Direct-ethanol fuel cell

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Direct-ethanol fuel cells or DEFCs are a category of

Advantages

DEFC uses Ethanol in the fuel cell instead of the more toxic methanol. Ethanol is an attractive alternative to methanol because it comes with a supply chain that's already in place. Ethanol also remains the easier fuel to work with for widespread use by consumers.

are some of the most efficient materials for the oxidation of small organic molecules.

Reaction

The DEFC, similar to the

are transported through an external circuit from anode to cathode, providing power to connected devices.

The half-reactions are:

	Equation
Anode	${\displaystyle \mathrm {C_{2}H_{5}OH+3\ H_{2}O\to 12\ H^{+}+12\ e^{-}+2\ CO_{2}} }$ oxidation
Cathode	${\displaystyle \mathrm {3\ O_{2}+12\ H^{+}+12\ e^{-}\to 6\ H_{2}O} }$ reduction
Overall reaction	${\displaystyle \mathrm {C_{2}H_{5}OH+3\ O_{2}\to 3\ H_{2}O+2\ CO_{2}} }$ redox reaction

Issues

Platinum-based catalysts are expensive, so practical exploitation of ethanol as fuel for a

. In practice tiny metal particles are fixed onto a substrate in such a way that they produce a very active catalyst.

A polymer acts as electrolyte. The charge is carried by the hydrogen ion (proton). The liquid ethanol (C₂H₅OH) is oxidized at the anode in the presence of water, generating CO₂, hydrogen ions and electrons. Hydrogen ions travel through the electrolyte. They react at the cathode with oxygen from the air and the electrons from the external circuit forming water.

Bio-Ethanol based fuel cells may improve the well-to-wheel balance of this biofuel because of the increased conversion rate of the fuel cell compared to the internal combustion engine. But real world figures may be only achieved in some years since the development of direct methanol and ethanol fuel cells is lagging behind hydrogen powered fuel cells.^[3]

Recent accomplishments

On 13 May 2007 a team from the University of Applied Sciences in Offenburg presented the world's first vehicle powered by a DEFC at Shell's Eco-marathon in France. The car "Schluckspecht" completed a successful test drive on Nogaro Circuit, powered by a DEFC stack giving an output voltage of 20 to 45 V (depending on load).^[4]

Various prototypes of Direct Ethanol Fuel Cell Stack mobile phone chargers have been built^[5] featuring voltages from 2V to 7V and powers from 800 mW to 2W^[6] were built and tested.

Sources

• Membranes for DEFC -Fraunhofer Institute for Interfacial Engineering and Biotechnology
• DEFC membrane

See also

• Alkali anion exchange membrane
• Glossary of fuel cell terms
• Timeline of alcohol fuel

References

Further reading

• "New catalyst boosts hydrogen as transport fuel". By Alok Jha. 21 August 2008. The Guardian.