In-situ evolution of microstructural transformation from crystalline to amorphous in PtPb/Pt nanoplates induced by Kr ion irradiation

Ion irradiation is a highly effective approach to boost the catalytic activity in the platinum-lead/platinum (PtPb/Pt) core-shell nanoplates (NPs) through tuning their microstructures for fuel cell technology. We report on the evolution of crystalline to amorphous (c-a) transformation induced by Kr ion irradiation in the PtPb NPs in detail by using in-situ transmission electron microscopy. The results show that PtPb NPs first generate small amorphous domains, followed by a gradual amorphous transition from their edge to inner and finally are changed to be completely amorphous during in-situ Kr ion irradiation. The c-a transformation appears at the edge of NPs at first, which is attributed to high energy of grain boundary and surface. The crystal-amorphous interfaces and geometrical defects induced by moderate irradiation in PtPb NPs are the key factors to enhance the catalytic activity. This study provides the understanding of the microstructural transition of PtPb NPs and the guidance for using ion irradiation approach to boost catalytic properties of nanomaterials by tuning their microstructures.