Dispersed CdS Research Articles

A cation exchange strategy to construct highly dispersed copper-doped CdS nanoparticles for photocatalytic hydrogen production

Developing facile methods to modulate the structure and performance of photocatalysts plays a pivotal role in the potential large-scale application of photocatalytic hydrogen production. Herein, a series of uniformly sized and highly dispersed copper-doped cadmium sulfide (CdS) nanoparticles (NPs) were successfully synthesized through a facile cation exchange strategy. The resulting Cu-doped CdS samples exhibited a remarkable photocatalytic hydrogen production rate of 2459.3 μ mol·h−1g−1, nearly 11 times that of pure CdS. The introduction of Cu+ ions effectively reduced the band gap, leading to enhanced light absorption, as well as improved charge carrier separation and transfer efficiency. Meanwhile, the theoretical investigation further confirmed that Cu+ doping substantially decreased the free energy of hydrogen adsorption and provided more suitable active sites, thereby promoting the photocatalytic hydrogen production activity on CdS NPs. This work provides compelling evidence for the exploration of novel transition metal-doped photocatalysts for hydrogen production using the cation exchange method.

Natural Wollastonite-Derived Two-Dimensional Nanosheet Ni3Si2O5(OH)4 as a Novel Carrier of CdS for Efficient Photocatalytic H2 Generation

Ni3Si2O5(OH)4 rods (NS) were synthesized via a hydrothermal method, employing natural wollastonite as a template. The hierarchical Ni3Si2O5(OH)4 rods exhibited vertically oriented nanosheets, resulting in a substantial increase in the specific surface area (from 2.24 m2/g to 178.4 m2/g). Subsequently, a CdS/Ni3Si2O5(OH)4 composite photocatalyst (CdS/NS) was prepared using a chemical deposition method. CdS was uniformly loaded onto the surface of the Ni3Si2O5(OH)4 nanosheets, successfully forming a heterojunction with Ni3Si2O5(OH)4. The CdS/NS photocatalyst in the presence of lactic acid as a sacrificial agent demonstrated an impressive H2 production rate of 4.05 mmol h−1 g−1, around 40 times higher than pure CdS. The photocorrosion of CdS was effectively solved after loading. After four cycles, the performance of CdS/NS remained stable, showing the potential for sustainable applications. After photoexcitation, electrons moved from Ni3Si2O5(OH)4 to the valence band of CdS, where they interacted with the holes via an enhanced interface contact. Simultaneously, electrons in CdS transitioned to its conduction band, facilitating hydrogenation. The enhanced performance was attributed to the improved CdS dispersion by Ni3Si2O5(OH)4 loading and efficient photogenerated carrier separation through the heterojunction formation. This work provides new perspectives for broadening the applications of mineral materials and developing heterojunction photocatalysts with good dispersibility and recyclability.

Ultrafast electron transfer from CdS quantum dots to atomically-dispersed Pt for enhanced H2 evolution and value-added chemical synthesis

Photocatalytic hydrogen production is enchanting in solar energy utilization. And mechanism elucidation in interfacial electron transfer rate is a prerequisite for performance improvement. Herein, atomically dispersed Pt-modified CdS quantum dots (Pt-CdS QDs), prepared by a facile one-step in-situ deposited method, are used as a prototype. Benefiting from the maximized utilization of Pt cocatalyst as well as the strong electronic metal-support interaction, ultrafast electron transfer from CdS to Pt (∼1.7 ps) is achieved, as revealed by femtosecond transient absorption spectra. The optimal sample simultaneously realizes photocatalytic hydrogen evolution coupled with selective oxidation of 2-thiophene methanol (TM) into 2-thiophenecarboxaldehyde (TD). Specifically, it exhibits an enhanced H2-evolution rate, which is 70-fold higher than pristine CdS QDs. Moreover, a TM conversion rate of 95.3 % with a TD selectivity of 87.2 % is reached after 4 h. This work will provide some guidance for the design of photocatalytic systems with efficient interfacial electron transfer.

