Identification of catalytic sites in cobalt-nitrogen-carbon materials for the oxygen reduction reaction

Andrea Zitolo, Nastaran Ranjbar-Sahraie, Tzonka Mineva, Jingkun Li, Qingying Jia, Serban Stamatin, George F. Harrington, Stephen Mathew Lyth, Petr Krtil, Sanjeev Mukerjee, Emiliano Fonda, Frédéric Jaouen

Research output: Contribution to journalArticlepeer-review

255 Citations (Scopus)

Abstract

Single-atom catalysts with full utilization of metal centers can bridge the gap between molecular and solid-state catalysis. Metal-nitrogen-carbon materials prepared via pyrolysis are promising single-atom catalysts but often also comprise metallic particles. Here, we pyrolytically synthesize a Co-N-C material only comprising atomically dispersed cobalt ions and identify with X-ray absorption spectroscopy, magnetic susceptibility measurements and density functional theory the structure and electronic state of three porphyrinic moieties, CoN4C12, CoN3C10,porp and CoN2C5. The O2 electro-reduction and operando X-ray absorption response are measured in acidic medium on Co-N-C and compared to those of a Fe-N-C catalyst prepared similarly. We show that cobalt moieties are unmodified from 0.0 to 1.0 V versus a reversible hydrogen electrode, while Fe-based moieties experience structural and electronic-state changes. On the basis of density functional theory analysis and established relationships between redox potential and O2-adsorption strength, we conclude that cobalt-based moieties bind O2 too weakly for efficient O2 reduction.

Original languageEnglish
Article number957
JournalNature communications
Volume8
Issue number1
DOIs
Publication statusPublished - Dec 1 2017

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Physics and Astronomy(all)

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