Model catalysts fabricated by electron beam lithography: AFM and TPD surface studies and hydrogenation/dehydrogenation of cyclohexene + H_2 on a Pt nanoparticle array supported by silica

摘要

Pt nanoparticle model catalysts with 28 +- 2 nm diameters and 100 +- 2 nm square periodicity have been fabricated with electron beam lithography on silica substrates. The reactivity of the Pt/SiO_2 arrays was compared to a Pt foil for cyclohexene + H_2 at 100 deg C. The overall reactivity of the Pt particle arrays was higher by a factor of two, the selectivity towards dehydrogenation was three times higher, and the rate of deactivation was about the same as for the Pt foil. Since the primary difference between the nanoparticle array and the Pt foil was the interface between the Pt and the SiO_2, the interfacial region was most likely responsible for the changes in reactivity on the arrays. Using AFM, SEM, and TPD, the arrays were characterized before and after being exposed to reaction conditions. AFM images of a sample cleaned by ion sputtering showed that the pattern of the Pt nanoparticle array was replicated in the silica during the sputtering process.