Synthesis and characterization of nanoporous Bi₃NbO₇ films: Application to photoelectrochemical water splitting

Nanostructured Bi₃NbO₇ films were successfully prepared via an ultrasonic spray pyrolysis method by using Bi(NO ₃)₃·5H₂O and Nb₂O₅ as precursors. The as-prepared films were systematically characterized by X-ray diffraction, Atomic Force Microscopy (AFM), field emission scanning electron microscopy (FESEM), UV-vis absorption spectra and X-ray photoelectron spectroscopy. The characterization results revealed that the nanostructured Bi₃NbO₇ possessed a cubic structure, nanoporous morphology and a visible light absorption with an optical band gap of about 2.8 eV. Moreover, electrochemical and photoelectrochemical measurements were carried out and a maximum photocurrent density of 2.8 μA cm^-2 at the potential of 0.7 V vs. SCE was obtained for the Bi₃NbO₇ film deposited at 350 °C. The improvement of the film photoelectrochemical properties was contributed by novel nanoporous morphology that supply sufficient electrode-solution contact area. By addition of methanol into the solution, the photocurrent increased by 60%. The photoelectrochemical results reveal that the prepared films have the potential for hydrogen production via splitting water.