Photocatalytic hydrogen evolution activity over MoS 2 /ZnIn 2 S 4 microspheres

Anion vacancy engineered Cu/ZnIn2S4-VS/TiO2-VO S-scheme heterojunction for enhancing photocatalytic overall water splitting

Heterojunction materials for photocatalytic overall water splitting (POWS) become popular in recent times. However, even in the superior S-scheme heterojunction, the two semiconductor materials still do not have an efficient activity to separate and migrate photogenerated carriers. To further improve the charge separation and enhance the activity of POWS, a novel S-scheme heterojunction photocatalyst, Cu/ZnIn2S4-VS/TiO2-VO, was synthesized using solvothermal and calcination methods. The photocatalyst consists of Cu/ZnIn2S4 with sulfur vacancies (Cu/ZIS-VS) and TiO2 with oxygen vacancies (TiO2-VO). The resultant photocatalyst exhibited optimal hydrogen and oxygen evolution rates of 1245.3 μmol/g/h and 621.4 μmol/g/h, respectively. The apparent quantum efficiency reached 5.8 % at 365 nm. The corresponding characterization and theoretical calculations demonstrated the S-scheme heterojunction between Cu/ZIS-VS and TiO2-VO was successfully synthesized and resulted in a notable enhancement in the effective separation of carriers. Sulfur and oxygen vacancies in ZIS and TiO2, respectively, led to a reduction in their band gaps, which is beneficial for electron migration. Moreover, copper doping augmented the light absorption capabilities. Sulfur vacancies caused charge delocalization which facilitated the transfer of electrons and consequently enhanced the photocatalytic activity. This research provided an innovative perspective on the exploration and development of S-scheme heterojunctions aimed at POWS.

Dual S-scheme MoS2/ZnIn2S4/Graphene quantum dots ternary heterojunctions for highly efficient photocatalytic hydrogen evolution

The layered chalcogenide ZnIn2S4 (ZIS) exhibits photo-stability and a tunable band gap but is limited in photocatalytic applications, such as hydrogen (H2) production, due to rapid carrier recombination and slow charge separation. To overcome these limitations, we have synthesized a ternary MoS2/ZIS/graphene quantum dots (GQDs) heterojunction, wherein MoS2 and GQDs are strategically attached to ZIS interlaced nanoflakes, enhancing light absorption across the 500-1500 nm range. This heterojunction benefits from dual S-scheme interfaces between MoS2-ZIS and ZIS-GQDs, establishing directed internal electric fields (IEFs). These IEFs accelerate the transfer of photoinduced electrons from the conduction bands of MoS2 and GQDs to the valence band of ZIS, promoting rapid recombination with holes and facilitating efficient catalytic reactions with plentiful photoinduced electrons stemmed from the conduction band of ZIS. As a result, the photocatalytic H2 production rate of the MoS2/ZIS/GQDs heterojunction is measured at 21.63 mmol h-1 g-1, marking an increase of 36.7 times over pure ZIS. This research provides valuable insights into designing novel heterojunctions for improved charge separation and transfer for solar energy conversion applications.

A compendium of all-in-one solar-driven water splitting using ZnIn2S4-based photocatalysts: guiding the path from the past to the limitless future

Photocatalytic water splitting represents a leading approach to harness the abundant solar energy, producing hydrogen as a clean and sustainable energy carrier. Zinc indium sulfide (ZIS) emerges as one of the most captivating candidates attributed to its unique physicochemical and photophysical properties, attracting much interest and holding significant promise in this domain. To develop a highly efficient ZIS-based photocatalytic system for green energy production, it is paramount to comprehensively understand the strengths and limitations of ZIS, particularly within the framework of solar-driven water splitting. This review elucidates the three sequential steps that govern the overall efficiency of ZIS with a sharp focus on the mechanisms and inherent drawbacks associated with each phase, including commonly overlooked aspects such as the jeopardising photocorrosion issue, the neglected oxidative counter surface reaction kinetics in overall water splitting, the sluggish photocarrier dynamics and the undesired side redox reactions. Multifarious material design strategies are discussed to specifically mitigate the formidable limitations and bottleneck issues. This review concludes with the current state of ZIS-based photocatalytic water splitting systems, followed by personal perspectives aimed at elevating the field to practical consideration for future endeavours towards sustainable hydrogen production through solar-driven water splitting.

