Over the past decade, non-precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) have received significant of attention as a possible replacement of precious-metal catalysts in fuel cells and metal-air batteries. A successful cathode catalyst must combine high ORR activity with good long-term stability � a major challenge in the strongly acidic environment of the polymer electrolyte fuel cell (PEFC) cathode. In response to the catalyst cost challenge, we have been developing non-precious metal ORR catalysts capable of minimizing the performance gap to platinum-based catalysts at a cost sustainable for high-power fuel cell applications. We have used several organic compounds, polymeric and non-polymeric, as nitrogen and carbon precursors for high-temperature synthesis of catalysts in the presence of transition metals (Fe and/or Co). When used at a sufficiently high loading, the most active catalysts come within ca. 60 mV of the activity exhibited by state-of-the-art carbon-supported Pt catalysts in the acid electrolyte. At the same time, best performing catalyst has demonstrated superior performance to Pt catalysts in alkaline media. In this presentation, we will offer a critical overview of the current state of non-precious metal catalysis of oxygen reduction. We will also discuss our recent effort in exploring the active reaction sites using density functional theory (DFT). We will highlight the role of highly-graphitic carbon nanostructures, in-situ formed in the NPMCs through a high-temperature approach, which may serve as a matrix for hosting ORR-active nitrogen or metal moieties. The major challenge of non-precious metal electrocatalysis of oxygen reduction reaction continues to be the lack of knowledge of the active catalytic sites and reaction mechanism. Further progress in the development of NPMCs will likely depend on the ability to characterize and understand the source(s) of the activity of the catalysts that have already been developed and are under development today.

Carbon composite non-precious metal catalysts for oxygen reduction in electrochemical energy conversion

248th National Meeting (2014)

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