Decoration of silver on ZnS for enhancement of sunlight-driven photodegradation of reactive red azo dye and norfloxacin antibiotic

Abstract

High charge carrier recombination rate is the major difficulty affecting low photocatalytic performance of the UV-responsive ZnS photocatalyst. To overcome the problem, well dispersion of noble metals on the ZnS surface can be regarded as one of the useful strategies to enhance the photocatalytic efficiency. This is due to a synergy of creation of heterojunction structure and surface plasmon resonance effect. In the present work, the surface of the hydrothermally grown ZnS photocatalyst was modified with 10 wt %silver. The hexagonal Ag/ZnS photocatalyst provided high sunlight-active photocatalytic performance toward removal of anionic azo dye and norfloxacin antibiotic with the efficiency of about 99 % and 70 %, within 120 min, respectively. The improvement of the resultant photoactivity is attributed to increasing of charge separation capacity at the interface. Well distribution of silver on ZnS surface results in the generation of the Schottky barrier at the Ag/ZnS interface. This will end up with the increment of quantum efficiency and enlargement of the photocatalytic activity. Additionally, after modification of ZnS surface by addition of silver, a red shift in the light absorption toward visible region was found. This is assigned to the effect of surface plasmon resonance (SPR) of Ag on ZnS surface. The synthesized Ag/ZnS reveals high structural stability with enhanced performance even after the fifth cycle. This work demonstrates a new avenue for creation of a silver-modified ZnS for complete degradation of toxic organic contaminants including dyes and antibiotics by use of the abundant solar energy.