Oral Heterojunction Coupling Interventional Optical Fiber Mediates Synergistic Therapy for Orthotopic Rectal Cancer

Catalytic therapy has shown great potential for clinical application. However, conventional catalytic therapies rely on reactive oxygen species (ROS) as "therapeutic drugs," which have limitations in effectively inhibiting tumor recurrence and metastasis. Here, a biomimetic heterojunction catalyst is developed that can actively target orthotopic rectal cancer after oral administration. The heterojunction catalyst is composed of quatrefoil star-shaped BiVO4 (BVO) and ZnIn2S4 (ZIS) nanosheets through an in situ direct growth technique. Poly-norepinephrine and macrophage membrane coatings afford the biomimetic heterojunction catalyst (BVO/ZIS@M), which has high rectal cancer targeting and retention abilities. The coupled optical fiber intervention technology activates the multicenter coordination of five catalytic reactions of heterojunction catalysts, including two reduction reactions (O2→·O2 - and CO2→CO) and three oxidation reactions (H2O→·OH, GSH→GSSG, and LA→PA). These catalytic reactions not only induce immunogenic death in tumor cells through the efficient generation of ROS/CO and the consumption of GSH but also specifically lead to the use of lactic acid (LA) as an electron donor to improve catalytic activity and disrupt the LA-mediated immunosuppressive microenvironment, mediating synergistic catalysis and immunotherapy for orthotopic rectal cancer. Therefore, this optical fiber intervention triggered the combination of heterojunction catalytic therapy and immunotherapy, which exhibits prominent antitumor effects.

S-scheme homojunction of 0D cubic/2D hexagonal ZnIn2S4 for efficient photocatalytic reduction of nitroarenes

The targeted conversion of toxic nitroarenes to corresponding aminoarenes presents significant promise in simultaneously addressing environmental pollution concerns and producing value-added fine chemicals. In this study, we synthesize a 0D/2D ZnIn2S4 homojunction (CH-ZnIn2S4) by in situ growth of cubic ZnIn2S4 (C-ZnIn2S4) quantum dots onto the surface of ultrathin hexagonal ZnIn2S4 (H-ZnIn2S4) nanosheets for photocatalytic reduction of nitroarenes to aminoarenes using water as a hydrogen donor. The optimal performance of photocatalytic nitro reduction over the 0D/2D CH-ZnIn2S4 homojunction reaches 96.1% within 20 min of visible light irradiation, which is 2.45 and 1.52 times than that of C-ZnIn2S4 (39.3%) and H-ZnIn2S4 (63.3%), respectively. The improved photocatalytic performance can be attributed to the formation of a step-type S-scheme homojunction, characterized by identity chemical composition and natural lattice matching. The configuration enables continuous band bending and a low energy barrier of charge transportation, benefiting the charge transfer across the interface while maximizing their redox capabilities. Furthermore, the 2D structure of H-ZnIn2S4 nanosheets offers abundant surface sites to immobilize the 0D C-ZnIn2S4 that provides ample exposed active sites with low overpotential for HER, thereby ensuring high hydrogenation reduction activity of nitroarenes. The study is expected to inspire further interest in the reasonable design of homojunction structures for efficient and sustainable photocatalytic redox reactions.

Semimetal 1T' phase molybdenum sulfide decorated on zinc indium sulfide with S-scheme heterojunction for enhanced photocatalytic hydrogen evolution

Heterojunction engineering is an effective strategy to improve photocatalytic performance. Two-dimensional (2D)/2D semimetal 1T' phase molybdenum sulfide/zinc indium sulfide (1T'-MoS2/ZnIn2S4) S-scheme heterojunctions with tight and stable interfaces were synthesized by a simple hydrothermal synthesis method. Under the optimal 1T'-MoS2 loading ratio (5 wt%), the hydrogen production rate of 1T'-MoS2/ZnIn2S4 composites reaches 11.42 mmol h-1 g-1, which is 3.1 and 1.4 times higher than that of pure ZnIn2S4 (2.9 mmol h-1 g-1) and ZnIn2S4/Pt (8.01 mmol h-1 g-1), and the apparent quantum efficiency (AQE) reaches 53.17 % (λ = 370 nm). Semimetal 1T' phase MoS2 on ZnIn2S4 broadens the light absorption range, enhances the light absorption ability, promotes electron transfer, and offers abundant active sites. The establishment of S-scheme heterojunctions achieves the spatial separation of photogenerated charges and increases the reduction potential. This work provides insights for the design of novel photocatalysts.