CdS supported on ZIF-67-derived Co-N-C as efficient nano polyhedron photocatalysts for visible light induced hydrogen production

Hydrogen energy is vital important for solving pollution of environment and energy shortage. Hydrogen production via solar energy and semiconductor photo-splitting water is one of the most environmentally friendly strategies at present. In this work, Co-N-C, a non-noble metal-based ZIF-67 derivative, was employed as a co-catalyst to achieve an in situ growth of spherical CdS via simple one-step hydrothermal. Due to the large specific surface area of Co-N-C, the agglomeration of CdS is avoided and the photocorrosion phenomenon is weakened. Under irradiation of visible light, the hydrogen generation activity of Co-N-C/CdS was achieved 905 μmol g−1 h−1. It is 6 times that of pure CdS with excellent stability. At the contact interface of the Co-N-C and CdS, the transfer and the separation of photoinduced carriers had been enhanced by a great many of channels. DFT calculation further showed that Co nanoclusters, as the active sites of hydrogen production, significantly enhanced photocatalytic hydrogen evolution activity. Therefore, Co-N-C not only acts as electron acceptor, but also serves as support of highly dispersed CdS to promote the stability of system during photocatalytic hydrogen generation. This work demonstrates the advantages of CdS binding MOF derivatives to construct composite photocatalysts with enhanced dispersibility and hydrogen production activity.

Composite CdS/TiO2 Powders for the Selective Reduction of 4-Nitrobenzaldehyde by Visible Light: Relation between Preparation, Morphology and Photocatalytic Activity

A series of composite CdS/TiO2 powders was obtained by nucleation of TiO2 on CdS nanoseeds. This combination presents the appropriate band edge position for photocatalytic redox reactions: visible light irradiation of CdS allows the injection of electrons into dark TiO2, increasing the lifetimes of separated charges. The electrons have been used for the quantitative photoreduction of 4-nitrobenzaldehyde to 4-aminobenzaldehyde, whose formation was pointed out by 1H NMR and ESI-MS positive ion mode. Concomitant sacrificial oxidation of 2-propanol, which was also the proton source, occurred. The use of characterization techniques (XRD, N2 adsorption-desorption) evidenced the principal factors driving the photocatalytic reaction: the nanometric size of anatase crystalline domains, the presence of dispersed CdS to form an extended active junction CdS/anatase, and the presence of mesopores as nanoreactors. The result is an efficient photocatalytic system that uses visible light. In addition, the presence of TiO2 in combination with CdS improves the stability of the photoactive material, enabling its recyclability.

Highly dispersed CdS on C3N4 for selective cleavage of Cβ-O-4 bonds in lignin model compound under blue light

Photocatalytic cleavage of lignin Cβ-O-4 bonds is a very effective method to promote the high-value utilization of lignin because lignin can provide a large number of aromatics. However, the higher carrier recombination rate severely inhibits the efficiency of photocatalytic cleavage of Cβ-O-4 bonds in lignin model compound. Here, heterojunction photocatalysts CdS-C3N4 were successfully synthesized through the photodeposition of different masses of CdS on the surface of C3N4. The obtained photocatalyst CdS-C3N4 can effectively break the lignin Cβ-O-4 bonds in 2-Phenoxy-1-phenylethanol (lignin model compound) and the products formed are mainly phenol (Phol) and acetophenone (Ap). More importantly, the yields of Phol and Ap were up to 86.5% and 74.3%, after only irradiation for 1.5 h, respectively, under optimum conditions. A mechanistic study showed that photocatalytic reaction follows a photogenerated electron-hole coupled mechanism. The high photocatalytic performance of CdS-C3N4 is mainly ascribed to the fast photogenerated electron-hole separation capability and good dispersion of CdS on C3N4. This work offers an idea for selective cleavage of lignin Cβ-O-4 bonds by constructing a heterojunction photocatalyst.

