The catalytic oxidation of toluene to CO2 and H2O over nanoflower spinel CoMn2O4 synthesized by the oxalic acid sol–gel method has been investigated, and it demonstrates lower activation energy (35.5 kJ/mol) for toluene oxidation compared with that using the metal oxides (Co3O4, MnO x , and Co3O4/MnO x ), which shows nearly 100% conversion of toluene at 220 °C in the presence or absence of water vapor (2.0 vol %). Compared with the metal oxides (Co3O4/MnO x , MnO x , and Co3O4), the obtained spinel CoMn2O4 has a larger surface area, rich cationic vacancy, and high mobility of oxygen species, which are the reasons for its high activity for toluene oxidation. The different oxygen species shows the different role in VOCs oxidation, and the in situ designed-TP techniques are conducted to investigate the involvement of surface lattice oxygen, bulk lattice oxygen, and gaseous oxygen in catalytic oxidation of toluene over the spinel CoMn2O4 and Co3O4/MnO x catalysts. For spinel CoMn2O4, the surface lattice oxygen is the reactive oxygen species, which first induces the catalytic reaction. Furthermore, the gaseous oxygen moves to the bulk phase lattice and then migrates to the surface to form the surface lattice oxygen, which is different from the mixed-metal oxides Co3O4/MnO x that dissociates and activates gaseous oxygen only on the surface of the catalyst and requires a higher temperature. In addition, it is found that the toluene oxidation occurs via the benzyl alcohol–benzoate–anhydride–acetate reaction pathway over spinel CoMn2O4, and the conversion of the surface anhydride is the rate-controlling step, especially at 200–210 °C, which is also different from the mixed-metal oxides Co3O4/MnO x . These results could provide a considerable experimental basis for understanding the mechanism by which oxygen species participate in toluene oxidation.

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Novel iron-tungsten catalysts were first developed for the selective catalytic reduction of NO by NH in diesel exhaust, achieving an excellent performance with a wide operating temperature window above 90% NO conversion from 225 or 250 to 450 °C (GHSVs of 30 000 or 50 000 h). It also exhibited a pronounced stability and relatively high NO conversion in the presence of HO, SO and CO. The introduction of W resulted in the formation of α-FeO and FeWO species obtained by HRTEM directly. The synergic effect of two species contributed to the high SCR activity, because of the increased surface acidity and electronic property. The FeWO with octahedral [FeO]/[WO] structure acted as the Brønsted acid sites to form highly active NH species. Combining DFT calculations with XPS and UV-vis results, it was found that the fine electron interaction between α-FeO and FeWO made the electron more easily transfer from W sites to Fe sites, which promoted the formation of NO. Judging by the kinetics and SCR activity studies, the FeWO with an appropriate W amount showed the strongest interaction, and thereby the lowest activation energy of 39 kJ•mol and optimal catalytic activity. These findings would be conducive to the reasonable design of NH-SCR catalysts by adjusting the fabrication.

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