Direct-formic acid fuel cells or DFAFCs are a subcategory of proton exchange membrane 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 as well as larger fixed power applications and vehicles.
Contents
Advantages
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 non-flammable 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 oxygen into carbon dioxide and water to produce energy. Formic acid oxidation 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
History
During previous investigations, researchers dismissed formic acid as a practical fuel because of the high overpotential shown by experiments: this meant the reaction appeared to be too difficult to be practical. However, in 2005 - 2006, 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. As of April 2006, Tekion held the exclusive license to DFAFC fuel cell technology using PEM membranes and formic-acid fuel from the University of Illinois at Urbana-Champaign, and with an investment from Motorola, was partnering with BASF to design and manufacture power packs by late 2007, but development appears to have stalled, and almost all information was removed from Tekion's web site before April 24, 2010.
According to the Nov/Dec 2014 issue of Aerospace Manufacturing and Design (www.onlineamd.com), Neah Power Systems, Inc. and Silent Falcon UAS Technologies will work together to integrate formic acid reformer fuel cell technology into the Silent Falcon's unmanned aerial system (UAS), aka "drone". See www.neahpower.com and www.silentfalconuas.com for more details.