States of Pt in Pt/C catalyst precursors after impregnation, drying and reduction steps Original Research Article

The characterization of Pt/C catalysts after impregnation and activation steps has been carried out by using different techniques: TPD; TPR; XPS; EXAFS and H2 chemisorption. Furthermore, the catalytic activity of the samples has been tested in the cyclohexane dehydrogenation. The catalysts were prepared from a purified peach pit derived carbon and two H2O2-functionalized supports obtained from it. Results showed that the interaction of H2PtCl6 with the carbon implies a redox process in which after impregnation and drying steps, the metal complex is stabilized as Pt2+ on the carbon surface. The functionalization treatment seems to have no effect on the resulting state of platinum. During the activation step (thermal treatment in H2), apart from the reduction of Pt species to Pt0, catalyzed and non-catalyzed reactions involving CO and CO2 desorbed from the carbon surface, take place. It was also found that the Pt2+ species are reduced to zerovalent Pt even by thermal treatment of the dried samples with He. The electronic state of reduced platinum is not modified by the differences in the support surface chemistry.