A ZIF-67-derived lamellar CoP@C cocatalyst for promoting photocatalytic hydrogen evolution from water

Photocatalytic hydrogen evolution from water is one of the top issues to achieve green hydrogen energy and utilize solar energy. Construction of cocatalyst is a major part for efficient photocatalysts. Lamellar flower-like CoP@C cocatalyst is synthesized via the phosphating of cobalt precursor derived from metal-organic framework ZIF-67. Different from usual phosphating of ZIF-67 directly, a typical solvothermal treatment of ZIF-67 contributes to tuning the formation of C nanodots on the lamellar CoP. CoP@C as cocatalyst exhibits a remarkable role of improving photocatalytic activity for hydrogen evolution. CoP@C/CdS composite shows a photocatalytic hydrogen evolution rate of 164.4 mmol g^?1 h^?1, which is much higher than those of pure CdS and other CoP/CdS photocatalysts. The heterojunction and interaction are verified between CoP@C and CdS. Light absorption and photoelectric properties of CoP@C/CdS are enhanced accompanying with strong reduction ability. A type-Ⅱ transfer path of photoelectrons is underway in CoP@C/CdS photocatalyst, accelerating the separation of electron-hole pairs and the transfer of carriers, and further resulting in the promoted photocatalytic performance. This work provides a suitable way to achieve carbon nanodots involved metal compound cocatalysts for efficient hydrogen production.     

Well-designed NiS/CdS nanoparticles heterojunction for efficient visible-light photocatalytic H2 evolution

Heterojunction photocatalysts based on semiconducting nanoparticles show excellent performance in many photocatalytic reactions. In this study, 0D/0D heterojunction photocatalysts containing CdS and NiS nanoparticles (NPs) were successfully synthesized by a chemical precipitation method. The NiS NPs were grown in situ on CdS NPs, ensuring intimate contact between the semiconductors and improving the separation efficiency of hole-electron pairs. The obtained NiS/CdS composite delivered a photocatalytic H₂ evolution rate (7.49 mmol h^?1 g^?1), which was 39.42 times as high as that of pure CdS (0.19 mmol h^?1 g^?1). This study demonstrates the advantages of 0D/0D heterojunction photocatalysts for visible light-driven photocatalytic hydrogen production.     

Efficient interfacial charge transfer of 2D/2D CoP/CdS heterojunction for extremely boosted photocatalytic H2 evolution performance

Constructing 2D/2D heterojunction photocatalysts has attracted great attentions due to their inherent advantages such as larger interfacial contact areas, short transfer distance of charges and abundant reaction active sites. Herein, 2D/2D CoP/CdS heterojunctions were successfully fabricated and employed in photocatalytic H₂ evolution using lactic acid as sacrificial reagents. The multiple characteristic techniques were adopted to investigate the crystalline phases, morphologies, optical properties and textual structures of heterojunctions. It was found that integrating 2D CoP nanosheets as cocatalysts with 2D CdS nanosheets by Co–S chemical bonds would significantly boost the photocatalytic H₂ evolution performances, and the 7 wt% 2D/2D CoP/CdS heterojunction possessed the maximal H₂ evolution rate of 92.54 mmol g^?1 h^?1, approximately 31 times higher than that of bare 2D CdS nanosheets. Photoelectrochemical, steady photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements indicated that there existed an effective charge separation and migration over 2D/2D CoP/CdS heterojunction, which then markedly lengthened the photoinduced electrons average lifetimes, retarded the recombination of charge carriers, and caused the dramatically boosted photocatalytic H₂ evolution activity. Moreover, the density functional theory (DFT) calculation further corroborated that the efficient charge transfer occurred at the interfaces of CoP/CdS heterojunction. This present research puts forward a promising strategy to engineer the 2D/2D heterojunction photocatalysts endowed with an appealing photocatalytic H₂ evolution performance.     

