0D/2D heterojunction constructed by high-dispersity Mo-doped Ni2P nanodots supported on g-C3N4 nanosheets towards enhanced photocatalytic H2 evolution activity

Development of low cost and efficient non-noble-metal cocatalyst is still a hot topic to improve the activity of g-C₃N₄ in photocatalytic water splitting to produce H₂. As a potential cocatalyst in photocatalytic application, transition metal phosphides (TMPs) have been proved to greatly enhance the photocatalytic H₂ evolution performance comparable to noble metal Pt. Modifying TMPs by incorporation of hetero-metal has also been reported as an effective strategy for their electronic structure regulation and optimizing the intermediates absorption energy, however, which is rarely reported in the field of photocatalysis. Herein, the 0D/2D heterojunction is constructed by high-dispersity Mo-doped Ni₂P nanodots supported on g-C₃N₄ nanosheets, which exhibits the significantly improved photocatalytic H₂ evolution performance compared with that of Ni₂P/g-C₃N₄ and Pt/g-C₃N₄. Specifically, the optimal H₂ evolution rate reaches 67.6 μmol h⁻¹ over Mo–Ni₂P/g-C₃N₄ sample, which is 6.0 and 2.4 times higher than those of Pt/g-C₃N₄ and Ni₂P/g-C₃N₄, respectively. The fascinating result mainly stems from the improved separation efficiency of charge carriers and more effective electron donating reaction sites resulted from the electronic structure adjustment through doping Mo element into Ni₂P as cocatalyst. This work provides a valid evidence for the modification of cocatalyst to realize high H₂ evolution performance, opening up new opportunities and possibilities for the application of TMPs in the photocatalytic field.     

Enhanced photocatalytic hydrogen evolution on TiO2 employing vanadium carbide as an efficient and stable cocatalyst

In an attempt to construct efficient and robust photocatalysts/systems for solar H₂ evolution from water splitting, the development of highly active and stable H₂ evolution cocatalysts is crucial yet remains a great challenge. Herein, we present that vanadium carbide (VC) can serve as an efficient cocatalyst when integrated with TiO₂ for photocatalytic H₂ evolution. With 15 wt% VC, the obtained TiO₂/VC (15 wt%) composite photocatalyst (denoted as TV15) shows the highest photocatalytic H₂ evolution rate of 521.4 μmol h⁻¹ g⁻¹, while the pristine TiO₂ hardly shows H₂ evolution activity. The apparent quantum efficiency (AQE) of H₂ evolution reaches up to 2.3% under light irradiation of 365 nm. Notably, the TV15 exhibits excellent photocatalytic stability for H₂ evolution over four cycles of continuous light irradiation of 20 h. The enhanced activity of TV15 can be attributed to the cocatalyst effects of VC, which can not only effectively capture the photogenerated electrons of TiO₂ to greatly enhance the charge separation efficiency but also significantly reduce the overpotential of H₂ evolution reaction, thus enhancing the photocatalytic activity of TiO₂/VC towards H₂ evolution. This work provides a new insight to rationally design and develop efficient photocatalysts using active and stable transition metal carbides as cocatalysts.     

Synergistic enhancement of photocatalytic H2 production by Ni decorated 2D bubble-like carbon nitride

In this paper, a novel 2D bubble-like g-C₃N₄ (B–CN) with a highly porous and crosslinked structure is successfully synthesized via a cost-effective bottom-up process. The as-prepared B–CN photocatalyst delivers a considerably expanded specific surface area and increased active sites. Moreover, the 2D bubble-like structure can afford shortened diffusion paths for both photogenerated charge carriers and reactants. As a result, the photocatalytic H₂ evolution rate of B–CN reached 268.9 μmol g^?1 h^?1, over 5 times more than that of bulk C₃N₄. The Ni ions were further deposited on B–CN as a cocatalyst to enhance the photocatalytic activity. Benefit from the synergy of 2D bubble-like structure and Ni species cocatalyst, recombination of photoinduced charges was greatly inhibited and the hydrogen evolution reaction (HER) was significantly accelerated. The resulted catalyst achieved a dramatically high H₂ evolution rate of 1291 μmol g^?1 h^?1. This work provides an alternative way to synthesize novel porous carbon nitride together with non-noble metal cocatalysts toward enhanced photocatalytic activity for H₂ production.     

