The photoelectrochemical degradation of selected aromatic substances, acid orange 7 (AO7), salicylic acid (SA), benzoic acid (BA), and 4-chlorophenol (4-CP) was studied on hematite (α-Fe2O3) and compared with titanium dioxide (TiO2), both deposited as thin films on conducting substrates (FTO/glass). Batch type reactors were used under backside and front side illumination. Electrical bias was applied on the semiconducting electrodes, such that only valence band processes leading to oxidative pathways were followed. The initial Faradaic efficiency, f0, of degradation processes was determined from the UV-Vis absorbance decrease of the starting materials. f0 for 1 mM AO7 degradation in 0.01 M sulphuric acid was found to be 7.5%. When the pH of the solution was neutral (pH 7.2) or alkaline (pH 13), f0 decreased to 1.7%. For 1 mM SA, f0 was 6.2% on hematite photoanodes and 6.1% on titanium dioxide. For 1 mM benzoic acid and 4-chlorophenol, f0 was an order of magnitude lower, but only on hematite. This is ascribed to the lack of OH· radical formation on hematite, which seems to be essential for the photooxidation of these compounds.

Department of Inorganic Technology University of Chemistry and Technology Prague Technická 5 16628 Prague 6 Czech Republic

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Schneider, J., Matsuoka, M., Takeuchi, M., Zhang, J., Horiuchi, Y., Anpo, M., & Bahnemann, D. W. (2014). Understanding TiO PubMed DOI

Kennedy, J. H., & Frese, K. W. (1978). Photooxidation of water at α-Fe DOI

Pourbaix, M. (1963). Atlas d’Équilibres Électrochimiques (p. 307). Gauthier-Villars et Cie.

Kennedy, J. H., & Anderman, M. (1983). Photoelectrolysis of water at α-Fe DOI

Steier, L., Herraiz-Cardona, I., Gimenez, S., Fabregat-Santiago, F., Bisquert, J., Tilley, S. D., & Grätzel, M. (2014). Understanding the role of underlayers and overlayers in thin film hematite photoanodes. Advanced Functional Materials, 24(48), 7681–7688. https://doi.org/10.1002/adfm.201402742 DOI

Kment, Š, Riboni, F., Paušová, Š, Wang, L., Wang, L., Han, H., Hubička, Z., Krýsa, J., Schmuki, P., & Zboril, R. (2017). Photoanodes based on TiO PubMed DOI

Neumann-Spallart, M., Shinde, S. S., Mahadik, M., & Bhosale, C. H. (2013). Photoelectrochemical degradation of selected aromatic molecules. Electrochimica Acta, 111, 830–836. DOI

Mahadik, M. A., Shinde, S. S., Kumbhar, S. S., Pathan, H. M., Rajpure, K. Y., & Bhosale, C. H. (2015). Enhanced photocatalytic activity of sprayed Au doped ferric oxide thin films for salicylic acid degradation in aqueous medium. Journal of Photochemistry and Photobiology B: Biology, 142, 43–50. PubMed DOI

Shinde, S. S., Bhosale, C. H., & Rajpure, K. Y. (2011). Photocatalytic oxidation of salicylic acid and 4-chlorophenol in aqueous solutions mediated by modified AlFe DOI

Chen, S., Li, J., Bai, J., Xia, L., Zhang, Y., Li, L., Xu, Q., & Zhou, B. (2018). Electron blocking and hole extraction by a dual-function layer for hematite with enhanced photoelectrocatalytic performance. Applied Catalysis B: Environmental, 237, 175–184. DOI

Mahadik, M. A., Shinde, S. S., Mohite, V. S., Kumbhar, S. S., Moholkar, A. V., Rajpure, K. Y., Ganesan, V., Nayak, J., Barman, S. R., & Bhosale, C. H. (2014). Visible light catalysis of rhodamine B using nanostructured Fe PubMed DOI

Mahadik, M. A., Shinde, S. S., Rajpure, K. Y., & Bhosale, C. H. (2013). Photocatalytic oxidation of rhodamine B with ferric oxide thin films under solar illumination. Materials Research Bulletin, 48(10), 4058–4065. DOI

Krýsa, J., Baudys, M., Zlámal, M., Krýsová, H., Morozová, M., & Klusoň, P. (2014). Photocatalytic and photoelectrochemical properties of sol–gel TiO DOI

Imrich, T., Krýsová, H., Neumann-Spallart, M., & Krýsa, J. (2021). Fe DOI

Krýsa, J., Imrich, T., Paušová, Š, Krýsová, H., & Neumann-Spallart, M. (2019). Hematite films by aerosol pyrolysis: Influence of substrate and photocorrosion suppression by TiO DOI

Hirano, K., & Bard, A. J. (1980). Semiconductor electrodes: XXVIII. Rotating ring-disk electrode studies of photo-oxidation of acetate and iodide at n-TiO DOI

Bourikas, K., Stylidi, M., Kondarides, D. I., & Verykios, X. E. (2005). Adsorption of acid orange 7 on the surface of titanium dioxide. Langmuir, 21(20), 9222–9230. PubMed DOI

Guinea, E., Arias, C., Cabot, P. L., Garrido, J. A., Rodríguez, R. M., Centellas, F., & Brillas, E. (2008). Mineralization of salicylic acid in acidic aqueous medium by electrochemical advanced oxidation processes using platinum and boron-doped diamond as anode and cathodically generated hydrogen peroxide. Water Research, 42(1), 499–511. PubMed DOI

Momeni, S., & Nematollahi, D. (2017). New insights into the electrochemical behavior of acid orange 7: Convergent paired electrochemical synthesis of new aminonaphthol derivatives. Scientific Reports, 7(1), 41963. PubMed DOI PMC

Arts, A., van den Berg, K. P., de Groot, M. T., & van der Schaaf, J. (2021). Electrochemical oxidation of benzoic acid and its aromatic intermediates on boron doped diamond electrodes. Current Research in Green and Sustainable Chemistry, 4, 100217. DOI

Colucci, J., Montalvo, V., Hernandez, R., & Poullet, C. (1999). Electrochemical oxidation potential of photocatalyst reducing agents. Electrochimica Acta, 44(15), 2507–2514. DOI

Rodrigo, M. A., Michaud, P. A., Duo, I., Panizza, M., Cerisola, G., & Comninellis, C. (2001). Oxidation of 4-chlorophenol at boron-doped diamond electrode for wastewater treatment. Journal of the Electrochemical Society, 148(5), D60. DOI

Armstrong, D. A., Huie, R. E., Lymar, S., Koppenol, W. H., Merényi, G., Neta, P., Stanbury, D. M., Steenken, S., & Wardman, P. (2013). Standard electrode potentials involving radicals in aqueous solution: Inorganic radicals. BioInorganic Reaction Mechanisms, 9(1–4), 59–61.

Atkinson, R. J., Posner, A. M., & Quirk, J. P. (1967). Adsorption of potential-determining ions at the ferric oxide-aqueous electrolyte interface. The Journal of Physical Chemistry, 71(3), 550–558. DOI

Kosmulski, M. (2020). The pH dependent surface charging and points of zero charge. VIII. Update. Advances in Colloid and Interface Science, 275, 102064. PubMed DOI

Xu, Y., & Schoonen, M. A. A. (2000). The absolute energy positions of conduction and valence bands of selected semiconducting minerals. American Mineralogist, 85(3–4), 543–556. DOI