Air Contamination of Platinum-Group Metal-free Fuel Cell Cathodes with Atomically Dispersed Iron Active Sites

Abstract

In a wide variety of applications, proton exchange membrane (PEM) fuel cells must be tolerant to contaminants from the ambient air and the degradation of the system components. Previous work has demonstrated the effects of some of the most common air contaminants on platinum-group metal (PGM) cathode fuel cells. However, the results of air contamination on the degradation in a side-by-side comparison between PGM and PGM-free based cathode fuel cells has yet to be shown. Herein, we investigate the effects of air contamination by acetonitrile and sulfur dioxide (SO2) on operating PGM and PGM-free cathode fuel cells. This was done by monitoring the changes in current density at a constant voltage hold before, during, and after sulfur dioxide and acetonitrile contamination. In addition, air polarization curves, cyclic voltammetry, and electrochemical impedance spectroscopy characterized the overall contamination effects of each cell. It is found that acetonitrile at 20 ppm and SO2 at 4.6 ppm do not result in any additional degradation in iron (Fe)-metal–organic framework (MOF) derived cathode fuel cells during operation, while current density losses greater than 70% are seen in platinum (Pt)-based cathode fuel cells. This tolerance to contaminants is an often-overlooked advantage of PGM-free catalyst cathode fuel cells, which suffered no additional degradation due to the introduction of air contaminants in this study.