Efficient photocatalytic hydrogen evolution on amorphous MoSx-modified CdS/KTaO3 heterojunctions under visible light irradiation

Constructing heterostructures with efficient charge separation is a promising route to improve photocatalytic hydrogen production. In this paper, MoS_x/CdS/KTaO₃ ternary heterojunction photocatalysts were successfully prepared by a two-step method (hydrothermal method and photo deposition method), which improved the photocatalytic hydrogen evolution activity. The results show that the rate of hydrogen evolution for the optimized photocatalyst is 2.697 mmol g^?1·h^?1under visible light, which is 17 times and 2.6 times of the original CdS (0.159 mmol g^?1 h^?1) and the optimal CdS/KTaO₃(1.033 mmol g^?1 h^?1), respectively, and the ternary photocatalyst also shows good stability. The improvement on photocatalytic hydrogen evolution performance can be attributed to the formation of heterojunction between the prepared composite materials, which effectively promotes the separation and migration of photo-generated carriers. Amorphous MoS_x acts as an electron trap to capture photogenerated electrons, providing active sites for proton reduction. This provides beneficial enlightenment for hydrogen production by efficiently utilizing sunlight to decompose water.     

Hydrogen generation by photocatalytic reforming of glucose with heterostructured CdS/MoS2 composites under visible light irradiation

A binary heterostructured CdS/MoS₂ flowerlike composite photocatalysts was synthesized via a simple one-pot hydrothermal method. This photocatalyst demonstrated higher photocatalytic hydrogen production activity than pure MoS₂. The heterojunction formed between MoS₂ and CdS seems to promote interfacial charge transfer (IFCT), suppress the recombination of photogenerated electron–hole pairs, and enhance the hydrogen generation. Based on the good match between the conduction band (CB) edge of CdS and that of MoS₂, electrons in the CB of CdS can be transferred to MoS₂ easily through the heterojunction between them, which prevents the accumulation of electrons in the CB of CdS, inhibiting photocorrosion itself and greatly enhancing stability of catalyst. Hydrogen evolution reaction (HER) using Na₂S/Na₂SO₃ or glucose as sacrificial agents in aqueous solution was investigated. The ratio between CdS and MoS₂ plays an important role in the photocatalytic hydrogen generation. When the ratio between CdS and MoS₂ reaches 40 wt%, the photocatalyst showed a superior H₂ evolution rate of 55.0 mmol g⁻¹ h⁻¹ with glucose as sacrificial agent under visible light, which is 1.2 times higher than using Na₂S/Na₂SO₃ as sacrificial agent. Our experimental results demonstrate that MoS₂-based binary heterostructured composites are promising for photocorrosion inhibition and highly efficient H₂ generation.     

Free-standing CuS–ZnS decorated carbon nanotube films as immobilized photocatalysts for hydrogen production

Free-standing carbon nanotube films (CNTF) with entangled carbon nanotubes (CNT) were used as conductive supports for the preparation of CuS–ZnS/CNTF composite as immobilized photocatalysts for H₂ production. The surface morphology, crystalline property, surface chemistry, and optical properties of the CuS–ZnS/CNTF photocatalysts were investigated. The effects of forming CuS–ZnS heterojunction and conductive CNTF on the separation of photogenerated charges and photocatalytic hydrogen production activity of CuS–ZnS/CNTF photocatalysts were evaluated by the photocatalytic hydrogen production tests. Conductive CNT films can prevent the recombination of photogenerated electron–hole pairs. The deposition of CuS nanoparticles on the ZnS/CNTF leads to higher photocatalytic activity which can be attributed to the effective electron–hole separation. Introducing ZnS and CuS makes the photocatalyst surface more hydrophilic. The porous structure contributed to the effective contact between the sacrificing agents and the photocatalysts, leading to enhanced H₂ production activity.     

