CdS NRs Research Articles

Enhanced photocatalytic hydrogen evolution over semi-crystalline tungsten phosphide

Increasing the separation efficiency and transfer rate of photogenerated charges is the dominant factor for improving photocatalytic activity. Herein, we successfully prepared semi-crystalline WP (SC-WP) with good optical properties and as a cocatalyst to modify CdS nanorods (CdS NRs) to construct SC-WP/CdS (PD) composite catalyst by simple electrostatic self-assembly method for photocatalytic hydrogen evolution. Two high-efficiency and stable photocatalytic hydrogen evolution systems were constructed with 1.0 M ammonium sulfite solution and 10 vol% lactic acid solution as sacrificial agents, respectively. Surprisingly, the maximum photocatalytic H2 production rate of 15446.21 μmol h−1 g−1 is obtained over 10PD composite, which is 10.58 times greater than that of pure CdS. The improved photocatalytic activity can be attributed to the fact that the SC-WP nanoparticles provides a large number of exposed active sites on the surface of CdS for hydrogen evolution reaction, which can efficiently capture photogenerated electrons from CdS nanorods and promotes the transport and separation of light-induced charges. And the introduction of SC-WP nanoparticles with excellent optical properties can efficiently improve the visible light absorption range and the utilization rate of the absorbed light of the PD composite. In addition, the SC-WP nanoparticles show semi-crystalline state, which is also conducive to enhancing the photocatalytic activity.

Design, synthesis and characterization of a co-photocatalyst based on a copper (II) complex of S,S′-bis(2-pyridylmethyl)-1,2-thioethane for hydrogen production under visible light

The reaction of S,S′-bis(2-pyridylmethyl)-1,2-thioethane (bpte) and CuCl2 afforded a copper (II) complex, [(bpte)CuCl2] that can serve as a catalyst for photochemical driven hydrogen evolution from water. Under blue light, combining with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, [(bpte)CuCl2] can catalyze hydrogen generation in heterogeneous environments and can last for 40 h. Under an optimal condition, the system achieves a turnover number (TON) of 2293 mol H2 per mole of catalyst during 10 h irradiation, and the highest apparent quantum yield (AQY) is ~10.78% at 469 nm.

A photocatalytic system with a bis(thiosemicarbazonato)‑nickel over CdS nanorods for hydrogen evolution from water under visible light

Diacetyl‑2‑(4‑N‑methyl‑3‑thiosemicarbazone)‑3‑(4‑N‑amino‑3‑thiosemicarbazone) (H2ATSM) reacts with NiCl2 to form a new nickel(II) complex, Ni-ATSM, a new co-catalyst for hydrogen production. Under photoirradiation with blue light (λ = 469 nm), together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, the nickel complex can photocatalyze hydrogen evolution with a turnover number (TON) of 11,500 mol H2 per mol of catalyst (mol of cat−1) during 80 h irradiation in a heterogeneous environment.

CdS nanorods decorated with inexpensive NiCd bimetallic nanoparticles as efficient photocatalysts for visible-light-driven photocatalytic hydrogen evolution

In order to obtain the high H2 evolution activity, an inexpensive and efficient photocatalyst CdS nanorods decorated with NiCd bimetallic nanoparticles has been designed and successfully prepared via an ingenious in situ deposition method. The experiment results indicate that NiCd bimetallic cocatalysts can efficiently inhibit the recombination of the photoinduced electron-hole pairs and promote the interfacial charge transfer, resulting in a significant improvement in photocatalytic H2 production performance. The NiCd/CdS NRs sample exhibits an excellent photocatalytic H2 evolution activity under visible light irradiation (λ > 410 nm), and the corresponding H2 evolution rate is 11.57 mmol·h−1·g−1, which is about 64.8, 17.2 and 2.3 times as that of pristine CdS NRs, Cd/CdS and Ni/CdS, respectively. This work is expected to provide a new inspiration for rationally designing highly efficient and practical hybrid photocatalyst systems.

Photocatalytic system with water soluble nickel complex of S,S′-bis(2-pyridylmethyl)-1,2-thioethane over CdS nanorods for hydrogen evolution from water under visible light

In this paper, we report a new nickel complex, [(bpte)NiCl2] (bpte = S,S′-bis(2-pyridylmethyl)-1,2-thioethane) that can serve as a catalyst both for electrochemical and photochemical driven hydrogen production from water. As an electrocatalyst, [(bpte)NiCl2] can electrocatalyze hydrogen generation from a neutral buffer with a turnover frequency (TOF) of 555.78 mol of hydrogen per mole of catalyst per hour (mol H2/mol catalyst/h) at an overpotential (OP) of 837.6 mV. Together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, the nickel complex also can photocatalyze hydrogen evolution in heterogeneous environments and can work for 107 h. Under an optimal condition, the photocatalytic system can afford 24900 mol of H2 per mole of catalyst during 83 h irradiation, with a TOF of 300H2 per catalyst per hour. The average value of apparent quantum yield (AQY) is ∼24% at 420 nm.

