Influence of nitrogen doping on oxygen reduction electrocatalysis at carbon nanofiber electrodes

Stephen Maldonado, Keith J. Stevenson

Research output: Contribution to journalArticlepeer-review

788 Citations (Scopus)

Abstract

Nondoped and nitrogen-doped (N-doped) carbon nanofiber (CNF) electrodes were prepared via a floating catalyst chemical vapor deposition (CVD) method using precursors consisting of ferrocene and either xylene or pyridine to control the nitrogen content. Structural and compositional differences between the nondoped and N-doped varieties were assessed using TEM, BET, Raman, TGA, and XPS. Electrochemical methods were used to study the influence of nitrogen doping on the oxygen reduction reaction (ORR). The N-doped CNF electrodes demonstrate significant catalytic activity toward oxygen reduction in aqueous KNO 3 solutions at neutral to basic pH. Electrochemical data are presented which indicate that the ORR proceeds by the peroxide pathway via two successive two-electron reductions. However, for N-doped CNF electrodes, the reduction process can be treated as a catalytic regenerative process where the intermediate hydroperoxide (HO 2 -) is chemically decomposed to regenerate oxygen, 2HO 2 - ⇀ O 2 + 2OH -. The proposed electrocatalysis mechanisms for ORR at both nondoped and N-doped varieties are supported by electrochemical simulations and by measured difference in hydroperoxide decomposition rate constants. Remarkably, ∼100 fold enhancement for hydroperoxide decomposition is observed for N-doped CNFs, with rates comparable to the best known peroxide decomposition catalysts. Collectively the data indicate that exposed edge plane defects and nitrogen doping are important factors for influencing adsorption of reactive intermediates (i.e., superoxide, hydroperoxide) and for enhancing electrocatalysis for the ORR at nanostructured carbon electrodes.

Original languageEnglish
Pages (from-to)4707-4716
Number of pages10
JournalJournal of Physical Chemistry B
Volume109
Issue number10
DOIs
Publication statusPublished - 17 Mar 2005
Externally publishedYes

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