Formation of CdS quantum dots on zeolitic imidazolate framework-67 dodecahedrons as S-scheme heterojunctions to enhance charge separation and antibacterial activity

Synthesising a heterojunction structure with a tight interface and sufficient contact area is critical for yielding photogenerated carriers with superior migration efficiencies; however, this remains a significant challenge. Herein, zeolitic imidazolate framework-67 (ZIF-67) was synthesised via four different methods. Using methanol as the medium, the as-prepared ZIF-67 (denoted as ZM) exhibited a uniform morphology and good crystallinity. Subsequently, a well-designed step-scheme (S-scheme) CdS@ZM heterojunction was fabricated via the in-situ coating of CdS quantum dots (QDs) on the ZM dodecahedrons. We utilized the exposed Co centres in the ZM as the “trapping baits” to anchor S2– precursors and yield a highly dispersed CdS QD coating. Owing to the in-situ coating of CdS QDs, the obtained S-scheme CdS@ZM composites exhibited excellent interfacial contacts and uniform morphological distributions. Under visible light irradiation (λ ≥ 420 nm), the 40%CdS@ZM heterojunctions displayed an excellent photocatalytic sterilisation rate of 97.6 % within 15 min in the disinfection of Staphylococcus aureus, which was higher than those of pure ZM (51.0 %) and CdS (21.9 %). Finally, the S-scheme charge transfer pathway of CdS@ZM was confirmed using X-ray photoelectron spectroscopy, scanning Kelvin probe microscopy, and electron spin resonance analyses.

Fantastic properties of polydopamine boost photocatalytic activity of ATP@PDA@CdS for formaldehyde removal

Eco-friendly photocatalysts with full-spectrum light utilization and all-day-long photocatalytic activities are highly desired for formaldehyde (HCHO) removal. Polydopamine (PDA) is wrapped on the attapulgite (ATP) surface as a fantastic intermediate layer to construct ATP@PDA@CdS photocatalyst with Pt nanoparticles (NPs) as the cocatalyst. PDA is beneficial for homogeneous deposition and dispersion of CdS and Pt NPs and efficient in absorbing the energy beyond ultraviolet light (UV) to produce an excellent photothermal effect for photocatalysis. The reductive surface of PDA can also hinder the photocorrosion of CdS for long-term operation. The factors, such as relative humidity and particle size, affecting the photocatalytic activity and the all-day-long photocatalysis by Pt NPs are also discussed.

Optica characterization of PVA/CdS nanostructure

CdS nanostructure has been synthesized of varied sizes in polyvinyl alcohol. The characterization of transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicates the well dispersed CdS uniform sphere nanoparticles. The infrared spectral data confirmed that it has coordinated site to aggregate the Cd ions and different uniform sizes of CdS nanoparticles. The blue shift and optical band gap as a function of the particle sizes were studied form the UV-Visible spectra. Dielectric properties were studied in the frequency range from (2.5-5 MHz) as a function of temperature and the effect of particle sizes on the relaxation time were discussed.

Construction of S-scheme CdS/g-C3N4 nanocomposite with improved visible-light photocatalytic degradation of methylene blue

Within moderate band gap, g-C3N4 and CdS are both promising visible light driven photocatalysts. However, their intrinsic high recombination rate of photo-induced electron-hole pairs along with the poor susceptibility in photocorrosion of CdS is main limitations hindering their practical application. In this study, the CdS/g-C3N4 composites with various weight ratios of CdS to g-C3N4 were solvothermal prepared from the dispersion of components, g-C3N4 and CdS, in ethanol. The physicochemical characterizations demonstrate the success in the fabrication of well-dispersed CdS nanoparticles in the g-C3N4 matrix. The enhanced photocatalytic activity of the g-C3N4/CdS composite over the degradation of methylene blue under visible light was ascribed to the effective photo-induced electron-hole separation via the step scheme (S-scheme) pathway in which the main contribution of high oxidative hydroxyl radicals (•OH) was demonstrated. Furthermore, via S-scheme model, we also clarify the depletion of photo-induced holes on CdS which is ascribed as the reason for improvement in resistance to photocorrosion of composites.

Ordered Macroporous Carbonous Frameworks Implanted with CdS Quantum Dots for Efficient Photocatalytic CO2 Reduction.

