Degradation Analysis for Platinum Group Metal-Free Fuel Cell Cathodes

Abstract

Recent advancements in platinum-group metal-free (PGM-free) catalysts have overwhelmingly prioritized improving initial electrocatalytic activity rather than focusing on catalyst stability. Unfortunately, this emphasis has led to less significant progress in addressing catalyst degradation, ultimately falling well below the level required for commercialization. Shifting the focus towards understanding and mitigating degradation unlocks the true potential of PGM-free catalysts and paves the way for their successful implementation in commercial applications. This work explores methods to mitigate degradation and expand models to predict PGM-free cathode fuel cell degradation due to voltage cycling, specifically current density loss over time. The tested PGM-free cathode fuel cells, using iron (Fe)-based catalyst, were electrochemically characterized before and after the accelerated stress tests (AST) using H2/N2 electrochemical impedance spectroscopy, cyclic voltammetry, and air polarization curves. This study reports the functions of each acceleration factor due to changes in temperature, cycling upper potential limits, and relative humidity are reported. The data indicates that degradation rates increase as temperature, upper potential limit, and relative humidity increase in Fe-based cathode proton exchange membrane fuel cells (PEMFCs). This finding is essential to more accurately quantify losses in active site density with respect to temperature, varying upper potential cycling limit, and relative humidity. More generally, these results can aid in predicting Fe-based cathode fuel cell degradation due to changes in operational conditions.