CdS MoS2 Research Articles

Impact of Nitrogen-Enriched 1T/2H-MoS2/CdS as an Electrode Material for Hybrid Supercapacitor.

Transition metal chalcogenides (TMX) have attracted energy researchers due to their role as high-performance electrode materials for energy storage devices. A facile one-pot hydrothermal technique was adopted to synthesize a molybdenum disulfide/cadmium sulfide (MoS2/CdS) (MCS) composite. The as-prepared samples were subjected to characterization techniques such as XRD, FT-IR, SEM, TEM, and XPS to assess their structure, morphology, and oxidation states. The MoS2/CdS (MCS) composites were prepared in three different ratios of molybdenum and cadmium metals. Among them, the MCS 1:2 (Mo:Cd) ratio showed better electrochemical performance with a high specific capacitance of 1336 F g-1 (high specific capacity of 185.83 mAh g-1) at a specific current of 1 A g-1 for half-cell studies. Later, a hybrid supercapacitor (HSC) device was fabricated with N-doped graphene (NG) as an anode and MCS (1:2) as a cathode, delivering a high specific energy of 34 Wh kg-1 and a specific power of 7500 W kg-1. The high nitrogen content in the MoS2 structure in MCS composites alters the device's performance, where CdS supports the composite structure through its conductivity and encourages the easy accessibility of ions. The device withstands up to 10 000 cycles with a higher Coulombic efficiency of 97% and a capacitance retention of 90.25%. The high-performance NG//MCS (1:2) HSC may be a potential candidate alternative to the existing conventional material.

MoS2–CdS composite photocatalyst for enhanced degradation of norfloxacin antibiotic with improved apparent quantum yield and energy consumption

This study introduces an advanced visible light-activated photocatalyst for the efficient degradation of norfloxacin in aqueous environments. CdS nanorods were synthesized on MoS2 through a solution-processable solvothermal method. The resulting MoS2–CdS composite exhibited exceptional photocatalytic oxidative degradation of norfloxacin antibiotic in aquatic media. The optimal degradation efficiency (87.5 %) and degradation rate constant (0.09 min−1) were achieved with the 10 wt% MoS2–CdS composite under light illumination, surpassing pure CdS nanorods by 1.5 and 2.25 times, respectively and the highest apparent quantum yield was obtained for 10 wt% MoS2–CdS composite, which is 1.5 times higher than CdS nanorod, while maintaining consistent experimental conditions. The electrical energy per order for the degradation of norfloxacin in an aqueous solution by 20 mg of CdS in 40 ml aqueous solution is 9.7 kW h m−3/order. This value reduces to 4.8 kW h m−3/order for an equal amount of 10 wt% MoS2–CdS composite. The transfer of photogenerated electrons from the CdS nanorod to MoS2 reduces the recombination probabilities of photogenerated charge carriers and consequently enhancing the photo degradation efficiency of the composite. This research may offer novel insights into the rational design and straightforward synthesis of bimetallic sulfide photocatalysts with commendable performance and cost-effectiveness for the degradation of antibiotics in aqueous environments.

Multi-synergies of hollow CdS cubes on MoS2 sheets for enhanced visible-light-driven photocatalysis

Formation of intimate interfaces in semiconductor-based heteronanostructures (HNSs) is widely adopted to enhance the efficiency of photocatalytic hydrogen evolution via water splitting because of their efficient light harvesting, charge carrier separation, and transfer capability originating from intimate interface. Here, we employ a multi-step approach, involving the direct growth of the photocatalytically active semiconductor (Cu2O) on MoS2 sheets, along with anion exchange and cation exchange methods to design hollow CdS cube/MoS2 sheet HNSs (H-CdS/MoS2 HNSs) consisting of intimate interfaces between hollow CdS cubes and MoS2 sheets. These distinctive morphological and compositional features endow H-CdS/MoS2 HNSs with exceptional charge transfer capability, intrinsic catalytic activity, and light-harvesting capacity. Consequently, H-CdS/MoS2 HNSs demonstrate significantly enhanced photocatalytic performance and stability for hydrogen evolution reactions and pollutant degradation under visible light irradiation compared to their binary and unary photocatalyst counterparts. This design strategy demonstrates the significance of forming intimate interfaces using hollow semiconductors in HNSs for advanced photocatalysis.

