Cathode diffusion layer and current collector with slotted foam stainless steel for a micro direct methanol fuel cell

Abstract

In order to reduce the contact and mass transfer impedance of the diffusion layer and current collector of a Micro Direct Methanol Fuel Cell (μDMFC), a novel Membrane Electrode Assembly (MEA) structure is designed by using Foam Stainless Steel (FSS) with a slotting rate of 38.47% for both the cathode diffusion layer and the current collector. Electrochemical tests are performed on the Foam Stainless Steel Membrane Electrode Assembly (FSS-MEA) and the Conventional Carbon Paper Membrane Electrode Assembly (CCP-MEA) μDMFCs. The experimental results show that the maximum power density of FSS-MEA μDMFC is 46.55 mW cm⁻² at 343 K, which is 42.88% higher than that of CCP-MEA μDMFC, and the optimum working concentration of FSS-MEA μDMFC is 2.5 mol L⁻¹, which is 1 mol L⁻¹ higher than that of CCP-MEA μDMFC. Electrochemical Impedance Spectroscopy (EIS) test results show that the contact impedance of FSS-MEA μDMFC is 0.55 Ω cm⁻², which is 15.38% lower than that of CCP-MEA μDMFC. The mass transfer impedance of FSS-MEA μDMFC is 0.99 Ω cm⁻², which is 25.56% lower than that of CCP-MEA μDMFC. This implies that the novel slotted FSS-MEA structure alleviates the methanol crossover and reduces the contact and mass transfer impedance, thus improving μDMFC power density.