Identification of platinum phases on γ-alumina by XPS

Analysis of Pt supported on alumina by XPS is complicated by overlapping Al2p and Pt4f lines. The interference problem is eliminated when the Pt4d52 lines are used instead. Although these lines are relatively broad, they can be used to discriminate between particulate and dispersed phase Pt on alumina. The discrimination is based on the Pt binding energy measured after an oxidized sample has been exposed to hydrogen at 150°C. Within the limitation of XPS sampling depth, this method is useful in studying sintering and redispersion of Pt on alumina.