Modulating the Electronic Structures of Pt on Pt/TiO₂ Catalyst for Boosting Toluene Oxidation

Surface hydroxyl groups commonly exist on the catalyst and present a significant role in the catalytic reaction. Considering the lack of systematical researches on the effect of the surface hydroxyl group on reactant molecule activation, the PtO/TiO₂ and PtO(OH)/TiO₂ catalysts were constructed and studied for a comprehensive understanding of the roles of the surface hydroxyl group in the oxidation of volatiles organic compounds. The PtO/TiO₂ formed by a simple treatment with nitric acid presented greatly enhanced activity for toluene oxidation in which the turnover frequency of toluene oxidation on PtOx/TiO₂ was around 14 times as high as that on PtO(OH)/TiO₂. Experimental and theoretical results indicated that adsorption/activation of toluene and reactivity of oxygen atom on the catalyst determined the toluene oxidation on the catalyst. The removal of surface hydroxyl groups on PtO promoted strong electronic coupling of the Pt 5d orbital in PtO and C 2p orbital in toluene, facilitating the electron transfers from toluene to PtO and subsequently the adsorption/activation of toluene. Additionally, the weak Pt-O bond promoted the activation of surface lattice oxygen, accelerating the deep oxidation of activated toluene. This study clarifies the inhibiting effect of surface hydroxyl groups on PtO in toluene oxidation, providing a further understanding of hydrocarbon oxidation.