Ti and Sn co-doped anodic α-Fe2O3 films for efficient water splitting

Hematite (α-Fe2O3) films were produced by anodic FeOOH deposition on FTO, followed by TiCl4 decoration and an appropriate heat treatment. Optimizing the amount of Ti addition (1.5 μL cm− 2 of 0.2 M TiCl4) and annealing to 600 °C/750 °C allows to reach 1.4 mA cm− 2 at 1.23 V (vs. RHE) with a maximum photocurrent of 3.1 mA cm− 2 at 1.8 V (vs. RHE) in 1 M KOH under AM 1.5 (100 mW cm− 2) simulated solar illumination. This comparably high photoresponse can be attributed to a combined Ti/Sn effect, the latter causing thermal Sn doping from the FTO. Photocurrent transients show that the main combined influence of Ti addition/Sn doping is a strong suppression of charge carrier recombination. This may be attributed to electronic effects but also to a different morphology observed for Ti treated samples. The work shows that simple anodic nanoporous films have a high potential for optimization towards highly efficient hematite based photoelectrodes.

► Hematite films are produced by a simple anodic deposition technique by combining a TiCl4 treatment and Sn doping.
► The combined Ti/Sn effect is a strong suppression of charge carrier recombination.
► The optimized films show a photocurrent of 3.1 mA cm− 2 at 1.8 V (vs. RHE) in 1 M KOH under AM 1.5 (100 mW cm− 2) simulated solar illumination.