Relations of water management and degradation processes in PEFC

Abstract

The life-time of fuel cells is one of the main barrier for using fuel cells as electric power generators or sources in mass market products. Therefore, in the last years the research activi-ty to investigate the degradation processes and mechanisms of fuel cells – especially of polymer electrolyte membrane fuel cells (PEFC) has intensified significantly. Consequently, many degradation processes in PEFC have been identified and some of the degradation mechanisms are understood qualitatively. However, not all significant degradation mecha-nisms are understood sufficiently and the relation of the degradation rates and the operating conditions are unclear for most degradation processes. For many degradation processes the water management especially a liquid water phase inside the cell is a crucial factor for the degradation processes. Although for some of the degradation mechanisms the influence of water is well-understood most degradation processes still need clarifying in this respect. In this contribution the known degradation processes are summarized and evaluated with respect to the influence of liquid water. Some processes, in particular the agglomeration of the catalyst particles and the decomposition of PTFE are discussed in detail. In addition to the direct influence of the water on the individual degradation, the water man-agement will also changed by the degradation processes, e.g. by the decrease of the hydropho-bicity. Consequently, the water induces complex interactions involving various degradation processes.