Preparation of CdS/BiOCl/Bi2O3 double composite system for visible light active photocatalytic applications

An efficient visible-light-harvesting (lambda >= 420 nm) three component system heterojunction photocatalyst, CdS/ BiOCl/Bi2O3 was prepared by anchoring of CdS nanoparticles on the surface of BiOCl/Bi2O3 composite. The effect of CdS nanoparticles on the surface of BiOCl/Bi2O3 composite photocatalyst had been justified in enhancing photocatalytic activity towards the degradation of organic pollutants in gas as well as aqueous phase. With the loading of CdS on to the BiOCl/Bi2O3 heterojunction composite photocatalyst, the photocatalytic activity of the CdS/BiOCl/Bi2O3 composite structure has been appreciably improved for the decomposition of 2-propanol (IPA) in gas phase and salicylic acid (SA) in aqueous phase under visible light irradiation (lambda >= 420 nm). The amount of loading of CdS nanoparticles was optimized to 2 mol% CdS/BiOCl/Bi2O3. Compare to bare BiOCl/Bi2O3 photocatalyst, CdS/BiOCl/Bi2O3 heterojunction demonstrated 2 times decomposition of IPA in gas phase and 1.8 times of SA in aqueous phase after 120 min. of visible light irradiation. At the same time, with this composition the evolution of CO2 from degradation of IPA was 1.9 times higher than that of BiOCl/Bi2O3 composite. The enhanced photocatalytic efficiency is deduced from the electron (e(-)) and hole (h(+)) transfer among the component semiconductor nanoparticles Bi2O3, BiOCl and CdS due to their relative energy band positions. Several experimental evidences were also provided to confirm the electron-hole transfer among the semiconductors and a mechanistic way has been proposed.