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Two-site H(2)O(2) photo-oxidation on haematite photoanodes

H(2)O(2) 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 H(2)O(2) photo-oxidation on haematite (α-Fe(2)O(3)) photoanodes. We found that the photocurrent voltammograms display non-monotonous behaviour u...

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Detalles Bibliográficos
Autores principales: Avital, Yotam Y., Dotan, Hen, Klotz, Dino, Grave, Daniel A., Tsyganok, Anton, Gupta, Bhavana, Kolusheva, Sofia, Visoly-Fisher, Iris, Rothschild, Avner, Yochelis, Arik
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group UK 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6177486/
https://www.ncbi.nlm.nih.gov/pubmed/30301897
http://dx.doi.org/10.1038/s41467-018-06141-0
Descripción
Sumario:H(2)O(2) 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 H(2)O(2) photo-oxidation on haematite (α-Fe(2)O(3)) photoanodes. We found that the photocurrent voltammograms display non-monotonous behaviour upon varying the H(2)O(2) 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 H(2)O(2) 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 H(2)O(2) concentrations. This prediction is confirmed experimentally by observing a hysteresis loop in the photocurrent voltammogram measured in the predicted coexistence range.