A novel photothermal-assisted FeNi2S4@Mn0.3C0.7S S-scheme heterojunction for enhanced photo-catalytic hydrogen evolution

In addition to the intrinsic driving force of photocatalysis, the external thermal field from the photothermal effect can provide additional energy to the photo-catalytic system to improve the photo-catalytic hydrogen-evolution (PHE) efficiency. Herein, based on the results of density functional theory, we designed and constructed a hollow core-shell FeNi2S4@Mn0.3Cd0.7S (NFS@MCS) S-scheme heterojunction with a photothermal effect, thereby realising a significant enhancement of the PHE performance due to the thermal effect, S-scheme heterojunction and hollow core-shell morphology. As a light collector and heat source, the hollow NFS could absorb and convert photons into heat, resulting in the increased local temperature of photocatalyst particles. Moreover, the S-scheme charge path at the interface not only improved the carrier separation efficiency but also retained a higher redox potential. All these are favourable to increase the PHE activity. The PHE tests show that 0.5 %-NFS@MCS exhibits the highest PHE rate of 17.11 mmol·g-1·h-1, 7.7 times that of MCS. Moreover, through a combination of theoretical calculation and experimental evidence, the PHE mechanism of the NFS@MCS system is discussed and clarified in-depth.

Amorphous Cobalt Polyselenides with Hyperbranched Polymer Additive as High-Capacity Magnesium Storage Cathode Materials Through Cationic and Anionic Co-Redox Mechanism

Rechargeable magnesium batteries (RMBs) are a promising energy-storage technology with low cost and high reliability, while the lack of high-performance cathodes is impeding the development. Herein, a series of amorphous cobalt polyselenides (CoSex, x>2) is synthesized with the assistance of organic amino-terminal hyperbranched polymer (AHP) additive and investigated as cathodes for RMBs. The coordination of cobalt cations with the amino groups of AHP leads to the formation of amorphous CoSex rather than crystalline CoSe2. The amorphous structure is favorable for magnesium-storage reaction kinetics, and the polyselenide anions provide extra capacities besides the redox of cobalt cations. Moreover, the organic AHP molecules retained in CoSex-AHP provide an elastic matrix to accommodate the volume change of conversion reaction. With a moderate x value (2.73) and appropriate AHP content (11.58%), CoSe2.7-AHP achieves a balance between capacity and cycling stability. Amorphous CoSe2.7-AHP provides high capacities of 246.6 and 94 mAh g‒1, respectively, at 50 and 2000 A g‒1, as well as a capacity retention rate of 68.5% after 300 cycles. The mechanism study demonstrates CoSex-AHP undergoes reversible redox of Co2+/3+↔Co0 and Sen 2‒↔Se2‒. The present study demonstrates amorphous polyselenides with cationic-anionic redox activities is as a feasible strategy to construct high-capacity cathode materials for RMBs.

Efficient Photocatalytic Hydrogen Production over NiS-Modified Cadmium and Manganese Sulfide Solid Solutions

In this work, new photocatalysts based on Cd_1-xMn_xS sulfide solid solutions were synthesized by varying the fraction of MnS (x = 0.4, 0.6, and 0.8) and the hydrothermal treatment temperature (T = 100, 120, 140, and 160 °C). The active samples were modified with Pt and NiS co-catalysts. Characterization was performed using various methods, including XRD, XPS, HR TEM, and UV-vis spectroscopy. The photocatalytic activity was tested in hydrogen evolution from aqueous solutions of Na₂S/Na₂SO₃ and glucose under visible light (425 nm). When studying the process of hydrogen evolution using an equimolar mixture of Na₂S/Na₂SO₃ as a sacrificial agent, the photocatalysts Cd_0.5Mn_0.5S/Mn(OH)₂ (T = 120 °C) and Cd_0.4Mn_0.6S (T = 160 °C) demonstrated the highest activity among the non-modified solid solutions. The deposition of NiS co-catalyst led to a significant increase in activity. The best activity in the case of the modified samples was shown by 0.5 wt.% NiS/Cd_0.5Mn_0.5S (T = 120 °C) at the extraordinary level of 34.2 mmol g^-1 h^-1 (AQE 14.4%) for the Na₂S/Na₂SO₃ solution and 4.6 mmol g^-1 h^-1 (AQE 2.9%) for the glucose solution. The nickel-containing samples possessed a high stability in solutions of both sodium sulfide/sulfite and glucose. Thus, nickel sulfide is considered an alternative to depositing precious metals, which is attractive from an economic point of view. It worth noting that the process of photocatalytic hydrogen evolution from sugar solutions by adding samples based on Cd_1-xMn_xS has not been studied before.

