A flexible direct methanol micro-fuel cell based on a metalized, photosensitive polymer film

This paper presents and investigates a concept for a flexible direct methanol micro-fuel cell (FDMMFC) based on the microstructuring of a Cr/Au metalized, thin polymer film of photosensitive SU-8. The inscribed microchannels in the electrodes are 200 μm × 200 μm in crosssection and spanning an active fuel cell area of 10 mm × 10 mm with a Pt-black catalyst on the cathode side of the membrane electrode assembly (MEA) and a Pt–Ru alloy catalyst on the anode side. Subsequently, the paper focuses on a thorough electrical characterization of the FDMMFC, under the employment of a variable resistor simulating an electrical load as well as a classical galvanostatical measurement technique. The fuel cell is also tested while operating in a bent, non-flat configuration. An extensive parameter study revealed an optimal and long-term stable operating condition for the fuel cell employing for both electrodes a serpentine flow field and a volume flow rate of 0.14 ml min−1 of a 1 M methanol solution at the anode side with a gas volume flow rate of 8 ml min−1 of humidified O2 at the cathode side yielding a power density of 19.0 mW cm2 at 75 mA cm2 at a temperature of 60 °C.Furthermore, a flow-visualization of the two-phase flow occurring at the anode side has been performed by utilizing fluorescence microscopy. The strong influence of the two-phase flow on the performance of a fuel cell at high current densities becomes apparent in correlating the observed flow patterns with the corresponding current density of the polarization curve. The paper also investigates the functionality of the present FDMMFC under different bent conditions. The tests showed an insignificant drop of the electrical performance under bending due to an inhomogeneous contact resistance.