Towards visible light driven photoelectrocatalysis for water treatment: Application of a FTO/BiVO/AgS heterojunction anode for the removal of emerging pharmaceutical pollutants.

Pharmaceuticals have been classified as emerging water pollutants which are recalcitrant in nature. In the quest to find a suitable technique in removing them from contaminated water, photoelectrocatalytic oxidation method has attracted much attention in recent years. This report examined the feasibility of degrading ciprofloxacin and sulfamethoxazole through photoelectrocatalytic oxidation using FTO-BiVO/AgS with p-n heterojunction as anode. BiVO/AgS was prepared through electrodeposition and successive ionic layer adsorption/reaction on FTO glass. Structural and morphological studies using XRD, SEM, EDS and diffusive reflectance UV-Vis confirmed the successful construction of p-n heterojunction of BiVO/AgS. Electrochemical techniques were used to investigate enhanced charge separation in the binary electrode. The FTO-BiVO/AgS electrode exhibited the highest photocurrent response (1.194 mA/cm) and longest electron lifetime (0.40 ms) than both pristine BiVO and AgS electrodes which confirmed the reduction in recombination of charge carriers in the electrode. Upon application of the prepared FTO-BiVO/AgS in photoelectrocatalytic removal of ciprofloxacin and sulfamethoxazole, percentage removal of 80% and 86% were achieved respectively with a low bias potential of 1.2 V (vs Ag/AgCl) within 120 min. The electrode possesses good stability and reusability. The results obtained revealed BiVO/AgS as a suitable photoanode for removing recalcitrant pharmaceutical molecules in water.