MoS2 grown in situ on CdS nanosheets for boosted photocatalytic hydrogen evolution under visible light

A novel nano-heterojunction photocatalysts of CdS/MoS₂ with appropriate interfacial contact was successfully obtained by the facile two-step hydrothermal synthesis. The MoS₂ ultrathin layer was well combined with CdS nanosheets and formed the interaction, which facilitated the transfer and separation of charges. The CdS/MoS₂ 15 wt% possessed much higher H₂ evolution photocatalytic performance (35.24 mmol h^?1 g^?1), exhibiting an 85.95 times enhancement as compared to that of pure CdS (0.41 mmol h^?1 g^?1). Moreover, the photochemical stability of CdS/MoS₂ heterojunctions was excellent, which showed no significant decrease in activity after four cycles of experiments. The finding provides a novel method to integrate the structure of MoS₂ with CdS, which exhibits great potential in solar energy conversion.     

An efficient ternary Mn0.2Cd0.8S/MoS2/Co3O4 heterojunction for visible-light-driven photocatalytic H2 evolution

An efficient ternary Mn_0.2Cd_0.8S/MoS₂/Co₃O₄ heterojunction was prepared and displayed excellent photocatalytic performance. The ternary Mn_0.2Cd_0.8S/MoS₂/Co₃O₄ heterojunction with 0.62 wt% of MoS₂ and 1.51 wt% of Co₃O₄ achieved the highest H₂ evolution activity (16.45 mmol g⁻¹ h⁻¹), which was well above Mn_0.2Cd_0.8S (2.72 mmol g⁻¹ h⁻¹). The improved H₂ evolution activity was ascribed to the synergistic effect of the Mn_0.2Cd_0.8S/Co₃O₄ p–n heterojunction and the modification of MoS₂ as a co-catalyst. This work can offer a new perspective for the application of Mn_xCd_1−xS-based ternary heterojunction towards solar energy conversion.     

Designing of a novel Mn0.2Cd0.8S@ZnO heterostructure with Type-II charge transfer path for efficient photocatalytic hydrogen evolution reaction

The development of photocatalysts with efficient hydrogen evolution activity has been the goal for sustainable hydrogen production. In this work, heterojunction composite photocatalyst is formed by hydrothermal coupling of ZnO and Mn_0.2Cd_0.8S. Compared with pure ZnO and Mn_0.2Cd_0.8S, the composite photocatalyst has the ability to provide more abundant active sites and better photogenerated carriers separation efficiency. The optimized composite photocatalyst shows a 9.36-fold increase in hydrogen evolution activity (4297.99 μmol g^?1 h^?1) compared to Mn_0.2Cd_0.8S (459.31 μmol g^?1 h^?1) and exhibits excellent cycling stability. Density functional theory calculations identifies Type-II charge transfer path in the composite photocatalyst, achieving effective separation in space of photogenerated electrons from holes and suppressing recombination within the semiconductor. The results show that the construction of Type-II heterojunction in this work achieves a significant enhancement of the hydrogen evolution activity of the photocatalyst by constructing carrier transport channels at the contact interface of the heterojunction.     

A novel hierarchical Bi2MoO6/Mn0.2Cd0.8S Heterostructured Nanocomposite for Efficient Visible-light hydrogen production

In this work, a series of Mn_xCd_1-xS solid solutions as efficient photocatalysts for hydrogen evolution with visible light response were synthesized via a co-precipitation method firstly. Then, the hierarchical Bi₂MoO₆/Mn_0.2Cd_0.8S heterostructured composite was prepared by combining Mn_0.2Cd_0.8S composite with Bi₂MoO₆ nanocrystalline through a hydrothermal process. The optimized Mn_0.2Cd_0.8S composite's photocatalytic activity is more than 3 times of pristine CdS and the prepared Bi₂MoO₆/Mn_0.2Cd_0.8S nanocomposites exhibited a significantly improved photocatalytic activity for hydrogen evolution from water with visible light response comparing with single Mn_0.2Cd_0.8S composite. The optimized photocatalytic activity of Bi₂MoO₆/Mn_0.2Cd_0.8S composite is around 10 times of pristine CdS. The excellent photocatalytic activity of Bi₂MoO₆/Mn_0.2Cd_0.8S composite might be ascribed to the well-matched energy band structures of the Bi₂MoO₆ and Mn_0.2Cd_0.8S. Furthermore, the heterojunctions in Bi₂MoO₆/Mn_0.2Cd_0.8S composite might also do some contributions to improve its photocatalytic activities to some extent. A possible photocatalytic mechanism was proposed. Due to its excellent photocatalytic activity and good stability for hydrogen evolution from water, the obtained hierarchical Bi₂MoO₆/Mn_0.2Cd_0.8S composite has potential application in photocatalytic hydrogen evolution from water by using solar power.     

