Managing Fuel Crossover in Direct Methanol Fuel Cells By Optimizing the Anode Microporous Layer

Abstract

Direct methanol fuel cells (DMFCs) have been considered a promising candidate as a replacement for small scale and portable power applications, however, there are technical barriers that have prevented widespread use of DMFCs in commercial applications. Of these technical barriers, unreacted methanol crossing over from the anode to the cathode has been identified as a primary limiting factor of DMFCs as this phenomenon results in lowered efficiency and reduced open circuit voltages (OCVs) on the cathode, and ultimately limits the OCV of the cell itself.1 In this work, the authors used an anode design proposal provided by (Metzger et al, 2021, JEECS-20-1185) to create a strongly hydrophilic microporous layer (MPL) on the anode gas diffusion layer (GDL) to reduce methanol crossover by increasing the capillary pressure in the pores of the MPL required for the methanol to crossover prior to reacting.2 The authors fabricated three membrane electrode assemblies. (MEAs) MEA 1 was fabricated using a traditional hydrophobic MPL on the anode GDL, whereas MEAs 2 and 3 were fabricated using customized hydrophilic MPLs. The GDL for MEA 2 was heat treated at 165 F for one hour and the GDL for MEA 3 was dried in atmospheric conditions for 24 hours. A peak power density of 71 mW/cm2 was observed using 1M methanol solution with MEA 1. Using this approach, the authors were able to achieve a peak power density of 68.1 mW/cm2 and 70.1 mW/cm2 with MEAs 2 and 3, respectively, using 3M methanol solution. Additionally, the authors achieved a peak power density of 32 mW/cm2 and 30.7 mW/cm2 using 7.5M methanol solution. This study provides a framework for creating low-cost hydrophilic MPLs that can be utilized on the anode GDL to reduce fuel crossover in DMFCs. Figure 1