Hybridizing MoS2 and C60 via a van der Waals heterostructure toward synergistically enhanced visible light photocatalytic hydrogen production activity

Molybdenum disulfide (MoS₂) as a representative transition-metal dichalcogenide (TMD) has been extensively used as a noble-metal-free cocatalyst for photocatalytic hydrogen (H₂) production, but suffers from poor photocatalytic activity due to the catalytic inactivity of its basal plane. Herein, by bounding another metal-free cocatalyst, C₆₀, with MoS₂, we report the first MoS₂-C₆₀ hybrid featuring a van der Waals heterostructure prepared via a facile and eco-friendly solid-state mechanochemical route. C₆₀ bounding onto the edge of MoS₂ nanosheets leads to the decreases of both the number of layers and the size of MoS₂ nanosheets, as well as a negative shift of the conduction band minimum along with a positive shift of valance band maximum relative to the bulk MoS₂ and MoS₂ ball-milled without C₆₀ (MoS₂-BM). Under the optimized weight ratio of MoS₂:C₆₀ (1:1) in the raw mixture subject to ball-milling, MoS₂-C₆₀ hybrid containing 2.8 wt% C₆₀ shows an exceptional visible light photocatalytic H₂ production rate of 6.89 mmol h^?1 g^?1 in the presence of a photosensitizer Eosin Y (EY), which is significantly enhanced relative to the bulk MoS₂ and pristine C₆₀, both of which show almost no photocatalytic H₂ activity. Thus, the synergistic enhancement of photocatalytic activities of both MoS₂ and C₆₀ is revealed.     

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.     

Facile synthesis of CeO2/g-C3N4 nanocomposites with significantly improved visible-light photocatalytic activity for hydrogen evolution

Ceria dioxide supported on graphitic carbon nitride (CeO₂/g-C₃N₄) composites were facilely synthesized to be application for photocatalytic hydrogen (H₂) generation in this present work. The physical and chemical properties of CeO₂/g-C₃N₄ nanocomposites were determined via a series of characterizations. The CeO₂/g-C₃N₄ composites prepared by facile thermal annealing and rotation-evaporation method exhibit excellent photocatalytic H₂ evolution with visible-light illumination. The best hydrogen generation rate of CeO₂/g-C₃N₄ composite with 1.5 wt% Pt is 0.83 mmol h⁻¹ g⁻¹, which is almost same as that of composite with 3 wt% Pt prepared by simple physical mixing method. The significantly developed photocatalytic activity of CeO₂/g-C₃N₄ composite is majorly ascribed to the stronger interfacial effects with the more visible-light absorbance and faster electron transfer. This work reveals that construction of the CeO₂/g-C₃N₄ composite with high disperse and close knit by the facile thermal annealing and rotation-evaporation method could be an effective method to achieve excellent photocatalytic hydrogen evolution performance.     

MoS2 supported on MOF-derived carbon with core-shell structure as efficient electrocatalysts for hydrogen evolution reaction

In this work, the porous carbon polyhedra were firstly obtained by carbonizing the zeolite imidazole framework (ZIF-8). Then the carbon polyhedra and precursors of MoS₂ were successfully combined by a hydrothermal reaction, forming the C-MoS₂ composites with different carbon contents. The well-tuned C-MoS₂ sample possesses a core-shell morphology, in which the carbon substrate is well decorated by vertically aligned MoS₂ ultrathin nanosheets. The resulting composites can be used as electrocatalysts of hydrogen evolution reaction (HER), displaying significantly superior activities to pure MoS₂ and carbon. It's found that the carbon content largely affects the architectures and HER behaviors of catalysts. In particular, the optimized catalyst yields the best catalytic activity with the lowest onset potential (35 mV), smallest Tafel slope (53 mv dec^?1), lowest overpotential (200 mV at 10 mA cm^?2), as well as extraordinary long-term stability in H₂SO₄. The enhanced HER activity can be attributed to the unique core-shell structure, where abundant active edge sites of MoS₂ are exposed and the underlying carbon substrate effectively improves the conductivity of the electrode.     

