Catalysts

Polymer Electrolyte Membrane Fuel Cells   

3. Non-precious Metal Oxygen Reduction Reaction Catalysts

Today’s fuel cells rely on platinum to act as a catalyst for both oxidation of hydrogen and reduction of oxygen. While platinum is ideal for this application, its use is not sustainable in the long term. Platinum is not only a rare precious metal but it is also very expensive. To make fuel cells both more sustainable and cheaper, a non-precious metal alternative to platinum is required. Given the slow kinetics of oxygen reduction, the cathode typically requires more platinum than the anode. Thus, non-noble alternatives to oxygen reduction at the cathode would significantly reduce the amount of platinum required. Metals such as iron or cobalt, heated under inert atmosphere in the presence of nitrogen on high surface area carbon black yield highly active catalysts towards oxygen reduction

Our work employs a chemisorption approach which involves grafting nitrogen-containing functionalities directly onto the carbon surface that can coordinate iron species. The main advantage of chemisorption over physisorption is that we have more control over the placement of both the nitrogen and iron species, which leads to a higher number of active sites being formed. Our work explores the impacts of nitrogen content, heat treatment temperature, carbon black, on the activity towards oxygen reduction. Methods of characterization including thermogravimetric analysis, inductively coupled plasma – optical emission spectrometry, and rotating ring-disk electrode voltammetry are utilized to evaluate various properties of the catalysts generated. As the adjacent plot demonstrates, iron based catalysts were generated that are comparable Dodelet’s1 which are among the best non-noble catalysts currently available.  

More details on our research in this area can be found in the following publications:

  1. A.D. Pauric, A. W. Pedersen, T. Andrusiak, E. B. Easton, "A Surface Modification Route to Non-Precious Metal Fuel Cell Catalysts", J. Electrochem. Soc., 157, B370-B375 (2010).http://dx.doi.org/10.1149/1.3283100

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