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Direct-formic acid fuel cells or DFAFCs are a subcategory of proton-exchange fuel cells where, the fuel, formic acid, is not reformed, but fed directly to the fuel cell. Their applications include small, portable electronics such as phones and laptop computers.
Similar to methanol, formic acid is a small organic molecule fed directly into the fuel cell, removing the need for complicated catalytic reforming. Storage of formic acid is much easier and safer than that of hydrogen because it does not need to be done at high pressures and (or) low temperatures, as formic acid is a liquid at ambient temperature.
There are two important advantages that formic acid possesses over methanol for use in the fuel cell. First, formic acid does not cross over the polymer membrane, so its efficiency can be higher than that of methanol. Second, formic acid does not cause blindness as does methanol, making it a somewhat safer fuel in case of leakage.
DFAFCs convert formic acid and oxygen into carbon dioxide and water to produce energy. Formic acid oxiation occurs at the anode on a catalyst layer. Carbon dioxide is formed and protons (H+) are passed through the polymer membrane to react with oxygen on a catalyst layer located at the cathode. Electrons are passed through an external circuit from anode to cathode to provide power to an external device.
Anode: HCOOH → CO2 + 2 H+ + 2 e-
Cathode: 1/2 O2 + 2 H+ + 2 e- → H2O
Net reaction: HCOOH + 1/2 O2 → CO2 + H2O
During previous investigations, researchers dismissed formic acid as a practical fuel because of the high electrochemical overvoltage shown by experiments: this meant the reaction appeared to be too difficult to be practical.
However, in recent years, other researchers (in particular Richard Masel's group at the University of Illinois at Urbana-Champaign) found that the reason for the low performance was the usage of platinum as a catalyst, as it is common in most other types of fuel cells: using palladium instead, they claim to have obtained better performance than equivalent direct methanol fuel cells.
Tekion holds the exclusive license to formic-acid fuel cell technology from the University of Illinois at Urbana-Champaign. The company now is focusing on developing a miniature hybrid battery/fuel-cell unit called the Formira Power Pack and hopes to introduce the packs in the fourth quarter of 2007. The Power Packs rely on the fuel cell, instead of a conventional electrical source like a wall outlet, to recharge the batteries. When the fuel is exhausted, users simply replace the empty fuel cartridge with a fresh one. Because of the high power density of the fuel cell, it should provide about double the time between charges. This technology is expected to only cost about 10-15% more than traditional batteries, and it will result in total freedom from the power grid.
- ^ S. Ha, R. Larsen, and R. I. Masel, "Performance characterization of Pd/C nanocatalyst for direct formic acid fuel cells," Journal of Power Sources, 144, 28-34 (2005)
- ^ http://www.chemicalprocessing.com/industrynews/2006/035.html
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