Ni(OH)2 modified Mn0.5Cd0.5S with efficient photocatalytic H2 evolution activity under visible-light

Developing high-efficiency photocatalysts for water decomposition is one of the major challenges in converting solar energy to chemical energy. In this paper, Ni(OH)₂ modified Mn_0.5Cd_0.5S solid solution without the use of precious metals is successfully synthesized via hydrothermal method followed by precipitation, the photocatalytic activity for hydrogen evolution and stability of composite samples present significant improvement with respect to the pristine Mn_0.5Cd_0.5S. These improvements are attributed to that Mn_0.5Cd_0.5S CB potential (−0.7 V vs. NHE) is more negative than the potential of Ni²⁺/Ni (−0.23 V vs. NHE), which promotes the transfer of photo-generated electrons from Mn_0.5Cd_0.5S CB to Ni(OH)₂ for H₂ production as well as partial reduction of Ni²⁺ to Ni⁰, leaving VB holes to oxidize the sacrificial reagents. The metal Ni atoms with conductivity and Ni(OH)₂ nanoparticles not only boost the segregation and transfer of photo-induced carriers but also act as water-reduction promoter, thereby promoting the photocatalytic activity for hydrogen release. A novel visible light responsive Mn_xCd_1-xS-based photocatalytic material promising for practical applications is provided in this subject.     

Mn0.2Cd0.8S nanorods assembled with 0D CoWO4 nanoparticles formed p-n heterojunction for efficient photocatalytic hydrogen evolution

In this work, p-type semiconductor CoWO₄ nanoparticles was successfully anchored on the surface of n-type Mn_0.2Cd_0.8S nanorods, and p-n type heterostructure photocatalysts with low cost and high efficiency were synthesized. By optimizing the loading of CoWO₄ nanoparticles, the hydrogen evolution rate of the compound can reach a maximum, the peak is 408 μmol/5 h. Under visible light irradiation, it is equivalent to 3.61 times pure Mn_0.2Cd_0.8S. In addition, the composite catalyst has favorable durability and structural stability. In terms of morphology, the combination of nanorods (S_BET = 24 m²g^-1) and nanoparticles (S_BET = 12 m²g^-1) increased the specific surface area of the composite catalyst (S_BET = 31 m²g^-1), thus the composite exposed more active sites. In terms of heterojunction, the conduction bands of two semiconductors were determined by UV–vis diffuse reflection and Mott-Schottky, and the construction of p-n heterojunction was verified. The results of photochemical experiment further indicate that the built-in electric field in the p-n type heterostructure not only accelerates the electron-hole pair transfer, but vastly enhances the carrier average lifetime. In this paper, the morphology of the photocatalyst was modified and p-n heterojunction was constructed. The result is that the performance of Mn_0.2Cd_0.8S MCS was improved and the possible mechanism of photocatalytic hydrogen evolution was proposed.     

In-situ growth of mesoporous Nb2O5 microspheres on g-C3N4 nanosheets for enhanced photocatalytic H2 evolution under visible light irradiation

Large-surface-area mesoporous Nb₂O₅ microspheres were successfully grown in-situ on the surface of g-C₃N₄ nanosheets via a facile solvothermal process with the aid of Pluronic P123 as a structure-directing agent. The resultant g-C₃N₄/Nb₂O₅ nanocomposites exhibited enhanced photocatalytic activity for H₂ evolution from water splitting under visible light irradiation as compared to pure g-C₃N₄. The optimal composite with 38.1 wt% Nb₂O₅ showed a hydrogen evolution rate of 1710.04 μmol h^?1 g^?1, which is 4.7 times higher than that of pure g-C₃N₄. The enhanced photocatalytic activity could be attributed to the sufficient contact interface in the heterostructure and large specific surface area, which leads to effective charge separation between g-C₃N₄ and Nb₂O₅.     

