Composite Nafion-Functionalized PDMS Electrospun Fibers for Direct Methanol Fuel Cells

Abstract

Direct methanol fuel cells (DMF) have received great attention as a promising portable device due to its high power density, low overall emission and longtime power supply. As the key component of the DMFC system, proton exchange membranes (PEM) are extensively studied since the conception of of proton electrolyte membrane fuel cells in early 1960s. An efficient membrane essentially provides two main functionalities: (1) physically separating the anode from the cathode, and (2) providing proton pathways for inter-electrode proton transport. Nafion is the most widely used PEMs due to its high proton conductivity. Water is of an important element during proton transfer mechanism; however it causes membrane swelling, resulting in serious methanol permeation. To overcome swelling and excessive methanol crossover, a novel PDMS reinforced Nafion membrane is developed in this paper. PDMS has good liquidity before crosslinking due to its flexible molecular structure. Its hydrophobicity also effectively limits membrane swelling in a high relative humidity environment. In this study, Nafion solution is electrospun into mats and the morphological structures are observed via a scanning electron microscopy. Different ratios of Nafion are also mechanically dispersed into PDMS and mixture is successfully infiltrated into the void space among fibers to improve the connectivity of proton transport. The performances of different fabricated composite membranes are compared against a simple Nafion membrane in terms of water swelling and uptake, and the fuel cell performance.