Enhancing the photocatalytic efficiency of the BiOCl/Bi3O4Cl composite modified with WO3 for environmental purification under visible light

Abstract

Covering the BiOCl/Bi₃O₄Cl composite with a monolayer of WO₃ resulted in a significant increase in the photocatalytic activity of WO₃/BiOCl/Bi₃O₄Cl in the presence of visible light (λ ≥ 420 nm). The decomposition of gaseous isopropyl alcohol (IPA) and aqueous salicylic acid (SA) in the presence of visible light was maximized when 0.2 mol% of WO₃ was attached to the surface of BiOCl/Bi₃O₄Cl. However, while the amount of WO₃ on the surface of BiOCl/Bi₃O₄Cl was less or more than 0.2 mol%, the photocatalytic activity was found to be abruptly reduced. At this composition, WO₃/BiOCl/Bi₃O₄Cl demonstrated 2.1 and 5.2 times better activity than the BiOCl/Bi₃O₄Cl composite and Degussa P25 (TiO₂ nanoparticle) for evolving CO₂ from the decomposition of IPA in gas phase under the identical conditions. These results suggest that 0.2 mol% WO₃/BiOCl/Bi₃O₄Cl was the optimized composition to achieve the highest photocatalytic activity covering of BiOCl/Bi₃O₄Cl through the formation of a monolayer by molecular WO₃. On the surface of BiOCl/Bi₃O₄Cl, the function of WO₃ is to offer increasing OH⁻, H₂O or organics towards WO₃/BiOCl/Bi₃O₄Cl by increasing the adsorption affinity of WO₃/BiOCl/Bi₃O₄Cl. Furthermore, the chemical durability of BiOCl/Bi₃O₄Cl was increased due to the covering of BiOCl/Bi₃O₄Cl with WO₃. Considering the above findings, the role of WO₃ in enhancing the photocatalytic efficiency of BiOCl/Bi₃O₄Cl has been explained in detail.