Solar-driven photocatalytic CO2 reduction is regarded as a promising way to simultaneously mitigate the energy crisis and CO2 pollution. However, achieving high efficiency of photocatalytic CO2 reduction, especially without the assistance of sacrifice reagents or extra alkaline additives, remains a critical issue. Herein, a photocatalyst of 3D ordered macroporous N-doped carbon (NC) supported CdS quantum dots (3DOM CdSQD/NC) is successfully fabricated toward photocatalytic CO2 reduction via an in situ transformation strategy. Additionally, an amines oxidation reaction is introduced to replace the H2 O oxidation process to further boost the photocatalytic CO2 reduction efficiency. Impressively, 3DOM CdSQD/NC exhibits superior activity and selectivity in photocatalytic CO2 reduction coupled with amines oxidation, affording a CO production rate as high as 5210 µmol g-1 h-1 in the absence of any sacrificial agents and alkaline additives. Moreover, 3DOM CdSQD/NC achieves an apparent quantum efficiency of 2.9% at 450 nm. Mechanism studies indicate that the 3D ordered macropores in the NC matrix are beneficial to the transfer of photogenerated carriers. Furthermore, the highly dispersed CdS QDs on the NC skeleton are able to significantly promote the adsorption of both CO2 and amine molecules and depress the CO2 activation energy barriers by stabilizing the *COOH intermediate, directly contributing to the high activity.

CdS/MoS2 Nanoparticles on Nanoribbon Heterostructures with Boosted Photocatalytic H2 Evolution under Visible‐light Irradiation

AbstractThe construction of the heterostructures with intimate contacts and prominent sunlight absorption capacity are essential for achieving the highly effective photocatalytic H2 evolution. Here, the CdS/MoS2 heterostructures constituted by CdS nanoparticals loaded on uniform MoS2 nanoribbons were synthesized through solid‐gas reaction and hydrothermal treatments. In the as‐prepared CdS/MoS2 heterostructures, there are large‐area contact interfaces between the external highly dispersed small CdS nanoparticals and MoS2 nanoribbons. Impressively, the optimized CdS/MoS2‐8 photocatalyst delivered the highest hydrogen production rate of 91.2 μmol h−1, which is 9 times that of CdS. It demonstrates that the formation of the heterostructures could effectively promote the separation and transfer of photogenerated charge carriers due to the intimate contacts between CdS nanoparticals and MoS2 nanoribbons. This work would provide a new method to develop efficient photocatalysts for photocatalytic H2 evolution.

Voltage-Switchable Biosensor with Gold Nanoparticles on TiO2 Nanotubes Decorated with CdS Quantum Dots for the Detection of Cholesterol and H2O2.

A thin layer of gold nanoparticles (Au NPs) sputtered on cadmium sulfide quantum dots (CdS QDs) decorated anodic titanium dioxide nanotubes (TNTs) (Au/CdS QDs/TNTs) was fabricated and explored for the nonenzymatic detection of cholesterol and hydrogen peroxide (H2O2). Morphological studies of the sensor revealed the formation of uniform nanotubes decorated with a homogeneously dispersed CdS QDs and Au NPs layer. The electrochemical measurements showed an enhanced electrocatalytic performance with a fast electron transfer (∼2 s) between the redox centers of each analyte and electrode surface. The hybrid nanostructure (Au/CdS QDs/TNTs) electrode exhibited about a 6-fold increase in sensitivity for both cholesterol (10,790 μA mM-1 cm-2) and H2O2 (78,833 μA mM-1 cm-2) in analyses compared to the pristine samples. The hybrid electrode utilized different operational potentials for both analytes, which may lead to a voltage-switchable dual-analyte biosensor with a higher selectivity. The biosensor also demonstrated a good reproducibility, thermal stability, and increased shelf life. In addition, the clinical significance of the biosensor was tested for cholesterol and H2O2 in real blood samples, which showed maximum relative standard deviations of 1.8 and 2.3%, respectively. These results indicate that a Au/CdS QDs/TNTs-based hybrid nanostructure is a promising choice for an enzyme-free biosensor due to its suitable band gap alignment and higher electrocatalytic activities.

Efficient and Selective Visible-Light-Driven Oxidative Coupling of Amines to Imines in Air over CdS@Zr-MOFs.

