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 and Arik Yochelis ()
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Yotam Y. Avital: Ben-Gurion University of the Negev
Hen Dotan: Technion – Israel Institute of Technology
Dino Klotz: Technion – Israel Institute of Technology
Daniel A. Grave: Technion – Israel Institute of Technology
Anton Tsyganok: Technion – Israel Institute of Technology
Bhavana Gupta: Ben-Gurion University of the Negev
Sofia Kolusheva: Ben-Gurion University of the Negev
Iris Visoly-Fisher: Ben-Gurion University of the Negev
Avner Rothschild: Technion – Israel Institute of Technology
Arik Yochelis: Ben-Gurion University of the Negev

Nature Communications, 2018, vol. 9, issue 1, 1-10

Abstract: 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.

Date: 2018
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DOI: 10.1038/s41467-018-06141-0

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