Boosting Toluene Combustion by Tuning Electronic Metal-Support Interactions in In Situ Grown Pt@Co3O4 Catalysts.

Electronic metal-support interaction (EMSI) has attracted great attention in volatile organic compound (VOC) abatement. Herein, Pt@Co3O4 catalysts were prepared via a metal-organic framework (MOF) in situ growth approach to boost toluene degradation. The partial electron transfer from Co3O4 to Pt species was induced by the EMSI effect to generate the electron-rich Pt and Co3+ species. The electrophilic O2 molecules could be activated by picking up the electrons from electron-rich Pt species to form nucleophilic oxygen species, which is conducive to attack C-H bonds in toluene. The redox ability and surface oxygen species activity of catalysts were improved due to strong EMSI. As expected, the excellent toluene activity was achieved, meanwhile exhibiting satisfactory water resistance and long-term stability for toluene combustion. In situ diffuse reflectance infrared Fourier transform spectroscopy results elucidated that surface lattice oxygen species should deeply participate in toluene degradation, which could be efficiently replenished by gaseous oxygen. This work may provide a new idea for exploring the relationship between the electron transfer effect and efficient catalytic performance of VOCs.

Metal organic framework-templated fabrication of exposed surface defect-enriched Co3O4 catalysts for efficient toluene oxidation.

Exposed surface defect-enriched Co3O4 catalysts derived from metal organic framework (MOF) were fabricated by the promotion of surface Mn species for toluene oxidation. The incorporation of Mn species into Co3O4 surface lattice could give rise to the local lattice distortion in spinel structure, resulting in highly exposed surface defect rather than bulk defect. More Co3+ species were also exposed on the surface of MnOx/Co3O4 samples owing to the electron transfer from Co to Mn species by the occupation of surface Mn in octahedral Co3+ sites. Accordingly, the low-temperature reducibility and high mobility of lattice oxygen were significantly improved in virtue of the highly exposed surface defect and predominately surface Co3+ sites, thus promoting the catalytic activity and stability for toluene oxidation. Moreover, the toluene conversion decreased with the increase of weight hourly space velocity (WHSV). In situ DRIFTS results confirmed the continuous oxidation process for toluene degradation, and the conversion of benzoate into maleic anhydride should be the rate-controlling step.

Boosting benzene combustion by engineering oxygen vacancy-mediated Ag/CeO2-Co3O4 catalyst via interfacial electron transfer.

Oxygen vacancy (Ov) engineering is a widely accepted effective strategy to manipulate the catalytic activity for volatile organic compounds (VOCs) abatement. Herein, we report the oxygen vacancy-mediated Ag/CeO2-Co3O4 catalyst to boost benzene combustion. The incorporation of Ag species in Ag/CeO2-Co3O4 induces the predominately exposed surface Co3+ sites and structural distortion of Co3O4 as well as rich oxygen vacancy owing to the improved interfacial electron transfer, which promote the adsorption of benzene and the dissociation of oxygen. The low-temperature reducibility and mobility of oxygen species are also improved due to the generation of oxygen vacancy. The isotopic 18O2 exchange experiments demonstrate that abundant oxygen vacancies contribute to the rapid generation of active oxygen species, and the consumed oxygen vacancies can be compensated steadily during benzene oxidation. In-situ DRIFTS results reveal that benzene oxidation is a continuous oxidation process, and active oxygen species plays a crucial role in the deep oxidation of benzene by engineering oxygen vacancy. This work provides an efficient strategy for designing high-performance environmental catalysts for VOCs abatement.