Effects of Mg2+ contamination on the performance of proton exchange membrane fuel cell

Highlights: • Effect of Mg²⁺ contamination on PEM fuel cell performance is studied. • Mg²⁺ and its concentration significantly affect PEM fuel cell performance. • The performance decreases with the increase of Mg²⁺ concentration and time. • Degradation mechanism of PEM fuel cell performance for Mg²⁺ is proposed. • The degradation mechanism is due to ion exchange reaction in PEM. -- Abstract: Contamination ions from bipolar plates and elastomeric gaskets for degradation play an important role on the long-term stability and durability of proton exchange membrane (PEM) fuel cells. In this paper, the effects of Mg²⁺ contamination on PEM fuel cell performance were investigated experimentally. Five levels of Mg²⁺ concentrations were used in this work. Electrochemical performance tests were performed by adding the various Mg²⁺ concentration solutions into the anode H₂ fuel stream of the PEM fuel cell. And then scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) were employed to study degradation mechanism of the PEM fuel cell performance for Mg²⁺ contamination. The test results show that both Mg²⁺ concentration and contamination time had significant effects on PEM fuel cell performance. The voltage and maximum power density of the PEM fuel cell decreased with the increase of Mg²⁺ concentration and contamination time. EDS and EPMA results indicate that the Magnesium mainly appeared in the PEM for the Mg²⁺ contaminating of the PEM fuel cell, and the Magnesium increased with the increasing Mg²⁺ concentration over time. The degradation mechanism of the PEM fuel cell performance for the Mg²⁺ contamination could be due to ion exchange reaction between Mg²⁺ and the proton of sulfonic acid groups in the PEM to form the new sulfonate structure.