Direct-
formic acid fuel cells or DFAFCs are a subcategory of
proton exchange membrane fuel cellProton exchange membrane fuel cells, also known as polymer electrolyte membrane fuel cells , are a type of fuel cell being developed for transport applications as well as for stationary fuel cell applications and portable fuel cell applications...
s 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
methanolMethanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with formula CH3OH . It is toxic: drinking 10 ml will cause blindness, and as little as 100 ml will cause death...
,
formic acidFormic acid is the simplest carboxylic acid. Its formula is HCOOH or CH2O2. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings.In nature, it is found in the stings and bites of many insects of the order...
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
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
because it does not need to be done at high pressures and (or) low temperatures, as formic acid is a liquid at standard temperature and pressure.
Direct-
formic acid fuel cells or DFAFCs are a subcategory of
proton exchange membrane fuel cellProton exchange membrane fuel cells, also known as polymer electrolyte membrane fuel cells , are a type of fuel cell being developed for transport applications as well as for stationary fuel cell applications and portable fuel cell applications...
s 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.
Advantages
Similar to
methanolMethanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with formula CH3OH . It is toxic: drinking 10 ml will cause blindness, and as little as 100 ml will cause death...
,
formic acidFormic acid is the simplest carboxylic acid. Its formula is HCOOH or CH2O2. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings.In nature, it is found in the stings and bites of many insects of the order...
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
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
because it does not need to be done at high pressures and (or) low temperatures, as formic acid is a liquid at standard temperature and pressure. Formic acid does not cross over the polymer membrane, so its efficiency can be higher than that of methanol.
Reactions
DFAFCs convert formic acid and
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
into
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
and
waterWater is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
to produce energy. Formic acid oxiation occurs at the
anodeAn anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID . Electrons flow in the opposite direction to the electric current...
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
cathodeA cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .A widespread misconception is that cathode polarity is always negative...
. Electrons are passed through an external circuit from anode to cathode to provide power to an external device.
Anode: HCOOH → CO
2 + 2 H
+ + 2 e
-
Cathode: 1/2 O
2 + 2 H
+ + 2 e
- → H
2O
Net reaction: HCOOH + 1/2 O
2 → CO
2 + H
2O
History
During previous investigations, researchers dismissed formic acid as a practical fuel because of the high
electrochemicalElectrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor , and which involve electron transfer between the electrode and the electrolyte or species in solution.If a chemical reaction is...
overvoltageWhen the voltage in a circuit or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous...
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-ChampaignThe University of Illinois at Urbana-Champaign is a public research university in the state of Illinois, United States. It is the oldest and largest campus in the University of Illinois system....
) found that the reason for the low performance was the usage of
platinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements...
as a catalyst, as it is common in most other types of fuel cells: using
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
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.
See also
- Glossary of fuel cell terms
The Glossary of fuel cell terms lists the definitions of many terms used within the fuel cell industry. The terms in this fuel cell glossary may be used by fuel cell industry associations, in education material and fuel cell codes and standards to name but a few. -...
- Portable fuel cell applications
Portable fuel cell applications are portable fuel cell applications that are either used as micropower in consumer electronic devices to provide power or as portable power in emergency power systems for critical areas.-Codes and standards:Portable fuel cell applications is a classification in FC...