A novel design of bipolar interconnect plate for self-air breathing micro fuel cells and degradation issues

Abstract

The optimal utilisation of fuels such as hydrogen and methanol in micro fuel cells (MFC) in combination with effective fuel storage solutions can offer much longer operational and standby time and shorter recharging time compared to batteries. Therefore, MFCs have an immense potential to replace or to be used in combination with batteries for portable power applications. However, the overall fuel cell system is required to be compact to suit the appliance, have a simple support system, manufacturable at a mass scale with low cost materials and fabrication technologies, and have lifetimes significantly longer than batteries. In a fuel cell stack, the interconnect plates occupy majority of the volume of the stack, and reducing their size (thickness) and weight would be enormously beneficial in terms of improving the power density of the device. Therefore, the purpose of this study is to investigate design options of the interconnect plate for operation of the stack under ambient and passive conditions. Three stacks (power output in the 3–12 We range) were built using two designs and lifetime tests were performed up to 21,000 h using industrial grade hydrogen under both constant and simulated cyclic loads. The voltage–current characteristics of the stacks were analysed by model equations and the overall performance was assessed by performing energy balance calculations. The major source of cell degradation, increasing amplitude of voltage fluctuations and manifestation of limiting current behaviour for some cells have been discussed and appear to be related to the poisoning of Pt catalyst by impurities such as S, Hg and CO present in the industrial grade hydrogen used in the study, leading to increasing loss of electrochemical active surface area of the catalyst with time.