Now that fuel cell technology has proven its potential in numerous test vehicles of many international car manufacturers over many years, it is planned to commercialise it in mass-produced vehicles by 2020. However, in order to reach the cost targets, several technological breakthroughs are still needed. To achieve this, detailed understanding of the strongly coupled electrochemical and thermodynamic processes in a fuel cell is needed. Five leading institutions are contributing their expertise in the ”GECKO” research project to investigate the complex processes, such as two-phase transport or degradation processes.
Fraunhofer ISE is analysing the inhomogeneity which occurs at the cell level both in stationary and dynamic operation with the help of segmented fuel cells and a unique multi channel characterization system. The optimisation potentials for design, materials selection and operating strategies are derived from this analysis.
Automotive fuel cells have cell areas of up to 400 cm². With current densities of up to 3 A/cm², appreciable depletion of the reaction gases accompanied by simultaneously increasing humidity is the result. These can cause inhomogeneity which can greatly affect performance or cause degradation. In order to locally characterize the operating state of the cell up to a total current of 780 A, we are equipped with a system containing 68 synchronously operating potentiostats. It allows us to measure both current generation and electrochemical impedance at different frequencies with high spatial resolution. The spatially resolved characterization in combination with modelling work at the cell level enables us to unravel the complex interaction between processes caused by inhomogeneity. For instance, we can separate the loss mechanisms with regard to their time constants. The resulting knowledge at the cell level is transferred within the ”GECKO” project to the stack level and correlated with single-cell impedance spectra measured simultaneously in the stack.