Recent advances in the development of direct alcohol fuel cells (DAFC)

The electrooxidation of some low molecular weight alcohols, such as ethanol, ethylene glycol and n-propanol, is discussed in terms of reaction mechanisms and catalytic activity of the anode material Some examples of a single cell, using a proton exchange membrane (PEM) as electrolyte, are given to illustrate interesting results, particularly for the direct electrooxidation of ethanol This alcohol may replace methanol in a direct alcohol fuel cell

Electrocatalytic oxidation of aliphatic alcohols: Application to the direct alcohol fuel cell (DAFC)

Recent progress in the direct ethanol fuel cell: development of new platinum–tin electrocatalysts

In the present work several Pt-based anode catalysts supported on carbon XC-72R were prepared with a novel method and characterized by means of XRD, TEM and XPS analysis. It was found that all these catalysts are consisted of uniform nanosized particles with sharp distribution and Pt lattice parameter decreases with the addition of Ru or Pd and increases with the addition of Sn or W. Cyclic voltammetry (CV) measurements and single direct ethanol fuel cell (DEFC) tests jointly showed that the presence of Sn, Ru and W enhances the activity of Pt towards ethanol electro-oxidation in the following order: Pt1Sn1/C>Pt1Ru1/C>Pt1W1/C>Pt1Pd1/C>Pt/C. Moreover, Pt1Ru1/C further modified by W and Mo showed improved ethanol electro-oxidation activity, but its DEFC performance was found to be inferior to that measured for Pt1Sn1/C. Under this respect, several PtSn/C catalysts with different Pt/Sn atomic ratio were also identically prepared and characterized and their direct ethanol fuel cell performances were evaluated. It was found that the single direct ethanol fuel cell having Pt1Sn1/C or Pt3Sn2/C or Pt2Sn1/C as anode catalyst showed better performances than those with Pt3Sn1/C or Pt4Sn1/C. It was also found that the latter two cells exhibited higher performances than the single cell using Pt1Ru1/C, which is exclusively used in PEMFC as anode catalyst for both methanol electro-oxidation and CO-tolerance. This distinct difference in DEFC performance between the catalysts examined here would be attributed to the so-called bifunctional mechanism and to the electronic interaction between Pt and additives. It is thought that an amount of –OHads, an amount of surface Pt active sites and the conductivity effect of PtSn/C catalysts would determine the activity of PtSn/C with different Pt/Sn ratios. At lower temperature values or at low current density regions where the electro-oxidation of ethanol is considered not so fast and its chemisorption is not the rate-determining step, the Pt3Sn2/C seems to be more suitable for the direct ethanol fuel cell. At 75 °C, the single ethanol fuel cell with Pt3Sn2/C as anode catalyst showed a comparable performance to that with Pt2Sn1/C, but at higher temperature of 90 °C, the latter presented much better performance. It is thought from a practical point of view that Pt2Sn1/C, supplying sufficient –OHads and having adequate active Pt sites and acceptable ohmic effect, could be the appropriate anode catalyst for DEFC.

Pt based anode catalysts for direct ethanol fuel cells

On the mechanism of ethanol electro-oxidation on Pt and PtSn catalysts: electrochemical and in situ IR reflectance spectroscopy studies

The direct platinisation of a solid polymer electrolyte (Nafion® membrane) was realized by chemical reduction of a platinum salt. The Pt–PEM electrodes thus obtained were modified by tin to improve the electrocatalytic activity towards the electrooxidation of ethanol. The Pt–PEM and Pt–Sn–PEM electrodes were characterized by TEM, EDX and XRD analysis, cyclic voltammetry, and their polarisation curves for the electrooxidation of ethanol were determined under quasisteady state conditions.

Enhancement of the electrooxidation of ethanol on a Pt–PEM electrode modified by tin. Part I: Half cell study

Nafion® can be used as a solid polymer electrolyte in a PEM fuel cell. Direct platinization of the membrane was realized by chemical reduction of a platinum compound. The platinization procedure was modified to enhance the roughness factor and thus to improve the electrocatalytic activity towards ethanol electrooxidation. The Pt–PEM electrodes were characterized by TEM, atomic absorption analysis, cyclic voltammetry and their polarization curves for ethanol electrooxidation.

F. Delime

Papers

Enhancement of the electrooxidation of ethanol on a Pt–PEM electrode modified by tin. Part I: Half cell study

Optimization of platinum dispersion in Pt-PEM electrodes: application to the electrooxidation of ethanol