Hexagonal CdS Research Articles

Synthesis and physical characterization of novel Ag2S-CdS /Ag /GNP ternary nanocomposite

A new type of Ag2S-CdS/Ag/GNP nanocomposite material was successfully synthesized in the presented work. The structural and physical properties of compounds were studied separately and together. Ag2S-CdS/Ag/GNP nanocomposite materials were studied by Xray diffraction (XRD), Ultraviolet-Visible (UV-Vis), Fourier Transform Infrared (FTIR), Raman spectroscopy and Scanning Electron Microscopy (SEM). Based on the results, Ag nanowires (NWs) were successfully synthesized, and then it was determined that during the hybridization process, two phases of acanthite Ag2S and the cubic crystal system of Ag2O were formed. Then, Ag2S-CdS NWs were formed from mixed monoclinic Ag2S and hexagonal CdS. In the absorption spectrum of Ag NWs, the main absorbance peaks were observed at 357.3 nm and 380.2 nm. The energy gap (Eg) values of the Ag sample are 3.8 eV. The band gap value of Ag2S (2.5, 3.8, 4.6 eV) and Ag2S-CdS (2.5, 3.8, 4.8 eV) have a triple value due to the formation of a hybrid structure. The Raman spectrum of Ag2S-CdS belongs to longitudinal-optical (LO) phonon modes of zinc-blende phase CdS and for the 1, 2, and 3 times spin-coated samples on the surface of GNP/PVA have observed all characteristic Raman peaks, which belong to NWs at 485.13 cm-1, and 960.22 cm-1.

Wurtzite CdS ratio tunability on α-Fe2O3/CdS synergistic heterostructure for enhanced UV-induced photocatalytic decomposition of rhodamine 6G dye pollutant

Hematite α-Fe2O3 exhibits a slow catalytic reaction rate and low performance in aqueous pollutant decomposition. In this work, α-Fe2O3/CdS binary heterostructure composites were created by introducing different ratios of wurtzite CdS into α-Fe2O3 within 0–100 wt% via precipitation and impregnation methods. The photocatalytic performance of α-Fe2O3/CdS was enhanced for the decomposition of aqueous rhodamine 6G (R6G) dye under ultraviolet (UV) irradiation. SEM images reveal that higher CdS loading results in increased interfacial contact between rod-like CdS and spherical-shaped α-Fe2O3. XRD and FTIR results confirm the coexistence of rhombohedral α-Fe2O3 and hexagonal CdS phases, with peak strength proportional to the ratio of component loading, as the respective elements were verified through EDX analysis. The UV-Vis spectroscopic analysis exhibits an enhancement in optical absorption and band gap broadening as the CdS loading rises. α-Fe2O3/CdS with increased CdS loading exhibits faster and more efficient R6G degradation under UV exposure, as evidenced by greater rate constants and degradation efficiency, with optimal CdS loading of 90 wt% achieving a maximum efficiency of 79.14%. The present heterostructure could be employed in future wastewater remediation for effective removal of organic dye pollutants, further promoting clean water preservation for global environmental sustainability.

Advanced Synthesis and Characterization of CdO/CdS/ZnO Heterostructures for Solar Energy Applications.

This study introduces an innovative method for synthesizing Cadmium Oxide /Cadmium Sulfide/Zinc Oxide heterostructures (CdO/CdS/ZnO), emphasizing their potential application in solar energy. Utilizing a combination of electrochemical deposition and oxygen annealing, the research provides a thorough analysis of the heterostructures through scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy. The findings reveal a complex surface morphology and a composite structure with significant contributions from hexagonal CdS and cubic CdO phases. The study highlights the uniformity in the distribution of luminescent centers and the crystalline quality of the heterostructures, which is evident from the PL analysis. The redshift observed in the emission peak and the additional peaks in the excitation spectrum indicate intricate optical properties influenced by various factors, including quantum confinement and lattice strain. The research demonstrates these heterostructures' potential in enhancing solar cells' efficiency and applicability in optoelectronic devices. This comprehensive characterization and analysis pave the way for future optimization and application in efficient and sustainable solar energy solutions.