Systematic investigation of MoS2-metal sulfides (Metal = In, Sn, Cu, Cd) heterostructure via metal-sulfur bond for photocatalytic CO2 reduction

Heterojunctions between MoS2 and metal sulfides (Metal = In, Sn, Cu, Cd) were successfully constructed via the metal-sulfur bond, and their application of CO2 photoreduction into chemical values could address the problem of global warming effectively. Among all MoS2/metal sulfides, the same lamellar morphology between MoS2 and In2S3 could be ascribed for the high photocatalytic performance, which revealed the high specific surface area and benefitted for the generation of build-in electric field, thus leading to the outstanding separation and migration ability. In the opposite, the dissatisfactory photoreduction performance was emerged on the heterostructure between rod-like morphology of CdS and lamellar MoS2. Moreover, the feature of small gap between valence band minimum and Fermi level in In2S3 was remained in MoS2/In2S3 composite, which could promote more carriers to be excited. Hence, the optimal MoS2/In2S3 composite reached 10.09 μmol·h−1·g−1 of CO, 68.41 μmol·h−1·g−1 of CH4 and 6.66 μmol·h−1·g−1 of CH3OH, and the mix-coordination of CO2 adsorption and the carbene pathway over MoS2/In2S3 was revealed via in-situ DRIFTS.

CdS/MoS2 nanoparticles anchored on oxygen-doped g-C3N4 nanosheets all-solid-state Z-scheme heterojunctions for efficient H2 evolution

Hydrogen evolution by photocatalysis is an ideal method to relieve the energy crisis. In this work, an all-solid-state Z-scheme photocatalytic system is developed via a simple hydrothermal strategy to anchor CdS–MoS2 hybrid nanoparticles onto oxygen-doped g-C3N4 nanosheets (OCN). The presence of MoS2 nanosheets serves as both an intermediary for electron transfer to enhance charge separation and enhance the durability of the CdS. Compared to the unmodified CdS, the H2 generation efficiency of the CdS–MoS2/OCN Z-scheme heterojunctions is significantly enhanced. Additionally, the optimized photocatalyst exhibits a remarkable 20.7-fold increase in H2 production rate compared to the pristine CdS. Based on the systematical characterization, the enhanced photocatalytic hydrogen evolution performance arises from the enhanced light absorption, the enlarged specific surface areas, as well as the improved charge separation. The systematic characterizations provided evidence for the demonstration of the Z-scheme photocatalytic mechanism. This work presents a novel perspective on the design of photocatalytic systems with an all-solid-state Z-scheme configuration.

Linker-Assisted Assembly of Ligand-Bridged CdS/MoS2 Heterostructures: Tunable Light-Harvesting Properties and Ligand-Dependent Control of Charge-Transfer Dynamics and Photocatalytic Hydrogen Evolution.

