Bi2S3/TiO2 and CdS/TiO2 heterojunctions as an available configuration for photocatalytic degradation of organic pollutant

Bi2S3/TiO2 and CdS/TiO2 heterojunctions were prepared by direct mixture of both constituents and by precipitation of the sensitizer with commercial TiO2 at different concentrations. UV-Vis spectroscopy analysis showed that the junctions-based Bi2S3 and CdS are able to absorb a large part of visible light (respectively up to 800 and 600 nm). This fact was confirmed by photocatalytic experiment performed under visible light. A part of charge recombination that can take place when both semiconductors are excited was observed when photocatalytic experiment was performed under UV-Vis illumination. Orange II, 4-hydroxybenzoı̈que acid (4-HBZ) and benzamide (BZ) were used as pollutants. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena taking place in each case are discussed.