Influence of dispersion solvent for catalyst ink containing sulfonated poly(ether ether ketone) on cathode behaviour in a direct methanol fuel cell

Electrode properties are key determinants of the performance of the membrane-electrode assembly (MEA) in fuel cells. In this study, the influence of dispersion solvent for the catalyst ink on cathode properties and also on the cell performance is investigated. Cathodes containing sulfonated poly(ether ether ketone) (sPEEK) as an electrode binder are prepared with different dispersion solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP). When DMF is used as a casting solvent, the sPEEK membrane exhibits a particular low proton conductivity. The high boiling points of DMSO and NMP as dispersion solvents for the cathode lead to a reduction in the pore volume of the cathode and, consequently, cause poor transport of oxygen at the cathode. A MEA based on a cathode using DMAc as a dispersion solvent gives the highest performance due to the high proton conductivity and good morphology of the cathode.