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Open Access Publications from the University of California

On the chemical state of Co oxide electrocatalysts during alkaline water splitting

  • Author(s): Friebel, D
  • Bajdich, M
  • Yeo, BS
  • Louie, MW
  • Miller, DJ
  • Sanchez Casalongue, H
  • Mbuga, F
  • Weng, TC
  • Nordlund, D
  • Sokaras, D
  • Alonso-Mori, R
  • Bell, AT
  • Nilsson, A
  • et al.

Resonant inelastic X-ray scattering and high-resolution X-ray absorption spectroscopy were used to identify the chemical state of a Co electrocatalyst in situ during the oxygen evolution reaction. After anodic electrodeposition onto Au(111) from a Co2+-containing electrolyte, the chemical environment of Co can be identified to be almost identical to CoOOH. With increasing potentials, a subtle increase of the Co oxidation state is observed, indicating a non-stoichiometric composition of the working OER catalyst containing a small fraction of Co4+ sites. In order to confirm this interpretation, we used density functional theory with a Hubbard-U correction approach to compute X-ray absorption spectra of model compounds, which agree well with the experimental spectra. In situ monitoring of catalyst local structure and bonding is essential in the development of structure-activity relationships that can guide the discovery of efficient and earth abundant water splitting catalysts. © 2013 the Owner Societies.

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