Surface Partial-Charge-Tuned Enhancement of Catalytic Activity of Platinum Nanocatalysts for Toluene Oxidation

Abstract

The ability to tune the surface partial charge of noble metal catalysts at the nanoscale size dimension is essential for harnessing the activity of nanocatalysts in many important environmental catalytic reactions, such as hydrocarbon oxidations. We report herein a synthetic pathway to control the catalyst–support interactions and enable a surface partial-charge-tuned enhancement of the nanocatalytic activity using titania-supported Pt nanoparticles for oxidation of toluene as a model system. This pathway involved the one-pot wet-chemical synthesis of TiO2-supported ultrasmall Pt nanoparticles (1–5 nm) with a controlled morphology and size. The catalysts showed greatly enhanced activities for toluene oxidation, exhibiting a strong dependence on the support morphology (e.g., nanopowders, nanowires, nanotubes, and mesoporous structures). The tunable partial negative charges on Pt were achieved by suppressing roughening of the support surface, favoring O2 spillover from TiO2 to Pt. In situ DRIFT data further reveal two parallel pathways responsible for oxidation of the methyl group and opening of the aromatic ring, the latter of which is favored by the partial negatively charged Pt, leading to a high activity. These findings provided insights into tuning nanoscale catalytic properties, which has significant implications for the design of supported noble metal nanocatalysts for environmental catalysis.