Anodized TiO2 Nanotubes Sensitized with Selenium Doped CdS Nanoparticles for Solar Water Splitting

In this research, TiO2 nanotubes (NTs) were produced by electrochemical anodization of a Ti substrate where different NH4F wt.% in the electrolyte was added. NTs with diameter of 65–90 nm and 3.3–4.9 µm length were obtained and sensitized with binary cadmium chalcogenides nanoparticles, CdS and CdSe, by successive ionic layer adsorption and reaction method (SILAR). Additionally, both anions S and Se were deposited onto Cd, labeled as CdSSe and CdSeS, to evaluate the effect of the deposition order of the anion from the precursor solution to form cadmium chalcogenides. The structural, optical, and electrochemical performance were analyzed through the SEM, XRD, XPS, UV-VIS, lineal voltammetry and chronoamperometry characterizations. The increase of NH4F wt.% from 1.5% to 4.5% produced a decrement of the diameter and length attributed to the fluoride ions concentration causing solubility of the NTs. XRD confirmed the TiO2 anatase and hexagonal CdS structures. From the EDS and XPS results, the presence of small amount of Se in the sensitized samples demonstrated the doping effect of Se instead of forming ternary semiconductor. With the sensitization of the TiO2 NTs with the nanoparticles, an improved hydrogen generation was observed (reaching 1.068 mL h−1 cm−2) in the sample with CdSSe. The improvement was associated to a synergetic effect in the light absorption and higher cadmium chalcogenide amount deposited when sulfur ions were deposited before selenium.

Exploring the dual phases of cadmium sulfide: synthesis, properties, and applications of hexagonal wurtzite and cubic zinc blende crystal structures

The distinctive properties of hexagonal and cubic CdS illuminate their electronic, optical, and structural features, with practical implications explored through their applications in various fields.

Heterojunctions of ZnS with Zn vacancies and hexagonal CdS pyramids for photocatalytic hydrogen production

Metal sulfides with suitable morphology typically possess efficient solar light utilization and suitable band structures for photocatalytic hydrogen production.

Role of CdTe Interface Structure on CdS/CdTe Photovoltaic Device Performance.

Glancing angle deposition (GLAD) of CdTe can produce a cubic, hexagonal, or mixed phase crystal structure depending upon the oblique deposition angles (Φ) and substrate temperature. GLAD CdTe films are prepared at different Φ at room temperature (RT) and a high temperature (HT) of 250 °C and used as interlayers between the n-type hexagonal CdS window layer and the p-type cubic CdTe absorber layer to investigate the role of interfacial tailoring at the CdS/CdTe heterojunction in photovoltaic (PV) device performance. The Φ = 80° RT GLAD CdTe interlayer and CdS both have the hexagonal structure, which reduces lattice mismatch at the CdS/CdTe interface and improves electronic quality at the heterojunction for device performance optimization. The device performance of HT CdS/CdTe solar cells with Φ = 80° RT with 50 to 350 nm thick GLAD CdTe interlayers is evaluated in which a 250 nm interlayer device shows the best device performance with a 0.53 V increase in open-circuit voltage and fill-factor product and a 0.73% increase in absolute efficiency compared to the HT baseline PV device without an interlayer.

Heterostructured CdS Buffer Layer for Sb2Se3 Thin Film Solar Cell

The antimony selenide thin film solar cells technology becomes promising due to its excellent anisotropic charge transport and brilliant light absorption capability. Especially, the device performance heavily relies on the vertically oriented Sb2Se3 grain to promote photoexcited carrier transport. However, crystalline orientation control has been a major issue in Sb2Se3 thin film solar cells. Herein, a new strategy has been developed to tailor the crystal growth of Sb2Se3 ribbons perpendicular to the substrate by using the structural heterostructured CdS buffer layer. The heterostructured CdS buffer layer is formed by a dual layer of CdS nanorods and nanoparticles. The hexagonal CdS nanorods passivated by a thin cubic CdS nanoparticle layer can promote [211] and [221] directional growth of Sb2Se3 ribbons using a close space sublimation approach. The improved buffer/absorber interface, reduced interface defects, and recombination loss contribute to the improved device efficiency of 7.16%. This new structural heterostructured CdS buffer layer can regulate Sb2Se3 nanoribbons crystal growth and pave the way to further improve the low‐dimensional chalcogenide thin film solar cell efficiency.

