Effect of Pt Particle Size and Valence State on the Performance of Pt/TiO₂ Catalysts for CO Oxidation at Room Temperature

Abstract

A series of Pt/TiO2 catalysts with various Pt particle sizes and valence states were prepared and tested for CO oxidation at room temperature. Field-emission transmission electron microscopy and X-ray photoelectron spectroscopy analyses confirmed that the activity of the Pt/TiO2 catalyst was influenced by the particle size and valence state of the catalyst particles. Excellent CO oxidation activity was observed at room temperature using highly dispersed, small metallic Pt particles. Increasing the Ptmetallic/Pttotal ratio resulted in an increase of turnover frequencies. According to the Fourier-transform infrared spectroscopy results, the linear CO species that was adsorbed on metallic Pt sites at 25 °C reacted with atmospheric O2 and was easily desorbed. However, linear CO species adsorbed on PtO x (x ≥ 2) sites was only desorbed at temperatures ≥100 °C, confirming the lack of CO oxidation activity at room temperature with ionic Pt catalysts.

Tuning of catalytic sites in Pt/TiO2 catalysts for the chemoselective hydrogenation of 3-nitrostyrene

“…The possibility of improving the metal dispersion in favour of small Pt particles by performing consecutive calcination and reduction treatments has been observed before. 26,27 Our microstructural observations correlate very well with the measured catalytic activites for these various Pt/TiO2 catalysts, indicating that smaller Pt particles with high dispersion and narrow size distribution lead to a higher overall catalytic activity.…”

Active oxygen species adsorbed on the catalyst surface and its effect on formaldehyde oxidation over Pt/TiO2 catalysts at room temperature; role of the Pt valence state on this reaction?

“…20,[32][33][34][35][36] The band at 2048 cm À1 was assigned to linearly adsorbed CO on metallic Pt (kink) sites, while the band at 1770 cm À1 was assigned to CO bridged between two Pt metal particles. 20,37 Peaks at 1570 and 1360 cm À1 indicated the presence of formate, while negative bands were observed at 1635 cm À1 and broad bands were observed in the range 3600-3200 cm À1 . 36 Generally, the broader peaks at 3200-3600 cm À1 and strong peaks at 1635 cm À1 were assigned to the O-H stretching vibrations of water, -OH groups, and hydrated species on the catalyst surface.…”

Transformation of a Pt–CeO2 Mechanical Mixture of Pulsed‐Laser‐Ablated Nanoparticles to a Highly Active Catalyst for Carbon Monoxide Oxidation

“…There, the oxidation state of platinum, its dispersion, and microstructure substantially depend on the reaction mediumu sed for the catalyst treatment. [24,25,[33][34][35][36][37] Av ariety of platinum states is formed through as trongc hemical interaction with the support (SMSI effect), so that platinum can be in cationic states and in different metallicc luster species. [37][38][39][40][41][42][43][44][45] The interaction of metallic platinum particlesw ith ceria, studied in many publications,w as shown to increase the catalytic activity per platinum atom in comparison, for example, with the Pt/Al 2 O 3 catalyst.…”

“…In distinction to platinum catalysts on irreducible oxides, the behavior of supported platinum on reducible and mixed‐valence oxides, such as CeO 2 , SnO 2 , and TiO 2 , is more diversified. There, the oxidation state of platinum, its dispersion, and microstructure substantially depend on the reaction medium used for the catalyst treatment . A variety of platinum states is formed through a strong chemical interaction with the support (SMSI effect), so that platinum can be in cationic states and in different metallic cluster species .…”