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Open Access Publications from the University of California

Direct Mapping of Band Positions in Doped and Undoped Hematite during Photoelectrochemical Water Splitting

  • Author(s): Shavorskiy, A
  • Ye, X
  • Karslloǧlu, O
  • Poletayev, AD
  • Hartl, M
  • Zegkinoglou, I
  • Trotochaud, L
  • Nemšák, S
  • Schneider, CM
  • Crumlin, EJ
  • Axnanda, S
  • Liu, Z
  • Ross, PN
  • Chueh, W
  • Bluhm, H
  • et al.

© 2017 American Chemical Society. Photoelectrochemical water splitting is a promising pathway for the direct conversion of renewable solar energy to easy to store and use chemical energy. The performance of a photoelectrochemical device is determined in large part by the heterogeneous interface between the photoanode and the electrolyte, which we here characterize directly under operating conditions using interface-specific probes. Utilizing X-ray photoelectron spectroscopy as a noncontact probe of local electrical potentials, we demonstrate direct measurements of the band alignment at the semiconductor/electrolyte interface of an operating hematite/KOH photoelectrochemical cell as a function of solar illumination, applied potential, and doping. We provide evidence for the absence of in-gap states in this system, which is contrary to previous measurements using indirect methods, and give a comprehensive description of shifts in the band positions and limiting processes during the photoelectrochemical reaction.

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