Sustainable and stable hydrogen production over petal-shaped CdS/FeS2 S-scheme heterojunction by photocatalytic water splitting

One-dimensional CdS nanorods have garnered interest because of their highly visible light response, narrow bandgap, and negative potential at the conduction band edge, which are suitable for proton reduction. However, their poor charge separation and surface photocorrosion remain unresolved. In this study, CdS was synthesized with a 3D dendrite-like morphology to reduce its surface instability and junctioned with inexpensive FeS₂ particles to extend the absorption region toward visible light and improve its photoactivity. The photocurrent density was increased 8.3 times, and the photoluminescence reduced by half in petal-shaped CdS/15% FeS₂ compared with pure CdS. The petal-shaped CdS/15% FeS₂ heterojunction catalyst exhibited significantly enhanced photostability and photocatalytic activity; when 10% lactic acid was used as a hole scavenger, the hydrogen generation rate was 22.91 mL g^?1 for 10 h in pure CdS particles and 107.56 mL g^?1 in the petal-shaped CdS/15% FeS₂ particles. Moreover, the amount of hydrogen generated was maintained until 8th recycling experiments. The Cd and S ions eluted via photocorrosion were not detected after the reaction was complete. This was attributed to the petal-shaped CdS/FeS₂ heterojunction system which protected the unstable CdS surface owing to its controlled morphology. The FeS₂ junction improved visible light absorption facilitating the separation of photogenerated charges.     

Self-assembled CdS@BN core-shell photocatalysts for efficient visible-light-driven photocatalytic hydrogen evolution

CdS@BN NRs core-shell photocatalysts for hydrogen evolution were synthesized by a solvothermal and chemical adsorption method. CdS NRs coated by 5 wt% boron nitride (BN) shell exhibited remarkably visible-light photocatalytic hydrogen evolution activity of up to 30.68 mmol g⁻¹ h⁻¹, nearly 6.79 times higher than that of pure CdS NRs, and the apparent quantum efficiency at 420 nm was 7.5%. Transmission electron microscopy showed the CdS NRs were coated with a thin (~5 nm) BN layer, which together with the hydrogen evolution results proved the photocatalytic ability of CdS NRs was significantly improved. The hydrogen evolution rate of CdS NRs coated by 5 wt% BN remained at 91.4% after four cycles, indicating the photocorrosion of CdS NRs was effectively alleviated. Moreover, the large and close coaxial interfacial contact between the CdS core and the BN shell was beneficial to the separation and transfer of photogenerated electron-hole pairs.     

Cu2ZnSnS4 decorated CdS nanorods for enhanced visible-light-driven photocatalytic hydrogen production

Design and preparation of high performance photocatalysts are always the keys for photocatalytic hydrogen production by using green and unlimited solar energy. In this work, we present the synthesis of Cu₂ZnSnS₄ (CZTS) decorated CdS nanorods and their use for visible-light-driven photocatalytic hydrogen production. The as-synthesized CZTS decorated CdS nanorods exhibit much higher visible-light-driven photocatalytic hydrogen production performance than that of individual CdS nanorods and individual CZTS nanoparticles. Specifically, the hydrogen production rate of representative CZTS decorated CdS nanorods was 48-times and 165-times higher than that of individual CdS nanorods and individual CZTS nanoparticles. The enhanced photocatalytic hydrogen production performance may be contributed by the p-n heterojunction as well as the synergistic effect between CdS nanorods and CZTS particles. The present work not only reported new low-cost and highly efficient photocatalysts for visible-light-driven photocatalytic hydrogen production, but also provided new method for the design and preparation of high performance visible-light-driven heterostructured photocatalysts for photocatalytic hydrogen production.     

Cation exchange synthesis of hollow-structured cadmium sulfide for efficient visible-light-driven photocatalytic hydrogen evolution

Efficient solar absorption and photoinduced charge separation are extremely important for solar-energy conversion on semiconductor photocatalysts. To advance the photocatalytic performance, we developed a general templated-assisted reverse cation exchange strategy to successfully synthesize hollow-structured CdS semiconductors with the textile structural surface. The crystal phase, particle morphology, optical/electrical properties, and photocatalytic performance of the as-syntheszied sample are investiagted by XRD, SEM, TEM, XPS, DSR, PL, ESR photoelectrochemical measurements, and Photocatalytic H₂ evolution test. The final CdS sample exhibits an enhanced photocatalytic hydrogen evolution rate of up to 965 μmol·g⁻¹ h⁻¹, 2.8 times higher than the reported CdS nanorods. Based on the experimental and characterization results, the improved photocatalytic activity of the cadmium sulfide semiconductor can be ascribed to the special hollow cubic structure with a thin shell, which can enhance the light-harvesting ability and provide abundant photocatalytic active sites for facilitating the separation of photogenerated electron/hole pairs. This synthetic strategy may pave a new path for the rational design of efficient sulfur-based semiconductor photocatalysts for solar driven H₂ production.     

