Electrochemical Evaluation of Non-precious Metal Catalysts for Fuel Cell Applications

Samantha Medina, Gabriel Goenaga, Nelly Cantillo, Asa Roy, Thomas Zawodzinski

Abstract


Copper and Iron-based catalysts for the oxygen reduction reaction (ORR) in proton electrolyte membrane (PEM) and anion electrolyte membrane (AEM) fuel cells have not outperformed platinum catalysts. The objective of this investigation is to determine the synthesis parameters to achieve optimal catalytic activity for pyrolyzed Cu and Fe carbon-supported catalysts for the ORR at the cathode in low temperature fuel cells. We synthesized catalysts by mixing the metal salt, nitrogen source, and carbon black support using a mortar and pestle, followed by pyrolysis under nitrogen gas. The metal salts used were: acetates, sulfates, and nitrates.  Three different nitrogen rich sources were also studied and we found that only one nitrogen source contributed significantly to the electrochemical activity. After pyrolysis, an improvement in the catalytic activity was observed, however depending on the metal salt combination and metal content, as well as on the electrolyte used during the experiment, the ideal heat treatment temperature for each catalyst combination was different. The electrochemical activity was measured using the rotating ring disk electrode (RRDE) experiment in 0.1 M H2SO4 and 0.1M KOH electrolytes to mimic the acidic and alkaline environments of PEM and AEM fuel cells. The best catalyst overall was the optimized 5 w.t% metal content FeSO4 carbon-supported catalyst heat-treated at 900°C. Fuel cell performance was measured for this catalyst at the cathode in both PEM and AEM fuel cells. A typical AEM fuel cell performance for NPGM catalysts was achieved for the FeSO4 catalyst making it a good candidate for AEMFC applications.


Keywords


Catalysts, Fuel Cells, RRDE, Electrochemistry, Non-Precious Metal Catalysts

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