Enhanced performance of a passive direct methanol fuel cell with decreased Nafion aggregate size within the anode catalytic layer

The decrease in Nafion ionomer size within the anode catalytic layer for a passive direct methanol fuel cell (DMFC) results in a significant enhancement in fuel cell’s performance. Dynamic light scattering measurement demonstrates that the agglomerate size of Nafion ionomer in the solution decreases and the aggregate particle size distribution becomes narrow until a monodispersed Nafion ionomer was obtained with an increase in heat treatment temperature. The improved performance of the passive DMFC with smaller Nafion ionomer agglomerates within the anode catalytic layer can be ascribed to a decrease in charge-transfer resistance of anodic reaction obtained by electrochemical impedance analysis and to an improvement in catalyst utilization verified by cyclic voltammetric measurement. Furthermore, the small congeries formed between catalyst nanoparticles and Nafion ionomers could lead to a decrease in Nafion loading within the catalytic layer. This study confirms that the decrease in Nafion aggregation within the catalytic ink is beneficial to an improvement in both catalyst and Nafion ionomer utilization, thus enhancing fuel cell’s performance.

► The decreased Nafion ionomer size enhanced the effective contact between catalyst and electrolyte.
► The use with small size of Nafion ionomer leads to an improved performance of a DMFC.
► It can be ascribed to a decrease in charge-transfer resistance of the anodic reaction.