Efficient photocatalytic hydrogen evolution with high-crystallinity and noble metal-free red phosphorus-CdS nanorods

The photocatalytic production of H₂ by low-cost semiconductors is a promising approach to store solar energy. Photocatalysts with heterojunctions convert visible light into H₂ faster because of more efficient charge separation. The morphology, the structure, and the crystallinity are additional factors to consider when developing a photocatalyst. Here, highly-crystalline CdS nanorod (NR) were synthesized by a facile one-pot process. Under visible light, pure CdS NR produced H₂ 2.1 times faster than conventional CdS nanoparticles (NP). CdS NR were then combined with the semiconductor red phosphorus (RPh). A CdS NR-based heterojunction photocatalyst with RPh_5% had an excellent photocatalytic H₂ evolution rate of 11.72 mmol g⁻¹ h⁻¹, which was 3.6 times higher than pure CdS NR. The apparent quantum efficiency of RPh_5%/CdS NR was 19.57%. Furthermore, RPh_5%/CdS NR exhibited a superior photogenerated charge separation efficiency and was stable with little photocorrosion compared to CdS NP showing the high potential of this heterojunction photocatalyst.     

Facile preparation of ZnS/CdS core/shell nanotubes and their enhanced photocatalytic performance

In this paper, ZnS/CdS core/shell nanotubes were successfully synthesized by combining hydrothermal treatment and ion exchange conversion, and the significant influence of CdS content in the shell on photo absorption and photocatalytic activity was also investigated. The core/shell nanotubes structure of CdS deposition on both sides of ZnS nanotube was confirmed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The room temperature PL spectra of ZnS/CdS core/shell nanotubes indicated that CdS on the shell can reduce the recombination of photon-generated electron and hole. The photocatalytic activity tests prove that ZnS/CdS nanotubes have much higher photocatalytic hydrogen production activity than ZnS nanotube and CdS nanotube. Under the irradiation of visible light, the highest photocatalytic hydrogen production rate of 110 μmol h⁻¹ g⁻¹ is observed over the ZnS/CdS core/shell nanotubes with CdS/ZnS molar ratio of 1:4, which is about 11.02 and 5.56 times more active than ZnS nanotube and CdS nanotube, respectively. The improved performance of ZnS/CdS samples can be due to the strong photo response in the visible light region and the efficient separation of electron–hole pairs.     

Designing large-sized cocatalysts for fast charge separation towards highly efficient visible-light-driven hydrogen evolution

A key challenge in photocatalysts is their rapid recombination of photo-generated electron-hole pairs. To decrease the recombination probability, significant studies have been devoted to increasing potential active sites of photocatalytic systems for fast charge separation. Here we demonstrate a strategy to boost active sites that is different from conventional approaches, in which large-sized Mxene nanosheets were employed as cocatalysts, while small-sized CdS nanosheets were used as photocatalysts forming effective nanocomposites. Based on our designed strategy, the enrichment of transfer routes guides the fast separation of electrons from CdS nanosheets and transferred onto large-sized Mxene nanosheets. The visible-light-driven hydrogen production of our innovatively designed composites has been improved from 2.8 mmol/g of pure CdS nanosheets to 17.5 mmol/g of the CdS@Mxene optimized composite. The obvious improvement of hydrogen production verifies the feasibility of our design strategy as a unique way to design photocatalytic systems for fast charge separation and highly efficient photocatalytic properties.     

