Pulsed Laser Deposited Fe₂TiO₅ Photoanodes\nfor Photoelectrochemical Water Oxidation

Abstract

Pulsed\nlaser deposition (PLD) is an appealing technique to fabricate\nthin films with specific film orientation, stoichiometry, and morphology\nthrough tuning of experimental parameters. Here, we present Fe₂TiO₅, one of the promising photoanode materials,\ngrown on fluorine-doped tin oxide (FTO) substrates through PLD. The\nstructural and morphological properties of Fe₂TiO₅ films grown at room temperature and under varying oxygen pressure\nwere studied. After deposition, all films were annealed in air at\n650 °C for 2 h for phase crystallization. Films grown under\nvacuum (1.1 × 10^–6 mbar) were compact and dense\nand had the anticipated stoichiometry but lacked the long-range order\nexpected for a crystalline phase in X-ray diffraction. In contrast,\nusing an oxygen pressure (<i>p</i>_O₂) of around 9.7 × 10^–2 mbar during growth\nresulted in nanoporous, crystalline, and near-stoichiometric films\nof the orthorhombic Fe₂TiO₅ pseudobrookite phase.\nThese films demonstrated a photocurrent density of around 0.16 mA/cm² at 1.23 V versus RHE and a negative shift in onset potential\nby 150 mV under backside illumination as compared to the films grown\nunder vacuum. Notably, these films exhibited a preferred (101) orientation\nof the pseudobrookite grains. This study proposes a viable strategy\nto fabricate pure-phase and anisotropic Fe₂TiO₅ photoanodes on FTO through PLD. This will pave a way to the synthesis\nof other complex metal oxide photoelectrodes with precise control\nover critical properties such as crystallinity, stoichiometry, and\nporosity that are imperative for their application in solar energy\nconversion.