METAL NANOPARTICLES – ZEOLITE MODIFIED ANODE FOR DIRECT METHANOL FUEL CELL

Abstract

Direct alcohol fuel cells (DMFCs) are considered a promising future energy source for portable electronic devices. However, low activity of the methanol electro-oxidation catalysts in addition to its costly price as well as its poisoning by poisoned species produced during the electrooxidation is one of challenges facing the direct methanol fuel cell (DMFC) technology. A brief introduction followed by reviewing literature relevant to the present work is summarized. Results and discussion section include the suggestion of promising electrocatalysts for methanol electro-oxidation either in acid or alkaline medium (2nd and 3rd parts of results and discussion). This was preceded by studying the electrochemical behavior of methanol at polycrystalline platinum and the possible in situ recovery of the poisoned electrodes following various scenarios of recovery (1st part of results and discussion).

In the second part of the results' section, the electrochemical behavior of methanol on a binary catalyst composed of platinum nanoparticles and bismuth electrodeposited consecutively onto a pre-electro-activated glassy carbon electrode has been investigated. Either platinum was deposited first followed by bismuth or the reverse. Modified electrodes, i.e., Pt/Bi/GC (Bi deposited first followed by Pt) and Bi/Pt/GC electrodes (Pt deposited first) were electrochemically characterized using cyclic voltammetry and chronoamperometry, and morphologically using SEM, EDX and XRD. It has been found that the electrocatalytic activity critically depends on the order of the deposition of platinum and bismuth. The Bi/Pt/GC electrode presented a larger electrocatalytic activity towards methanol oxidation compared to Pt/Bi/GC and Pt/GC electrodes. The higher activity obtained at the former electrode is attributed to the cooperative effect of Pt and Bi towards methanol oxidation. In the third part, platinum and ruthenium (Pt-Ru) electrodeposited onto zeolite and/or Nafion was investigated for methanol oxidation in acid medium. Involving zeolite in the underlying substrate enhanced the electrocatalytic behavior of the Pt-Ru binary catalyst towards methanol oxidation. The modified electrodes were morphologically characterized using scanning electron microscopy and their composition were probed using energy dispersive x-ray.

Keywords: Catalysts, zeolite, Cyclic voltammetry, Methanol electrooxidation, Chronoamperometric, Glassy carbon electrode.