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Study on the Synthesis of the Polypyrrole-Cobalt Oxides and Their Catalytic Behavior for the Electro

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Tutor: WangGuiLing
School: Harbin Engineering University
Course: Applied Chemistry
Keywords: Polypyrrole,Transition metal,Co3O4 nano- line,H2O2 power reduction,Non- precious
CLC: O643.32
Type: Master's thesis
Year:  2011
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Abstract:
The fuel cells using H2O2 as oxidant have simple structure, high energy density and can operaite without air. Therefore, the fuel cell using H2O2 as oxidant is good candidates of underwater and space power. Current cathode catalysts for Fuel cells using hydrogen peroxide as oxidant are noble metals, but they are so expensive and scarce that they will raise the costs of the fuel cells largely. Ppy-based transitional metal catalyst demonstrates excellent catalytic activity and durability with the special structure and characteristics, and is regarded as a kind of promising cathode catalyst, much attention has been paid to it in recent years.In this paper, we synthesized a cobalt-polypyrrole-carbon (Co-ppy-C) composite via a simple chemical method, without resorting to pyrolysis. It was characterized by X-diffraction spectroscopy (XRD)、transmission electron microscopy (TEM)、scanning electron microscopy (SEM). XRD pattern indicated that the structure of the Co-ppy-C includedβ-Co(OH)2. SEM and TEM characterization show that the Co-ppy-C nanoparticle with dimension of 20-30 nm. The performance for hydrogen peroxide electro-reduction in KOH solution and H2SO4 solution were investigated by cyclic voltammogram and chronoamperometry test. Results revealed that Co-ppy-C electrodes exhibit high activity and good stability for electrocatalytic reduction of H2O2 in 3.0 mol·dm-3 KOH solution. A current density of as high as-45 mA-cm-2 was achieved on the Co-ppy-C electrode when hydrogen peroxide concentration was 0.4 mol·dm-3 the potential was-0.4V; Co-ppy-C electrodes exhibit low activity in H2SO4 solution. A current density of as high as-45 mA-cm-2 was achieved on the Co-ppy-C electrode when hydrogen peroxide concentration was 0.4 mol·dm-3、the potential was 0.0 V.Constant current was adopted to obtain conducting polypyrrole chemically modified Co3O4 nanowires electrodes under same conditions. The polymerization time and dopant concentration were studied, it demonstrated that the polypyrrole modified Co3O4 nanowires electrodes were formed by 0.1 mol·dm-3 pyrrole for 10 s show better activity. Comparing to the Co3O4 nanowires electrode, these polypyrrole modified electrodes show better activity and greater stability. In 3.0 mol-dm-3 KOH solution, the polypyrrole modified Co3O4 nanowires electrode show the current density of-120 mA-cm-2, which is 15 mA-cm-2 higher than the Co3O4 nanowires electrodes without polypyrrole show.From above obtained results, it can be concluded that the Co-ppy-C and the polypyrrole modified Co3O4 nanowires catalyst have demonstrated a rather promising possibility to substitute commercialized platinum catalyst. It is belived that these achievements in this research has given a certain contribution to the development of the fuel cell using H2O2 as oxidant.
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