Loading Effect on the Fuel Cell Performance of Catalyst Layers Based on Non-noble Metal Catalysts
Proton exchange membrane fuel cells (PEMFCs) are promising energy conversion devices for environmentally friendly transportation applications, but the high Pt loadings required at their cathode to catalyze the oxygen reduction reaction (ORR) prevent their deeper market penetration. One strategy to reduce catalyst cost is replacing these Pt-based materials with non-noble metal catalysts (NNMCs) that have recently been shown to display initial ORR activities similar to those of Pt-nanoparticles . However, to reach such high performances, NNMC cathode loadings are much higher (typically, ≈ 4 mgNNMC·cm−2) than those of Pt-based catalyst layers (CLs, with loadings of ≤ 0.3 mgPt·cm−2), to compensate for the NNMCs’ lower ORR activities. This results in thick (≈ 100 μm) NNMC CLs that suffer from mass transport issues and consequently prevent them from reaching the high current densities at high potentials required for automotive applications.
In this context, our group recently proposed a novel NNMC-synthesis approach  that yields materials with a high initial ORR activity in PEMFC but poor mass transport properties. This was caused by these catalysts’ low open porosity and large particle size, which we have recently decreased by modifying one of the steps in the catalysts’ synthesis. Preliminary PEMFC results with a loading of 1 mgNNMC.cm-2 confirmed that these novel materials display a better high current density performance indicative of their enhanced mass transport properties. Building on these results, in this project NNMC CLs with loadings increasing from ≈ 1 to ≈ 4 mgNNMC·cm-2 in ≈ 0.5 - 1 mgNNMC·cm-2 increments will be prepared by automated spraying and PEMFC-tested, to unveil the effect of the CL-loading on the performance and stability of these materials. Specifically, electrochemical diagnostic techniques will be used to quantify proton transfer and O2-transport resistances along with the CLs.
Number of weeks offered: 10 - 14, between June and October 2021.
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