Precursor Investigation in the Synthesis of PtPb Nanocatalysts
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Precursor Investigation in the Synthesis of PtPb Nanocatalysts Nathan Porter1, Hong Wu1, Minji Kong1, Kai Sun2, Amar Kumbhar3 and Jiye Fang1,* Department of Chemistry and Materials Science & Engineering Program, State University of New York at Binghamton, Binghamton, New York 13902, United States 2 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States 3 Chapel Hill Analytical and Nanofabrication Laboratory, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States 1
ABSTRACT In recent years, platinum-based single crystalline nanoalloys as nanoscale catalysts, such as Pt-M (M = Ni, Co, Fe..etc.), have exhibited improved catalytic performance due to the increase in the surface-to-volume ratio. Some Pt-M nanopolyhedra such as nanocubes and nano-octahedra have been reported with enhanced activity when being used as electrocatalysts. In order to further establish a correlation between the exposed nanocrystal facets (shapes) and their corresponding activities, a pursuit of shape-controlled nanocatalyst synthesis is essential. Although PtPb nanoalloys have been prepared using solution-based methods, few studies have highlighted their catalytic activity as a function of the nanocrystal shape. This work focuses on a modified polyol synthesis technique and an adjustment of the Pb-metal precursor, which serves as a “buffer” in the nucleation stage of the shape-controlled nanoalloy development. Using this developed synthetic strategy, shape-controlled hexagonally close-packed PtPb nanoalloys can be prepared in a one-pot synthesis without additional post-treatment. The as-prepared PtPb nanocrystals demonstrate an improved anode electrocatalytic performance. INTRODUCTION Searching for effective Pt-based electrocatalysts in nanoscale has proved a most difficult venture with chemical conversion efficiencies not meeting the requirements necessary for largescale implementation [1,2] In order to meet these requirements, an operating current density of at least 1.5A/cm2 is required [3]. In order to achieve current density outputs, two reactions are employed when using Proton Exchange Membrane Fuel Cells (PEMFCs): hydrogen or small organic molecule oxidation reaction at the anode and oxygen reduction reaction (ORR) at the cathode. When considering the oxidation occurring at the anode, inert intermediates plague the active sites causing reduced current densities. Electrochemical studies are performed on formic acid model test system due to its simple oxidation pathway and availability [4]. Platinum (Pt) is used as the electrocatalyst for a PEMFC due to its strong resistance to corrosion and its excellent catalytic performance. Pt-binary alloy with an incorporation of an oxophilic secondary metal may further achieve some improvements in terms of the electrocatalysis, due to the fact that these Pt-alloys from due to the shifting of their d-band electronic structure away from the Fermi energy level with a geometric modification of the “original”
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