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Study On Electrocatalytic Activities For Anodic Oxidation Of Small Ogratic Molecules Of Pt Composite Catalyts Prepared By Electrochemical Methods

Posted on:2008-12-25Degree:MasterType:Thesis
Country:ChinaCandidate:Z PengFull Text:PDF
GTID:2121360242964836Subject:Applied Chemistry
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The fuel cell was considered as a high energy density and pollution-free power source in the 21st century. Among the fuel cells direct methanol fuel cells and direct ethanol fuel cells have been widely investigated, which have a variety of benefits such as high energy density, simple structure, abundant fuel sources and low price and thus can be a potential and suitable power source of the vehicles and the mobile instruments. At present, the key point on the investigations of this field is to develop and prepare the catalysts for the small organic molecules anodic oxidation with good electrocatalytic activity, long-term stability and low cost. In this paper, the metal hydroxide or oxide /Pt composite electrodes were prepared by the electrochemical methods, and their electrocatalytic activities for the formaldehyde and ethanol anodic oxidation were studied in detail. The investigation results are as follows:1. The Sn/PANI electrodes were prepared through depositing Sn onto the PANI electrode by the pulse galvanostatic method (PGM). After electro-oxidized by cyclic voltammetry (CV) method in 0.5 M H2SO4 solution or 0.2 M H2O2 + 0.5 M H2SO4 solution respectively, the Sn/PANI electrodes were modified with Pt microparticles by PGM, thus two kinds of Pt/Sn hydroxide/PANI electrodes were prepared. The electrocatalytic activities of these two kinds of electrodes for formaldehyde anodic oxidation were investigated by cyclic voltammetry method. The investigation results show that the electrocatalytic activities of the two kinds of Pt/Sn hydroxide/PANI electrodes were much higher than that of the Pt/Sn /PANI electrode. Further more, the Pt/Sn hydroxide/PANI electrode electro-oxidized in 0.2 M H2O2 + 0.5 M H2SO4 (Pt/Sn hydroxide/PANI electrode I) shows better electrocatalytic activity for formaldehyde anodic oxidation than the electrode electro-oxidized in 0.5 M H2SO4 (Pt/Sn hydroxide/PANI electrode II).2. The effects of the electrochemical preparation and reaction parameters on the electrocatalytic activities of the Pt/Sn hydroxide/PANI electrodes for formaldehyde anodic oxidation were studied. The results present that the peak current densities of the formaldehyde anodic oxidation on both Pt/Sn hydroxide /PANI electrodes were as large as two times of that on the Pt/PANI electrode. The best deposition charge density (Qdep) of PANI is 102 mC/cm2. For Pt/Sn hydroxide/PANI electrode I, the best Qdep of Sn is 945 mC/cm2, and the electrocatalytic activity for formaldehyde anodic oxidation tends to stabilize gradually after Qdep of Pt > 750 mC/cm2. For Pt/Sn hydroxide/PANI electrode II, the best Qdep of Sn is 1215 mC/cm2 and the electrocatalytic activity for formaldehyde anodic oxidation tends to stabilize gradually after Qdep of Pt > 600 mC/cm2. The effects of scan rate of CV and formaldehyde concentration on the peak current density of formaldehyde anodic oxidation on Pt/Sn hydroxide/PANI electrode I were also investigated. The results show that formaldehyde anodic oxidation on Pt/Sn hydroxide/PANI electrode I was mainly affected by the diffusion process of formaldehyde or intermediates when formaldehyde concentration was below 2 M.3. The Pt/ stainless steel (SS) electrode was prepared through depositing Pt onto a SS electrode by PGM. Then the MnOX particles were dispersed on the Pt/ SS electrode surface by pulse potential method, which prepared the MnOX/Pt/SS electrode. The research results show that the electrocatalytic activity especially the long-term stability of the MnOX/Pt/SS electrode was higher than that of the Pt/SS electrode. The deposition current density decreased with the increase of the number of the deposition cycle number, and the best number of the deposition cycle was 6. The electrocatalytic activity of the MnOX/Pt/SS electrode for ethanol anodic oxidation decreased gradually after Qdep of Pt > 600 mC/cm2. The effects of scan rate of CV and ethanol concentration on the electrocatalytic current density of ethanol anodic oxidation on the MnOX/Pt/SS electrode were investigated. The results indicate that ethanol anodic oxidation on the MnOX/Pt/SS electrode might be controlled by the diffusion process of ethanol molecule or its intermediates.
Keywords/Search Tags:small organic molecules, polyaniline, Sn hydroxide, MnOX, electrocatalytic activity
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