Glutathione-sensitized SnS2 nanoflake/CdS nanorod heterojunction for enhancing cathodic protection of 304 stainless steel with remarkable photoelectric conversion performance

An effective way to enhance photochemical performance can be achieved by optimizing the microstructure of composite semiconductor materials. Here, a two-step hydrothermal method was used to synthesize SnS2/CdS composite photoanodes for photocathode protection applications, and glutathione was introduced as a structure-directing agent to enhance the separation efficiency of photogenerated electron-hole pair of SnS2/CdS. In the presence of glutathione, SnS2 became a smaller and thinner nanoflake and hexagonal CdS extended into a rod shape, the combination of them resulted in larger light collection area and higher charge transfer rate. The electrochemical test results demonstrated that the open circuit potential of 304 SS coupled with SnS2/CdS/GSH photoanode was negatively shifted to about −0.5 V under light, which not only far exceeded the self-corrosion potential of 304 SS (-0.18 V), but also improved from −0.42 V of SnS2/CdS. Further, the photogenerated current density of SnS2/CdS/GSH was nearly three times that of SnS2/CdS, EIS and polarization curve results also indicated that glutathione enhances the PEC performance of SnS2/CdS. Obviously, the type-II heterojunction formed by glutathione-sensitized SnS2/CdS provides more electrons for 304 SS, which is beneficial to achieve better photocathodic protection.

Synthesis of Zn0.1Sn0.1Cd0.8Sx Solid Solutions for Photocatalytic Reduction of Cr(VI): Bandgap Structure and Sulfur Vacancy Regulation.

Ternary metal sulfides (TMSs) solid solutions have been regarded as ideal semiconductors in various photocatalytic reactions due to theiroutstanding redox reversibility, high electron conductivity, and great stability. In this work, a series of Zn0.1Sn0.1Cd0.8S x (ZSCS) solid solutions were synthesized by a simple hydrothermal methodand applied in the photocatalytic reduction of Cr(VI). The Cr(VI) reduction efficiency of ZSCS-5 quickly reached nearly 100% within 3 min under visible light irradiation. The controlling of sulfur content in ZSCS induced the transformation of cubic to hexagonal CdS, regulating the energy band structure and sulfur vacancy (SV) content, both of which further influenced the redox properties of ZSCS samples. The morenegativeconduction band position and more sulfur vacancies contributed to the enhanced photocatalytic reduction performance of ZSCS-5 toward Cr(VI). The active species 1O2, O2•－,and e－were all involved and 1O2played a pivotal rolein the photocatalytic reaction. This work provided an excellent photocatalyst for reduction of Cr(VI) and strongly confirmed the regulation of energy band structure and sulfur vacancies in photocatalysts through controlling the precursorcontent.

Constructing nano CdS-decorated porous biomass-derived carbon for multi-channel synergetic photocatalytic hydrogen evolution under solar lighting

Developing noble-metal-free photocatalysts for boosting photocatalytic hydrogen evolution reaction (HER) under solar lighting has long been desired. In this work, hierarchical heteroarchitectures comprised of zero-dimensional (0D) hexagonal CdS nanoparticles (NPs) with 60 nm in size decorating onto 3D porous biomass-derived carbon (PBC) honeycomb-like architectures are fabricated by a microwave-assisted aqueous chemical reaction, where PBC is derived from the agriculture discarded bagasse. The significantly boosted photocatalytic hydrogen generation of CdS/PBC composite is ascribed to the multi-channel synergetic effect on the heteroarchitectures with the closely interfacial connection, as a result of increasing the wide-spectrum solar absorption, promoting the photoinduced charges migration rate, and accelerating kinetically the mass-transfer efficiency by the photothermal effect. The H2-evolving efficiency over the optimal CdS/PBC-3 achieves 14.67 mmol∙g−1∙h−1 under simulated solar irradiation, which is 43.1 times higher than that of pure CdS counterpart. The maximum apparent quantum efficiency over CdS/PBC-3 is 22.68% at 420 nm. The step-scheme (S-scheme) electron transfer pathway for CdS/PBC is proposed based on the band energy alignments. This work develops a new way to fabricate non-precious biochar composites for efficient conversion of solar energy in photocatalysis.