Amorphous CoSx decorated Cd0.5Zn0.5S with a bulk-twinned homojunction for efficient photocatalytic hydrogen evolution

Amorphous CoSx was combined with Twinned-Cd0.5Zn0.5S to construct homo-heterojunction for efficient photocatalytic H2 evolution. This work provides new ideas for constructing noble metal-free photocatalyst with homo-heterojunction.

PVP influence on Mn-CdS for efficient photocatalytic activity

Wastewater treatment is the most serious problem in this upcoming era. A harmful effluent like organic dyes, heavy metals, acids from industries mixed in wastewater is deteriorating the environment. To get rid of these poisonous materials and to recycle wastewater for domestic purposes, there are many steps which included photocatalytic dye degradation. PVP assisted Mn-CdS nanoparticles was prepared by novel hydrothermal technique. The characteristic behavior of pure and PVP (1% and 2%) assisted Mn-CdS samples were studied by further analysis. The structural, optical, vibrational, morphological, chemical composition behavior of synthesized pristine and surfactant induced Mn-CdS nanoparticles were analyzed. UV-Vis spectra revealed the optical behavior of the prepared pure and PVP (1% and 2%) assisted Mn-CdS samples. The bandgap obtained was 2.2, 2.06 and 1.99 eV for pure Mn-CdS, 1% PVP-Mn-CdS and 2% PVP- Mn-CdS. The narrow bandgap is one of the advantage of the material. Mn-CdS, 1% PVP-(Mn-CdS) and 2% PVP- (Mn-CdS) morphology were further investigated by Scanning Electron Microscopic studies (SEM). The surfactant (PVP) was added to enhance the morphology development and decrease agglomeration on the surface and the SEM images revealed a clear evidence for enhancement of morphology in all three samples. 2% PVP-(Mn-CdS) sample showed a good development in morphology when compared with other two samples and the best sample showed formation of nanorods below the surface of nanoparticles. Further, Mn-CdS, 1% PVP-(Mn-CdS) and 2% PVP- (Mn-CdS) was indulged to investigate the cationic degradation. The photocatalytic activities of three samples were carried out with loading different amount of the catalysts and 30 mg catalyst 2% PVP- (Mn-CdS) loaded dye solution showed a considerable degradation of methylene blue dye. The 30 mg catalyst (2% PVP-Mn-CdS) showed 98% efficiency under visible light irradiation for about 2 h. The best candidate, 30 mg catalyst (2% PVP-Mn-CdS) investigated for its reusability. The catalyst showed almost 98% of efficiency up to three cycles which confirmed the level of potential of the sample. 2% PVP-(Mn-CdS) sample would be promising candidate in wastewater treatment. It can be further utilized for removing dyes from wastewater in wastewater remediation process.

Visible-light-driven two dimensional metal-organic framework modified manganese cadmium sulfide for efficient photocatalytic hydrogen evolution

The morphology modification and the construction of heterojunction of the photocatalyst are considered as the main means to significantly improve the performance of photocatalytic hydrogen evolution. In this study, Mn_0.2Cd_0.8S nanorods are successfully assembled on the surface of Ni-MOF-74 with flake morphology. Specifically, the Ni-S bond is constructed between Ni-MOF-74 and Mn_0.2Cd_0.8S, which provides a unique transfer channel for photo-induced carriers. Meanwhile, the electrons in the conduction band of Mn_0.2Cd_0.8S can be injected into the conduction band of Ni-MOF-74 quickly due to the potential energy difference between the two. This shows that the recombination of photogenerated carriers in Mn_0.2Cd_0.8S can be greatly inhibited. Fluorescence spectroscopy and electrochemical characterization reveal that the composite catalyst has the longest carrier lifetime, the fastest charge transfer rate and the lowest overpotential compared with the Mn_0.2Cd_0.8S and Ni-MOF-74. The optimal hydrogen production rate of the composite can reach 7.104 mmol g^-1h^-1, which is 6.96 times that of Mn_0.2Cd_0.8S. This work provides a novel strategy for the modification of MnCdS-based photocatalysts by metal-organic framework materials.

