

Multi-carbon air pollutants pose serious hazards to the environment and health, especially soot and volatile organic compounds (VOCs). Catalytic oxidation is one of the most effective technologies for eliminating them. The oxidation of soot and most hydrocarbon VOCs begins with C-H (or edge-CH) activation, so this commonality can be targeted to design active sites. Rationally designed interface nanostructures optimize metal-support interactions (MSIs), providing suitable active sites for C-H activation. Meanwhile, the interfacial reactant spillover facilitates the further decomposition of activated intermediates. Thus, rationally exploiting interfacial effects is critical to enhancing catalytic activity. In this review, we analyzed recent advances in the following aspects: I. Understanding of the interface effects and design; II. Optimization of the catalyst-reactant contact, metal-support interface, and MSIs; III. Design of the interfacial composition and perimeter. Based on the analysis of the advances and current status, we provided challenges and opportunities for the rational design of interface nanostructures and interface-related stability. Meanwhile, a critical outlook was given on the interfacial sites of single-atom catalysts (SACs) for specific activation and catalytic selectivity.

Roles of Oxygen Species in Low-Temperature Catalytic o-Xylene Oxidation on MOF-Derived Bouquetlike CeO2

To realize efficient low-temperature catalytic o-xylene oxidation, MOF-derived CeO₂-X catalysts were prepared via the pyrolysis of MOF precursors with different ratios of cerium nitrate to trimesic acid. Among the synthesized catalysts, the bouquet like CeO₂-1 exhibited the best activity with T₅₀ and T₉₀ of 156 and 198 °C and the lowest activation energy of 60.67 kJ·mol^-1 (WHSV= 48 000 mL·g^-1·h^-1, o-xylene concentration = 500 ppm). o-Xylene was completely mineralized, and no change in conversion efficiency or CO₂ yield was found at 5 vol % H₂O for over 50 h. The rich active oxygen species (XPS: O_sur/O_latt = 0.69) and abundant oxygen vacancies (Raman: I_D/I_F2g = 0.036) of CeO₂-1 made crucial contribution to its superior catalytic activity. The O₂-TPD and H₂-TPR results confirmed that CeO₂-1 had more surface active oxygen and better mobility of bulk oxygen. Moreover, the reaction routes under different atmospheres were probed through in situ DRIFTS, in which oxygen vacancy played a key role in promoting the adsorption and activation of molecular oxygen and facilitating the migration of the bulk lattice oxygen.