Towards a High-Performance DMFC Membrane Electrode Assembly Using Iron-Doped Metal Organic Framework Catalysts on the Cathode

Abstract

Direct methanol fuel cells (DMFC) have several advantages for a broad spectrum of energy density demanding applications, ranging from portable devices to stationary backup power. DMFCs deliver power at high efficiencies compared to internal combustion technologies and use high energy density methanol as the fuel. However, DMFCs face several challenges, including methanol crossover at the cathode and slow methanol oxidation reaction (MOR) kinetics at anode that impede its performance. Hence, high loadings of a platinum group metal (PGM) catalyst are normally needed on both the anode and cathode, leading to high raw material catalyst costs. In this work, a PGM-free iron catalyst derived from metal organic framework precursors (Fe-MOF) is used on the cathode side to catalyze the oxygen reduction reaction (ORR). The PGM-free cathode has shown a high tolerance to methanol crossover relative to standard PGM catalysts and high performance relative to previously reported DMFC PGM-free cathode performances in the field. A wide range of operating conditions were tested, and we evaluated the maximum power density using pure oxygen and air with varying methanol concentration. We conducted our tests with a custom, integrated H2 reference electrode that separately provided the anode and cathode overpotentials. This is necessary for cell and electrode optimization since DMFC anode overpotentials are large relative to that of H2 PEMFCs and cannot be used as a quasi-reference electrode. Furthermore, we performed long term durability tests to evaluate PGM-free catalyst stability in the DMFC environment. This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office (FCTO) under Award Number DE-EE0008440.