An environmentally friendly Z-scheme WO3/CDots/CdS heterostructure with remarkable photocatalytic activity and anti-photocorrosion performance

As a representative artificial photosynthetic system, direct Z-scheme WO3/CdS is a promising photocatalyst system for water purification. However, this system is still limited due to low electron transfer efficiency and serious photocorrosion. Here, we designed and precisely fabricated a novel all-solid-state Z-scheme WO3/CDots/CdS system. The CDots, as a nonmetallic electron mediator, could promote interfacial charge carrier separation and eliminate photocorrosion with enhanced photocatalytic activity. The phase, morphologies, microstructures, and optical and electrical properties of as-obtained Z-scheme WO3/CDots/CdS heterojunctions were investigated in detail. The photocatalytic performance of as-prepared catalysts was evaluated by the decomposition of 4-chlorophenol (4-CP), rhodamine B (RhB), and tetracycline hydrochloride (TCH) and the reduction of aqueous Cr(VI) in visible light. The optimized Z-scheme WO3/CDots/CdS-2 photocatalyst exhibited the highest photocatalytic activity for degrading and mineralizing 4-CP (similar to 70.0% and 48.3% in 7 h, respectively), both of which exceeded the rates observed in WO3/CdS samples under the same conditions by 2 times. In addition, the WO3/CDots/CdS-2 showed excellent stability and reusability with negligible change at similar to 2.2% difference for 4-CP degradation in eight cycles. The release percentage of SO42- (transformed from S2-) and Cd2+ was only similar to 0.77% and 0.79%, respectively, when compared with the initial concentration, which was far less than for the WO3/CdS system (similar to 5.64% and 5.70%). The results indicated that a thorough and complete Z-scheme charge carrier transfer route was achieved. Toxicity assessment authenticated good biocompatibility and low cytotoxicity of WO3/CDots/CdS. This study showed that the Z-scheme WO3/CDots/CdS was a promising photocatalyst for water purification. (C) 2017 Elsevier Inc. All rights reserved.