Photoelectrochemical Oxygen Evolution on Mesoporous Hematite Films Prepared from Maghemite Nanoparticles

• Published in: Journal of the Electrochemical Society 2022-05, Vol.169 (5), p.56522
• Main Authors: Verissimo, N. C., Ren, D., Kleiner, C. C. C., Hesse, F. A. B., Zakeeruddin, S. M., Grätzel, M., Bertazzoli, R.
• Format: Article
• Language: English
• Subjects: hematite; high-performance; hydrothermal synthesis
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1945-7111/ac70fd

Iron oxides, especially hematite ( α -Fe 2 O 3 ), are promising materials for applications in photoelectrochemical cells and photo-redox catalysis. However, realizing high-performance hematite photoanodes via an environmentally-friendly route remains a great challenge. In this work, we employed a novel approach to prepare mesoscopic hematite photoelectrodes with remarkable performance for water oxidation. Hydrothermally-synthesized maghemite nanoparticles of high crystallinity with a mean particle size of 3.3 nm were deposited onto fluorine doped tin oxide (FTO) transparent conducting glass substrates, followed by heat treatment to convert them into a homogeneous mesoporous hematite layer. A hematite photoanode with a thickness of 220 nm, delivered a maximum photocurrent density of 1.8 mA cm −2 for water oxidation to oxygen at 1.23 V RHE under simulated AM 1.5 irradiation. Upon treating the surface of the hematite photoelectrode with Co(II) cations the photocurrent density nearly doubled at the same potential to 3.32 mA cm −2 placing our new photoelectrode among the best hematite-based photocatalysts for visible light induced water splitting. Further photoelectrochemical analysis provided insights into the factors boosting the performance of the hematite photoanode.