A novel approach for high-yield solid few-layer MoS2 nanosheets with effective photocatalytic hydrogen evolution

Few-layer molybdenum disulfide (MoS₂) nanosheets are well applied in many field, but the lack of simple methods for the preparation of solid few-layer MoS₂ nanosheets with high yield and quality has greatly restricted their development. In this work, a facile solvothermal treatment coupled with the liquid exfoliation strategy was conducted to produce solid monodispersed few-layer MoS₂ nanosheets from the MoS₂ stack, and the output can reach as high as approximately 0.3 g/g. The few-layer features were confirmed by characterizations of SEM, TEM, Raman spectra, UV–vis absorption spectrum and PL spectrum. The obtained MoS₂ nanosheets exhibit fantastic dispersity and stability in an NMP solution, which can remain uniform even after one year. In general, pure MoS₂ catalysts show no or poor activity for photocatalytic hydrogen evolution as reported in the literature, however, the prepared MoS₂ nanosheets in this work display excellent photocatalytic H₂ evolution performance of 1241.3 μmol g⁻¹ h⁻¹ due to the synergistic structural and electronic modifications, including a bigger specific surface area, additional exposed active edge sites, superior charge separation and transfer efficiency, and higher reduction potential.     

Defective-MoS2/rGO heterostructures with conductive 1T phase MoS2 for efficient hydrogen evolution reaction

As a two-dimensional material, molybdenum disulfide (MoS₂) exhibits great potential to replace metal platinum-based catalysts for hydrogen evolution reaction (HER). However, poor electrical conductivity and low intrinsic activity of MoS₂ limit its application in electrocatalysis. Herein, we prepare a defective-MoS₂/rGO heterostructures material containing 1T phase MoS₂ and evaluate its HER performance. The experimental results shown that defective-MoS₂/rGO heterostructures exhibits outstanding HER performance with a low overpotential at 154.77 mV affording the current density of 10 mA cm^?2 and small Tafel slope of 56.17 mV dec^?1. The unique HER performance of as-prepared catalyst can be attributed to the presence of 1T phase MoS₂, which has more active sites and higher intrinsic conductivity. While the defects of as-prepared catalyst fully expose the active sites and further improve catalytic activity. Furthermore, the interaction between MoS₂ and rGO heterostructures can accelerate electron transfer kinetics, and effectively ensure that the obtained catalyst displays excellent conductivity and structural stability, so the as-prepared catalyst also exhibits outstanding electrochemical cycling stability. This work provides a feasible and effective method for preparation of defective-MoS₂/rGO heterostructures, which also supplies a new strategy for designing of highly active and conductive catalysts for HER.     

Solvothermal synthesis of oxygen-incorporated MoS2-x nanosheets with abundant undercoordinated Mo for efficient hydrogen evolution

Activating the inert basal planes of layered molybdenum disulfide (MoS₂) is critical to deliver its high hydrogen evolution reaction (HER) efficiency. Herein, oxygen-incorparated MoS_x with abundant undercoordinated Mo atoms is fabricated by a facile solvothermal procedure, which realizes synergistically structural and electronic regulations of MoS₂ inert basal planes. Experiment results reveal that oxygen incoparation can effectively modulate the electronic structure and further optimize the intrinsic conductivity, while the defect-rich structure with abundant undercoordinated Mo atoms increases the number of active sites. Moreover, the influence of solvothermal temperature on activity of MoS_2-x is also investigated. The achieved MoS_x electrocatalyst prepared at 220 °C exhibits a superior activity for HER with a low overpotential of 191 mV at 10 mA cm⁻², a small Tafel slope of 67 mV dec⁻¹, and an excellent stability due to the largest surface area and superior conductivity.     

Fabrication of the SnS2/ZnIn2S4 heterojunction for highly efficient visible light photocatalytic H2 evolution

A series of SnS₂/ZnIn₂S₄ (x-SS/ZIS) photocatalysts with different mass ratios of SnS₂ were prepared by a hydrothermal method. The resulted composites were used for photocatalytic hydrogen evolution under visible light excitation. All the SS/ZIS composites exhibited significantly enhanced photocatalytic activity for H₂ evolution. Obviously, the highest H₂ evolution rate of 769 μmol g^?1 h^?1 was observed over 2.5-SS/ZIS, which was approximately 10.5 times that of the ZnIn₂S₄ (73 μmol g^?1 h^?1). The enhanced photocatalytic performance was attributed to the successful construction of SnS₂/ZnIn₂S₄ heterojunctions, leading to rapid charge separation and fast transfer of the photo-generated electrons and holes under light irradiation. On the basis of PL, electrochemical impedance spectroscopy (EIS), photocurrent measurements and the H₂ evolution tests, a plausible photocatalytic mechanism was proposed.     