A nickel(II) complex of S,S′-bis(2-pyridylmethyl)-1,2-thioethane, a cocatalyst for photochemical driven hydrogen evolution from water under visible light

In the presence of KSCN, the reaction of S,S′‑bis(2‑pyridylmethyl)‑1,2‑thioethane (bpte) with NiCl2 formed a new nickel(II) complex, [(bpte)Ni(SCN)2], a new cocatalyst for photochemical driven hydrogen production from water. Under photoirradiation with blue light (λmax = 469 nm), together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, the nickel complex acts as a catalyst for hydrogen evolution in heterogeneous environments. Under an optimal condition, this photocatalytic system achieved a turnover number (TON) of 23,800 mol H2 per mol of catalyst (mol of cat−1) during 60 h irradiation. The highest apparent quantum yield (AQY) was ~32.1% at 420 nm.

A water soluble cocatalyst based on a cobalt(II) complex of S,S’-bis(2-pyridylmethyl)-1,2-thioethane for photochemical driven hydrogen evolution from water under visible light

The reaction of S,S’-bis(2-pyridylmethyl)-1,2-thioethane (bpte) and CoCl2 formed a new cobalt(II) complex, [(bpte)CoCl2], a new cocatalyst for photochemical driven hydrogen evolution from water. Several physico-chemical and spectroscopic methods were used to characterize the cobalt complex. Under photoirradiation with blue light (λmax = 469 nm), together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, the cobalt complex can catalyze hydrogen evolution in heterogeneous environments and can remain for 120 h. Under an optimal condition, this photocatalytic system achieved a turnover number (TON) of 9810 mol H2 per mol of catalyst (mol of cat−1) during 95 h irradiation.

Rational design and facile in situ coupling non-noble metal Cd nanoparticles and CdS nanorods for efficient visible-light-driven photocatalytic H2 evolution

Non-noble metal Cd nanoparticles, as an efficient cocatalyst, are successfully constructed onto the surface of hexagonal CdS nanorods (CdS NRs) for the photocatalytic hydrogen evolution reaction by a facile in situ chemical reduction approach based on a thermal treatment process. The in situ introduction of Cd can significantly improve the photocatalytic H2 production performance of CdS NRs in sodium sulfide and sodium sulfite aqueous solutions under visible light irradiation. The superior electrical conductivity of metallic Cd and the intimate interfacial contact between Cd and CdS NRs are suggested to account for the enhanced light absorption intensity, more efficient charge separation, and faster interfacial charge migration, resulting in the dramatically promoted photocatalytic H2 production activity. This work provides a new route for the in situ deposition of Cd nanoparticles onto CdS and other Cd-containing semiconductor photocatalysts with desired morphologies.

Construction of CdS/CoOx core-shell nanorods for efficient photocatalytic H2 evolution

Efficient separation of electrons and holes, associated with the reduction or oxidation reactions, is of great significance in a photocatalytic system. In this study, we demonstrate the novel CdS/cobalt oxide core-shell nanorods (CdS/CoOx core-shell NRs) prepared by a facile impregnation-calcination method. The negatively charged surface of CdS induces the in situ growth of CoO and Co3O4 (abbreviated as CoOx here) as the outer shell, which efficiently captures the photogenerated holes and renders drastically improved charge separation efficiency to CdS/CoOx core-shell NRs. Moreover, the intimate interfacial contact between the CdS core and CoOx shell offers rectified charge transfer directions, which further boosts the charge separation. In consequence, the severe photocorrosion is effectively alleviated, and nearly ca. 43-folds higher of H2 production rate is achieved on CdS/CoOx core-shell NRs compared to the pristine CdS NRs. We believe that this work not only provides new approaches toward photocatalysts with steerable charge flows and enhanced photostability, but also contributes to design other efficient photocatalytic systems.

Construction of CdS/Ag2S-based broad-spectrum photoelectrochemical immunosensor for simultaneous assessment of ochratoxins by multivariable linear regression

A broad-spectrum photoelectrochemical (PEC) immunoassay was established to detect ochratoxins by using the CdS nanorod arrays (CdS NRs)/Ag2S on FTO as the photoelectrode and the CuO@secondary antibody (Ab2) label as the signal amplification. Due to the advantages of broad-spectrum antibody, such immunosensor exhibits high sensitivity to detect a low concentration of 0.67 ng/L ochratoxin A (OTA), 0.85 ng/L ochratoxin B (OTB) and 0.46 ng/L ochratoxin C (OTC), respectively. Especially, the orthogonal test was used to simulate an actual mixture containing OTA, OTB and OTC, then a multivariable linear regression model was applied to analyze the relationship of the total response with each substance. Finally, the detection of unknown mixture containing different ochratoxins was achieved by the standard addition. Such immunosensor also provided a credible selectivity and stability, suggesting its potential to detect ochratoxins or other similar compounds in food and environment.

