Shape-controlled Synthesis Of Platinum And Alloy Nanocrystal For Eletrocatalytic Application

With the accelerated depletion of fossil fuels and increasing environmental concerns, thedevelopment of new technology for producing new alternative energy conversion and storagedevices such as solar cell, supercapacitor, and lithium ion battery, etc. is very important forsolving the present energy crisis. Fuel cell, as an environmentally friendly energy device, hasbeen intensely studied because of their numerous advantages, which include high-energydensity, low environmental impacts. At present, tremendous research efforts have beendedicated to the fabrication of efficient fuel cells with high performance. In all of the Nobelmetal nanomaterials （NMNs）, Pt and Pt-based nanomaterials are still indispensable and themost effective catalysts for fuel cells. However, one of the major obstacles for fuel cellcommercialization is the cost and reliability issues of Pt nanocatalysts used. Thus, design andsynthesis of advanced catalysts to meet the requirements of reducing Pt loading amounts andmeantime increasing the activity and stability of the Pt-based catalyst is highly desired. In thispaper, we studied shape controlled synthesis PtNi nanocrystals and high index facet Ptnanocrystals to reach such effect.We used a high temperature co-reduction approach by the different heat ramping rate ofpreparing monodisperse Pt₃Ni alloy nanoflower and PtNi polyhedron, respectively. Thecurrent density on Pt₃Ni alloy nanoflowers at its peak potential was nearly4times that of Pt/C.In the current density vs. time curves recorded at0.25V for900seconds, the Pt₃Ni alloynanoflowers maintained a current density that was13times higher than that of Pt/C,demonstrating a significantly enhanced poisoning tolerance and thus electrocatalytic activity.Furthermore, through the K-L plots, Pt₃Ni alloy nanoflowers could catalyze the oxygenreduction to water through the direct four-electron-transfer process in ORR.We also used hydrothermal method by preparing the Pt cancave nanocubes having （411）high index facet. The current density on Pt cancave nanocubes at its peak potential was nearly3.5times that of Pt/C. In the current density vs. time curves recorded at0.15V for900seconds, the Pt cancave nanocubes maintained a current density that was7.7times higher thanthat of Pt/C. Furthermore, by the2000circles electrocatalytic stability test, the Pt cancavenanocubes were damping5%vs67%of the Pt/C. That demonstrate that the concave Pt nanocrystals with （411） high index facet displayed excellent activity and stability during theelectrochemical measurements.