Abstract
In this work gas diffusion electrode (GDE) half-cells experiments are proposed as powerful tool in fuel cell catalyst layer evaluation as it is possible to transfer the advantages of fundamental methods like thin-film rotating disk electrode (TF-RDE) such as good comparability of results, dedicated elimination of undesired parameters etc. to relevant potential ranges for fuel cell applications without mass transport limitations. With the developed setup and electrochemical protocol, first experiments on different Pt/C loadings confirm excellent reproducibility. Thereby mass-specific current densities up to 30 A mgPt−1 at 0.6 V vs. RHE are achieved. From a methodological perspective, good comparability to single cell measurements is obtained after theoretical corrections for temperature and concentration effects. In comparison to previous studies with GDE half-cells, polarization curves without severe mass transport limitations are recorded in a broad potential window. All these achievements indicate that the proposed method can be an efficient tool to bridge the gap between TF-RDE and single cell experiments by providing fast and dedicated insights into the effects of catalyst layers on oxygen reduction reaction performance. This method will enable straightforward and efficient optimization of catalyst layer composition and structure, especially for novel catalysts, thereby contributing to the performance enhancements of fuel cells with reduced Pt loading.
Highlights
To meet the 2°C target set in the Paris Agreement[1] global annual greenhouse gas (GHG) emissions have to be radically reduced to net zero in not later than 30 years.[2]
The thicknesses of the catalyst layer (CL) were each averaged over eight different scanning electron microscope (SEM) images at different locations along the gas diffusion electrode (GDE)
GDE experiments are a powerful tool to close the gap between fundamental electrocatalysis with thin film rotation disk electrode (TF-RDE) and applied fuel cell research via membrane electrode assembly (MEA) testing
Summary
To meet the 2°C target set in the Paris Agreement[1] global annual greenhouse gas (GHG) emissions have to be radically reduced to net zero in not later than 30 years.[2]. Zalitis et al.[24] introduced a different approach, the floating electrode setup, where a small electrode with an ultra-thin catalyst layer (∼200 nm, 4.9 μgPt cm−2) was placed floating on top of the electrolyte Thereby they were able to achieve high current densities up to 185 mA cmspec−2 (∼800 mA cmgeo−2) and claimed not to be affected by mass transport limitations in the relevant range for fuel cells (0.6 – 0.8 V). Pinaud et al.[18] observed transport-limitations using this technique (i) at current densities higher than 500 mA cmgeo−2, especially when the sample size was increased beyond 1 cm[2] (due to the lack of forced convective flow) and (ii) when a membrane was added to the catalyst layer to further mimic real fuel cell conditions (due to flooding) They have developed a setup (see Figure S1A in the supporting information) introducing a flow-field that enforces a convective flow over the whole electrode area. By investigating the impact of Pt loading on the GDE’s ORR performance, we confirm on the one hand the suitability of the approach, and implicitly demonstrate the achievements possible toward enhanced fuel cell performance
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