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

Abstract The “build-up” methodology, the importance of the order of the semiconductor layers in WO 3 ‐TiO 2 /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 TiWO x 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 WO 3 was applied. As the ratio of the mentioned materials was reduced, active composites were obtained, but the previously noticed TiWO x disappeared. Therefore, it was proven, that in the case of WO 3 -TiO 2 /MWCNT nanocomposite system several photocatalytic activity enhancement factors can be introduced, but not simultaneously (the disappearance of TiWO x at low MWCNT and WO 3 contents and the appearance of highly crystalline anatase).