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.

Automated summary

In this study, a facile surface treatment method using Fe2+ ions was demonstrated to enhance the photo-electrochemical water oxidation of nanostructured tungsten oxide (WO3) film. The optimized WO3 film with a Fe:W ratio of -1:25 showed a 3 times higher and more stable photocurrent under back illumination compared to untreated WO3, indicating the success of the surface treatment. The improved performance was attributed to the enhanced charge transfer process at the interface, resulting in the reduction of unwanted recombination.