Ternary compound heterojunction from isomerism h-CdS/c-CdSe exhibits boosting photoelectrochemical and hydrogen evolution reaction properties

A novel h-CdS/c-CdSe ternary compound heterojunction catalyst CdSS is constructed from isomerism hexagonal CdS and cubic CdSe. The isomerism hexagonal CdS and cubic CdSe is the key factor to obtain the CdSS heterojunction, as compared, ternary compound CdSSe can only be prepared from isomorphic hexagonal CdS and hexagonal CdSe. Under different S:Se ratio, the main XRD peaks of CdSS displayed continuous shift between related CdS and CdSe peaks that confirms the S and Se atoms embedding CdSe and CdS lattice respectively to form atomic level ternary compound heterojunction. The photoelectrochemical and electrocatalytic results show that the CdSS catalysts have boosting properties. Under an optimal S:Se ratio, the photocurrent density of the CdSS reach 8.23 μA/cm2, which was 4.5 times that of original CdS (1.83 μA/cm2), 4.9 times of CdSe (1.67 μA/cm2) and 5.1 times of CdSSe (1.60 μA/cm2). The hydrogen evolution reaction Tafel slope of CdSS also declined 60% compared with CdS and 64% compared with CdSe. The electrocatalytic impedance and fluorescence spectra fully show that CdSS has lower internal resistance and low electron-hole recombination efficiency due to the atomic level heterojunction. The work develops a new strategy to construct high efficiency atomic level ternary compound heterojunction between isomerism homologous element compounds.

Sulfur vacancy and CdS phase transition synergistically boosting one-dimensional CdS/Cu2S/SiO2 hollow tube for photocatalytic hydrogen evolution

Constructing an efficient photoelectron transfer route to improve carrier separation efficiency is crucial for photocatalytic hydrogen evolution. In this work, CdS/Cu2S/SiO2 heterostructure with one-dimensional hollow tube morphology was designed by the solvothermal method using CuO/SiO2 hollow tube as carrier. The hexagonal phase CdS and sulfur vacancies were adjusted simultaneously by the reduction strategy of NaBH4 aqueous solution. CdS/CuS/SiO2 with cubic phase CdS was synthesized in the absence of NaBH4 aqueous solution. CdS/Cu2S/SiO2 was characterized by SEM, TEM, XRD, XPS, SPV and so on. The results showed that hexagonal CdS and sulfur vacancies benefited the separation of photo-generated carriers. As a consequence, the CdS/Cu2S/SiO2-10 composite exhibited a high photocatalytic hydrogen production rate (1196.98 μmol/g/h), and its performance almost 7.18 times than that of CdS/CuS/SiO2. Moreover, CdS/Cu2S/SiO2-10 showed an excellent cyclic stability. This was attributed to the strong electron interaction of CdS/Cu2S/SiO2 heterostructure and the sulfur vacancy acted as an electron trap, enhancing the separation of photo-induced electrons and holes.

Facile synthesis of hierarchical CdS nanoflowers for efficient piezocatalytic hydrogen evolution.

Piezocatalytic hydrogen evolution has emerged as a promising field for the collection and utilization of mechanical energy, as well as for generating sustainable energy throughout the day. Hexagonal CdS, an established semiconductor photocatalyst, has been widely investigated for its ability to split water into H2. However, its piezocatalytic performance has received less attention, and the relationship between its structure and piezocatalytic activity remains unclear. In this study, we prepared 3D ultrathin CdS nanoflowers with high voltage electrical response and low impedance. In pure water, without the use of any cocatalyst, CdS exhibited a piezoelectric catalytic hydrogen production rate of 1.46 mmol h-1 g-1, which was three times higher than that of CdS nanospheres (0.46 mmol h-1 g-1). Furthermore, the value-added oxidation product H2O2 was produced during the process of piezoelectric catalysis. These findings provide new insights for the design of high-efficiency piezoelectric catalytic hydrogen production.

