Elucidating the special role of strong metal–support interactions in Pt/MnO2 catalysts for total toluene oxidation

Abstract

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.