A Facile Template‐Free Approach for the Large‐Scale Solid‐Phase Synthesis of CdS Nanostructures and Their Excellent Photocatalytic Performance

Abstract

The simple, template-free, low-temperature, large-scale synthesis of nanostructured CdS with the hexagonal wurtzite phase from bulk cadmium oxide under solid-phase conditions is demonstrated for the first time. The novel approach involves the homogenization of cadmium oxide (CdO) and thiourea in various stoichiometric ratios at moderate temperature. Among the different molar ratios of CdO and thiourea studied, the CdO/NH(2) CSNH(2) molar ratio of 1:2 is found to be the best to obtain highly pure CdS. The obtained CdS nanostructures exhibit excellent cubic morphology and high specific surface area with a particle size in the range of 5-7 nm. The bandgap of the nanostructured CdS is in the range of 2.42 to 2.46 eV due to its nanocrystalline nature. In photoluminescence studies, emission is observed at 520.34 and 536.42 nm, which is characteristic of the greenish-yellow region of the visible spectrum. Considering the bandgap of the CdS is within the visible region, the photocatalytic activity for H(2) generation and organic dye degradation are performed under visible-light irradiation. The maximum H(2) evolution of 2945 μmol h(-1) is obtained using nanostructured CdS prepared in the 1:2 ratio, which is three times higher than that of bulk CdS (1010 μmol h(-1) ). CdS synthesized using the 1:2 molar ratio shows maximum methylene blue degradation (87.5%) over a period of 60 min, which is approximately four times higher than that of bulk CdS (22%). This amazing performance of the material is due to its nanocrystalline nature and the high surface area of the CdS. The proposed simple methodology is believed to be a significant breakthrough in the field of nanotechnology, and the method can be further generalized as a rational preparation scheme for the large-scale synthesis of various other nanostructured metal sulfides.

CdS aerogels as efficient photocatalysts for degradation of organic dyes under visible light irradiation

“…The synthesis of CdS nanostructures with different morphologies (e.g. cubelike nanostructures 8 , mesoporous nanospheres 9 , hollow spheres, 10, 11 dendritic nanoarchitectures 12 , branched nanowires 13 ) is the most general approach to increase the surface area of the catalysts. With respect to recombination of photogenerated charge carriers, this can be suppressed by enhancing the charge separation efficiency via formation of nanocomposites with semiconductors (e.g.…”

Photocatalytic activity of CdS and Ag2S quantum dots deposited on poly(amidoamine) functionalized carbon nanotubes

“…Among the semiconductor photocatalysts, TiO 2 is the most explored one, while the wide band gap energy (3.2 eV) has hindered its sufficient utilization of photo-energy. In view of this CdS and Ag 2 S with band gap energy of 2.42 and 1.0 eV, respectively are considered to be excellent photo-responsive catalysts [13–18]. However, CdS and Ag 2 S quantum dots (QDs) are known to form aggregation during synthesis, which results in the reduction of their photocatalytic efficiency.…”

Synergistic synthesis of quasi-monocrystal CdS nanoboxes with high-energy facets

“…Cadmium sulfide (CdS), an important semiconductor with a band gap of 2.4 eV at room temperature, has attracted considerable interest in photocatalysis 21,22 , light-emitting diodes 23 , solar cells 24 , and other optoelectronic applications 25 . Many synthesis methods, such as electrochemical deposition 26 , solvothermal (hydrothermal) synthesis 22,27 , chemical vapor deposition (CVD) 28 and microwave irradiation 29 , have been developed to prepare CdS nanostructures, among which are irregular-shaped nanoparticles 21,30 , nanotubes 31 , nanowires 22 , nanorods 32 , nanobelts 33 , and so on.…”

“…Many synthesis methods, such as electrochemical deposition 26 , solvothermal (hydrothermal) synthesis 22,27 , chemical vapor deposition (CVD) 28 and microwave irradiation 29 , have been developed to prepare CdS nanostructures, among which are irregular-shaped nanoparticles 21,30 , nanotubes 31 , nanowires 22 , nanorods 32 , nanobelts 33 , and so on. Nevertheless, the reported CdS catalysts usually expose low-energy facets due to surface energy minimization during the crystal-growth processes [34][35][36] , which limits their catalytic performance 37,38 .…”