Olivier-Fourcade Josette, Womes Manfred, Jumas Jean-Claude, Le Peltier Fabienne, Morin Stéphane, Didillon Blaise
Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques (UMR 5072 CNRS), Université Montpellier II CC 15, Place E. Bataillon, 34095 Montpellier 5, France.
Chemphyschem. 2004 Nov 12;5(11):1734-44. doi: 10.1002/cphc.200400184.
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.
通过119Sn穆斯堡尔谱对在各种条件下氧化和还原后的氧化铝负载的Sn和PtSn颗粒进行了研究。观察到的Sn(IV)、Sn(II)和Sn(0)物种被分为几类，每一类都具有独特的结构特性。确定了与载体或铂接触的锡相。这些结果被用于建立一个模型，描述在氧化或还原条件下PtSn颗粒中发生的相变。特别关注了控制H2/O2双滴定的还原/再氧化机制。证明了与铂接触会导致锡对氧的反应性增加。结果表明，在第一个滴定循环中，锡通过将Sn(II)催化转化为氧金属相Pt(x)Sn(O)，促进了铂的氧吸收VO1。第二个循环的氧滴定VO2仅归因于O2在铂上的化学吸附。
