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Preparation and Research of Novel Pd-based and Pt-based Electrocatalyst for Methanol Oxidation

Author: ZhanZuo
Tutor: ZhaoYanQing
School: Guangxi Normal University
Course: Physical and chemical
Keywords: Direct methanol fuel cell Electrocatalytic oxidation Pd MnO2 Graphene Pt
CLC: O643.36
Type: Master's thesis
Year: 2011
Downloads: 119
Quote: 0
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Abstract


Direct methanol fuel cell (DMFC) has a non-polluting fuel sources, the high rate of energy conversion, storage and transportation convenient, is a green energy technologies. Methanol oxidation reaction is often carried out in an acidic medium, resulting in a lower methanol oxidation activity on the anode, a serious impediment to the DMFC application and development. In addition, methanol oxidation in acidic media often use the the Pt funds are nanomaterials as catalyst, the price is expensive, so much the focus of attention to improve the study of metal catalytic activity. When the oxidation reaction is carried out in alkaline medium, on the one hand, can reduce the potential of the methanol oxidation, so that oxidation can occur in the lower potential, the oxidation reaction is more easily performed; other hand, some of the transition metal from low-cost in acidic medium methanol catalytic activity in alkaline medium has good reactivity, in order to reduce the catalyst preparation costs, improve its catalytic activity, has important practical significance to study alkaline direct methanol fuel cell (ADMFC) . This article focuses on the study of Pd and Pt-based catalysts for methanol electro-catalytic oxidation resistance, the text of which is divided into two parts: the first part: DMFC advantages, the reaction in different media principles and DMFC different method of catalyst preparation and research status Overview. Part II: research papers, including the development of a new carrier, the use of low-cost additive metal catalytic activity and doped with other elements to improve the carrier activity in three areas, the specific contents are as follows: 1. MnO2 prepared using a simple and novel approach modified Multi-walled carbon nanotubes (MWCNTs) load of Pd Nanoparticles the catalyst (Pd-Mn02/MWCNTs). With a scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD), respectively, on the morphology of the catalyst composition and Crystal Structure Characterization, The results showed that The the Pd-MnO2/MWCNTs have been successfully prepared and the Pd nanoparticles in MnO2/MWCNTs surface having high dispersibility. By cyclic voltammetry and timing current law The Electrocatalytic Oxidation Pd-MnO2/MWCNTs conduct characterized, the results show Pd-MnO2/MWCNTs than Pd / MWCNTs and Pd / Vulcan (commercial Vulcan carbon black supported Pd nanoparticles catalyst) has better electrical activity and stability. CO stripping voltammetry and impedance spectroscopy (EIS) results show that compared with Pd / MWCNTs and Pd / Vulcan Pd-MnO2/MWCNTs has a larger electrochemically active surface area (EAS) and a smaller charge transport impedance . Prepared polypyrrole modified graphene supported Pd nanoparticles catalyst (Pd / PPy-of graphene). By infrared spectroscopy (FT-IR) and Raman spectra (RS), SEM, TEM and XRD structure, morphology and crystal structure of the catalyst characterization, EDS for the elemental composition of the catalyst was measured, the results show that graphene a good catalyst carrier, and Pd nanoparticles can be well dispersed in the graphene surface of the polypyrrole modified. The catalyst for the methanol oxidation activity by cyclic voltammetry and Amperometric characterization results show that compared with the traditional commercial catalyst, Pd / PPy-graphene catalyst for the methanol has a higher oxidation activity and stability. PD / PPy-graphene good catalyst activity depends on the electrochemical active surface area (EAS), the stronger the electrical conductivity and charge transfer capabilities. The polypyrrole modified graphene vector provides a number of active sites for the deposition of Pd nanoparticles to improve the load rate and the utilization of Pd nanoparticles. The above results are noted, with polypyrrole can effectively improve the the graphene activity, there will be a good prospect of application in the field of study of the electro-catalytic graphene. 3 800 ° C high temperature calcination of poly-o-toluidine method of preparation of the new nitrogen-containing amorphous carbon (CXN) carrier, the nitrogen content of about 8.5%. SEM, EDS, XRD and RS, respectively, on the morphology of the catalyst composition and crystal structure characterization, the results show that the Pd has been successfully loaded on CxN surface of the carrier, and the new CxN carrier having good integrity. Were characterized by cyclic voltammetry, chronoamperometry and multiple cycles scanning Pd / CxN Electrocatalytic Oxidation, the results show the Pd / CxN than Pd / POT (poly-o-toluidine load Pd Nanoparticles catalyst) and Pd / Vulcan has better electrocatalytic activity and stability. The Pd / CxN reason has strong catalytic activity, because the presence of a nitrogen element so that the carrier having a polar, significantly improve the chemical activity of the carrier, to provide a large number of active sites for the deposition of the metal nanoparticle, conducive Pd nanoparticles deposition and dispersion, the the Pd / CXN catalyst has a large electrochemical active surface area, has high catalytic activity and stability for methanol oxidation in alkaline medium, indicating that CxN in the direct methanol fuel cell research is a very there is the potential of the catalyst carrier. Simple method of sulfur and nitrogen-doped MWCNTs solution of sodium borohydride as reducing agent the PtCl62-to prepare flower-like Pt nano-catalyst ((Pt / SN-MWCNT). Element analysis Pt / SN-MWCNT subjected to elemental analysis, the results indicate that the sulfur and nitrogen successfully doped MWCNTs respectively on the morphology and crystal structure of the catalyst were characterized by SEM, TEM and XRD results show that the flower-shaped Pt nanoparticles successfully \activity and stability of the reason why this flower-shaped Pt nano-catalyst has good electrocatalytic activity as sulfur and nitrogen doped MWCNTs, improve the Pt nanoparticles dispersed on its surface, so that Pt/SN- MWCNT catalyst having a larger surface area of ??the electrochemical activity.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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