Effect of water management in membrane and cathode catalyst layers on suppressing the performance hysteresis phenomenon in anion-exchange membrane fuel cells

Abstract

Anion exchange membrane fuel cells (AEMFCs) are vulnerable to water management problems, since water is produced at the anode and consumed at the cathode. Previously we found severe voltage losses when increasing the current density in an AEMFC with a commercial Fe–N–C cathode catalyst. In the present work, we have clearly identified the problem as being related to water management and developed two approaches to alleviating the problem: by use of a thin hydrophilized membrane, the diffusivity of water at the surface was improved, and the severe I–V hysteresis was suppressed, despite the cell using an Fe–N–C cathode catalyst with a high water absorption rate. The voltage loss was also alleviated by the use of a recently developed Fe–N–C catalyst with higher hydrophobicity, which decreased the absorption of back-diffusing water into the catalyst layer and increased the amount of water supplied to the reaction sites These improvements have demonstrated that water transport is the main limitation for the previously reported hysteresis and provide strategies to achieve higher performance AEMFCs through proper water management and formation of water transport pathways.