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

110 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

Bibliographical note

Funding Information:
This work was supported as part of the Center for Alkaline Based Energy Solutions (CABES) an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award No. DESC0019445. This work is based upon research conducted at the Cornell High Energy Synchrotron Source (CHESS) which is supported by the National Science Foundation under award DMR-1332208. This work made use of SEM/TEM facilities of the Cornell Center for Materials Research (CCMR), which are supported through the National Science Foundation Materials Research Science and Engineering Center (NSF MRSEC) program (DMR-1719875). This work was also financially supported by the National Natural Science Foundation of China (21872108, 91545205). We appreciate the assistance with the device fabrication from Stephan Felix and Chris Cowulich from the machine shop in the Laboratory of Atomic and Solid State Physics (LASSP) at Cornell University. We are grateful to Xinran Feng at Cornell University for the help with XANES data analysis. We acknowledge the help from Dr. Xiaoming Wang and Prof. Yoshiharu Uchimoto at Kyoto University for some synchrotron tests. We also thank Wei Liu at Wuhan University for his help with powder XRD measurements.

Publisher Copyright:
© 2019 American Chemical Society.

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry

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