Preparation of hybrid photoelectrode based on defect-poor Zn-CuInSe₂ QDs sensitized nanoporous ZnO nanosheets with an application in azo dye removal

The glutathione (GSH) and mercaptopropionic acid (MPA) modified internal defect-rich, surface defects-poor near infrared (NIR) Zn–CuInSe₂ (ZCISe) QDs were synthesized. Nanoporous ZnO nanosheets (NS) were firstly loaded with those ZCISe QDs to improve photoelectrochemical response in the NIR light region. Then loading Mn doping CdS thin film onto the ZCISe/ZnO NS was further used to reduce the interfacial recombination between different components of hybrid photoelectrode, in addition to enhance the light absorption and resist the photo-oxidation decomposition of the photocatalysts. Successively introducing ZCISe and Mn–CdS onto ZnO NS can increase the photocurrent intensities from 1 mA/cm² for naked ZnO NS, 2.2 mA/cm² for ZCISe/ZnO NS, to 9 mA/cm² for Mn–CdS/ZCISe/ZnO NS. Here, excellent performance of ZCISe based ZnO NS photoelectrode is mainly attributed to an intrinsic defect state-related donor–acceptor pair (DAP) in ZCISe QDs with long-lived photogenerated carriers. Photocatalytic properties of Mn–CdS/ZCISe/ZnO NS were evaluated by removing azo dyes with an efficiency of 83%, an enhancement of 97% compared to that of ZnO NS.