Competitive Photo-Oxidation of Water and Hole Scavengers on Hematite Photoanodes: Photoelectrochemical and Operando Raman Spectroelectrochemistry Study

Vivek Ramakrishnan, Anton Tsyganok, Elena Davydova, Mariela J. Pavan, Avner Rothschild, Iris Visoly-Fisher

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Hematite (α-Fe2O3) is one of the most studied photoanode materials due to its stability in alkaline electrolytes and visible light absorption. However, its reported performance lags significantly behind its theoretical limit. Toward determining routes for efficient photo-oxidation on hematite, we investigated the role of hole-trapping surface states as reaction intermediates using sacrificial reductant reagents as hole scavengers, H2O2 and FeCN. Photoelectrochemical characterization at low scavenger concentrations and intermediate potentials, as opposed to previous studies at high scavenger concentrations, has shown the reaction mechanism to include competitive photo-oxidation between water molecules and the hole scavengers, similar for both H2O2 and FeCN. Using operando Raman spectroelectrochemistry, we show similar transient features for both scavengers, interpreted as scavenger adsorption to a two-site reaction intermediate participating in the photogenerated hole transfer of water photo-oxidation, hence the competition. These findings strengthen the significance of hole-trapping surface states for water photo-oxidation on hematite and the previously suggested two-site reaction pathway for efficient hole transfer in this reaction. A better understanding of the mechanisms of photoelectrochemical water splitting can assist in improving the efficiency of solar hydrogen production.

Original languageEnglish
Pages (from-to)540-549
Number of pages10
JournalACS Catalysis
Volume13
Issue number1
DOIs
StatePublished - 6 Jan 2023

Keywords

  • hematite
  • hole scavenger
  • operando Raman spectroelectrochemistry
  • photo-oxidation
  • surface states

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry

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