Heterostructured boron doped nanodiamonds@g-C3N4 nanocomposites with enhanced photocatalytic capability under visible light irradiation

Boron doped nanodiamonds (BDND) were coupled with graphitic carbon nitride (g-C₃N₄) nanosheets to form a heterojunction via a facile pyrolysis approach. The BDND@g-C₃N₄ heterojunction exhibits enhanced visible-light absorbance, improved charge generation/separation efficiency and prolonged lifetime of carriers, which lead to the enhanced photocatalytic activities for the hydrogen evolution and organic pollution under visible-light irradiation. The optimal H₂ evolution rate and apparent quantum efficiency at 420 nm of the BDND@g-C₃N₄ heterojunction is 96.3 μmol h⁻¹ and 6.91%, which is about 5 and 2 times higher than those of pristine g-C₃N₄ nanosheets (18.2 μmol h⁻¹ and 3.92%). No obvious decrease in hydrogen generation rate is observed in the recycling experiment due to the high photo-stabilization of the BDND@g-C₃N₄ composite. The degradation kinetic rate constant of organic pollution of the BDND@g-C₃N₄ structure is 0.1075 min⁻¹, which is 3 times higher compared to pristine g-C₃N₄. This work may provide a promising route to construct highly efficient non-metal photocatalysts for hydrogen evolution and organic pollution degradation under visible light irradiation.     

In-situ synthesis of PdAg/g-C3N4 composite photocatalyst for highly efficient photocatalytic H2 generation under visible light irradiation

Novel PdAg bimetallic alloy nanoparticle modified graphitic carbon nitride (g-C₃N₄) nanosheet was designed and prepared by an in situ chemical reduction procedure. By optimizing the loading content of the PdAg alloy NPs, the PdAg/g-C₃N₄ composite photocatalyst showed a champion photocatalytic hydrogen generation rate of 3.43 mmol h⁻¹ g⁻¹, and the apparent quantum yield (AQY) was determined to be 8.43% at 420 nm. Moreover, the photoluminescence and photoelectrochemical experimental results suggest that a higher separation efficiency of photo-induced charge carriers (e^- and h⁺) was obtained after loading PdAg alloy NPs on g-C₃N₄. The experimental outcomes indicate that there is a synergistic effect formed between PdAg and g-C₃N₄, which could significantly promote the charge transfer photo-induced charge carriers in the hybrid sample. A reasonable catalytic mechanism for the enhanced photocatalytic performance of the composite photocatalyst was proposed and verified by TRPL measurement, which could be taken as a guidance for the development of novel high performance catalytic system.     

Construction of 1D/0D/2D Zn0.5Cd0.5S/PdAg/g-C3N4 ternary heterojunction composites for efficient photocatalytic hydrogen evolution

A high-efficiency and easy-available approach was developed to obtain a ternary heterojunction composites with advanced hydrogen evolution reaction (HER) performance under visible light by water split. PdAg bimetallic nanoparticles make a close contact interface between g-C₃N₄(CN) and Zn_0.5Cd_0.5S(ZCS). Under visible light irradiation, CN and ZCS are both excited to generate electron-hole pairs, PdAg bimetallic nanoparticles act as a bridge between CN and ZCS. Not only can the photogenerated electrons from CN be captured, but they can also be quickly transferred to the surface of ZCS and participate in the photocatalytic reaction to release H₂, and the recombination of charge carriers between the contact interface of ZCS and CN can be significantly inhibited. In addition, the thin CN layer reduces the photocorrosion of the ZCS and enhances the specific surface area of the composite material. After testing, the composite material with 30 wt% ZCS and 4 wt% PdAg demonstrates hydrogen evolution performance, up to 6250.7 μmol g^?1h^?1, which is 753 times the hydrogen evolution rate of single-component CN and 12.6 times of ZCS/CN. Compared with single-component and two-component photocatalysts, the ternary ZCS/PdAg/CN photocatalyst achieves significantly enhanced photocatalytic activity.     

