Two-site H2O2 photo-oxidation on haematite photoanodes

Yotam Y. Avital, Hen Dotan, Dino Klotz, Daniel A. Grave, Anton Tsyganok, Bhavana Gupta, Sofia Kolusheva, Iris Visoly-Fisher, Avner Rothschild, Arik Yochelis

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

H2O2 is a sacrificial reductant that is often used as a hole scavenger to gain insight into photoanode properties. Here we show a distinct mechanism of H2O2 photo-oxidation on haematite (α-Fe2O3) photoanodes. We found that the photocurrent voltammograms display non-monotonous behaviour upon varying the H2O2 concentration, which is not in accord with a linear surface reaction mechanism that involves a single reaction site as in Eley–Rideal reactions. We postulate a nonlinear kinetic mechanism that involves concerted interaction between adions induced by H2O2 deprotonation in the alkaline solution with adjacent intermediate species of the water photo-oxidation reaction, thereby involving two reaction sites as in Langmuir–Hinshelwood reactions. The devised kinetic model reproduces our main observations and predicts coexistence of two surface reaction paths (bi-stability) in a certain range of potentials and H2O2 concentrations. This prediction is confirmed experimentally by observing a hysteresis loop in the photocurrent voltammogram measured in the predicted coexistence range.

Original languageEnglish
Article number4060
JournalNature communications
Volume9
Issue number1
DOIs
Publication statusPublished - Dec 1 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Physics and Astronomy(all)

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