Modified Nafion membranes for direct alcohol fuel cells: An overview

Direct alcohol fuel cells (DAFCs) have attracted considerable attention recently as alternative energy resources due to their high efficiency compared with other types of fuel cells. Currently, the two most common types of DAFCs are direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs), which use methanol and ethanol solutions as fuel, respectively. The most widely used polymer membrane for DAFCs is Nafion because it exhibits superior proton conductivity and excellent mechanical properties and chemical stability. However, Nafion membranes for DAFCs are expensive, have limited device lifetimes due to chemical and mechanical degradation, and have higher fuel crossovers through the membrane. Typically, to improve Nafion membranes, many researchers have modified Nafion membranes by modifying the Nafion matrix with organic or inorganic materials with different structures, sizes and compositions, modification techniques, or multilayered systems in order to improve the physical properties of Nafion. The characterization, properties, and performance of DAFCs from various types of modified Nafion membranes are critically reviewed by giving detailed examples. The challenges and future prospects for the modification of Nafion membranes for DAFC applications are also discussed.