Structural control and impedance analysis of cathode for direct methanol fuel cell

The effect of the Nafion content and loading method in the catalyst layer of the cathode for a Direct Methanol Fuel Cell (DMFC) was investigated. The impedance of the full cell and cathode were determined by ac impedance spectroscopy. The Nafion content of 1.0 mg cm−2 improved the current density at a cell voltage of 0.4 V up to 258 mA cm−2 versus 128 mA cm−2 at a content of 0.5 mg cm−2. The increase in the Nafion content decreased the diameter of the arc at low frequencies. For the electrode prepared by the spray method (SME), the cell performance and cathode performance using a dynamic hydrogen electrode (DHE) as the reference electrode was higher than those of the electrode prepared by the paste method (PME) by decreasing the cathode potential. From the ac impedance measurement of the cathode, the diffusion resistance of the SME electrode had the lowest interfacial resistance of the cathode electrodes. The higher cell performance was mostly dependent on the diffusion resistance. The SME with a porous structure and a catalyst layer thickness of 50 μm were characterized by SEM and BET adsorption measurements.