Jian Hong

Binghamton University, Binghamton, NY, United States

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Publications (3)9.02 Total impact

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    ABSTRACT: The understanding of nanoscale alloying or the phase segregation effect of alloy nanoparticles on the catalytic properties is important for a rational design of the desired catalysts for a specific reaction. This paper describes findings of an investigation into this type of structural effect for carbon-supported bimetallic gold-platinum nanoparticles as cathode catalysts in a rechargeable lithium-oxygen battery. The nanoscale structural characteristics in terms of size, alloying and phase segregation were shown to affect the catalytic properties of the catalysts in the Li-O(2) battery. In addition to the composition effect, the catalysts with a fully alloyed phase structure were found to exhibit a smaller discharge-charge voltage difference and a higher discharge capacity than those with a partial phase segregation structure. This finding is significant for the design of alloy nanoparticles as air cathode catalysts in rechargeable lithium-air batteries, demonstrating the importance of the control of the nanoscale composition and phase properties.
    Nanotechnology 08/2012; 23(30):305404. · 3.84 Impact Factor
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    ABSTRACT: The understanding of factors controlling electrocatalytic activity and stability of carbon-supported multimetallic catalysts is essential for advancing the design of fuel-cell electrocatalysts for oxygen reduction. The structural and compositional changes of trimetallic PtVFe/C catalysts have been investigated by several techniques, including XRD, X-ray absorption fine structure (XAFS), and inductively coupled plasma (ICP) analyses, in addition to electrochemical and fuel-cell performance tests. The investigation aims at understanding whether the base metals incorporated into the multimetallic catalysts are stable and how the base metals in the Pt-alloy are stabilized mechanistically. Changes are detected for the lattice properties and the composition of the base metals in the PtVFe nanoparticles after long-term exposure to air, after thermal treatment at different temperatures, and after use in proton-exchange membrane (PEM) fuel cells. These changes show certain correlations with the structure, activity, and stability of the catalysts. The fcc alloy phase is found to be predominant for catalysts treated at low temperature, but changes to a tetragonal-type alloy phase when the catalysts are treated at a higher temperature. In the low-temperature-treated catalyst, Fe has more bonds with O atoms, whereas in the high-temperature-treated catalyst, Fe has fewer O neighbors and FeFe bonds are detected. Analysis of the catalysts after testing in fuel cells indicates that the percentage of iron oxide is reduced, reflecting the propensity of dissolution of Fe oxide in the electrolytes. The smaller lattice parameter for the higher-temperature treated catalyst is considered to be an important factor in determining the catalyst stability under conditions related to fuel-cell operation.
    ChemCatChem 03/2011; 3(3). · 5.18 Impact Factor
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    ABSTRACT: Proton exchange membrane fuel cells (PEMFCs) are attractive because of their high conversion efficiency, low pollution, lightweight, and high power density. A major area of challenges is the design and engineering of active, robust, and low-cost electrocatalysts. This report discusses recent findings of our investigations of the design and nano-engineering of platinum–vanadium–iron catalysts for use in PEMFC. The membrane electrode assembly was prepared using nano-engineered PtVFe nanoparticles with controlled composition and size supported on carbon as cathode electrocatalysts. The electrocatalytic activity and stability of the catalysts have been characterized by both rotating disk electrode and membrane electrode assembly measurements. The trimetallic catalysts have been shown to exhibit excellent electrocatalytic performance in PEMFC in comparison with commercial platinum catalysts. The results exhibited a good agreement between obtained these two types of measurements in terms of the dependence on particle size, composition, and thermal treatment condition. The catalysts also showed good stability, which are potentially useful for practical application in PEMFCs.
    Electrochimica Acta. 01/2010; 55(27):8230-8236.