Electrochemical analysis of active species in a low iron content oxygen reduction reaction catalyst and aluminium covetic materials

In an effort to move away from fossil fuels and towards cleaner energy, the cleaner energy options need to be efficient and practical. Low temperature fuel cells have significant promise, yet must be improved before widespread use is reached. One major way to reduce the price of fuel cells and increase fuel cell efficiency is to improve the oxygen reduction reaction (ORR) catalyst so that Pt is no longer used. Changing catalysts has proven to be difficult since it is not understood how the reaction proceeds on a non-precious metal (NPM). In the current work, a low Fe content, high activity ORR catalyst was prepared and characterized to elucidate the active species. The prepared catalyst went through several activating and deactivating treatments in order to elucidate active species for the ORR. Mӧssbauer spectroscopy determined that the Fe species present in the as-prepared catalyst was FeN4 rather than metallic Fe. Cyclic voltammetry was utilized to study activity changes throughout treatments on the catalyst. The as-prepared catalyst exhibits a competitive activity of 0.9 V vs RHE and poisoning studies with CN- suggests the activity is not solely due to the Fe in the catalyst. Attempts were made to alter the C in the catalyst and the C was studied via 13C solid state nuclear magnetic resonance spectroscopy (ssNMR). In addition to a study of ORR catalysts, the corrosion characteristics of covetic Al materials were also studied. Linear polarization curves show that the corrosion potential of covetic materials is increased compared to base alloy materials. However, Tafel fitting of the polarization curves indicate the rate of corrosion is also increased for covetic Al materials