Anion exchange membrane fuel cells (AEMFCs) have attracted extensive attention in the recent years, primarily due to the distinct advantage potentials they have over the mainstream proton exchange membrane fuel cells. The anion exchange membrane (AEM) is the key component of AEMFC systems. Due to the unique characteristics of water management in AEMFCs, understanding the water mobility through AEMs is key for this technology, as it significantly affects (and limits) overall cell performances. This work presents a study of the equilibrium state and kinetics of water uptake (WU) for AEMs exposed to vapor source H2O. We investigate different AEMs that exhibit diverse water uptake behaviors. AEMs containing different backbones (fluorinated and hydrocarbon-based backbones) and different functional groups (various cations as part of the backbone or as pendant groups) were studied. Equilibrium WU isotherms are measured and fitted by the Park model. The influence of relative humidity and temperature is also studied for both equilibrium and dynamic WU. A characteristic time constant is used to describe WU kinetics during the H2O sorption process. To the best of our knowledge, this is the first time that WU kinetics has been thoroughly investigated on AEMs containing different backbones and cationic functional groups. The method and analysis described in this work provides critical insights to assist with the design of the next generation anion conducting polymer electrolytes and membranes for use in advanced, high-performance AEMFCs.

Exposing operating AEMFCs to CO2 leads to performance-robbing overpotentials, linked to fundamental thermodynamics, transport and kinetics – the impact of which can be reduced through careful systems design and selection of operating conditions.

There is a need to understand the water dynamics of alkaline membrane fuel cells under various operating conditions to create electrodes that enable high performance and stable, long-term operation. Here we show, via operando neutron imaging and operando micro X-ray computed tomography, visualizations of the spatial and temporal distribution of liquid water in operating cells. We provide direct evidence for liquid water accumulation at the anode, which causes severe ionomer swelling and performance loss, as well as cell dryout from undesirably low water content in the cathode. We observe that the operating conditions leading to the highest power density during polarization are not generally the conditions that allow for long-term stable operation. This observation leads to new catalyst layer designs and gas diffusion layers. This study reports alkaline membrane fuel cells that can be operated continuously for over 1000 h at 600 mA cm −2 with voltage decay rate of only 32-μV h −1the best-reported durability to date.

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