Construction of porous photoactive MOF-based composite systems is regarded as one of the most effective strategies to improve light harvesting, increase the surface area, provide plenty of exposed active sites, and promote the reduction and oxidation abilities of some organic photocatalytic reactions. Herein, we synthesized porous CdS@Zr-MOF photocatalysts based on the representative photocatalyst CdS and crystalline Zr-MOFs, such as MOF-808, NU-1000, and PCN-222, to illustrate their excellent photocatalytic performance for the synthesis of imines in air. The morphology and composition of these photocatalysts were investigated by X-ray powder diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), indicating their crystallinity, high porosity, and interfacial interaction between constituents. Compared with individual components, these porous CdS@Zr-MOF composites could remarkably promote photocatalytic activity for the oxidative coupling of amines under air and visible-light conditions. The photocatalytic reaction showed broad substrate suitability. More importantly, the conversion yield reached up to 95% for the inactive aliphatic amines, and imines were formed as the single product. The improvement of the photocatalytic performance of CdS@Zr-MOF composites can be mainly ascribed to their high surface areas, more exposed active sites, excellent dispersion of CdS, and special porous photocatalytic systems, which tune the band gap, broaden the light response range, and facilitate the carrier separation.

Synthesis and visible-light photocatalytic properties of BiOBr/CdS nanomaterials

The visible-light-responsive composite photocatalyst is beneficial to improve the solar energy utilization efficiency through the coupling of narrow bandgap materials. In this work, CdS nanowires were prepared by hydrothermal method, and then BiOBr/CdS composite materials with different mass ratios were successfully prepared by a simple two-step sonography-precipitation method using CdS nanowires as a deposition template. The photocatalysts were characterized by XRD, SEM, XPS, TEM, and other methods. Rhodamine B (RhB) was used as a model pollutant to evaluate the photocatalytic activity of BiOBr/CdS catalysts with different mass ratios. The photocatalytic test results show that the composite photocatalyst containing 60% BiOBr has the highest photocatalytic activity, which indicates that it is related to the decrease in photogenerated charge recombination rate. Subsequently, the electrochemical and physical methods were used to illustrate the electron transfer mechanism and the main active center of the as-prepared samples. Free radical capture experiments reveal that holes are the main active species in the photocatalytic process of composite samples. BiOBr/CdS composite photocatalyst was prepared by a simple precipitation method using dispersed one-dimensional CdS nanowires as a template. BiOBr/CdS heterostructure combined adsorption and catalysis to degrade RhB molecules more efficiently. Free radical trapping experiments reveal that holes are the main active species in the photocatalytic process of composite samples.

Flexible photocatalytic membrane based on CdS/PMMA polymeric nanocomposite films: multifunctional materials.

In this study, poly(methyl methacrylate) with different doping nano-cadmium sulfide (CdS/PMMA) is prepared and characterized. CdS/PMMA polymeric nanocomposite films were synthesized using solution casting methodology. SEM and XRD are used for structure analysis for the studied nanocomposite films. XRD revealed the amorphous domains of PMMA polymer, which increased with increasing CdS nanoparticle contents. SEM revealed the CdS dispersion within the PMMA matrix. CdS nanoparticles in the PMMA matrix are expected to be aggregated due to the casting technique. The optical energy gap is found to be decreased after the CdS addition. ε' and ε″ have the same behavior with the applied frequency. Maxwell-Wagner interfacial polarization is the responsible factor for higher values of ε'-ε″ at the higher frequencies. Electrical conductivity behavior σAC tends to obtain a constant value at lower frequencies that approach from its DC conductivity values. After doping PMMA with nano-CdS, an exponential increase after a critical frequency value and the values of σAC was also increased. Besides, a significant reduction in laser energy power is identified by the reduction of the output power. CdS/PMMA can attenuate the laser power due to its nonlinear effect. CdS/PMMA nanocomposite can act as a photocatalyst to improve the performance of the photodegradation of Rhodamine B (RhB). Among the different CdS/PMMA nanocomposite films, 3.33wt% CdS/PMMA demonstrates the highest efficiency in visible photocatalysis of Rhodamine B. CdS/PMMA can be utilized as multifunctional materials use like laser optical limiting to reduce the power of laser sources and as a photocatalyst membranes.

