Strategic design for promoting water behavior via ensemble of thermo-responsive polymer functionalized catalysts and reservoir carbon in anion exchange membrane fuel cells

Abstract

Efficient water management is considered a prerequisite to advance the commercialization of anion exchange membrane fuel cells because water imbalance not only results in flooding and drying issues in the electrodes, but also leads to performance degradation. Herein, strategic electrode structures to achieve desirable water behavior during operation are reported. Carbon supports are employed as reservoirs to store the produced water and as carbon-supported catalysts with poly(N-isopropylacrylamide), possessing hydrophobic characteristics at the operating temperatures, as the polymer entangles by itself. This polymer is preferentially functionalized on the carbon surface before the reduction of the precursors to minimize the blocking of the catalyst active sites. X-ray photoelectron spectroscopy and electrochemical analyses support that the electronic structures of the catalysts are not significantly affected even when the polymer is functionalized. Furthermore, the synergistic effect of the reservoir and thermo-responsive polymer is demonstrated in a real device exhibiting performance enhancement. The resulting electrode shows 11.9% increase in the current density at 0.6 V and 21.3% increase in the maximum power density compared to those observed with the conventional electrodes. This phenomenon is attributed to favorable water distribution, as confirmed by in-situ visualization via synchrotron X-ray imaging.