Direction and Management of Water Movement in Solid-State Alkaline Fuel Cells

In a solid-state alkaline fuel cell (SAFC), water reacts at the cathode and is generated at the anode, in contrast to proton-exchange membrane fuel cells (PEMFCs). Water behavior in the SAFC membrane electrode assembly is particularly important: without water movement, the relative humidity at the cathode, which affects the membrane resistance, cannot be enhanced, and flooding at the anode cannot be suppressed. Thus, optimization is required to establish design methodology for SAFCs. In this study, water movement in a SAFC system has been observed accurately using a water collection method. We confirm for the first time the movement of water from the anode to the cathode during an actual fuel cell performance test. Compared with a PEMFC, water movement occurs in the opposite direction leading to difficult water management in the SAFC. With the knowledge obtained, water management has been achieved in the SAFC by careful control of humidity.