We used linker-assisted assembly (LAA) to tether CdS quantum dots (QDs) to MoS2 nanosheets via L-cysteine (cys) or mercaptoalkanoic acids (MAAs) of varying lengths, yielding ligand-bridged CdS/MoS2 heterostructures for redox photocatalysis. LAA afforded precise control over the light-harvesting properties of QDs within heterostructures. Photoexcited CdS QDs transferred electrons to molecularly linked MoS2 nanosheets from both band-edge and trap states; the electron-transfer dynamics was tunable with the properties of bridging ligands. Rate constants of electron transfer, estimated from time-correlated single photon counting (TCSPC) measurements, ranged from (9.8 ± 3.8) × 106 s-1 for the extraction of electrons from trap states within heterostructures incorporating the longest MAAs to >5 × 109 s-1 for the extraction of electrons from band-edge or trap states in heterostructures with cys or 3-mercaptopropionic acid (3MPA) linkers. Ultrafast transient absorption measurements revealed that electrons were transferred within 0.5-2 ps or less for CdS-cys-MoS2 and CdS-3MPA-MoS2 heterostructures, corresponding to rate constants ≥5 × 109 s-1. Photoinduced CdS-to-MoS2 electron transfer could be exploited in photocatalytic hydrogen evolution reaction (HER) via the reduction of H+ to H2 in concert with the oxidation of lactic acid. CdS-L-MoS2-functionalized FTO electrodes promoted HER under oxidative conditions wherein H2 was evolved at a Pt counter electrode with Faradaic efficiencies of 90% or higher and under reductive conditions wherein H2 was evolved at the CdS-L-MoS2-heterostructure-functionalized working electrode with Faradaic efficiencies of 25-40%. Dispersed CdS-L-MoS2 heterostructures promoted photocatalytic HER (15.1 μmol h-1) under white-light illumination, whereas free cys-capped CdS QDs produced threefold less H2 and unfunctionalized MoS2 nanosheets produced no measurable H2. Charge separation across the CdS/MoS2 interface is thus pivotal for redox photocatalysis. Our results reveal that LAA affords tunability of the properties of constituent CdS QDs and MoS2 nanosheets and precise, programmable, ligand-dependent control over the assembly, interfacial structure, charge-transfer dynamics, and photocatalytic reactivity of CdS-L-MoS2 heterostructures.

CuInS2 Nanosheet Arrays with a MoS2 Heterojunction as a Photocathode for PEC Water Splitting

Developing cost-effective noble metal-free co-catalysts as alternatives to platinum group metals is an impeccable strategy to enhance photoelectrochemical (PEC) water splitting. In this report, we successfully fabricated CuInS2 nanosheet array-based photocathode modified with CdS and co-catalyst MoS2 in a green approach to improve water splitting under solar irradiation. The visible light absorption of the modified hybrid photocathode (CIS/CdS/MoS2) was significantly enhanced due to introducing CdS and MoS2. Photoluminescence, impedance spectroscopy, and Mott–Schottky analysis depicted improved separation of excited electron–hole pairs, minimized resistance of charge transfer, and increased excited-state charge carrier concentration, resulting in increased photocurrent. Typical results indicated that composite photoelectrodes delivered higher photocurrent (−1.75 mA/cm2 at 0 V vs RHE) and HC-STH conversion efficiency (0.42% at 0.49 V vs RHE) than those of CIS and CIS/CdS photoelectrodes. This improved PEC performance is accredited to the synergetic impact of CdS in charge generation and transfer and MoS2 as a cocatalyst with active surface sites for proton reduction. This study not only reveals the promising nature of CuInS2-based light absorber photocathodes for solar energy utilization but also recommends the use of MoS2 as a cocatalyst for the proton reduction reactions for widespread applications in solar to hydrogen conversion.

Consumable CdS nanolayer enables increased performance in kesterite solar cells

Although the ohmic-contact and electrostatic field can be regulated by the intermediate layer for efficient carrier extraction, challenges remain in high-quality back contact as well as improved quality of crystallized CZTSSe absorber layer simultaneously. Here, we introduce a controllable CdS nanolayer prepared by the chemical bath deposition (CBD) process between the CZTS precursors and Mo back contact. The results disclose that the surface chemistry of the naked Mo film can be modified by the formed CdS nanolayer and thus MoS2 complex during the chemical bath process. However, such CdS nanolayer and MoS2 complex can be readily consumed during the following selenization process, without deteriorating the ohmic-back contact. Simultaneously, the as-grown CZTSSe absorber is not only with high crystallinity and less composition fluctuations, but also doped by Cd2+. Subsequently the efficiency of CZTSSe solar cells is increased by 26% as CdS nanolayer is introduced. This work provides a cost-effective and universal approach to design and modify the interface or surface of photovoltaic and photoelectrochemical devices.

