Novel anode based on sulfonated polysulfone for medium temperature direct methanol fuel cells

Abstract

Preparation of well performing electrodes using non fluorinated polymer electrolytes is a challenge due to the transport properties of the ion conducting polymer as well as due to the solvents involved. Polymer perfluorinated sulfonic acids such as Nafion® are possible solvable as ionomer in the DMFC anode catalyst layer by concentrated methanol solution at temperatures above 100 °C; therefore more stable polymers are necessary. In this work, we studied the conditions to use sulfonated polysulfone (sPSU) as an ionomer in the anode of a direct methanol fuel cell (DMFC) operating at a temperature of 130 °C.For preparing catalyst dispersions, toxic and flammable solvents were substituted by water using the harmless surfactant Triton X-100 as an additive. As a result the preparation of the catalyst inks and MEAs was accelerated and simplified. The sPSU based anodes showed quite high performance for the methanol oxidation especially in a half cell. The best results were obtained with an anode catalyst layer containing 5% sPSU prepared from a water based ink containing 2% sPSU and 20% Triton X-100 sprayed on a Nafion® 115 membrane.