Morphology Control of Pt Nanoparticles Loaded with Nitrogen-Doped Reduced Graphene Oxide Induced by γ Rays for Oxygen Reduction Reaction

Abstract

As gamma irradiation is helpful to control the morphology and structure of metal nanoparticles anchored on carbon materials, it is expected to be one of the alternatives for the preparation of shaped Pt-based catalysts for its oxygen reduction reaction (ORR) performance free of shape inducer. In this work, to study the morphological evolution mechanism of platinum nanoparticles (PtNPs) and its influence on the catalytic behavior of the catalyst, different doses of γ rays were employed to prepare the polygonal angle PtNP composites assisted with in situ hydrolysis of urea. γ Rays can induce the generation of reducing free radicals in solution to reduce metal ions and have a fragmentation effect on metal particles, which is beneficial for the formation of polygonal PtNPs. The samples with polygonal angle PtNPs demonstrated an excellent ORR performance with enhanced onset potential (908 mV), half-wave potential (821 mV), and superior limit current density (6.65 mA·cm^–2) compared with the spherical PtNP catalysts. The enhanced ORR performance is attributed to the synergistic effect of pyridine N in reduced graphene oxide and the change in the structural morphology of PtNPs, which provides more catalytic active sites. The results indicate that the structural morphology of PtNPs under different doses of gamma irradiation is of great significance for the final performance of the obtained catalyst.