Amorphous/crystalline heterojunction interface driving the spatial separation of charge carriers for efficient photocatalytic hydrogen evolution

The basic energy conversion in the photosynthetic system is the process of separation, transfer and utilization of photogenerated charges. Here, an amorphous/crystalline heterojunction photocatalyst with spatial separation effect is prepared by assembling graphdiyne (GDY) flakes onto MoS2–CdS nanodumbbells. Graphdiyne flexible flakes were synthesized via a Glazer-Hay coupling reaction using cuprous bromide (CuBr) as a catalyst. One-dimensional MoS2–CdS nanodumbbells with symmetrical amorphous MoS2 tips can effectively promote the separation of electrons and holes in space, attracting photogenerated electrons to move along the one-dimensional nanorods. The GDY two-dimensional flexible sheet, which can promote the outward movement of photogenerated holes and isolate the surface oxidation sites, is like a “protective suit” on the dumbbell structure, thereby improving the resistance to photocorrosion. The MoS2–CdS/GDY-10% composite photocatalyst shows the highest photocatalytic water splitting activity of graphdiyne applied to photocatalytic systems so far, and the highest hydrogen production rate can reach 17.99 mmol g−1h−1, which is 161 times that of pure CdS. The conversion efficiency of solar energy to hydrogen energy can reach 3.2%. The highest quantum efficiency is 6.48% at 450 nm. The synergistic effect of the special spatial structure and the amorphous/crystalline heterojunction can significantly reduce the recombination of electron-hole pairs and prolong the lifetime of photogenerated carriers. This work inspires the construction of graphdiyne-based photocatalysts with high activity and high stability, demonstrating the promising future of graphdiyne for photocatalytic water splitting.

Covalent-anion-driven self-assembled cadmium/ molybdenum sulfide hybrids for efficient nitenpyram degradation

Photocatalytic technology is an attractive and promising approach for nitenpyram degradation; however, how to ensure the carrier separation efficiency and catalytic sites exposure is still great challenges. In this study, we construct CdS@MoS2 (CM) nanohybrids with a 3D hierarchical configuration to enhance the separation and transfer efficiency of the photo-induced electron by a covalent-anion-driven self-assembly method. The vertical orientation of MoS2 ultrathin nanosheets not only provides a large specific surface area for the oxidation and reduction reactions but also enables the active edge sites of MoS2 to be maximally exposed. As a result, this structure drastically facilitates the exposure of the catalytic active region and the performance of the carrier transfer and injection into photocatalytic degradation for nitenpyram (NTP). The optimal CdS–MoS2 has an impressive and stable NTP removal efficiency with a high reaction rate constant up to 0.078 min−1, which is 3.25 times higher than that of pure cadmium sulfide. The photocatalytic degradation mechanism and degradation pathway of NTP were presented by synthesizing the results of experimental analysis and density flooding theory (DFT) calculations. In further, for the first time, the cytotoxicity and genotoxicity of NTP on moving bed biofilm reactors (MBBRs) was disclosed and a continuous photocatalytic wastewater pretreatment device based on the CM is proposed for the stable biological nitrogen removal activity of MBBRs, which can degrade more than 80% NTP per hour.

Spatially separated catalytic sites supplied with the CdS–MoS2–In2O3 ternary dumbbell S-scheme heterojunction for enhanced photocatalytic hydrogen production

In2O3 hollow hexagonal prisms are combined with CdS–MoS2 dumbbell electrostatic self-assembly to weaken the surface oxidation kinetics. MoS2 promotes the CdS–In2O3 S-scheme heterojunction photocatalyst to show significant photocatalytic performance.

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.

Efficient spatial charge separation in unique 2D tandem heterojunction CdxZn1−xIn2S4–CdS–MoS2 rendering highly-promoted visible-light-induced H2 generation

Unique 2D heterostructures CdxZn1−xIn2S4–CdS–MoS2 with effective charge separation, excellent light-harvest, and abundant active sites are highly-efficient for photocatalytic H2 evolution.

