Fabrication and evaluation of membrane electrode assemblies by low-temperature decal methods for direct methanol fuel cells

In this study, a low-temperature decal transfer method is used to fabricate membrane electrode assemblies (MEAs) and the MEAs are tested for application in a direct methanol fuel cell (DMFC). The low-temperature decal transfer uses a carbon-layered decal substrate with a structure of ionomer/catalyst/carbon/substrate to facilitate the transfer of catalyst layers from the decal substrates to the membranes at a temperature as low as 140 °C, and also to prevent the formation of ionomer skin layer that is known to be formed on the surface of the transferred catalyst layer. The DMFC performance of the MEA (with carbon layer) fabricated by the low-temperature decal transfer method is higher than those of MEAs fabricated by the same method without a carbon layer, a conventional high-temperature decal method, and a direct spray-coating method. The improved DMFC performance of the MEA fabricated with carbon layer by the low-temperature decal transfer method can be attributed to the absence of an ionomer skin on the catalyst layer, which can streamline the diffusion of reactants. Furthermore, the intrinsic properties of the MEA fabricated by the low-temperature decal transfer method are elucidated by field-emission scanning electron microscopy (FESEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) techniques, and cathode CO₂ analysis.