Highly efficient photocatalytic H2 evolution over NiCo2S4/Mn0.5Cd0.5S: Bulk twinned homojunctions and interfacial heterojunctions

A twinned Mn_0.5Cd_0.5S (T-MCS) homojunction, consisting of wurtzite and zinc-blende Mn_0.5Cd_0.5S with different energy band structures, was fabricated using a facile hydrothermal method, resulting in the formation of a type-II bulk phase twinned homojunction. Furthermore, NiCo₂S₄ nanoparticles were deposited on the surface of T-MCS to form a surface heterojunction. The activities of T-MCS and NiCo₂S₄/T-MCS were tested in the photocatalytic H₂ evolution reaction. T-MCS exhibits a superior H₂ evolution rate of 61.4 mmol∙g^-1∙h^-1 under visible light (λ > 420 nm) irradiation owing to faster bulk phase charge separation, which is 8.2 and 1.9 times higher than those of wurtzite and zinc-blende Mn_0.5Cd_0.5S, respectively. Moreover, NiCo₂S₄ can facilitate interfacial electron transfer and can lower the H₂ evolution overpotential; the H₂ evolution rate is boosted to 127.3 mmol∙ g^-1∙h^-1 with an apparent quantum yield (AQY) of 23.4% with irradiation of 2 wt%-NiCo₂S₄/T-MCS under 400 ± 7.5 nm light. This work demonstrates that bulk phase twinned homojunctions and a surface heterojunction can combine to promote bulk and interfacial charge transfer and separation, simultaneously improving the kinetics of photocatalytic H₂ evolution.

Cauliflower-like Mn0.2Cd0.8S decorated with ReS2 nanosheets for boosting photocatalytic H2 evolution activity

A novel ReS2/Mn0.2Cd0.8S composite was fabricated and exhibited enhanced H2 evolution activity due to the modification of cauliflower-like Mn0.2Cd0.8S with ReS2 nanosheets.

A novel p-n Mn0.2Cd0.8S/NiWO4 heterojunction for highly efficient photocatalytic H2 production

Constructing a p-n heterojunction has been regarded as an effective way to restrain charge recombination and boost photocatalytic H2 production activity. Herein, a novel Mn0.2Cd0.8S/NiWO4 composite was fabricated by a hydrothermal process and which exhibited enhanced H2 production activity and excellent photostability. Particularly, the composite with 30 wt% of NiWO4 achieved the optimal H2 production rate of 17.76 mmol g-1 h-1, which was 2.9 times higher than that of Mn0.2Cd0.8S. The increased H2 production property was mainly due to the p-n heterojunction between Mn0.2Cd0.8S and NiWO4, which provided an efficient path for charge transfer and inhibited the photocorrosion of Mn0.2Cd0.8S. This work can offer technical support for the design and development of p-n heterojunctions that can be applied for photocatalytic H2 production.

MoS2-wrapped Mn0.2Cd0.8S nanospheres towards efficient photocatalytic H2 generation and CO2 reduction

MoS₂-wrapped Mn_0.2Cd_0.8S nanospheres with intimate interfacial contacts were fabricated, and exhibited excellent photocatalytic performances for H₂-generation and CO₂ reduction.

Simultaneous manipulation of ion doping and cocatalyst loading into Mn0.3Cd0.7S nanorods toward significantly improved H2 evolution

Ni₂P and Ni²⁺ jointly modified Mn_0.3Cd_0.7S photocatalysts were successfully fabricated via a facile solvothermal method. The loading of Ni₂P and the doping of Ni²⁺ proceeded simultaneously via a one-step process.

A sea-urchin-structured NiCo2O4 decorated Mn0.05Cd0.95S p–n heterojunction for enhanced photocatalytic hydrogen evolution

The development of low-cost and high-efficiency photocatalysts is an important way to realize photocatalytic hydrogen production.

O-MoS2/Mn0.5Cd0.5S composites with enhanced activity for visible-light-driven photocatalytic hydrogen evolution

The reaction mechanism of O-MoS₂/Mn_0.5Cd_0.5S for photocatalytic hydrogen evolution is put forward and the satisfactory hydrogen production rate of the optimized composite is superior to most of the Mn–Cd–S based catalysts reported.

Constructing highly dispersed 0D Co3S4 quantum dots/2D g-C3N4 nanosheets nanocomposites for excellent photocatalytic performance

The development of noble-metal-free catalysts with high efficiency photocatalytic properties is critical to the heterogeneous catalysis. Herein, zero-dimensional (0D) metal sulfide quantum dots/two-dimensional (2D) g-C₃N₄ nanosheets (Co₃S₄/CNNS) nanocomposites are synthesized by a two-step method, including the ways of in-situ deposition and water bath. The highly dispersed Co₃S₄ quantum dots (particle size is 2-4 nm) are evenly and tightly fixed on CNNS, which can be used as co-catalyst to effectively replace noble metals to improve the photocatalytic properties of CNNS. Co₃S₄/CNNS-900 has the apparent quantum efficiency, which is up to 7.85% at 400 nm. At the same time, the H₂ evolution rate of Co₃S₄/CNNS-900 is 20,536.4 μmol g^-1 h^-1, which is 555 times than CNNS. The excellent photocatalytic performance is due to the highly dispersed Co₃S₄ quantum dots on 2D CNNS, which facilitate the formation of more active sites, Co₃S₄/CNNS promotes the separation and migration of photogenerated carriers, shortens the migration distance of photogenerated carriers, and eventually leads to an increase of the photocatalytic performance.

