Enhanced photoelectrochemical water oxidation by Fe(II) modified nanostructured WO3 photoanode

Herein, we demonstrate a facile surface treatment of a nanostructured tungsten oxide (WO3) film by Fe2+ ions as a novel post-fabrication technique for enhanced photo-electrochemical water oxidation under sunlight. The structural, optical, morphological and elemental characterizations of the n-type WO3 nanoplates based electrodes have been done using X-ray diffraction, UV-visible diffuse reflectance spectroscopy, fluorescence spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy, respectively. The modified WO3 photoanodes have been subsequently examined for photoelectrochemical response by linear sweep voltammetry, photo-amperometry, electrochemical impedance spectroscopy (Nyquist plot) and Mott-Schottky analysis under AM 1.5 G solar simulated light. The optimized WO3 film with Fe:W ratio of -1:25, (Fe2+:Fe3+ ratio of -3:2) at the surface exhibited up to 3 times higher and more stable photocurrent under back illumination than that for untreated WO3 indicating the success of the surface treatment. Investigations revealed that the improved performance is a consequence of an improved charge transfer process at the interface resulting in lowering of unwanted recombination.