Mesoporous materials for fuel cells

Abstract

Fuel cell is the most efficient and environmentally friendly energy conversion technology to directly convert the chemical energy of fuels such as hydrogen, methane, methanol, ethanol and hydrocarbons into electricity with high efficiency and very low greenhouse gas emission. In fuel cells, porosity is a singular attribute, which controls not only the transport of fuel/oxidant to reactive sites but also the length or area of the three phase boundary or electrode/electrolyte interface where the electrochemical reaction occurs. Mesoporous materials with well-defined and highly ordered pore arrays in the range of 2-50 nm in diameter have attracted increasing attention as effective electrode and electrolyte materials for fuel cells in particular the low temperature proton exchange membrane fuel cells (PEMFCs) due to their unique water retention properties of ordered mesopores. This chapter starts with a brief review of the application of mesoporous materials in high temperature solid oxide fuel cells (SOFCs), followed by a detailed description and discussion of the advances in the synthesis and application of the mesoporous structured materials in PEMFCs, including mesoporous polymer membranes, such as mesoporous sulfonated block copolymers and meso-Nafion membrane, mesoporous inorganic/ polymer composite membranes, and mesoporous inorganic materials such as mesoporous silica. The development of mesoporous carbon and metal oxide as electrocatalysts and catalyst supports in PEMFCs is also reviewed. The fundamental relationship between space symmetry, pore size, porosity, ordering level of the mesoporous materials and their electrochemical and fuel cell performance has been discussed.