Photodegradation of orange G by the hetero-junction x%Bi2S3/TiO2 under solar light

The preparation and characterization of the hetero-junctions x%Bi2S3/TiO2 (x = 1, 5, 10 and 15%) and their photocatalytic performances for the degradation of orange G (OG) under visible light irradiation are reported. The hetero-junctions are synthesized by precipitation method from bismuth nitrate on TiO2. The forbidden bands of Bi2S3 and TiO2 are found to be 1.54 and 3.43 eV respectively. Bi2S3 acts as sensitizer and exhibits n-type conductivity evidenced from the anodic photocurrent and capacitance measurements. The degradation of OG is confirmed by spectrophotometry and chemical oxygen demand (COD). The photocatalytic efficiency of the hetero-junction is dependent on the proportion of Bi2S3. Under visible light, a fast degradation is obtained on 10% Bi2S3/TiO2 and the OG degradation (10 mg L−1) follows a first order kinetic with a rate constant of 0.32 h−1. The performance of the prepared hetero-junction is better than that of the direct mixture of compounds due to intimate contact Bi2S3/TiO2. Under solar light, the photoactivity is strongly enhanced with a rate constant of 3.42 h−1.