Synthesis and characterisation of Ga- and In-doped CdS by solventless thermolysis of single source precursors.

We report a facile and low temperature synthesis of Ga- and In-doped CdS nanoparticles from molecular precursors. Diethyldithiocarbamate complexes of Cd(II), Ga(III), and In(III), were synthesised and decomposed in tandem through solventless thermolysis, producing Ga- or In-doped CdS. The resultant MxCd1-xS1+0.5x (where M = Ga/In at x values of 0, 0.02, 0.04, 0.06, 0.08 and 0.1) particulate powder was analysed by powder X-ray diffraction, which showed that both Ga (through all doping levels) and In (at doping levels <8 mol%) were successfully incorporated into the hexagonal CdS lattice without any impurities. Raman spectroscopy also showed no significant change from CdS. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to investigate the morphology and elemental dispersion through the doped CdS materials, showing homogenous incorporation of dopant. The optical and luminescent properties of the doped MxCd1-xS1+0.5x materials were examined by UV-Vis absorption and photoluminescence spectroscopies respectively. All materials were found to exhibit excitonic emission, corresponding to band gap energies between 2.7 and 2.9 eV and surface defect induced emission which is more prominent for Ga than for In doping. Additionally, moderate doping slows down charge carrier recombination by increasing the lifetimes of excitonic and surface state emissions, but particularly for the latter process.

THE INFLUENCE OF POST-ANNEALING CdS THIN FILMS GROWN ON ZnO SEED LAYER FOR CdTe SOLAR CELLS

In this study, the effect of post-annealing temperature in CdS thin films grown on ZnO seed layer was investigated. CdS thin film and ZnO seed layer were coated by chemical bath deposition method and solution dropping technique, respectively. The structure of the post-annealed samples at 350°C and 400°C consisted of cubic CdS and CdSO3 oxide phases. As a result of recrystallization at 450°C, both hexagonal CdS and cubic CdO phases were formed. While the absorption edge was observed at around 500 nm in all samples, the best transmittance was observed in the sample annealed at 400°C. PL spectra proved the existence of defect types such as deep emission, sulfur vacancy for all samples. Ellipsometer measurements showed that the highest refractive index was in the sample annealed at 400°C. Among the samples, it was concluded that the most suitable window structure for CdTe solar cell applications is CdS thin film post-annealed at 400°C.

Cefotaxime degradation by the coupled binary CdS-PbS: characterization and the photocatalytic process kinetics.

Increased water pollution due to discharging industrial/urban/hospital wastewater has been adopted to introduce/develop novel removal techniques/catalyst/adsorbent. The hexagonal (wurtzite) CdS and the cubic PbS nanoparticles (NPs) were synthesized, coupled, and supported onto clinoptilolite NPs (CNP). Then, the sample was characterized by X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FTIR), and a scanning electron microscope equipped with an energy dispersive X-ray analyzer (SEM-EDX) techniques. The average crystallite size for CdS NPs, PbS NPs, CNP, and CdS-PbS/CNP samples was obtained at about 24, 36, 27, and 14nm using the Scherrer formula value of nanometer, by the W-H formula, 31, 17, 39, and 51, respectively. Only a detectable slope can be observed from the DRS spectra for CdS NPs at 591nm corresponding to an Eg value of 2.1eV. PbS NPs have a broad abruption peak that begins from the visible region and extends to the IR region of the light. A boosted photocatalytic activity of the supported binary catalysts towards cefotaxime (CT) was reached. An apparent first kinetic model was reached with a k-value of 0.021min-1 corresponding to the t1/2 value of 33min. A decreased COD trend for the photodegraded CT solutions was reached, and the chemical oxygen demand (COD) results in the Hinshelwood model showed a k-value of 0.016min-1, corresponding to a t1/2 value of 43min.