A High Catalytic Activity Photocatalysts Based on Porous Metal Sulfides/TiO2 Heterostructures

AbstractPorous metal sulfides/TiO2 (P‐MST) photocatalysts are successfully prepared via a low‐cost strategy. It is found that the P‐MST possesses a high crystallinity with average pore size of ≈500 nm, which greatly enhances the structural stability as well as catalytic activity. The catalytic properties of the P‐MST are examined by monitoring the degradation of rhodamine B (RhB) under visible‐light irradiation. Particularly, the optimized 7% Bi2S3–CdS–MoS2–TiO2 heterostructures exhibit a remarkable catalytic performance (i.e., the degradation of RhB of ≈98.9%) and long‐term cyclic stability (i.e., the catalytic activity of ≈91.7% even after 30 cyclic test), compared with that of other P‐MST heterostructures. The exceptional catalytic performance may be ascribed to the following benefits: i) the porous structure supplies ample carrier charge transfer channels and lots of surface reaction sites; and ii) the suitable amount of metal sulfides grown on TiO2 have contributed to significant improvement of the electrical conductivity and the light absorption capability.

Ternary CdS/MoS2/ZnO Photocatalyst: Synthesis, Characterization and Degradation of Ofloxacin Under Visible Light Irradiation

Ternary CdS/MoS2/ZnO (CMZ) photocatalyst was prepared that successfully degraded ofloxacin antibiotic under visible light irradiation. SEM mapping analyses of CMZ showed homogenous elemental distribution. The XRD analysis shows that ternary composites contained ZnO in the hexagonal wurtzite, CdS in cubic phase and MoS2 in the hexagonal structure. UV-DRS results of CMZ exhibited thresholds of ~ 430 nm. The photocatalytic degradation studies were performed with ofloxacin antibiotic (290 nm) under visible light irradiation. BET results presented Type III isotherm and H3 hysteresis. Ternary CMZ showed higher photoelectrochemical and photocatalyic activity due to prolonged lifetime of charge it carries, crystalline defect and surface plasmon resonance of CdS. The kinetic rate constant of ternary CMZ was 4 times higher than that of CdS/MoS2 (CM). This study presents an effective photocatalysis and the mechanism of ofloxacin degradation by CMZ ternary composite heterojunction.

Optimal synthesis of platinum-free 1D/2D CdS/MoS2 (CM) heterojunctions with improved photocatalytic hydrogen production performance

CdS nanophotocatalysts generally require precious metal Pt as a cocatalyst to enhance photocatalytic hydrogen production performance, but precious metal Pt reserves are scarce and expensive. Therefore, this study hopes to prepare CdS/MoS2 (CM) composites by uniformly distributing MoS2 nanosheets on the surface of CdS nanowires by a two-step method. After a series of tests, CM composite can expand the absorption range of visible light and improve the separation and transmittance of photogenerated electrons and holes. The results show the highest hydrogen production rate of 1.79 mmol•g−1•h−1 was obtained with the CdS/MoS2 ratio of 0.3, which is 35.8 times that of bare CdS nanowires. The excessive MoS2 nanosheets will block light adsorption of CdS and inhibit the hydrogen production performance of the CM composite. This study provides a new research direction for finding cheap cocatalysts to replace precious metal Pt.

Unique CdS@MoS2 Core Shell Heterostructure for Efficient Hydrogen Generation Under Natural Sunlight