Intense pulsed light, a promising technique to develop molybdenum sulfide catalysts for hydrogen evolution

We have demonstrated a simple and scalable fabrication process for defect-rich MoS₂ directly from ammonium tetrathiomolybdate precursor using intense pulse light treatment in milliseconds durations. The formation of MoS₂ from the precursor film after intense pulsed light exposure was confirmed with XPS, XRD, electron microscopy and Raman spectroscopy. The resulting material exhibited high activity for the hydrogen evolution reaction (HER) in acidic media, requiring merely 200 mV overpotential to reach a current density of 10 mA cm^-2. Additionally, the catalyst remained highly active for HER over extended durability testing with the overpotential increasing by 28 mV following 1000 cycles. The roll-to-roll amenable fabrication of this highly-active material could be adapted for mass production of electrodes comprised of earth-abundant materials for water splitting applications.

Environmentally Sustainable Synthesis of a CoFe2O4-TiO2/rGO Ternary Photocatalyst: A Highly Efficient and Stable Photocatalyst for High Production of Hydrogen (Solar Fuel)

Herein, a magnetically separable reduced graphene oxide (rGO)-supported CoFe₂O₄-TiO₂ photocatalyst was developed by a simple ultrasound-assisted wet impregnation method for efficient photocatalytic H₂ production. Integration of CoFe₂O₄ with TiO₂ induced the formation of Ti³⁺ sites that remarkably reduced the optical band gap of TiO₂ to 2.80 eV from 3.20 eV. Moreover, the addition of rGO improved the charge carrier separation by forming Ti-C bonds. Importantly, the CoFe₂O₄-TiO₂/rGO photocatalyst demonstrated significantly enhanced photocatalytic H₂ production compared to that from its individual counterparts such as TiO₂ and CoFe₂O₄-TiO₂, respectably. A maximum H₂ production rate of 76 559 μmol g^-1 h^-1 was achieved with a 20 wt % CoFe₂O₄- and 1 wt % rGO-loaded TiO₂ photocatalyst, which was approximately 14-fold enhancement when compared with the bare TiO₂. An apparent quantum yield of 12.97% at 400 nm was observed for the CoFe₂O₄-TiO₂/rGO photocatalyst under optimized reaction conditions. This remarkable enhancement can be attributed to synergistically improved charge carrier separation through Ti³⁺ sites and rGO support, viz., Ti-C bonds. The recyclability of the photocatalyst was ascertained over four consecutive cycles, indicating the stability of the photocatalyst. In addition, it is worth mentioning that the photocatalyst could be easily separated after the reaction using a simple magnet. Thus, we believe that this study may open a new way to prepare low-cost, noble-metal-free magnetic materials with TiO₂ for sustainable photocatalytic H₂ production.

In situ photodeposition of amorphous NixP on CdS nanorods for efficient visible-light photocatalytic H2 generation

Noble metal-free amorphous Ni_xP modified CdS with superior photocatalytic H₂ evolution activity has been successfully fabricated.

Synthesis of MnxCd1−xS nanorods and modification with CuS for extraordinarily superior photocatalytic H2 production

A series CuS/Mn_0.3Cd_0.7S photocatalysts with nanorod structures were successfully constructed and exhibited particularly high H₂ evolution performance from water splitting under visible light irradiation.

Photochemical route for synthesizing Co-P alloy decorated ZnIn2S4 with enhanced photocatalytic H2 production activity under visible light irradiation

A series of amorphous Co-P alloy modified ZnIn2S4 composite samples were synthesized through a one-step photochemical method. The as-prepared samples were systematically characterized and the photocatalytic activity for H2 production under visible-light irradiation was investigated. It was found that the Co-P/ZnIn2S4 composite samples exhibited higher photocatalytic activity, which is 44 times higher than that of pure ZnIn2S4 and higher than that of the 1 wt% Pt/ZnIn2S4 sample. After modifying with amorphous Co-P alloy, the composite samples showed enhanced photocurrent, reduced photoelectric impedance, weakened fluorescence intensity and extended fluorescence lifetime, which accelerate the separation and transfer of photoinduced charge effectively, thus improving the catalytic activity of the composite sample. This work could provide a new strategy for the design and synthesis of low-cost, high-efficiency composite materials for photocatalytic hydrogen evolution and is promising for energy conversion and utilization.

Construction of a novel BiSI/MoS2 nanocomposite with enhanced visible-light driven photocatalytic performance

A BiSI/MoS₂ nanocomposite was synthesized for the first time and used as a new efficient and stable visible light driven photocatalyst.