Methanol permeation through membrane electrode assembly under proton transmission

Abstract

This paper describes the phenomena of methanol permeation through a membrane electrode assembly (MEA) incorporating a proton exchange membrane (PEM) from anode to cathode under the proton transmission to clarify the methanol crossover, which diminishes the direct methanol fuel cell power. By using the MEA-installed single cell with a feed of a methanol-water solution to the anode and without any feed to the cathode, we measured (i) the hydrogen evolution rate and (ii) the methanol-water solution permeation rate, both observed at the cathode by single-cell electrolysis operation. As a result, when the current density of the electrolysis increased, the rates of hydrogen evolution and methanol-water permeation proportionally increased. Based on the observations, protons generated at the anode were transformed to hydrogen at cathode, accompanied by the generation of the methanol-water solution at the cathode. In addition, the methanol concentration of the methanol-water solution was found to be the same as that fed to the anode. According to these, protons solvated with methanol and water are transmitted through the PEM to generate the methanol-water solution at the cathode, which leads to a methanol crossover.