MOF-templated and phase-controlled synthesis of CdS hierarchical nanostructures for visible-light-driven photocatalytic applications

Developing delicate methods to synthesize well-controlled nanostructures is diffusely recognized as a potent tool to enhance photocatalysts’ performances in various photoreactions. Herein, phase-controlled CdS hierarchical nanostructures were synthesized using a MOF-templated strategy, where Co-MOF nanospheres were used as the starting material, followed by two steps of sulfidation and cation exchange. By rational collocations of the solvent and Cd source in the cation exchange process, cubic CdS hollow hierarchical nanospheres and hexagonal CdS hierarchical nanostructures can be obtained, respectively. Further tests revealed that during the photo-reduction reaction of CO2, the former exhibited high performance in producing H2. At the same time, the latter showed a superior activity and selectivity for CO generation, which embodies the potential of MOF-templated synthesis and selective applications of CdS hierarchical nanostructures with disparate phases.

The spontaneous polarization in CdS to enhance the piezo-PEC performance via phase transition stress engineering

The built-in electric field caused by piezoelectric polarization has emerged as one of the most effective strategies for photoelectrochemical (PEC) water splitting, but is challenged by low piezoelectric polarization efficiency. Herein, we firstly introduce residual stress into CdS through phase transition stress engineering for improving the spontaneous polarization of CdS with a view to revealing the mechanism of the piezoelectric PEC (piezo-PEC) performance of CdS is advanced by the spontaneous polarization. The spontaneous polarization of CdS caused via phase transition residual stress generated built-in electric field to advance carriers separation. Moreover, the spontaneous polarization of CdS is motived a greater potential under external force than hexagonal wurtzite CdS due to the existence of phase transition residual stress, which effectively improves the piezo-PEC performance of CdS. The photocurrent density of miscibility of cubic sphalerite and hexagonal wurtzite CdS (M−CdS) is 0.61 mA/cm2 at 1.23 V vs RHE, which is almost 1.79 times of hexagonal wurtzite (H-CdS). In addition, the value of M−CdS photocurrent density is reached 2.12 mA/cm2 at 1.23 V vs RHE after ultrasound, which is almost 6.2 times of H-CdS. Our detail work proves that this strategy not only stimulates the piezo-PEC performance of CdS, but also can be extended to other hexagonal wurtzite semiconductor phase transition piezoelectric fields.

Thermal evaporation–deposited hexagonal CdS buffer layer with improved quality, enlarged band gap, and reduced band gap offset to boost performance of Sb2(S,Se)3 solar cells

Chemical bath–deposited cadmium sulfide (CBD-CdS) is the most widely used buffer layer material for antimony selenosulfide (Sb2(S,Se)3) photovoltaic devices, but its medium band gap, large band gap offset with transparent conducting oxides, and surface defects must be addressed to improve its applicability. Hexagonal CdS films (60 nm thick) prepared using the thermal evaporation method were used as the buffer layers of Sb2(S,Se)3 photovoltaic devices. Compared with CBD-CdS (60 nm thick), thermal evaporation–deposited CdS (TED-CdS) films have a larger band gap and fewer surface defects. The Sb2(S,Se)3 film deposited on TED-CdS is more compact, and its 1D ribbons are stacked more vertically to the substrate. The band gap offset between CdS and fluorine-doped tin oxide glass decreases from 0.76 eV (CBD-CdS) to 0.60 eV (TED-CdS). Therefore, suppressed electron trap density and charge recombination, as well as improved light harvesting, are achieved. By replacing CBD-CdS with TED-CdS, the best device efficiency increases from 6.14 % to 7.16 %, with the open circuit voltage, short-circuit current density, and fill factor increasing from 0.660 V, 15.96 mA/cm2, and 58.37 % to 0.664 V, 17.39 mA/cm2, and 62.85 %, respectively. The device stability and reproducibility are also improved.