Benchmarking Performance and Degradation of Pt Supported on Different Carbons for PEMFC Applications Using Gas Diffusion Electrode Half-Cell

The performance of platinum nanoparticles in proton exchange membrane fuel cells (PEMFCs) depends on carbon support. In comparison to nonporous supports (Vulcan, Pt/V), porous supports (Ketjenblack, Pt/KB) reveal higher tolerance toward the decrease in the electrochemical active surface area (ECSA), which could be attributed to suppressed dissolution (net mass loss). However, distinguishing between different degradation mechanisms is challenging in membrane electrode assembly (MEA) tests. This study uses the gas diffusion electrode (GDE) half-cell setup to gain fundamental insights into the degradation of Pt/C. Several metrics are considered to benchmark GDE to MEA. First, we confirm that the optimal ionomer to carbon (I/C) ratios for Pt/V and Pt/KB of 0.65 and 1.0 are similar in both setups. The beginning of life (BOL) performance reveals that Pt/KB suffers from mass transport losses in the high current density region going up to 2 A cm–2. Further, an accelerated stress test (AST) consisting of 5000 potential cycles shows a decrease in ECSA for Pt/V of ∼40% and Pt/KB of ∼30%. Quantifying Pt dissolution during the AST using online inductively coupled plasma mass spectrometry (ICP–MS), similar for all studied catalyst layers, we conclude that, for the chosen AST protocols in this study, Ostwald ripening is the dominating degradation process in both supports.