Synthesis and characterization of MWCNT incorporated N, S-rGO supported CdS photocatalyst for the dissociation of water to hydrogen by visible light

In the present study, MWCNT-N,S-rGO supported CdS was synthesized at a higher temperature by the gas-solid reaction. Photoactivity was measured and compared with N, S-rGO supported CdS. Incorporation of MWCNT prevents the restacking of the graphene layer and provides the high surface area for the dispersion of CdS which result in increasing the photoactivity of catalyst. It also increases the electrical conductivity which reduces the charge transfer resistance. Catalysts were characterized by FTIR, XRD, XPS, Raman spectroscopy, BET surface area analyzer, TEM, HRTEM, UV–Vis spectroscopy, PL spectroscopy, electrochemical impedance spectroscopy (EIS) and Mott. Schottky analysis. The characterization results confirmed that incorporating MWCNT in N,S- rGO resulted in a higher rate of electron generation and also a higher rate of transfer of electrons to the solid-liquid interface and hence a higher activity.

One pot synthesis of CdS/BiOBr/Bi2O2CO3: A novel ternary double Z-scheme heterostructure photocatalyst for efficient degradation of atrazine

In this study, a simple one-step hydrothermal method was developed for morphology controlled synthesis of CdS/BiOBr/Bi2O2CO3 ternary heterostructure materials. The ternary system contained well dispersed CdS nanoparticles (50–80 nm) anchored over ultrathin BiOBr and Bi2O2CO3 nanoplates with high interfacial contact. A significant enhancement in visible light absorption, prolonged life time decay and improved charge carrier separation and migration property accounted for the excellent photocatalytic activity towards atrazine herbicide degradation (>95% in 30 min). A double Z-scheme electron transfer mechanism was proposed to explain the dramatic increase in photocatalytic activity which was deduced from photoelectrochemical measurements, scavenger and radical (OH and O2‾) trapping experiments. MTT assay study revealed that the photo-catalytically treated atrazine solution showed significant reduction in cytotoxicity. This study provides an effective strategy for facile synthesis of bismuth based ternary heterostructures with potential applications in the field of environmental remediation.

Synthesis of hierarchically meso-macroporous TiO2/CdS heterojunction photocatalysts with excellent visible-light photocatalytic activity

Photocatalysts with a hierarchically porous structure have attracted considerable attention owing to their wide pore size distribution and high surface area, which enhance the efficiency of transporting species to active sites. In this study, hierarchically meso-macroporous TiO2 photocatalysts decorated with highly dispersed CdS nanoparticles were synthesized via hydrolysis, followed by a hydrothermal treatment. The textural mesopores and interconnected pore framework provided more accessible active sites and efficient mass transport for the photocatalytic process. The light collection efficiency was enhanced because of multiple scattering of incident light in the macropores. Moreover, the formation of a heterojunction between the CdS and TiO2 nanoparticles extended the photoresponse of TiO2 to the visible-light range and enhanced the charge separation efficiency. Therefore, the hierarchically meso-macroporous TiO2/CdS photocatalysts exhibited excellent photocatalytic activity for the degradation of rhodaming B under visible-light irradiation. Trapping experiments demonstrated that superoxide radicals (O2−) and hydroxyl radicals (OH) were the main active species in photocatalysis. A reasonable photocatalytic mechanism of TiO2/CdS heterojunction photocatalysts was also presented.

Inhibition of photocorrosion of CdS via assembling with thin film TiO2 and removing formed oxygen by artificial gill for visible light overall water splitting

CdS is a well-known and important visible-light responsive photocatalyst for overall water splitting. However, the serious photocorrosion property limits its application in photocatalysis. Through modification TiO2 thin film over CdS surface, TiO2/CdS photocatalyst exhibited an obviously enhanced photocatalytic stability. The H2 evolution rate (3.074μmolh−1g−1) of modified Pt-TiO2/CdS under visible light toward overall water splitting was almost 6 times higher than that of CdS sample (0.534μmolh−1g−1). The application of artificial gill in photocatalytic overall water splitting system removed the newly formed oxygen from catalyst surface mainly inhibiting the hydrogen and oxygen back recombination to water and preventing the oxygen led oxidation or photocorrosion. By these two strategies, we fulfilled visible light induced overall water splitting in CdS dispersion and achieved satisfied stability during reaction.