Pulsed Laser Deposited Fe2TiO5 Photoanodes for Photoelectrochemical Water Oxidation

Pulsed laser deposition (PLD) is an appealing technique to fabricate thin films with specific film orientation, stoichiometry, and morphology through tuning of experimental parameters. Here, we present Fe2TiO5, one of the promising photoanode materials, grown on fluorine-doped tin oxide (FTO) substrates through PLD. The structural and morphological properties of Fe2TiO5 films grown at room temperature and under varying oxygen pressure were studied. After deposition, all films were annealed in air at 650 °C for 2 h for phase crystallization. Films grown under vacuum (1.1 × 10–6 mbar) were compact and dense and had the anticipated stoichiometry but lacked the long-range order expected for a crystalline phase in X-ray diffraction. In contrast, using an oxygen pressure (p O2 ) of around 9.7 × 10–2 mbar during growth resulted in nanoporous, crystalline, and near-stoichiometric films of the orthorhombic Fe2TiO5 pseudobrookite phase. These films demonstrated a photocurrent density of around 0.16 mA/cm2 at 1.23 V versus RHE and a negative shift in onset potential by 150 mV under backside illumination as compared to the films grown under vacuum. Notably, these films exhibited a preferred (101) orientation of the pseudobrookite grains. This study proposes a viable strategy to fabricate pure-phase and anisotropic Fe2TiO5 photoanodes on FTO through PLD. This will pave a way to the synthesis of other complex metal oxide photoelectrodes with precise control over critical properties such as crystallinity, stoichiometry, and porosity that are imperative for their application in solar energy conversion.