Dye-sensitized black phosphorus nanosheets decorated with Pt cocatalyst for highly efficient photocatalytic hydrogen evolution under visible light

Although black phosphorous (BP) and its derived materials have shown great potential for application in photocatalytic H₂ evolution reaction (HER), their HER activity and stability still remains unsatisfied mainly due to the insufficient charge separation, the lack of surface active sites, and the defect-riched nature of BP. Herein, we report that BP nanosheets decorated with in situ grown Pt (BP NSs/Pt) could act as a highly efficient catalyst for photocatalytic H₂ evolution in an Erythrosin B (ErB)-sensitized system under visible light irradiation (≥450 nm) in the presence of triethanolamine (TEOA) as sacrificial electron donor. It is found that BP NSs can provide large surface area for the confined growth of Pt nanoparticles with a high dispersion and a reduced size but also stabilize the loaded Pt nanoparticles by covalent bonds at the BP NSs/Pt interfaces. Moreover, BP NSs offer a fast electron transfer pathway to facilitate the photocatalytic HER over in situ grown Pt catalyst. As a result, BP NSs/Pt catalyst exhibits ∼6 times higher H₂ evolution activity than free Pt nanoparticles and an apparent quantum yield (AQY) of 0.57% at 500 nm irradiation in ErB-TEOA system. This work indicates the potential of BP NSs as an effective 2D matrix to construct numerous high performance photocatalysts and photocatalytic systems.     

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.     

MoS2/Ti3C2 heterostructure for efficient visible-light photocatalytic hydrogen generation

The MoS₂/Ti₃C₂ catalyst with a unique sphere/sheet structure were prepared by hydrothermal method. The MoS₂/Ti₃C₂ heterostructure loading 30% Ti₃C₂ has a maximum hydrogen production rate of 6144.7  μmol g⁻¹ h⁻¹, which are 2.3 times higher than those of the pure MoS₂. The heterostructure maintains a high catalytic activity within 4 cycles. The heterostructure not only effectively reduce the recombination of photogenerated electrons and holes, but also provide more activation sites, which promotes the photocatalytic hydrogen evolution reaction (HER). These works can provide reference for the development of efficient catalysts in photocatalytic hydrogen evolution.     

Oxidation co-catalyst modified In2S3 with efficient interfacial charge transfer for boosting photocatalytic H2 evolution

Constructing an efficient co-catalyst/photocatalyst system for charge separation boosting photocatalytic hydrogen generation is a vital challenge. Herein, highly-dispersed PdS nanoparticles (NPs) acting as an efficient hole co-catalyst has been decorated on the ultrathin In₂S₃ nanosheets. The strong interactions between PdS and In₂S₃ via Pd–S–In bonds enable an intimate interface junction. Due to the high capacity of PdS for the hole capture with the assistance of internal electric field, the photogenerated charge carriers are not only separated effectively, the semiconductor photocatalyst In₂S₃ is also protected from the photo-oxidation. As expected, a remarkable H₂ production rate of 142.27 μmol/h has been achieved for 3PdS/In₂S₃ nanocomposite, which is 149.8 times higher than that of the pristine In₂S₃ nanosheets, and 13.3 times superior to the In₂S₃ decorated with a reductive co-catalyst Pt. This work provides a new insight into the co-catalyst modification engineering for an efficient photocatalytic energy conversion.     

Facile synthesis of MoS2/CuS nanoflakes as high performance electrocatalysts for hydrogen evolution reaction

The fabrication of metal sulfides heterostructure is a promising strategy for enhancing catalytic activity. Herein, the MoS₂/CuS heterostructure was successfully grown on carbon cloth (MoS₂/CuS/CC) through an efficient method. The SEM results confirmed that the fabricated MoS₂/CuS/CC composites have a flake morphology, which can not only improves the surface area but also offers ample surface catalytic active sites. Particularly, the optimized MoS₂/CuS/CC-2 electrocatalyst showed a small overpotential of 85 mV@10 mA cm^?2 and exceptional long-term cycling durability for hydrogen evolution in 1 M KOH. The outstanding catalytic activity is attributed to the fact that the combination of MoS₂ with CuS can greatly enhance the charge transport rate and improve the structural stability. These results suggest that the MoS₂/CuS/CC heterostructure is a potential electrocatalyst for hydrogen production.