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

  • Author(s): Shavorskiy, Andrey;
  • Ye, Xiaofei;
  • Karslıoğlu, Osman;
  • Poletayev, Andrey D;
  • Hartl, Matthias;
  • Zegkinoglou, Ioannis;
  • Trotochaud, Lena;
  • Nemšák, Slavomir;
  • Schneider, Claus M;
  • Crumlin, Ethan J;
  • Axnanda, Stephanus;
  • Liu, Zhi;
  • Ross, Philip N;
  • Chueh, William;
  • Bluhm, Hendrik
  • et al.
Abstract

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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