The role of ion exchange membrane in vanadium oxygen fuel cell

• Published in: Journal of membrane science 2021-07, Vol.629, p.119271, Article 119271
• Main Authors: Charvát, Jiří, Mazúr, Petr, Paidar, Martin, Pocedič, Jaromír, Vrána, Jiří, Mrlík, Jindřich, Kosek, Juraj
• Format: Article
• Language: English
• Subjects: Gas diffusion electrode; Ion exchange membrane; Performance stability; Vanadium-oxygen fuel cell; Water management
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2021.119271

The effect of membrane properties on the vanadium-oxygen fuel cell performance was studied on a series of commercially available ion exchange membranes of different thickness and ion exchange capacity by selected characterization techniques including electrochemical impedance spectroscopy (ohmic and charge transfer resistance), steady load curves (performance stability) and galvanostatic charge-discharge cycles (efficiencies and capacity decay). Performance stability of the fuel cell was studied under defined conditions (state of charge, temperature, air flow rate) using continuous charging of vanadium electrolyte. In contrast to the previous studies, our results revealed that the membrane affects the fuel cell performance mainly via water management in the catalytic layer of gas diffusion cathode, while vanadium permeation across the membrane has only a minor impact. Generally, the fuel cell shows improved performance stability for more conductive membranes (thinner and with higher ion-exchange capacity), partially due to reduced ohmic losses, but more significantly due to the better ability of the membrane to drain water from the cathode via osmosis, which prevents the flooding of the cathodic catalytic layer. With the optimized membrane, we achieved stable fuel cell performance at the highest current and power density values reported (75 mA cm−2 and 57 mW cm−2 in 50% state of charge). [Display omitted] •Vanadium-oxygen fuel cell shows better performance with less resistive membranes.•Vanadium permeation across the membrane has small effect on fuel cell performance.•Water management in cathode is crucial for efficient and stable fuel cell operation.•Record peak power density achieved among reported vanadium-oxygen fuel cells.