Catalysis for direct methanol fuel cells

The direct methanol fuel cell (DMFC) is a particular case of a low-temperature proton exchange membrane (PEM) fuel cell (FC). A DMFC utilizes CH₃OH as anode fuel and O₂ as cathode fuel. Depending on the application, a DMFC is typically operated in the range of 40-80°C. DMFCs are very attractive due to the high energy density of CH₃OH, thus making them lightweight devices. In fact, DMFCs can have 15 times the energy density of a Li-ion battery. Other advantages are that DMFCs can be refueled on the fly within seconds, and CH₃OH is an inexpensive and readily available fuel. Furthermore, CH₃OH is a liquid, thus facilitating its distribution, and it can be taken on airplanes in designated cartridges. The impact of the eventual successful commercialization of DMFCs is estimated to be large and expands into the microelectronics industry. However, significant obstacles need to be overcome before DMFCs can be truly considered to be a viable technology. Some of these challenges are related to the anode catalyst such as lowering the cost of the catalyst used by lowering the amount of the noble metal component, as well as extending the lifetime of both the anode and cathode catalysts. A number of reviews describing the technical aspects of DMFCs as an entire device are available (Scott et al. J Power Sources 79:43-59, 1999; Lamm and Müller System design for transport applications. In: Vielstich et al. (ed) Handbook of fuel cells fundamentals technology and applications, Wiley, New York, 2003; Narayanan et al. DMFC system design for portable applications. In: Vielstich et al. (ed) Handbook of fuel cells fundamentals technology and applications, Wiley, New York, 2003; Gottesfeld Design concepts and durability challenges for mini fuel cells. In: Vielstich et al. (ed) Handbook of fuel cells fundamentals technology and applications, Wiley, New York, 2009). Therefore, these aspects are not covered in this chapter, which instead focuses on the catalysis aspects of the electrochemical CH₃OH oxidation reaction. However, cross-references to proton electrolyte fuel cells (PEMFCs) and related reactions are given where appropriate.