Hematite (α-Fe2O3) Photoanodes for the Photooxidation of Water

Nanostructured hematite films prepared by a sol-gel procedure were evaluated for the photo-induced oxygen evolution reaction (OER). Surface treatments such as plasma and post-annealing at 500 °C in oxygen gas flow were used in order to condition the electrode surface. Electrochemical measurements of the plasma treated samples revealed that the surface was reorganized in terms of enhanced catalytic properties and reduced recombination centers at the surface. Photocurrents in the milli-Ampere range were yielded at 0.92 V(NHE) in 1 M KOH. In contrast to the plasma samples, the post-annealing samples displayed higher bulk crystallinity resulting in a more enhanced photovoltage. XRD and TEM analysis confirmed the texturing of a beneficial highly oriented hematite film (110) parallel to the back contact. Nevertheless, lower photocurrents for this post-annealed sample compared to the plasma one indicated that the catalytic centers were not fully recovered at the surface.