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.