Plasma‐Polymerized Membranes with High Proton Conductivity for a Micro Semi‐Passive Direct Methanol Fuel Cell

Abstract

A proton exchange membrane has been synthesized by a pulsed plasma discharge technique using styrene, trifluoromethane sulfonic acid, and benzenesulfonyl fluoride as the monomers. It shows that the presence of benzenesulfonyl fluoride could reduce the degree of the fragmentation of the monomers by plasma discharge and the ablation of polymers or membranes by acid groups. The fabricated membrane is reported to have a high percentage of sulfonic acid groups and exhibits higher ion exchange capacity, water uptake, and proton conductivity and lower activation barrier for proton conduction and methanol permeability in comparison to the membranes synthesized with only using styrene and trifluoromethane sulfonic acid as the monomers and the commercial Nafion 117. The electrochemical results show that the micro semi‐passive direct methanol fuel cells (μsp‐DMFCs) assembled with the fabricated membrane can exhibit higher electrochemical performance than those with Nafion 117 and the membrane synthesized with only using styrene and trifluoromethane sulfonic acid as the monomers. The stability measurement also shows that the electrochemical performance of the μsp‐DMFCs assembled with this membrane is more stable than that of the μsp‐DMFCs with Nafion 117. These results clearly demonstrate the great potential of using such membranes as the PEMs to improve electrochemical performance of fuel cells.