Synthesis and characterization of composite visible light active photocatalysts MoS2–g-C3N4 with enhanced hydrogen evolution activity

Molybdenum disulfide (MoS₂) and graphitic carbon nitride (g-C₃N₄) composite photocatalysts were prepared via a facile impregnation method. The physical and photophysical properties of the MoS₂–g-C₃N₄ composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microcopy (HRTEM), ultraviolet–visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The photoelectrochemical (PEC) measurements were tested via several on–off cycles under visible light irradiation. The photocatalytic hydrogen evolution experiments indicate that the MoS₂ co-catalysts can efficiently promote the separation of photogenerated charge carriers in g-C₃N₄, and consequently enhance the H₂ evolution activity. The 0.5wt% MoS₂–g-C₃N₄ sample shows the highest catalytic activity, and the corresponding H₂ evolution rate is 23.10 μmol h⁻¹, which is enhanced by 11.3 times compared to the unmodified g-C₃N₄. A possible photocatalytic mechanism of MoS₂ co-catalysts on the improvement of visible light photocatalytic performance of g-C₃N₄ is proposed and supported by PL and PEC results.     

Phase controlled synthesis and the phase dependent photo-and electrocatalysis of CdS@CoMo2S4/MoS2 catalyst for HER

Herein we report a heterostructure with ultrathin nanosheets of Co-doped molybdenum sulfide on CdS nanorod array (donated as CdS@CoMo₂S₄/MoS₂) by hydrothermal synthesis. Firstly, elemental Co doping MoS₂ (CoMo₂S₄) delivers the double benefits of increased active sites and enhanced conductivity. Secondly, the structural characteristics maximally exposes the MoS₂ edges and enlarges interfacial contact area between the composite catalyst and electrolyte, as well as the efficient interfacial charge transfer. The ratio of CoMo₂S₄/MoS₂ in CdS@CoMo₂S₄/MoS₂ plays a crucial role for the enhanced photo-assistant electrocatalytic hydrogen evolution reaction (HER). We can tune the ratio of CoMo₂S₄/MoS₂ by controlling the preparation time or the ratio of precursor of Co/Mo. The catalyst with predominant MoS₂ phase shows superior photocatalytic HER performance with a high H₂ production rate of 46.60 μmol mg⁻¹ h⁻¹. Meanwhile, the catalyst with predominant CoMo₂S₄ phase exhibits not only relatively low overpotential of 172 mV at 10 mA cm⁻², which outperforms most values that have been reported on catalyst supported on ITO substrate, but also possesses H₂ production rate of 23.47 μmol mg⁻¹ h⁻¹. The superior photo-assistant electrocatalytic HER activity results from the synergistically structural and electronic modulations, as well as the proper energy band alignment between MoS₂ and CdS. This investigation could provide an approach to integrate the electro- and photocatalytic activities for HER, especially the photo responding behaviour at a bias potential which is meaningful to produce H₂ for actual application.     

Light-induced confined growth of amorphous Co doped MoSx nanodots on TiO2 nanoparticles for efficient and stable in situ photocatalytic H2 evolution

Amorphous molybdenum sulfide (a-MoS_x) prepared by in situ photoreduction method with an abundance of exposed active sites has been identified as an efficient cocatalyst for catalyzing photocatalytic H₂ evolution reaction (HER). However, the intrinsic activity of the a-MoS_x cocatalyst toward HER is low due to the unfavorable electronic structures of the active sites. Herein, we report a facile light-induced method for the confined growth of transition metal (TM) doped MoS_x (a-TM-MoS_x) cocatalysts on TiO₂ nanoparticles and their catalytic activity for in situ photocatalytic HER. It is found that doping Co into a-MoS_x can greatly enhance the activity of resulted a-Co-MoS_x cocatalyst for photocatalytic H₂ evolution over TiO₂ among the transition metal dopants (Co, Ni, Fe, Cu, Zn) tested. The most efficient a-Co-MoS_x cocatalyst (Co/Mo = 1/4 and 4 mol% loading) loaded TiO₂ (TiO₂/a-Co-MoS_x) shows a H₂ evolution rate of 133.8 μmol h⁻¹, which is 3.3 times higher than that of a-MoS_x loaded TiO₂ (TiO₂/a-MoS_x). Moreover, the TiO₂/a-Co-MoS_x photocatalyst shows excellent recycling H₂ evolution stability. The characterization results reveal that a-Co-MoS_x cocatalyst can not only effectively capture the photogenerated electrons of TiO₂ to greatly enhance the separation efficiency of photogenerated charges but also significantly reduce the overpotential of HER due to the formation of highly active “CoMoS” sites, thus synergistically enhancing the catalytic activity of TiO₂/a-Co-MoS_x. Moreover, the light-induced growth of a-Co-MoS_x on TiO₂ is found to readily couple with the in situ photocatalytic HER. Therefore, this work provides a simple and efficient strategy for designing high-performance a-MoS_x-based cocatalysts for stable in situ photocatalytic H₂ evolution.     

