MgTi₂O₅ thin films from single molecular precursor for photoelectrochemical water splitting

Magnesium dititanate MgTi₂O₅ thin films have been grown on fluorine doped tin oxide (FTO) substrates using a newly synthesized heterobimetallic single molecular precursor [Mg₂Ti₄(O)₂(OH)₄(TFA)₈(THF)₆]·THF (1) (where TFA=trifluroacetato and THF=tetrahydrofuran) using the aerosol assisted chemical vapor deposition technique (AACVD). The precursor complex (1), isolated in crystalline form by reacting magnesium (II) acetate tertahydrate with titanium (IV) isopropoxide and trifluroacetic acid in THF solution, was characterized by FTIR, single-crystal X-ray diffraction and thermogravimetric analyses. Thin films prepared at 500, 550 and 600 °C were inspected by X-ray diffraction (XRD), field emission gun-scanning electron microscopic (FESEM), and energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), which demonstrated the development of phase pure orthorhombic porous microspherical objects of MgTi₂O₅ with precise stoichiometry. The optical analysis showed that MgTi₂O₅ has a direct band gap of 3.4 eV. The photoelectrochemical (PEC) experiments on MgTi₂O₅ electrodes showed maximum anodic photocurrent density of 400 μA/cm² at 0.7 V vs. Ag/AgCl/3 M KCl under simulated solar irradiation of AM 1.5G (100 mW/cm²) in 1 M NaOH. The improved PEC performance of MgTi₂O₅ electrode was attributed to the increased photo absorption ability, elevated surface area, and more efficient electron/hole transfer which were confirmed by measurements such as linear sweep voltage, transient photocurrent and electrochemical impedance spectroscopy.