tailieunhanh - Báo cáo hóa học: " Size-dependent catalytic and melting properties of platinum-palladium nanoparticles"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Size-dependent catalytic and melting properties of platinum-palladium nanoparticles | Guisbiers et al. Nanoscale Research Letters 2011 6 396 http content 6 1 396 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Size-dependent catalytic and melting properties of platinum-palladium nanoparticles Gregory Guisbiers1 Gulmira Abudukelimu2 and Djamila Hourlier3 Abstract While nanocatalysis is a very active field there have been very few studies in the size shape-dependent catalytic properties of transition metals from a thermodynamical approach. Transition metal nanoparticles are very attractive due their high surface to volume ratio and their high surface energy. In particular in this paper we focus on the Pt-Pd catalyst which is an important system in catalysis. The melting temperature melting enthalpy and catalytic activation energy were found to decrease with size. The face centered cubic crystal structure of platinum and palladium has been considered in the model. The shape stability has been discussed. The phase diagram of different polyhedral shapes has been plotted and the surface segregation has been considered. The model predicts a nanoparticle core rich in Pt surrounded by a layer enriched in Pd. The Pd segregation at the surface strongly modifies the catalytic activation energy compared to the non-segregated nanoparticle. The predictions were compared with the available experimental data in the literature. PACS Introduction Bimetallic nanoparticles exhibit unusual physicochemical properties different from those of the bulk material or their individual constituents 1 2 . They are very used in catalysis fuel cells and hydrogen storage. These unusual properties are determined by their size shape and composition. When considering metallic catalysts platinum is a standard material but this material is most expensive than gold 3 . Therefore to reduce the amount of platinum and then the cost of the application one possible way is to use an alloy of platinum with another .