A heterogeneous photocatalytic system based on a nickel complex over a CdS nanorod photosensitizer for H2 generation from water under visible light

In this paper, we present a nickel complex, [BzPyN(CH3)2]2[Ni(mnt)2] 1 (mnt2−=maleonitriledithiolate), a cocatalyst for building a photocatalytic system for H2 generation from water. Under photoirradiation with blue light (λmax=469nm), 1, together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor in a pH2.5 aqueous solution, produces hydrogen with a turnover number (TON) of 70,970mol of H2 per mol of catalyst during 70h irradiation and the average value of AQY is ~18% during 10h of irradiation.

Visible-light-driven photocatalytic system based on a nickel complex over CdS materials for hydrogen production from water

Based on that the evolution of renewable H2 by using a photochemical method requires photoinduced electron transfer (ET) from a light harvester to an electrocatalyst in water, we present a nickel complex, [BzPyN(CH3)2]2[Ni(i-mnt)2] 1 (i-mnt2−=2,2-dicyanoethylene-1,1-dithiolate) that acts as both an electrocatalyst and a photocatalyst for H2 generation from water via an unstable nickel hydride intermediate. As an electrocatalyst, this nickel complex can catalyze hydrogen generation from a neutral buffer with a turnover frequency (TOF) of 577.4mol of hydrogen per mole of catalyst per hour (mol H2/mol catalyst/h) at an overpotential (OP) of 837.6mV. As a photocatalyst, combining with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, it can photocatalyze hydrogen evolution in heterogeneous environments and can work for 100h. Under an optimal condition, the highest hydrogen evolution turnover number (TON) reaches 85820mol of H2 per mol of catalyst during 70h irradiation, and the highest apparent quantum yield (AQY) is ∼23% at 420nm. And possible cycles for H2 production by the electrocatalytic and photocatalytic systems are afforded.

Delocalized Electron Accumulation at Nanorod Tips: Origin of Efficient H2 Generation

Photocatalytic hydrogen (H2) evolution requires efficient electron transfer to catalytically active sites in competition with charge recombination. Thus, controlling charge‐carrier dynamics in the photocatalytic H2 evolution process is essential for optimized photocatalyst nanostructures. Here, the efficient delocalization of electrons is demonstrated in a heterostructure consisting of optimized MoS2 tips and CdS nanorods (M‐t‐CdS Nrs) synthesized by amine‐assisted oriented attachment. The heterostructure achieves photocatalytic H2 activity of 8.44 mmol h−1 g−1 with excellent long‐term durability (>23 h) without additional passivation under simulated solar light (AM 1.5, 100 mW cm−2). This activity is nearly two orders of magnitude higher than that of pure CdS Nrs. The impressive photocatalytic H2 activity of M‐t‐CdS Nrs reflects favorable charge‐carrier dynamics, as determined by steady‐state PL and time‐correlated single photon counting correlation analysis at low temperature. The MoS2 cocatalysts precisely located at the end of the CdS Nrs exhibit ultrafast charge transfer and slow charge recombination via spatially localized deeper energy states, resulting in a highly efficient H2 evolution reaction in lactic acid containing an electrolyte.

Metallic 1T phase MoS2 nanosheets as a highly efficient co-catalyst for the photocatalytic hydrogen evolution of CdS nanorods

A 1T–MoS2/CdS NRs photocatalyst shows enhanced photocatalytic activity because of the ohmic contact with low resistance between 1T–MoS2 and CdS NRs.

A cocatalyst-free CdS nanorod/ZnS nanoparticle composite for high-performance visible-light-driven hydrogen production from water

Highly efficient, visible-light-induced hydrogen (H2) production via water splitting can be achieved without the help of a cocatalyst by using a noble-metal-free core–shell photocatalyst, in which zinc sulfide (ZnS) nanoparticles are anchored on cadmium sulfide nanorods (CdS NRs).

Core–shell amorphous cobalt phosphide/cadmium sulfide semiconductor nanorods for exceptional photocatalytic hydrogen production under visible light

We report that a photocatalyst made of amorphous cobalt phosphide (CoPx) integrated with CdS NRs for H2 production under visible light. The CoPx/CdS NRs gave an apparent quantum yield at ∼35% (λ = 450 nm).

