A novel tungsten trioxide (WO3)/ITO porous nanocomposite for enhanced photo-catalytic water splitting

Abstract

Hybrid nanocomposite films of ITO-coated, self-assembled porous nanostructures of tungsten trioxide (WO₃) were fabricated using electrochemical anodization and sputtering. The morphology and chemical nature of the porous nanostructures were studied by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS), respectively. The photoelectrochemical (PEC) properties of WO₃ porous nanostructures were studied in various alkaline electrolytes and compared with those of titania nanotubes. A new type of alkaline electrolyte containing a mixture of NaOH and KOH was proposed for the first time to the best of our knowledge and shown to improve the photocurrent response of the photoanodes. Here, we show that both the WO₃ nanostructures and titania nanotubes (used for comparison) exhibit superior photocurrent response in the mixture of NaOH and KOH than in other alkaline electrolytes. The WO₃ porous nanostructures suffered from surface corrosion resulting in a huge reduction in the photocurrent density as a function of time in the alkaline electrolytes. However, with a protective coating of ITO (100 nm), the surface corrosion of WO₃ porous nanostructures reduced drastically. A tremendous increase in the photocurrent density of as much as 340% was observed after the ITO was applied to the WO₃ porous nanostructures. The results suggest that the hybrid ITO/WO₃ nanocomposites could be potentially coupled with titania nanotubes in a multi-junction PEC cell to expand the light absorption capability in the solar spectrum for water splitting to generate hydrogen.