Optimum Deposition of Tungsten Oxide on Titania Nanotubular Arrays and Study the Photoactivity of Nano-Composite Photoanode

Abstract

The novelty of this research works in the two-step formation of tungsten oxide (WO3) -loaded TiO2 nanotube arrays composite film by study the optimum conditions of electrodeposition of WO3 nanoparticles on TiO2 nanotubes arrays based on their photo-activity performance. The W have been incorporated from a sodium tungstate-based aqueous electrolyte containing from 0.2 M sodium tungstate (Na2WO4) with addition of 0.13 M hydrogen peroxide (30%) and drops from H2SO4 up to get pH = 1; it accumulates to form a self independent structure of WO3 on the surface of the nanotubes. WO3 was deposited for several times intervals at room temperature and annealed at 350 ºC for 30 minutes. TiO2 nanotubes (TNTA) were successfully grown by anodizing of titanium foil (Ti) in organic (98% vol., ethylene glycol, 2 vol.% Di water and 0.5 wt% ammonium fluoride and acidic (0.5M phosphoric acid and 0.14M sodium fluoride) electrolyte. The possible growth of TiO2 nanotubes in the applied potential at 20V for 45 minutes was investigated. It were found such electrochemical condition resulted in formation of nanotube with average diameter 50 & 120 nm and the length 3.5 & 0.6 µm for organic and acidic electrolytes respectively. The anodized samples were annealed at 500 ºC in N2 gas for 3 hours. The structural, morphology and composition of TiO2 nanotubes and WO3/TiO2 nanotube were characterized with XRD, FESEM and EDX. FESEM results of the nanotubular arrays showed uniform arrays of titania nanotubular and showed. EDX results showed trace of tungsten has been incorporated into TiO2. The influences of tungsten content on the photocurrent densities of WO3/TiO2 nanotubular photoanodes were investigated by recording current-potential profiles. The preliminary results indicated that the WO3/TiO2 produced showed good photocurrent densities due to the behavior of W6+ ions which allows to electron traps that suppress electron-hole recombination and exploit the lower band gap of material to produce a water splitting process by increasing the charge separation and extending the energy range of photo-excitation for the system