Electronic structures of supported Pt and PtSn nanoparticles in the presence of adsorbates and during CO oxidation☆

CO-Induced Scavenging of Supported Pt Nanoclusters: A GISAXS Study

“…Conversely, there exists a series of reasons that favor the disruption of small clusters in the presence of CO. First, the energy per atom is expected to decrease in small clusters. 9,14,15 But the switch between that disruption and the agglomeration such as that described in the previous section is not clarified yet. 50 The average cohesion energy of 255 kJ.mol −1 found in Pt 10 is twice as small as that determined for bulk Pt (528 kJ.mol −1 ).…”

“…Based on the sensitivity of the vibrational spectrum of CO to sites and charges, the stretching frequency of the adsorbed CO molecules is commonly used to probe adsorption sites and charge transfer with the support and to stress the status of supported Pt nanoparticles. 9 Upon admission of CO on Pt supported on titania, alumina and silica in the 0.01-10 torr pressure range, Rasko 14 has assigned the increase in intensity of the 2112-2106 cm −1 band to the formation of monoatomic Pt 0 by disruption of crystallites. 6 Reduced Pt particles at 300 K were observed to disrupt into small carbonyl clusters when exposed to a mixture containing 1 % CO/ 1 % O 2 /He (10 mbar CO partial pressure) at the ignition temperature.…”

“…Beyond the achievement via synthesis processes of the optimum morphology that accounts for the combination of those constraints, great attention is paid to the phenomena which drive changes in shape, size, and structure of the clusters of catalysts in running conditions. Aside from the capability to resist high-temperature aging, a main concern is the sustainability of catalyst particles upon exposure to reactive atmospheres. ,− A prototypical case is the effect of CO on transition metals catalysts, of which supported platinum is a thoroughly studied example because it combines a strong practical relevance ,− with a puzzling stability behavior in the presence of CO. ,,− Active in CO oxidation, platinum is a major component of the three-way catalysts of automotive converters , in which the size of Pt nanoparticles is crucial since the smallest Pt particles on CeO 2 -based catalysts show both a higher stability due to Pt–O–Ce bonds and a higher oxygen storage and release capacity. , Moreover, the turnover rate for CO oxidation is structure-sensitive on oxygen-saturated Pt clusters, although in contrast it poorly depends on the particle dispersion for CO-saturated particle surfaces …”

Colloidal Synthesis and Structural Control of PtSn Bimetallic Nanoparticles

“…1,2 Bimetallic nanoparticles composed of a noble metal and a non-noble metal are very promising because of the high possibility of tailoring their electronic and catalytic properties, which are greatly affected by the structural characteristics of such nanoscopic materials such as the particle size, 3 shape, 4 and metal composition 5 as well as organic capping agents. 6 PtSn bimetallic nanoparticles are of great interest for applications in a variety of heterogeneous catalytic processes such as the low-temperature oxidation of CO, 7 the hydrogen-transfer reduction of unsaturated ketones, 8 the transformation of acetone 9 and acetic acid, 10 and the hydrogenation of alkenes, 11 ketones, 12 toluene, 13 chloronitrobenzene, 14 benzonitrile, 15 phenylacetylene, 16 and R,β-unsaturated aldehydes (e.g., acrolein, 17 citral, 18 furfuraldehyde, 19 crotonaldehyde, 20 and cinnamaldehyde 21 ). PtSn bimetallic catalysts also play a major role in the petroleum industry for reforming paraffins to olefins or aromatics, and they exhibit superior activity, selectivity, and stability against coke deposition in isomerization and the aromatization or dehydrogenation of ethane, 22 n-butane, 23 isobutane, 24 n-hexane, 25 cyclohexane, 26 n-heptane, 27 methylcyclopentane, 28 and n-propylbenzene.…”

“…PtSn bimetallic nanoparticles are of great interest for applications in a variety of heterogeneous catalytic processes such as the low-temperature oxidation of CO, the hydrogen-transfer reduction of unsaturated ketones, the transformation of acetone and acetic acid, and the hydrogenation of alkenes, ketones, toluene, chloronitrobenzene, benzonitrile, phenylacetylene, and α,β-unsaturated aldehydes (e.g., acrolein, citral, furfuraldehyde, crotonaldehyde, and cinnamaldehyde). PtSn bimetallic catalysts also play a major role in the petroleum industry for reforming paraffins to olefins or aromatics, and they exhibit superior activity, selectivity, and stability against coke deposition in isomerization and the aromatization or dehydrogenation of ethane, n -butane, isobutane, n -hexane, cyclohexane, n -heptane, methylcyclopentane, and n -propylbenzene .…”