Template-Free Synthesis of Nanostructured Cd_xZn_1–xS with Tunable Band Structure for H₂ Production and Organic Dye Degradation Using Solar Light

Abstract

We have demonstrated a template-free large-scale synthesis of nanostructured Cd(x)Zn(1-x)S by a simple and a low-temperature solid-state method. Cadmium oxide, zinc oxide, and thiourea in various concentration ratios are homogenized at moderate temperature to obtain nanostructured Cd(x)Zn(1-x)S. We have also demonstrated that phase purity of the sample can be controlled with a simple adjustment of the amount of Zn content and nanocrystalline Cd(x)Zn(1-x)S(x = 0.5 and 0.9) of the hexagonal phase with 6-8 nm sized and 4-5 nm sized Cd(0.1)Zn(0.9)S of cubic phase can be easily obtained using this simple approach. UV-vis and PL spectrum indicate that the optical properties of as synthesized nanostructures can also be modulated by tuning their compositions. Considering the band gap of the nanostructured Cd(x)Zn(1-x)S well within the visible region, the photocatalytic activity for H2 generation using H2S and methylene blue dye degradation is performed under visible-light irradiation. The maximum H2 evolution of 8320 μmol h(-1)g(-1) is obtained using nanostructured Cd(0.1)Zn(0.9)S, which is four times higher than that of bulk CdS (2020 μmol h(-1) g(-1)) and the reported nanostructured CdS (5890 μmol h(-1)g(-1)). As synthesized Cd(0.9)Zn(0.1)S shows 2-fold enhancement in degradation of methylene blue as compared to the bulk CdS. It is noteworthy that the synthesis method adapted provides an easy, inexpensive, and pollution-free way to synthesize very tiny nanoparticles of Cd(x)Zn(1-x)S with a tunnable band structure on a large scale, which is quite difficult to obtain by other methods. More significantly, environmental benign enhanced H2 production from hazardous H2S using Cd(x)Zn(1-x)S is demonstrated for the first time.

Ternary SnS2–xSex Alloys Nanosheets and Nanosheet Assemblies with Tunable Chemical Compositions and Band Gaps for Photodetector Applications

“…As expected, the main peak positions of SnS 2− x Se x alloys gradually shift toward lower angles with increasing Se content (Fig. 1b), indicating the increase of lattice constants and formation of solid solution rather than the mechanical mixture of two pure phases2728. The continuous peak shifting (lattice expanding) of ternary alloys might rule out the phase separation or separated nucleation of SnS 2 or SnSe 2 nanomaterials2930.…”

The deposition of thin films of cadmium zinc sulfide Cd1−x Zn x S at 250 °C from spin-coated xanthato complexes: a potential route to window layers for photovoltaic cells

“…3. Earlier reports have reviewed a nanostructured film with Cd 0.9 Zn 0.1 S hexagonal and Cd 0.5 Zn 0.5 S polytypic or cubic form existing in the hexagonal phase, while Cd 0.1 Zn 0.9 S shows the cubic phase [1,2,43].…”

Preparation and properties of CuO/Zn Cd1−S photocatalysts

“…As the Zn content in Zn x Cd 1 À x S increases, its conduction and valence bands shift to more negative and positive positions, respectively; this increases the bang-gap width and effectively decreases recombination of photogenerated electron-hole pairs [4]. Garaje et al [14] have shown a decreasing of photocatalytic degradation efficiency of organic dye from 98% to 78% although the band gap of Cd x Zn 1 À x S only has a small increase from 2.48 to 2.85 eV when the value of x in Cd x Zn 1 À x S increases from 0.1 to 0.5. Macías-Sánchez et al [15] have reported that the band gap increases from 2.15 to 2.23 eV, which causes the H 2 evolution amounts increasing from 520 μmol to 962 μmol, when the value of x in Cd x Zn 1 À x S/S15 increases from 0.1 to 0.2.…”

“…The photocatalytic activities of Zn x Cd 1 À x S are higher than that of CdS [14,15]. However, the reported photocatalytic activities are still low, and it is important to improve their photocatalytic properties by designing semiconductor composites to further suppress electron-hole pair recombination.…”