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 (WO(3)) 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 WO(3) 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 WO(3) nanostructures and titania nanotubes (used for comparison) exhibit superior photocurrent response in the mixture of NaOH and KOH than in other alkaline electrolytes. The WO(3) 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 WO(3) 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 WO(3) porous nanostructures. The results suggest that the hybrid ITO/WO(3) 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.

Nanostructured Tungsten Trioxide Thin Films Synthesized for Photoelectrocatalytic Water Oxidation: A review

“…[66] They found that in the multi-composite BiVO 4 /SnO 2 /WO 3 layers on the photoanode, the photocurrent at 1.23 V (vs. RHE) in 0.1 m carbonate electrolyte solution was more than 2.4 times higher than that in sul- Figure 17. [66] Ishihara et al, [6] found that the chemical nature of electrolytes played a crucial role in the efficient operation and energy conversion of a solar PEC cell. The inset represents the corresponding energy diagram for an n-type semiconductor and a metal as photoanode and photocathode, respectively.…”

“…Schematic representation of a PEC device for H 2 and O 2 evolution. [6] Hill and Choi [46] studied the various effects of different anions and cations contained in an electrolyte solution on the photocurrent conversion efficiency (Table 4). E F indicates the Fermi energy level.…”

“…Other advantages of cathodic electrodeposition include its potential for mass production as well as the ability to produce nanostructured WO 3 thin films with large surface area-to-volume ratios. (6) and (7)]: [30] 2 W þ 10 [12a] Meulenkamp proposed that the increase in efficiency of nanostructured WO 3 thin films was determined only to a good approximation by the reduction of peroxy tungstate. [12b] The latter mechanism is usually based on the generation of a localized high- --pH region near the electrode surface, which induces the electrodeposition of metal ions.…”

Enhanced Photocurrent Response of Titania‐Nanotube Heterojunction Devices Capped with Titanium Disilicide

“…The photocurrent response induced by the TiSi 2 ‐coating of the titania nanotubes is shown in Figure 5 (a) as a function of applied voltage vs. Ag/AgCl. An alkaline electrolyte containing a mixture of NaOH and KOH [0.5 M NaOH+0.3 m KOH+10 % ( v / v ) ethylene glycol+DI water] was used for the study, and the recipe was chosen based on the findings presented in our previous study 25. In that investigation, we discussed the fact that both titania nanotubes and porous tungsten nanostructures show the highest plateau‐photocurrent density (PPCD) for the electrolyte containing a mixture of NaOH and KOH.…”

Towards near-infrared photosensitization of tungsten trioxide nanostructured films by upconverting nanoparticles

“…The bandgap of this material is more suitable than TiO 2 (E g ≈ 3.2 eV) from the solar light application point of view. Indeed, unlike TiO 2 that absorbs only in the UV region of the solar spectrum, WO 3 can absorb wavelenght up to 500 nm [34]. Apart from its bandgap, WO 3 has many interesting features for technological applications.…”