FeOOH, α-Fe₂O_3, and ZnFe₂O₄ Thin Films Grown by Electrodeposition Method: Study for Photoanode Development

This work presents the development of a photoanode for oxygen evolution reaction (OER). The deposit of FeOOH precursor film was performed by electrodeposition on FTO substrates varying the deposition charge. The FeOOH electrodes were heated at 500°C for 2 hours with a ramp of 2°C/min to obtain α-Fe 2 0 3 films. Some of these FeOOH films were coated with a solution containing Zn ⁺² ions that, when heated, reacted to form ZnFe 2 O 4 . X-ray diffraction showed the formation of crystalline phases of each of these materials. As the thickness increases, the absorption edges of each material increase. Very similar morphologies are observed in the form of nanosheets in each of the samples. On the other hand, during the electrochemical characterization n-type behavior was observed. It is also observed that iron oxyhydroxides show electrocatalytic performance for OER with a starting potential at 1.2 V. Photocurrent measurements reveal that α-Fe 2 0 3 is the most stable of the 3 materials, ZnFe 2 O 4 also presents a photocurrent, however, it presents problems of recombination of photogenerated carriers. In general, these results show the potential use of α-Fe 2 O 3 and ZnFe 2 O 4 as photoanodes for water oxidation, however, together with other materials they can increase redox yields.