Synthesis of ZnO/CdS hierarchical heterostructure with enhanced photocatalytic efficiency under nature sunlight

Abstract

Hierarchical ZnO composed of ultrathin nanosheets as secondary structures were fabricated through a hydrothermal method. Afterwards, hexagonal wurtzite CdS with diameter between 50-100 nm were incorporated on the wurtzite ZnO sheets with the assistance of ultrasonic irradiation. The hybrid ZnO/ CdS samples were intensively investigated by SEM, TEM, HRTEM, XRD, XPS, PL and the UV-Vis absorption spectrum. The photocatalytic trials confirmed that the ZnO/CdS hierarchical heterostructures exhibit improved degradation efficiency compared to pure ZnO sample under natural sunlight. CdS nanoparticles are believed to serve as photo-sensitizers to extend the absorption spectrum to the visible region and the loading amount was also found to play a crucial role in influencing the degradation efficiency. Moreover, the photodegradation kinetics of RhB via using CdS/ZnO as photocatalysts were also systematically discussed. Finally, a mechanism based on this band-gap alignment was proposed to elucidate the efficiency enhancement of the hybrid photocatalysts.

Role of RGO support and irradiation source on the photocatalytic activity of CdS–ZnO semiconductor nanostructures

“…The enhanced activity under natural sun light could be attributed to the combined activity of both CdS and ZnO, wherein CdS absorbs in the visible region and ZnO absorbs in the UV region, and charge carriers are generated in both of these semiconductors. In this case, in addition to the electron transfer from the CB of CdS to the CB of ZnO, simultaneous hole transfers also occur from the VB of ZnO to VB of CdS, as the VB of CdS is more cathodic than the VB of ZnO [72]. Thus the recombination of photogenerated charges is suppressed more effectively under natural sunlight illumination, where both the semiconductor materials are active and more electron–hole pairs are generated, and their effective separation and rapid transport to the reaction site are responsible for the enhanced activity of the photocatalysts.…”

Study of mesoporous CdS-quantum-dot-sensitized TiO2 films by using X-ray photoelectron spectroscopy and AFM

“…The other peaks are attributed to oxidized forms of carbons, which are usually detected (286.2 eV (C–O); 287.8 eV (C=O, O–C–O) and 288.6 eV (COO) [18]. The Cd 3d 5/2 and Cd 3d 3/2 were found at 411.3 and 404.6 eV respectively for QDs−CdS/TiO 2 and were attributed to Cd 2+ in CdS [19]. The difference between the binding energies of Cd 3d 5/2 and Cd 3d 3/2 is 6.7 eV, which corresponds to the presence of the oxidation state +2 of Cd 3d at the surface [20].…”

Solvothermal synthesis of CdS QDs/MWCNTs nanocomposites with high efficient photocatalytic activity under visible light irradiation

“…However, the low separation efficiency of electron-hole pairs is one critical issue that limits the application of pure CdS [10]. To enhance the photocatalytic activity of CdS, many researchers have been focused on the composites combining CdS with other components, including noble metals [11,12], graphene [13,14], graphene oxide [15,16], TiO 2 [17,18], ZnO [19,20], CdSe [21], ZnS [22,23], or with carbon materials [24,25] and so on. Multi-walled carbon nanotubes (MWCNTs) are one-dimensional carbon nanomaterials which have attracted tremendous attention owing to their excellent properties, such as extraordinary structure, superior conductivity and good chemical stability [26][27][28].…”