In-situ construction of graphene oxide in microsphere ZnS photocatalyst for high-performance photochemical hydrogen generation

Exploring high-efficiency photocatalysts for hydrogen generation from water splitting has recently spurred enormous scientific interest. Herein, the formation of Pt/GO-ZnS photocatalysts via a step-wise strategy and the mechanism of improved hydrogen production efficiency are systematically studied. Thus-prepared optimal Pt/GO-ZnS composite (with the ratio of Pt and GO are 1 and 2 wt%, respectively) exhibits excellent photocatalytic hydrogen production performance of 1082 μmol h⁻¹ g⁻¹ under simulated sunlight irradiation, which stays 2.8 and 2.6 times higher than that of ZnS/GO (2 wt%) and ZnS/Pt (1 wt%), respectively. Exhaustive experimental studies reveal that the outstanding activity of Pt/GO-ZnS is attributed to the efficient interfacial charge transfer and enhanced visible light harvesting caused by the synergetic effects of GO and Pt. In further contexts, the photocatalytic mechanism is explored: Photo-generated electrons in the conduction band of ZnS can be immediately trapped through GO and rapidly transferred onto Pt nanoparticles thanks to the tight interface. This study represents an effective and facile strategy to rationally design advanced photocatalytic system in solar energy conversion.     

In-situ constructing cobalt incorporated nitrogen-doped carbon/CdS heterojunction with efficient interfacial charge transfer for photocatalytic hydrogen evolution

Designing an efficient heterojunction interface is an effective way to promote the electrons' transfer and improve the photocatalytic H₂ evolution performance. In this work, a novel hollow hybrid system of Co@NC/CdS has been fabricated and constructed. CdS nanospheres are anchored on the hollow-structured cobalt incorporated nitrogen-doped carbon (Co@NC) through a one-pot in-situ chemical deposition approach, forming an intimate interface and establishing an excellent channel to improve the electrons transfer and charge carriers separation between CdS and Co@NC cocatalyst, which immensely promotes the photocatalytic activity. The rate of photocatalytic H₂ evolution over hollow structured Co@NC/CdS heterojunction can be achieved 8.2 mmol g^?1 h^?1, which is about 45 times of pristine CdS nanospheres. The photocatalytic H₂ evolution mechanism has been investigated by the techniques of photoluminescence (PL) spectra, photocurrent-time (i-t) curves, electrochemical impedance spectroscopy (EIS) etc. This work aims to provide a new way in developing of high-performance advanced 3D heterojunction for photocatalytic hydrogen evolution.     

In2Se3/CdS nanocomposites as high efficiency photocatalysts for hydrogen production under visible light irradiation

Hydrogen energy is an important clean energy. Using visible light to produce hydrogen by semiconductor photocatalysts is one of the current research hotspots. In this work, In₂Se₃/CdS nanocomposite photocatalysts with different mass content of CdS are prepared. The In₂Se₃/CdS photocatalyst with 85.25% CdS mass content exhibits the optimal photocatalytic hydrogen evolution activity (1.632 mmol g^?1 h^?1), which is much higher than that of CdS (0.715 mmol g^?1 h^?1) and In₂Se₃ (trace). Moreover, the In₂Se₃/CdS photocatalyst still maintains a high hydrogen evolution rate after five cycles. The high photocatalytic activity and stability of the In₂Se₃/CdS nanocomposite is due to the formation of heterojunction between In₂Se₃ and CdS. The existence of heterojunction is confirmed by high resolution transmission electron microscopy image and X-ray photoelectron spectra. Theoretical calculations and experimental results indicate that the electron transfer route at the heterojunction is step-scheme. The step-scheme helps the separation of photogenerated electrons and holes, and maximize the hydrogen evolution activity. This work provides a high efficiency step-scheme photocatalyst for hydrogen production.     

