Abstract
As a key component of direct methanol fuel cells, proton exchange membranes with suitable thickness and robust mechanical properties have attracted increasing attention. On the one hand, a thinner membrane gives a lower internal resistance, which contributes highly to the overall electrochemical performance of the cell, on the other hand, strong mechanical strength is required for the application of proton exchange membranes. In this work, a sulfonated poly (fluorenyl ether ketone) (SPFEK)-impregnated polyimide nanofiber mat composite membrane (PI@SPFEK) was fabricated. The new composite membrane with a thickness of about 55 μm exhibited a tensile strength of 35.1 MPa in a hydrated state, which is about 65.8% higher than that of the pristine SPFEK membrane. The antioxidant stability test in Fenton’s reagent shows that the reinforced membrane affords better oxidation stability than does the pristine SPFEK membrane. Furthermore, the morphology, proton conductivity, methanol permeability, and fuel cell performance were carefully evaluated and discussed.
Highlights
Direct methanol fuel cells (DMFCs) are a type of proton exchange membrane fuel cell (PEMFC) and have potential applications in portable electronic devices
We present the fabrication and characterization of SPFEK-impregnated electrospun polyimide (PI) nanofiber mat composite membranes with optimal thickness and stronger mechanical strength
As a robust proton exchange membrane, the PI@SPFEK composite membrane shows acceptable and even higher power density when compared with that reported for other proton exchange membranes (PEMs) for DMFC applications [40,41]
Summary
Direct methanol fuel cells (DMFCs) are a type of proton exchange membrane fuel cell (PEMFC) and have potential applications in portable electronic devices. A common way to improve proton conductivity is to attach more sulfonic acid groups onto the polymer chain, but the high degree of sulfonation results in a deterioration of mechanical strength and an increase in methanol permeability because of the excessive membrane swelling and consequent increased electro-osmotic drag [19,20]. Another effective method is to control the thickness of the membrane. We present the fabrication and characterization of SPFEK-impregnated electrospun polyimide (PI) nanofiber mat composite membranes with optimal thickness and stronger mechanical strength. The microstructure, mechanical properties, proton conductivity, methanol permeability, and DMFC single cell performance of the as-prepared membranes were carefully evaluated and discussed
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