Structural modification of electrode for anion exchange membrane fuel cell by controlling ionomer dispersion

Abstract

An appropriate electrode microstructure design should be necessary to achieve high-performance anion exchange membrane fuel cells (AEMFCs). In general, the electrodes are fabricated from catalyst slurries which contain self-assembled agglomerates of catalyst particles with ionomer dispersed in a solvent. Therefore, solvent nature greatly affects the microstructure of the electrode, such as the pore structure and the formation of triple-phase boundaries for electrochemical reactions. Here, we investigate the influence of solvent on the microstructure of I2 ionomer-based electrode and its performance using three alcohol-based solvents (ethanol, 2-propanol, and 2-methyl-2-propanol [tBuOH)) with different dielectric constants and similar boiling points. Various physical and electrochemical characterization confirmed that the electrode pore structure changes significantly depending on the type of solvent while the electrochemically active surface area hardly changes. Furthermore, the efect of the three electrodes with different pore structures on AEMFC performance is observed for anode and cathode, respectively. It is demonstrated that the porous electrode with large pores is more advantageous in performance than a dense electrode at both the anode and the cathode for AEMFC. Consequently, the membrane electrode assembly with porous tBuOH-based electrodes exhibits more than 40% higher performance (1.32 W cm−2) than dense ethanol-based electrodes (0.94 W cm−2).