Investigation of redox properties of different PtSn/Al2O3 catalysts.
Alumina-supported Sn and PtSn particles are studied by 119Sn Mössbauer spectroscopy after oxidation and reduction under various conditions. The observed species of Sn(IV), Sn(II) and Sn(0) are grouped in several categories, each being characterised by distinct structural properties. Tin phases in contact with the support or with platinum are identified. The results are used to establish a model describing the phase transformations occurring in PtSn particles under oxidising or reducing conditions. Particular attention is paid to the reduction/reoxidation mechanisms governing H2/O2 double titrations. An increased reactivity of tin towards oxygen, induced by the contact with platinum, is demonstrated. It is shown that tin contributes to the oxygen uptake VO1 of a first titration cycle by platinum-catalysed transformation of Sn(II) into an oxometallic phase Pt(x)Sn(O). The oxygen titre VO2 of a second cycle is due to O2 chemisorption on platinum only.
Olivier-Fourcade
Josette
J
Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques (UMR 5072 CNRS), Université Montpellier II CC 15, Place E. Bataillon, 34095 Montpellier 5, France.
Womes
Manfred
M
Jumas
Jean-Claude
JC
Le Peltier
Fabienne
F
Morin
Stéphane
S
Didillon
Blaise
B
D000497:Alloys / Q000737:chemistry*; D000537:Aluminum Oxide / Q000737:chemistry*; D002384:Catalysis; D010084:Oxidation-Reduction; D010316:Particle Size; D010984:Platinum / Q000737:chemistry*; D014001:Tin / Q000737:chemistry*
D000497:Alloys; D010984:Platinum; D014001:Tin; D000537:Aluminum Oxide