Quantum-dot sensitized hierarchical NiO p-n heterojunction for effective photocatalytic performance.

A facile and low-cost pseudo successive ionic layer adsorption and reaction technique was used to deposit cadmium sulfide quantum dots (CdS QDs) on hierarchical nanoflower NiO to form an effective and intimate NiO/CdS p-n heterojunction system. The synthesized hierarchical p-n heterojunctions demonstrated effective photocatalytic activity due to the enhanced separation and transport of photogenerated charge carriers compared to standalone NiO. The dye degradation efficiency of optimized CdS QDs that form p-n heterojunctions was examined by rhodamine B and methylene blue dyes under UV-vis irradiation. The improved photocatalytic performance can be accredited to a large morphological surface, and the successful deposition of CdS QDs to form an active p-n junction for efficient charge separation and migration. The morphological, structural, optical, charge transfer and photocatalytic characteristics of synthesized hierarchical p-n junction photocatalyst were studied by scanning electron microscopy, UV-visible absorbance, X-ray diffraction, photoluminescence spectroscopy, electrochemical spectroscopy, and Fourier transform infrared spectra. Additionally, scavenging experiments were performed to find out the energetic species taking part in dye-degradation, and a rational reaction mechanism has been proposed.