Enhancing the photocatalytic activity of CdS nanorods for selective oxidation of benzyl alcohol by coating amorphous TiO2 shell layer

One dimension (1D) core–shell structural CdS@TiO2 was fabricated by a modified sol–gel method. The thickness of amorphous TiO2 (a-TiO2) layer was adjusted by changing the amount of ammonia. Although a-TiO2 shell layer diminishes the visible light absorption in a certain extent, it largely increases the surface area of photocatalyst and effectively promotes the separation rate of photogenerated electron–hole pairs. It was revealed that a-TiO2 shell layer can effectively enhance the photocatalytic activity of CdS NRs for benzyl alcohol (BA) to benzaldehyde (BAD) transformation. Moreover, the core–shell structural CdS@a-TiO2 showed high stability and reusability for the selective oxidation of BA.

Novel planar heterostructure perovskite solar cells with CdS nanorods array as electron transport layer

Hybrid organic–inorganic solar cells with planar heterostructure based on hydrothermal-synthesized CdS nanorods (CdS NRs) array and organometal trihalide perovskite CH3NH3PbI3 have been fabricated and characterized. Thermal annealing and Ultraviolet Ozone (UV–Ozone) treatment were applied to modify the surface of the CdS NRs, in which UV–Ozone treatment was proved to be more effective in improving the morphology of perovskite layer, as well as the charge transfer between CH3NH3PbI3 and CdS NRs. Devices structured as ITO/CdS NRs array/CH3NH3PbI3/2,29,7,79-Tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,99-spirobifluorene (spiro-MeOTAD)/MoO3/Ag produced short-circuit current density of 18.77mA/cm2, open-circuit voltage of 0.89V, and fill factor of 49.9%, leading to a best power conversion efficiency of 8.36% in the case of 10min UV–Ozone treatment.

Ultralong cylindrical micelles precisely located with semiconductor nanorods by solvent evaporation-driven self-assembly.

We demonstrate the efficient incorporation of PS-tethered cadmium sulfide nanorods (PS-CdS NRs) into polystyrene-block-poly(ethylene oxide) (PS-b-PEO) ultralong cylindrical micelles by solvent evaporation-driven self-assembly. The hexadecyl trimethyl ammonium bromide (CTAB) was used as the surfactant in chloroform-in-water emulsions. It is a prerequisite to improve the enthalpic compatibility between the CdS NRs and the PS block of PS-b-PEO to accomplish their cooperative assembly. We investigated the effects including the concentration of CTAB in the aqueous solution ([CTAB]), the weight fraction of CdS NRs (f), the volume ratio of the organic solvent to water and the magnetic stirring rate on the cooperative assembly behaviors. The different morphologies of hybrid assemblies formed at varied [CTAB] were rationalized in view of the adsorption of the aqueous surfactant and block copolymer at the oil-water interfaces, thereby leading to the disparate mechanisms by which the organic-water interfacial instabilities proceeded. This work presents an extremely precise location of the CdS NRs in the centers of the cylindrical micelles, i.e. 95.2% of the CdS NRs were distributed in the central ca. 4 vol% regions of the cylinders and all of them were dispersed in the central ca. 38% radial spans. The length of the hybrid cylindrical micelles can reach tens of micrometers. The ultralong cylindrical micelles functionalized by the CdS NRs in the central cores can lower the toxicity of the CdS NRs and improve the biocompatibility, which have potential applications in fluorescence probes, labels and many others.

A highly efficient photocatalytic H2 evolution system using colloidal CdS nanorods and nickel nanoparticles in water under visible light irradiation

A noble-metal-free photocatalytic system for highly efficient hydrogen production has been developed with colloidal nickel nanoparticles (Ni NPs), CdS nanorods (CdS NRs) and lactic acid (LA) as catalyst, photosensitizer and sacrificial electron donor, respectively, in aqueous solution without any organic solvent. The hydrogen evolution activity of the highly active Ni NPs (6nm) could amount to 80% of the well-known Pt nanoparticles (5nm) in equimolar amount at pH 3.0 water solution under visible light (λ≥420nm) irradiation. A maximum turnover number (TON) of 9710 based on Ni NPs (6nm) was obtained after 10h of irradiation at a catalyst concentration of 1.38×10−5M and turnover frequency (TOF) value of 1232 was achieved for the first 6h of photocatalytic reaction. A series of Ni nanoparticles colloids with different sizes plus Fe, Co nanoparticles were also tested for photocatalytic H2-evolution. The results showed the obvious effect of Ni NPs size on the hydrogen evolution activity and the smaller (6nm) Ni nanoparticles exhibited the highest activity compared with other nanoparticles of 11nm and 20nm in size. This work demonstrates the size control of non-precious metal nanoparticles could effectively enhance the photocatalytic hydrogen production, which provides an inexpensive means of developing efficient and low-cost photocatalytic systems for harnessing solar energy.