Alkaline fuel cells consisting of imidazolium-based graft-type anion exchange membranes: Optimization of fuel cell conditions to achieve high performance and durability

Water management in alkaline fuel cells through the dew point optimization for a series of imidazolium-based graft-type anion exchange membranes (AEMs) consisting of an ethylene-tetrafuluomethylene copolymer (ETFE) as a base film having three vinylimidazolium type and a styrylimidazolium type (StIm) anion-conducting units is compared with the standard vinylbenzyltrimethylammonium (BTMA)-based AEM. In the H-2/O-2 fuel cell tests at 60 degrees C, by optimizing dew points, the sterically hindered imidazolium containing StIm-based AEMs exhibited the highest power density (710 mW/cm(2)), which is one of the highest performances of imidazolium-type AEMs to date. Furthermore, it exhibited long-term durability in H-2/O-2 fuel cell at 60 degrees C, maintaining 0.52 V (56%) of initial voltage after 670 h of life time test, which is better than that of the standard BTMA-based AEM. The chemical characterization in post-durability characterization revealed that negligible degradation of conducting imidazolium groups in the 2MVIm-, 4VIm-, and StIm-based AEMs was observed. For the first time, the hydration level and DFT-based molecular calculations (LUMO energy) showed an acceptable correlation with the experimental in-situ durability results.

Automated summary

Water management in alkaline fuel cells was studied through dew point optimization using a series of imidazolium-based graft-type AEMs. It was found that AEMs with StIm units showed the highest power density and long-term durability in fuel cell tests at 60 degrees C. The chemical characterization and molecular calculations were in good agreement with the experimental results, providing valuable insights for future research.