Photoelectrochemical (PEC) water splitting using semiconductor electrodes has received much attention in the last decades. In this sense, hematite photoanode has appeared as a good candidate due to it is synthetized from cheap and abundant elements, non-toxicity and has a band gap of 2.1 eV that permits the absorption of visible light (Sivula, Le Formal, & Grätzel, 2011). However, their transport properties change drastically depending of synthesis method employed and the different morphologies obtained (Horiz et al., 2016). In this study, we report the electrochemical growth of hematite (α-Fe₂O₃) nanostructures by anodization process of carbon steel substrates in an ethylene glycol based medium. The influence of experimental parameters including the NH₄F concentration, anodization time and applied voltage were systematically investigated to study their electrochemical properties. The obtained films were heat treated to 500 ºC to obtain the hematite crystalline phase. The crystalline phase was determined using an X-ray diffraction and Raman spectroscopy. FE‑SEM images of the hematite nanostructures films provided morphological parameters. Photoelectrochemical characterization was achieved through OCP, LSV, CA and EIS procedures. A hard dependence between the synthesis variables and their photoelectrochemical properties for water splitting reaction was observed.

Horiz, N., Tamirat, A. G., Rick, J., Dubale, A. A., Su, W.-N., & Hwang, B.-J. (2016). Using hematite for photoelectrochemical water splitting: a review of current progress and challenges. Nanoscale Horizons, 1, 243–267. https://doi.org/10.1039/c5nh00098j

Sivula, K., Le Formal, F., & Grätzel, M. (2011). Solar water splitting: Progress using hematite (α-Fe2O3) photoelectrodes. ChemSusChem, 4(4), 432–449. https://doi.org/10.1002/cssc.201000416