Controlled synthesis of carbon-supported Pt 3Sn by impregnation-reduction and performance on the electrooxidation of CO and ethanol

Abstract

The paper discusses experimental features relevant to the synthesis of carbon-supported Pt 3Sn nanosized particles by impregnation-reduction of the salt precursors in carbon. Colloidal techniques are proposed as the most suitable ones for obtaining carbon-supported nanosized Pt 3Sn particles. In most cases, the electrocatalysts obtained have a wide range of Pt and Sn phases, including bimetallic ones. The synthesis of similar materials by impregnating readily available precursors such as SnCl 2 and H 2PtCl 6 yields Pt-enriched catalyst precursors. In order to obtain electrocatalysts with the desired Pt:Sn = 3 atomic stoichiometry, it is necessary to eliminate chloride ions prior to thermal treatments. Microscopy characterization and thermal stability studies of the fresh and treated bimetallic materials reveal that if such ions are present, Sn is eliminated as volatile SnCl x species at around 120–130 °C. Chloride elimination is achieved by ageing the catalyst precursor in water to ensure the complete hydrolysis of the SnCl 2 precursor. This treatment should be performed once SnCl 2 has been deposited on the carbon to avoid the formation of large Sn-oxide aggregates. A further thermal treatment in hydrogen results in the formation of the desired Pt 3Sn intermetallic phase. The performance of the Pt 3Sn/C samples in the CO and ethanol electrooxidation reaction has been studied by means of electrochemical techniques. The electrocatalysts prepared by the impregnation-reduction approach match the performance of the state-of-the-art Pt 3Sn samples prepared by colloidal techniques.