Water Movement in a Solid-State Alkaline Fuel Cell Affected by the Anion-Exchange Pore-Filling Membrane Properties

In contrast with proton-exchange membrane fuel cells (PEMFCs), in a solid-state alkaline fuel cell (SAFC) water reacts at the cathode and is generated at the anode. This systematic difference leads to the new challenge of water management for SAFCs. To explore the relationship between water movement in the cell and cell performance we used 3-methacryloylamino propyl trimethylammonium chloride and styrene as the electrolyte monomers to synthesize different hydrophilic/hydrophobic anion-exchange membranes (AEMs) using a pore-filling technique. We discovered that the cell performance changed remarkably by changing the AEM properties. The cell performance was affected significantly by the water movement in the cell, which also depends on the AEM properties. In a highly hydrophilic membrane, the water movement direction is from the anode to the cathode, which can increase the cathode relative humidity (RH) to improve the ion conductivity and suppress flooding at the anode. In contrast, the result is the opposite in a hydrophobic membrane. On the basis of experimental and calculation approaches, we show that the cell performance of SAFCs can be improved by promoting water movement from the anode to the cathode with a high water permeability AEM and adjustment of the anode RH.