A review of advancements in commercial and non-commercial Nafion-based proton exchange membranes for direct methanol fuel cells

Nafion membranes are commercially available for the application of direct methanol fuel cells (DMFCs) due to their unique nano-porous structure, high wettability, high ion exchange capacity due to sulfonic groups and high mechanical strength. However, its high cost and high swelling in water result in high methanol crossover, low chemical stability and low ion conductivity at elevated temperatures that limit its usage. Moreover, in commercial membranes when the thickness increases, the ion conductivity compromises and when the thickness decreases, the fuel crossover increases which disrupts the performance of the fuel cell. The modification of pre-existing Nafion membrane such as Nafion 115, Nafion 117, Nafion 212, Nafion 112 and laboratory recasted Nafion membrane is a promising requirement for their future applications. Additives such as organic, inorganic nanoparticles and polymers apply to the Nafion membrane that not only tune the physical aspects of the membrane but also improve the electrochemical properties of the membrane. This review article focuses on advances in different Nafion commercial membranes and laboratory recasted non-commercial Nafion membrane that make under special conditions after modifications. This paper provides challenges, advantages, and disadvantages, as well as future advances in the application of composite membranes in direct methanol fuel cells.