The hierarchical nanostructured CdS@MoS2 core shell was architectured using template free facile solvothermal technique. More significantly, the typical hexagonal phase of core CdS and shell MoS2 has been obtained. Optical study clearly shows the two steps absorption in the visible region having band gap of 2.4 eV for CdS and 1.77 eV for MoS2. The FESEM of CdS@MoS2 reveals the formation of CdS microsphere (as a core) assemled with 40–50 nm nanoparticles and covered with ultrathin nanosheets of MoS2 (Shell) having size 200–300 nm and the 10–20 nm in thickness. The overall size of the core shell structure is around 8 µm. Intially, there is a formation of CdS microsphre due to high affinity of Cd ions with sulfur and further growth of MoS2 thin sheets on the surface. Considering band gap ideally in visible region, photocatalytic hydrogen evolution using CdS@MoS2 core shell was investigated under natural sunlight. The utmost hydrogen evolution rate achieved for core shell is 416.4 µmole h−1 with apparent quantum yield 35.04%. The photocatalytic activity suggest that an intimate interface contact, extended visible light absorption and effective photo generated charge carrier separation contributed to the photocatalytic enhancement of the CdS@MoS2 core shell. Additional, the enhanced hole trapping process and effective electrons transfer from CdS to MoS2 in CdS@MoS2 core shell heterostructures can significantly contribute for photocatalytic activity. Such core shell heterostructure will also have potential in thin film solar cell and other microelectronic devices.

One-pot synthesized visible-light-responsive MoS2@CdS nanosheets-on- nanospheres for hydrogen evolution from the antibiotic wastewater: Waste to energy insight

MoS2@CdS with a nanosheets-on-nanospheres morphology has been synthesized successfully via a one-pot hydrothermal method. The physical and chemical properties were characterized by XRD, SEM, HRTEM, HADDF, Element Mapping, XPS, Raman Spectra and UV–vis Spectrum. The results indicated the strong chemical interaction between CdS and mixed phase MoS2 was favorable for the charge separation thus extremely improved the rate of H2 generation. Photocatalytic hydrogen evolution experiments were performed in an amoxicillin antibiotic wastewater system. Mixed phase MoS2 with a mole ratio of 5% to CdS achieved the highest efficiency of 87 μmol/h under visible light (λ > 420 nm), which can be attributed to the enhanced charge separation, as proved by the EIS and Photocurrent experiments. Meanwhile, the amoxicillin exhibited a degradation ratio of 16.4% in 6 h. The degradation products also have been analyzed by HPLC-MS method, which demonstrated that the amoxicillin molecules have been transformed into small molecules. In summary, this study provides a cost-effective and efficient way to convert antibiotic wastewater into hydrogen energy.

One-pot synthesis of CdS-MoS2/RGO-E nano-heterostructure with well-defined interfaces for efficient photocatalytic H2 evolution

Quality of interfaces is a key factor determining photoexcited charge transfer efficiency, and in turn photocatalytic performance of heterostructure photocatalysts. In this paper, we demonstrated CdS-MoS2/RGO-E (RGO-E: reduced graphene oxide modified by ethylenediamine) nanohybrid synthesized by using a facile one-pot solvethermal method in ethylenediamine, with CdS nanoparticles and MoS2 nanosheets intimately growing on the surface of RGO. This unique high quality heterostructure facilitates charge separation and transportation, and thus effectively suppressing charge recombination. As a result, the CdS-MoS2/RGO-E exhibits a state-of-the-art H2 evolution rate of 36.7 mmol g−1 h−1 and an apparent quantum yield of 30.5% at 420 nm, which is the advanced performance among all the same-type photocatalysts (see Table S1), and far exceeding that of bare CdS by higher than 104 times. This synthesis strategy gives an inspiration for the synthesis of other compound catalysts, and higher performance photocatalyst may be obtained.

Piezotronic Transistor Based on Topological Insulators.

Piezotronics and piezophototronics are emerging fields by coupling piezoelectric, semiconductor, and photon excitation effects for achieving high-performance strain-gated sensors, LEDs, and solar cells. The built-in piezoelectric potential effectively controls carrier transport characteristics in piezoelectric semiconductor materials, such as ZnO, GaN, InN, CdS, and monolayer MoS2. In this paper, a topological insulator piezotronic transistor is investigated theoretically based on a HgTe/CdTe quantum well. The conductance, ON/OFF ratio, and density of states have been studied at various strains for the topological insulator piezotronic transistor. The ON/OFF ratio of conductance can reach up to 1010 with applied strain. The properties of the topological insulator are modulated by piezoelectric potential, which is the result of the piezotronic effect on quantum states. The principle provides a method for developing high-performance piezotronic devices based on a topological insulator.