Enhanced performance of supercritical CO2 treated Nafion 212 membranes for direct methanol fuel cells

Supercritical carbon dioxide (Sc-CO2) thermal treatment to enhance performances of both Nafion 212 (NR212) commercial membranes with H-form and Na-form for direct methanol fuel cells (DMFCs) is described. XRD measurements show that the crystallinity of H-form NR212 membranes increases with increasing the treated temperature in the Sc-CO2 system, however, the crystallinity of Na-form NR212 membranes decreases with increasing the treated temperature. Since the bigger crystallites formed after the Sc-CO2 treatments, it improves the mechanical strength and dimensional stability of the Sc-CO2 treated NR212 membranes with H-form and Na-form. Compared with the as-received NR212 membranes, all the Sc-CO2 treated NR212 membranes show higher proton conductivity and better capacity of barrier to methanol crossover. From Fenton test, it can be found that the Sc-CO2 treated NR212 membranes have better chemical stability than that of NR212 membranes. Therefore, NR212 membranes treated by the Sc-CO2 method may be promising candidate electrolytes for DMFC applications.

► NR212 membranes are treated by using supercritical carbon dioxide for DMFCs.
► NR212 membranes with H-form and Na-form are treated.
► Proton conductivity of the treated NR212 membranes is improved.
► Methanol permeability of the treated NR212 membranes is lower than that of NR212.
► The treated NR212 membranes show better chemical stability.