TiO2/WO3 hybrid structures produced through a sacrificial polymer layer technique for pollutant photo- and photoelectrooxidation under ultraviolet and visible light illumination

Abstract

TiO 2 /WO 3 hybrid structures were produced on graphite substrates following a three step procedure: (i) electrochemical deposition of WO 3 under potentiostatic conditions, (ii) electrochemical deposition of TiO 2 -polyaniline (PANI) composite layers by potentiostatic polymerization of aniline in the presence of TiO 2 nanoparticles, (iii) high temperature (450°C) treatment for decomposition of the PANI structure. Experiments on the photoelectrochemical response of the composite layers were carried out by cyclic voltammetry and chronoamperommetry in the dark and under illumination by using low power lamps emitting in the visible and UV spectrum ranges. The oxidation of three pollutants-oxalate ions, methanol and malachite green was used to evaluate the photoelectrocatalytic activity of the TiO 2 /WO 3 structures. The photocurrents registered for the photooxidation of oxalate were higher than photocurrents measured at hybrid TiO 2 /WO 3 electrodes obtained in conventional two-step electrodeposition of WO 3 and subsequently TiO 2 from corresponding salt solutions. The efficiency of the malachite green photodegradation in our experiments was also about two orders of magnitude higher than that obtained in TiO 2 /WO 3 structures synthesized in a conventional way. These results are (very probably) due to the proposed synthetic approach involving PANI polymer layer as an immobilizing matrix and the opportunity to disperse homogeneously TiO 2 nanoparticles on the WO 3 surface provided.

Modified TiO2 For Environmental Photocatalytic Applications: A Review

“…Coupling between different semiconductors with different energy levels is another interesting approach, which has received great interest in the past decade. ,,, In photocatalytic systems, coupling TiO 2 with others semiconductors was designed to extend the absorption wavelength range into the visible light region and to alleviate the charge carrier recombination in individual photoelectrodes. , It has been reported by Zhang that the good matching of the conduction band and valence band of the two semiconductors could ensure an efficient transfer of the charge carriers from one to another. When the large band gap of TiO 2 is coupled with a small band gap semiconductor having more negative conduction band level, the electron can be injected from the small band gap of the semiconductor used as a sensitizer to the TiO 2 .…”

“…The TiO 2 /WO 3 hybrid system has received much attention in the field of photo-electrochemistry. ,, TiO 2 /WO 3 is a system of semiconductor-semiconductor coupled material, which has been widely used as a photocatalyst for decades . The band gap of WO 3 is lower (2.8 eV), and both the upper edge of the valence band and the lower edge of the conduction band of WO 3 are lower than those of TiO 2 .…”

WO3/TiO2 nanotube photoanodes for solar water splitting with simultaneous wastewater treatment.

“…Contrary to other bandgap narrowing approaches (e.g. doping), the coupling approach is expected to provide a better charge separation, which could also increase the charge transport efficiency [2].…”

Nano-indentation investigations of the mechanical properties of thin TiO2, WO3 and their composites layers, deposited by spray pyrolysis

“…That is why several investigations were focused on the synthesis and characterization of TiO 2 -WO 3 composites. [37][38][39][40][41] The energy band gap of WO 3 is~2.4-2.8 eV and both the upper edge of the valence band and the lower edge of the conduction band of WO 3 are lower than those of TiO 2 . Thus, the TiO 2 -WO 3 composite has a narrower energy band gap (compared to that of TiO 2 ) and shows enhanced photocatalytic activity with respect to its single components.…”