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.     

A novel pathway toward efficient and stable C3N4-based photocatalyst for light driven H2 evolution: The synergistic effect between Pt and CoWO4

A photocatalytic integrated system containing Pt nanoclusters, CoWO₄ nanoclusters and C₃N₄ nanosheets was achieved through a hydrothermal process followed by photodeposition. Meanwhile, the photocatalytic activity of the as-prepared system was explored for light driven H₂ evolution. Finally, the photocatalytic mechanism was explored roughly. The results show that there exists strong synergistic effect between Pt and CoWO₄. The photocatalytic activity of C₃N₄ can be significantly enhanced utilizing the aforementioned synergistic effect. When the as-prepared photocatalytic system is used, the fastest evolution rate of H₂ can be up to 14.2 μmol h⁻¹, which is 2.1 times as high as that over the Pt modified C₃N₄ nanosheets (6.7 μmol h⁻¹). And the quantum yield of the as-prepared photocatalytic system at 400 nm (0.018%) is also much higher than that of the Pt modified C₃N₄ nanosheets (0.004%). Here, this remarkable photocatalytic activity ought to be attributed to superior separation of the electro-hole pair caused by efficient charge transfer in the photocatalytic system which follows a Z-scheme-like mechanism. Therein, Pt nanoclusters may serve as an electron transfer pathway between CoWO₄ and C₃N₄ as well as active sites while CoWO₄ nanoclusters may play a water oxidation cocatalyst.     

Highly efficient white-LED-light-driven photocatalytic hydrogen production using highly crystalline ZnFe2O4/MoS2 nanocomposites

Designing efficient photocatalytic systems for hydrogen evolution is extremely important from the viewpoint of the energy crisis. Highly crystalline heterostructure catalysts have been established, considering their interface electric field effect and structural features, which can help improve their photocatalytic hydrogen-production activity. In this study, we fabricated a highly crystalline heterojunction consisting of ZnFe₂O₄ nanobricks anchored onto 2D molybdenum disulfide (MoS₂) nanosheets (i.e., ZnFe₂O₄/MoS₂) via a hydrothermal approach. The optimized ZnFe₂O₄/MoS₂ photocatalyst, with a ZnFe₂O₄ content of 7.5 wt%, exhibited a high hydrogen-production rate of 142.1 μmol h⁻¹ g⁻¹, which was 10.3 times greater than that for the pristine ZnFe₂O₄ under identical conditions. The photoelectrochemical results revealed that the ZnFe₂O₄/MoS₂ heterojunction considerably diminished the recombination of electrons and holes and promoted efficient charge transfer. Subsequently, the plausible Z-scheme mechanism for photocatalytic hydrogen production under white-LED light irradiation was discussed. Additionally, the influence of cocatalysts on the photocatalytic hydrogen evolution for the ZnFe₂O₄/MoS₂ heterostructure was investigated. This work has demonstrated a simplified coupling of one-dimensional or zero-dimensional structures with 2D nanosheets for improving the photocatalytic hydrogen production activity as well as confirmed that MoS₂ is a viable substitute for precious metal-free photocatalysis.     

Vanadium diboride as an efficient cocatalyst coupled with CdS for enhanced visible light photocatalytic H2 evolution

Exploiting active, stable, and cost-efficient cocatalysts is crucial to enhance the photocatalytic performance of semiconductor-based photocatalysts for H₂ evolution from water splitting. Herein, we report on using vanadium diboride (VB₂) as an efficient cocatalyst to enhance the photocatalytic H₂ evolution performance of CdS nanoparticles under visible light irradiation (λ ≥ 420 nm). The CdS/VB₂ composites prepared by a facile solution-mixing method exhibit much improved H₂ evolution activities in 10 vol% lactic acid (LA) solution relative to pristine CdS. The most efficient CdS/VB₂ composite with 20 wt% VB₂ (CB20) exhibits a H₂ evolution rate as high as 12.1 mmol h⁻¹ g⁻¹, which is about 11 times higher than that of CdS alone (1.1 mmol h⁻¹ g⁻¹). Moreover, the highest apparent quantum efficiency (AQE) of 4.4% is recorded on CB20 at 420 nm. The improved photocatalytic activity of CdS/VB₂ composite can be attributed to the excellent cocatalytic effect of VB₂, which can not only enhance the charge separation on CdS but also accelerate the H₂ evolution kinetics. This work demonstrates the great potential of using transition metal brodies (TMBs) as efficient cocatalysts for developing noble-metal-free and stable photocatalysts for solar photocatalytic H₂ evolution.     

