Electrocatalysis for the Direct Alcohol Fuel Cell - Fuel Cell Catalysis: A Surface Science Approach - page 338

& CHAPTER 11
Electrocatalysis for the Direct Alcohol
Fuel Cell
J.-M. LEGER, C. COUTANCEAU, and C. LAMY
Laboratoire de Catalyse en Chimie Organique, UMR 6503 CNRS, Equipe Electrocatalyse, Universit´ de
Poitiers, 40 Avenue du Recteur Pineau, F-86022 Poitiers, France
11.1 INTRODUCTION
Fuel cells are electrochemical devices transforming the heat of combustion of a fuel
(hydrogen, natural gas, methanol, ethanol, hydrocarbons, etc.) directly into electricity.
The fuel is electrochemically oxidized at the anode, whereas the oxidant (oxygen from
the air) is reduced at the cathode. This process does not follow Carnot's theorem, so
that higher energy efficiencies are expected: up to 40 - 50% in electrical energy and
80 - 85% in total energy (heat production in addition to electricity).
Typically, pure hydrogen or hydrogen-rich gases are used as fuel for proton
exchange membrane fuel cells (PEMFC), allowing the highest electrical efficiency.
However, the production, storage, and distribution of hydrogen are still strong limit-
ations on the development of such techniques [Gosselink, 2002; Str¨ bel et al.,
2002]. In this context, the use of hydrogen carriers such as alcohols (methanol, etha-
nol, etc.), in a direct alcohol fuel cell (DAFC), appears particularly convenient for two
main reasons: they are liquids (allowing easy storage) and their theoretical mass
energy density is rather high (6.1 and 8.0 kWh kg 21 for methanol and ethanol, respect-
ively), close to that of gasoline (10.5 kWh kg 21 ) [Lamy and L´ger, 1994].
Methanol [Bett et al., 1998; Wasmus and K¨ ver, 1999; Coutanceau et al., 2004;
Batista et al., 2004] and ethanol [Xia et al., 1997; Vigier et al., 2004a; Lamy et al.,
2004] are the most studied alcohols for DAFC application (in DMFCs and DEFCs,
respectively). As a consequence of the acidic environment of the ionomeric conduct-
ing membrane (Nafion) and of the low working temperatures of DAFCs (60 - 120 8C),
the use of platinum is impossible to avoid, owing to its catalytic properties to activate
C - H bond cleavage during the first adsorption steps, although this leads to rather poor