Facilitating Catalytic Purification of Auto-Exhaust Carbon Particles via the Fe2O3{113} Facet-dependent Effect in Pt/Fe2O3 Catalysts.

Abstract

The purification efficiency of auto-exhaust carbon particles in the catalytic aftertreatment system of vehicle exhaust is strongly dependent on the interface nanostructure between the noble metal component and oxide supports. Herein, we have elaborately synthesized the catalysts (Pt/Fe2O3-R) of Pt nanoparticles decorated on the hexagonal bipyramid α-Fe2O3 nanocrystals with co-exposed twelve {113} and six {104} facets. The area ratios (R) of co-exposed {113} to {104} facets in α-Fe2O3 nanocrystals were adjusted by the fluoride ion concentration in the hydrothermal method. The strong Pt-Fe2O3{113} facet interaction boosts the formation of coordination unsaturated ferric sites for enhancing adsorption/activation of O2 and NO. Pt/Fe2O3-R catalysts exhibited the Fe2O3{113} facet-dependent performance during catalytic purification of soot particles in the presence of H2O. Among the catalysts, the Pt/Fe2O3-19 catalyst exhibits the highest catalytic activities (T50 = 365 °C, TOF = 0.13 h-1), the lowest apparent activation energy (69 kJ mol-1), and excellent catalytic stability during soot purification. Combined with the results of characterizations and density functional theory calculations, the catalytic mechanism is proposed: the active sites located at the Pt-Fe2O3{113} interface can boost the key step of NO oxidation to NO2. The crystal facet engineering is an effective strategy to obtain efficient catalysts for soot purification in practical applications.