Bimetallic PtNi alloy modified 2D g-C3N4 nanosheets as an efficient cocatalyst for enhancing photocatalytic hydrogen evolution

Platinum-based alloy materials as effective cocatalysts in improving the performance of photocatalytic H₂ production have raised great interest. Herein, a facile strategy of chemical reduction is established to synthesize bimetallic PtNi nanoparticles on 2D g-C₃N₄ nanosheets with excellent photocatalytic activity. The addition of PtNi nanoparticles can provide new H⁺ reduction sites and increase more active sites of the material. The synergistic effect between PtNi alloy nanoparticles and 2D g-C₃N₄ nanosheets can regulate electronic structure, narrow the band, accelerate charge transfer efficiency and inhabit the recombination of photo-induced electron (e⁻) and hole pairs (h⁺), contributing to the improvement of hydrogen evolution activity. The optimal hydrogen evolution rate of Pt_0.6Ni_0.4/CN shows higher hydrogen evolution rate (9528 μmol·g⁻¹·h⁻¹), which is 13.1 times than that of pure g-C₃N₄ nanosheets. Besides, a possible mechanism of photocatalytic hydrogen generation has been brought up according to a series of physical and chemical characterization. This work also provides a potential idea of developing cocatalysts integrating metal alloys with 2D g-C₃N₄ nanosheets for promoting photocatalytic hydrogen evolution.     

Solvothermal fabrication of MoS2 anchored on ZnIn2S4 microspheres with boosted photocatalytic hydrogen evolution activity

The MoS₂/ZnIn₂S₄ composites with MoS₂ anchored on the surface of ZnIn₂S₄ microspheres were fabricated by a facile solvothermal method. To clarify the crystal phases, morphologies, chemical compositions, optical properties, and special surface areas of the obtained photocatalysts, the corresponding characterization measurements were performed. The photocatalytic H₂ evolution activities of MoS₂/ZnIn₂S₄ composites were evaluated and compared with using lactic acid as sacrificial reagents. The results showed that integrating MoS₂ with ZnIn₂S₄ could remarkably boost the photocatalytic H₂ evolution performance and the maximum H₂ evolution rate of 201 μmol h^?1 was achieved over 1 wt% MoS₂ loading on the ZnIn₂S₄, corresponding to the apparent quantum efficiency (AQE) about 3.08% at 420 nm monochromatic light. The photoelectrochemical tests and photoluminescence spectra (PL) versified that the efficient charge transfer and separation were achieved over MoS₂/ZnIn₂S₄ composite in contrast with single ZnIn₂S₄, which would significantly benefit the enhancement of photocatalytic H₂ activity. This work provides a desired strategy to design and synthesize the visible-light-response photocatalysts with MoS₂ as cocatalysts to enhance the photocatalytic activity.     

Interfacially bonded Co-N boosts photocatalytic H2 evolution in a closely coupled CoFe2O4/g-C3N4 composite structure

To create hybrid composites for highly effective photocatalytic hydrogen evolution reactions, the photogenerated charge separation efficiency at the hybrid interface and the surface reaction kinetics at the reactive sites are key factors. In this work, CoFe hydroxide nanosheets prepared by dealloying were first mixed with graphitic carbon nitride (g-C₃N₄) to synthesize a CoFe₂O₄/g-C₃N₄ composite with strong Co-N bonds at the interface by a simple hydrothermal method. It was found that the presence of Co-N bonds between the components in the composites enhances the separation and transfer by photogenerated carriers at the composite interface. Furthermore, the presence of Co-N bonds enhanced the synergistic effect of the hybrid, which significantly boosts their photocatalytic performance in comparison to their counterparts. Under full-spectrum light, the composite photocatalyst has a greater efficiency of photocatalytic water H₂ evolution (6.793 mmol/g⁻¹·h⁻¹) and exceptional stability when compared to pure g-C₃N₄ (0.236 mmol/g⁻¹·h⁻¹) and CoFe₂O₄ (0.088 mmol/g⁻¹·h⁻¹). Under visible irradiation, the photocatalytic activity of the composite (0.556 mmol/g⁻¹·h⁻¹) for H₂ evolution increased by factors of 28.37 and 75.8 when compared to pure g-C₃N₄ and CoFe₂O₄, respectively.     

