In Situ X-ray Absorption Spectroscopy of a Synergistic Co-Mn Oxide Catalyst for the Oxygen Reduction Reaction

Yao Yang, Ying Wang, Yin Xiong, Xin Huang, Luxi Shen, Rong Huang, Hongsen Wang, James P. Pastore, Seung-Ho Yu, Li Xiao, Joel D. Brock, Lin Zhuang, Héctor D. Abruña

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)

Abstract

Identifying the catalytically active site(s) in the oxygen reduction reaction (ORR), under real-time electrochemical conditions, is critical to the development of fuel cells and other technologies. We have employed in situ synchrotron-based X-ray absorption spectroscopy (XAS) to investigate the synergistic interaction of a Co-Mn oxide catalyst which exhibits impressive ORR activity in alkaline fuel cells. X-ray absorption near edge structure (XANES) was used to track the dynamic structural changes of Co and Mn under both steady state (constant applied potential) and nonsteady state (potentiodynamic cyclic voltammetry, CV). Under steady state conditions, both Mn and Co valences decreased at lower potentials, indicating the conversion from Mn(III,IV) and Co(III) to Mn(II,III) and Co(II), respectively. Rapid X-ray data acquisition, combined with a slow sweep rate in CV, enabled a 3 mV resolution in the applied potential, approaching a nonsteady (potentiodynamic) state. Changes in the Co and Mn valence states were simultaneous and exhibited periodic patterns that tracked the cyclic potential sweeps. To the best of our knowledge, this represents the first study, using in situ XAS, to resolve the synergistic catalytic mechanism of a bimetallic oxide. Strategies developed/described herein can provide a promising approach to unveil the reaction mechanism for other multimetallic electrocatalysts.

Original languageEnglish
Pages (from-to)1463-1466
Number of pages4
JournalJournal of the American Chemical Society
Volume141
Issue number4
DOIs
Publication statusPublished - 2019 Jan 30
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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