Elucidating the special role of strong metal–support interactions in Pt/MnO2 catalysts for total toluene oxidation†
With the aim to elucidate the role of strong metal–support interactions (SMSIs) in total toluene deep oxidation, herein, we prepared a series of Pt/MnO2 catalysts with different MnO2 crystal structures (α-, β-, γ- and hollow-MnO2); it was found that the structures and catalytic behaviors of the MnO2 crystals decorated by Pt nanoparticles (NPs) changed dramatically, especially the mobility of surface adsorbed oxygen and lattice oxygen. Among all these catalysts, the as-synthesized Pt/α-MnO2 exhibited best catalytic activity for total toluene oxidation (T90 = 170 °C). TGA, high-temperature XRD (HT-XRD) and quasi in situ XPS were applied to estimate the reconfiguration of gaseous oxygen on the surface of MnO2-based catalysts. A series of characterization results indicate that the SMSIs between the Pt NPs and MnO2 result in improved low-temperature reducibility, optimized surface chemical states, and the weakening of surface lattice oxygen species (Mn–O bands). The in situ DRIFTS study showed that the lattice oxygen could be involved in the activation of toluene without oxygen, whereas the presence of gas-phase oxygen was essential for the deep oxidation of toluene into CO2 and H2O on the surface of MnO2-based catalysts.