Well-dispersed CoSx nanoparticles modified tubular sulfur doped carbon nitride for enhanced photocatalytic H2 production activity

Appropriate dispersion of cocatalyst on semiconductor for improving photocatalytic H₂ production efficiency is a challenging work in semiconductor photocatalysis. Herein, we constructed the noble-metal-free CoS_x modified tubular sulfur doped carbon nitride (SCN) photocatalysts by chemical precipitation process. The amorphous CoS_x well dispersed on SCN served as H₂ production sites, which reduced the overpotential and inhibited the recombination of photogenerated carriers by interfacial charge transfer. Maximized H₂ production rate of 573.06 μmol g⁻¹ h⁻¹ under visible light irradiation was obtained by optimizing the CoS_x loading proportion to 2.4%, which was higher than that of 0.75 wt% Pt/SCN. In addition, a possible mechanism for improved H₂ production activity was proposed based on the experiments and discussion. This work provides a new strategy to design rational structure of non-noble metal cocatalyst modified photocatalyst to further improve H₂ production performance.     

Noble-metal-free CdS@MoS2 core-shell nanoheterostructures for efficient and stabilized visible-light-driven H2 generation

Photocatalytic water splitting is considered to be a green H₂ generation approach and has potential to be applied in the future. As a photocatalytic active material for H₂ evolution, CdS is a good candidate. However, the pristine CdS still suffers from low efficiency and poor stability. To address those issues, we developed noble-metal-free CdS@MoS₂ core-shell nanoheterostructures which exhibit outstanding photocatalytic H₂ evolution performance thus far with rate of 62.55 mmol g⁻¹ h⁻¹, which exceeds that of pristine CdS by a factor of 148. Meanwhile, the photocatalytic stability can be well retained with no deterioration of activity in 24 h reaction. The excellent performance can be reasonably attributed to the low crystallinity of MoS₂ with numerous active sites provided, and the band alignment of CdS and MoS₂ as determined by valence band-XPS and Mott-Schottky plots analysis, which significantly promotes charge transportation and separation. The enhanced photocatalytic stability here should be ascribed to the intimate growth of MoS₂ shells which significantly passivate the surface trap states of CdS cores and thus the photocorrosion is remarkably retarded. This novel strategy will inspire the fabrication of other photocatalytic systems, and may high-efficient photocatalysts be obtained.     

Multifunctional MoS2 ultrathin nanoflakes loaded by Cd0.5Zn0.5S QDs for enhanced photocatalytic H2 production

Two‐dimensional MoS₂ has been widely used as hydrogen evolution reaction (HER) cocatalyst to load onto nanostructured semiconductors for visible light‐response photocatalytic hydrogen production. However, its another important role as light harvester because of the band‐gap tunable property and beneficial band position has been rarely exploited. Herein, few layer‐thick MoS₂ nanoflakes with extended light absorption over the range of 400 to 680 nm and a photocatalytic HER rate of 0.98 mmol/h/g have been obtained. Then 7‐nm‐sized Cd_0.5Zn_0.5S quantum dots (QDs) are selectively grown upon ultrathin MoS₂ nanoflakes for enhanced photocatalytic H₂ generation. Upon the photocatalytic, light absorption, and charge transfer properties of the MoS₂‐Cd_0.5Zn_0.5S composites evolved with the amount of MoS₂ from 0 to 3 wt%, the multiple roles of MoS₂ as long‐wavelength light absorber, in‐plane carrier mediator, and edge site‐active HER catalyst have been revealed. An optimum H₂ generation rate of 8863 μmol/h/g and a solar to hydrogen (STH) efficiency of 2.15% have been achieved for 2 wt% MoS₂‐Cd_0.5Zn_0.5S flakes. Such a strategy can be applied to other cocatalysts with both the light response and HER activity for efficient photocatalytic property.