Visible-light-driven HSr2Nb3O10/CdS heterojunctions for high hydrogen evolution activity

In this study, layered perovskite HSr₂Nb₃O₁₀ ultrathin nanosheets (HSNO-ns) was successfully exfoliated within 2 h by a facile microwave-assisted method. Then, HSNO-ns/CdS heterojunction was fabricated through a facile hydrothermal route for deposition of CdS nanoparticles on HSNO-ns. The photocatalytic performances of composites were systematically investigated and discussed by varying the CdS content. The results illustrated that the photocatalytic hydrogen production rate of HSNO-ns were significantly increased by coupled CdS nanoparticles on the HSNO-ns. The optimized HSNO-ns/CdS3 composites without noble metal showed highest photocatalytic activity, which was about 8.38 times and 330 times higher than that of pristine CdS and HSNO-ns, respectively, under the visible light irradiation (≥420 nm) using triethanolamine as sacrificial agent. The enhanced photocatalytic H₂ production activity was predominantly attributed to the strong optical absorption capacity, high specific surface area and improved charge carrier separation efficiency. Our present work provides a new pathway into the design of two-dimension nanosheets-based photocatalysts and promotes their practical application in various environmental and energy issues.     

Hollow heterostructure CoS/CdS photocatalysts with enhanced charge transfer for photocatalytic hydrogen production from seawater

In recent years, there have been many studies on photocatalytic water splitting, but there are still few high-efficiency photocatalysts for photocatalytic seawater splitting. In this study, a series of hollow Co sulphide-supported CdS catalyst (H–CoS/CdS) composite photocatalysts were prepared by loading CdS onto the surface of H–CoS, which can be used for efficient H₂ production in pure water and simulated seawater. The heterojunction H–CoS/CdS exhibited H₂ production of 572.4 μmol g^?1 (4 h) from simulated seawater, which is 97.7 and 2.96 times those of H–CoS and CdS, respectively. The h-CoS cocatalyst extended the light absorption range of CdS, improved the chemical stability, and significantly enhances the charge separation efficiency. This study provides guidance for the reasonable design of a photocatalytic seawater-based H₂ production catalyst with high efficiency and low cost.     

The one-step hydrothermal synthesis of CdS nanorods modified with carbonized leaves from Japanese raisin trees for photocatalytic hydrogen evolution

The photocatalytic performance of the semiconductor CdS can be improved with carbon materials capable of limiting photocorrosion and the fast recombination of photogenerated charges. For this purpose, carbon derived from biomass exhibit several advantages including low cost, high abundance, and renewability. Here, photocatalytic CdS nanorods modified with carbon derived from the leaves of Japanese raisin trees were synthesized via a single hydrothermal step. Composite CdS nanorods with 5% biomass-derived carbon photocatalyzed H₂ evolution 1.8 times faster than unmodified CdS at a rate of 5.71 mmol g^?1 h^?1. The apparent quantum efficiency of 5%C/CdS nanorods was 14.96%. Furthermore, the addition of biomass-derived carbon to CdS nanorods augmented the stability of the semiconductor under visible light. The characterization of the composite PC indicated that a larger specific surface area, as well as upgraded charge separation caused by biomass-derived carbon, were involved in the acceleration of photocatalytic hydrogen production.     

Fabrication of CuO/MoO3 p-n heterojunction for enhanced dyes degradation and hydrogen production from water splitting

The development of excellent photocatalytic material is highly required for energy and environmental applications. In this study, visible light responsive p-n heterojunction photocatalysts based on CuO/MoO₃ with varying ratios of CuO were prepared by the facile hydrothermal method. The crystalline structure, surface morphology, chemical compositions and optical properties of the synthesized photocatalysts were studied using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL) techniques and UV–Vi's absorption spectroscopy. The results showed that the 5%CuO/MoO₃ nanocomposite displayed enhanced photocatalytic performance for the production of hydrogen (98.5 μmol h^?1g^?1) and degradation of dyes rhodamine B (RhB) and alizarine yellow (AY) than all other samples. Furthermore, 5% CuO/MoO₃ composite exhibited excellent stability after five consecutive cycles for both RhB and AY dyes. Overall, the improved photocatalytic performance of 5%CuO/MoO₃ composite was due to increased adsorption of visible light, good surface morphology, enhanced charge separation/transfer which inhibited recombination of electrons and holes. This study could encourage the synthesis of novel and effective p-n heterojunction photocatalysts for practical applications.