Novel synthesis approaches for WO3-TiO2/MWCNT composite photocatalysts-problematic issues of photoactivity enhancement factors

The build-up methodology, the importance of the order of the semiconductor layers in WO3-TiO2/MWCNT composite materials was studied in terms of the applied synthesis pathway, morpho-structural parameters (mean crystallite size, crystal phase composition, morphology) and photocatalytic efficiency (using oxalic acid as model pollutant). The appearance of TiWOX phase in the composites contributed to the enhancement of the photocatalytic efficiencies, as different synthesis approaches led to different crystal phase compositions. Although, it was proven that a beneficial phase's presence can be hindered if an excess of MWCNT or WO3 was applied. As the ratio of the mentioned materials was reduced, active composites were obtained, but the previously noticed TiWOX disappeared. Therefore, it was proven, that in the case of WO3-TiO2/MWCNT nanocomposite system several photo catalytic activity enhancement factors can be introduced, but not simultaneously (the disappearance of TiWOX at low MWCNT and WO3 contents and the appearance of highly crystalline anatase). (C) 2017 Elsevier B.V. All rights reserved.