Tailoring TiO2/WO3 composites for high-efficiency NOx abatement: Influence of synthesis method and tungsten source

The combination of tungsten doping and WO₃ composite formation represents a highly effective approach to enhancing the photocatalytic activity of TiO 2 . The primary objective of this modification is the elimination of NOx air pollutants through the application of a photocatalytic layer. In this study, TiO 2 ‑based composite photocatalysts incorporating both tungsten doping and a WO 3 cocatalyst were synthesized using three distinct methods. The synergistic effect of these two modifications alters the structural and optical properties, alongside the dynamics of photogenerated charge carriers, ultimately resulting in elevated photocatalytic performance. The NOx conversion performance of the prepared photocatalyst composites was investigated under both UV‑A and simulated solar illumination in accordance with the ISO 22197‑1 standard. Under UV‑A irradiation, the TiO 2 /WO 3 physical mixture composite containing 2 wt.% WO 3 exhibited optimal performance, achieving a photocatalytic efficiency of ∼0.29 μmol·m −2 ·mW −1 over 120 minutes. Conversely, under simulated solar irradiation, the highest activity was observed for the TiO 2 prepared by a sol–gel method, which featured simultaneous WO 3 incorporation and tungsten doping utilizing Na 2 WO 4 as the precursor. The measured efficiency for this sample series is one order of magnitude higher than that of the series where H 2 WO 4 was used as the tungsten source, as well as the TiO 2 /WO 3 physical mixture series. With an efficiency of 0.020 μmol·m −2 ·mW −1 , the best member of this series is the composite containing WO 3 at a nominal 10 wt.% (combined WO 3 content and tungsten doping). When converted to realistic environmental parameters, this result corresponds to ∼20.0 mmol·m −2 over 120 minutes.