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On the pathways of methanol and ethanol oxidation

Advances in Electrocatalysis, Materials, Diagnostics and Durability

Electrocatalyst materials for low temperature fuel cells

Fundamental catalysis models

  1. W. Vielstich,
  2. V. A. Paganin,
  3. O. B. Alves,
  4. E. G. Ciapina

Published Online: 15 DEC 2010

DOI: 10.1002/9780470974001.f500011

Handbook of Fuel Cells

Handbook of Fuel Cells

How to Cite

Vielstich, W., Paganin, V. A., Alves, O. B. and Ciapina, E. G. 2010. On the pathways of methanol and ethanol oxidation. Handbook of Fuel Cells. .

Author Information

  1. IQSC, Universidade de São Paulo, São Carlos, Brazil

Publication History

  1. Published Online: 15 DEC 2010

Abstract

The knowledge on the different oxidation pathways of liquid fuels like methanol and ethanol at Pt-based electrodes has improved recently. Parallel pathways are responsible for the kind of intermediates, the effective cell voltage, and for the amount of charge per fuel molecule. Both methanol and ethanol have a high thermodynamic energy density, 6000 and 8000 Wh kg−1, respectively. In alkaline media, better potential and current density data can be obtained. But the technical application is handicapped by carbonate formation and by a loss of OH electrolyte. Therefore, reactions in acid media are studied and used in fuel cell systems.

This chapter reviews detailed investigations of the pathways of methanol oxidation at different Pt-metal electrodes. Under optimized operating conditions, an optimum reaction sequence is obtained giving almost 6 e per molecule.

In contrast to CH3OH, the two C atoms C2H5OH shows, at temperatures up to 80 °C, and on PtRu, PtSn, or PtPd as catalysts, less than 4 e per molecule, i.e., at best acetic acid is formed. The main problem in the electrocatalysis of ethanol oxidation is the scission of the C-C bond, necessary for yielding CO2. The detection of intermediates and products and the form of possible parallel pathways are demonstrated. Temperatures around 100 °C and above are problematic for simple fuel cell systems. But under these conditions and using Raney-Pt catalysts, Sandstede demonstrated in the 1960s that an anodic oxidation of acetic acid is possible.

Keywords:

  • reaction pathways;
  • electrocatalysis;
  • energy efficiency;
  • FTIRS;
  • DEMS;
  • PtRu;
  • Raney Pt