Pilot-Scale Studies of WO 3 /S-Doped g-C 3 N 4 Heterojunction toward Photocatalytic NO x Removal.

Due to the rising concentration of toxic nitrogen oxides (NO x ) in the air, effective methods of NO x removal have been extensively studied recently. In the present study, the first developed WO 3 /S-doped g-C 3 N 4 nanocomposite was synthesized using a facile method to remove NOx in air efficiently. The photocatalytic tests performed in a newly designed continuous-flow photoreactor with an LED array and online monitored NO 2 and NO system allowed the investigation of photocatalyst layers at the pilot scale. The WO 3 /S-doped-g-C 3 N 4 nanocomposite, as well as single components, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller surface area analysis (BET), X-ray fluorescence spectroscopy (XRF), X-ray photoemission spectroscopy method (XPS), UV-vis diffuse reflectance spectroscopy (DR/UV-vis), and photoluminescence spectroscopy with charge carriers' lifetime measurements. All materials exhibited high efficiency in photocatalytic NO 2 conversion, and 100% was reached in less than 5 min of illumination under simulated solar light. The effect of process parameters in the experimental setup together with WO 3 /S-doped g-C 3 N 4 photocatalysts was studied in detail. Finally, the stability of the composite was tested in five subsequent cycles of photocatalytic degradation. The WO 3 /S-doped g-C 3 N 4 was stable in time and did not undergo deactivation due to the blocking of active sites on the photocatalyst's surface.