Comprehensive analysis of recovery procedures for SO2-contaminated proton exchange membrane fuel cells

Abstract

Proton exchange membrane fuel cells (PEMFCs) are critical in transitioning to a low-carbon future, especially in industries like heavy-duty transportation, maritime shipping, and aviation. However, the use of ambient air exposes Pt-based electrocatalysts to air contaminants, leading to performance loss and premature degradation. SO2 appears to be the most crucial air impurity for fuel cell operation due to the formation of strongly adsorbed S-containing species, like elemental S0 on the cathode Pt surface and a lack of self-recovery in pure air. This work evaluates the efficiency of potential cycling from 0.1 to 1.2 V and cathode purging with pure O2 for recovering PEMFC performance after 5 ppm SO2 exposure at 80 °C. Results indicate that SO2 contamination at higher operating current densities causes more pronounced loss in performance and electrochemical area as well as negatively affecting recovery. Both potential cycling and O2 purge methods show recovery efficiencies of up to 95 % for fuel cells contaminated at lower current densities (0.4 A cm-2) and 84 % at higher current densities (1.0 A cm-2). Interestingly, the end of test diagnostics further improved performance, reaching a recovery efficiency of 95-97 %. The findings suggest that while both recovery methods are effective, the O2 purge technique is more practical for field applications due to its simplicity and lack of need for auxiliary equipment. The study employs a segmented cell system to analyze localized performance variations and SO2 contamination impacts.