Uniform-embeddable-distributed Ni3S2 cocatalyst inside and outside a sheet-like ZnIn2S4 photocatalyst for boosting photocatalytic hydrogen evolution

The rational cocatalyst design is considered a significant route to boost the solar-energy conversion efficiency for photocatalytic H₂ generation. However, the traditional cocatalyst-loading on the surface of a photocatalyst easily leads to scarce exposed active sites induced by the agglomeration of cocatalysts and a hindrance of the light absorption of the photocatalyst, thus significantly limiting the enhancement of the photocatalytic H₂-generation performance. Herein, a new concept of uniform-embeddable-distributed cocatalysts is put forward. Consequently, uniform-embeddable-distributed cocatalysts of Ni₃S₂ were designed and constructed inside and outside of the nanosheet-like ZnIn₂S₄ photocatalyst to form a Ni₃S₂/ZnIn₂S₄ binary system (UEDNiS/ZIS). The unique uniform-embeddable-distributed Ni₃S₂ cocatalyst (UEDNiS) could provide abundant exposed active sites, facilitate the spatial separation and ordered transfer of charges inside and outside of ZnIn₂S₄ nanosheets, and reduce the hydrogen-adsorption free energy for photocatalytic H₂-generation reactions. As a result, UEDNiS/ZIS exhibited a high photocatalytic H₂-generation rate of 60 μmol h^-1 under visible-light irradiation, almost 7.8 and 2.8 times higher than pristine ZnIn₂S₄ and the traditional surface-loaded Ni₃S₂/ZnIn₂S₄ (TSLNiS/ZIS), respectively. This work represents a new cocatalyst-design approach to realize high-efficiency hydrogen evolution in binary heterostructured photocatalytic systems.

Ultrasensitive photoelectrochemical aptasensor for detecting telomerase activity based on Ag2S/Ag decorated ZnIn2S4/C3N4 3D/2D Z-scheme heterostructures and amplified by Au/Cu2+-boron-nitride nanozyme

Enzyme-mediated signal amplification strategies have gained substantial attention in photoelectrochemical (PEC) biosensing, while natural enzyme on the photoelectrode inevitably obstructs the interfacial electron transfer, in turn deteriorating the photocurrent responses. Herein, Au nanoparticles and Cu²⁺-modified boron nitride nanosheets (AuNPs/Cu²⁺-BNNS) behaved as nanozyme to achieve remarkable magnification in the PEC signals from a novel signal-off aptasensor for ultra-sensitive assay of telomerase (TE) activity based on Ag₂S/Ag nanoparticles decorated ZnIn₂S₄/C₃N₄ Z-scheme heterostructures (termed as Ag₂S/Ag/ZnIn₂S₄/C₃N₄, synthesized by hydrothermal treatment). Specifically, telomerase primer sequences (TS) were extended by TE in the presence of deoxyribonucleoside triphosphates (dNTPs), which was directly bond with the thiol modified complementary DNA (cDNA), achieving efficient linkage with the nanozyme via Au-S bond. The immobilized nanoenzyme catalyzed the oxidation between 4-chloro-1-naphthol (4-CN) and H₂O₂ to generate insoluble precipitation on the photo-electrode. By virtue of the inhibited PEC signals with the TE-enabled TS extension, an aptasensor for assay of TE activity was developed, showing the wide linear range of 50-5×10⁵ cell mL^-1 and a low detection limit of 19 cell mL^-1. This work provides some valuable guidelines for developing advanced nanozyme-based PEC bioanalysis of diverse cancer cells.

Construction of a hierarchical ZnIn2S4/C3N4 heterojunction for the enhanced photocatalytic degradation of tetracycline

Efficient charge separation and sufficiently exposed active sites are both critical limiting factors for solar-driven organic contaminant degradation. Herein, we describe a hierarchical heterojunction photocatalyst fabricated by the in situ growth of ZnIn₂S₄ nanosheets on micro-tubular C₃N₄ (denoted as ZIS/TCN). This ZIS/TCN heterojunction photocatalyst can take advantage of the hollow structure with stronger light absorption capacity and more active sites, and its heterostructure can accelerate the separation and transfer of photogenerated charge carriers. The optimized ZIS/TCN-3 exhibits superb photocatalytic efficiency for the degradation of tetracycline (86.1%, 60 min), maintains excellent stability and recyclability, and provides a facile strategy for the synthesis of efficient heterojuction photocatalysts towards wastewater treatment. In addition, the plausible photocatalytic degradation pathway of tetracycline is proposed according to the intermediates identified by LC-mass analysis.

Spatial carrier separation in cobalt phosphate deposited ZnIn2S4 nanosheets for efficient photocatalytic hydrogen evolution

Developing photocatalyst with effective charge separation and fast surface reaction kinetics is crucial to high-efficiency photocatalytic H₂ evolution. Herein we spatially separate the reductive and oxidative reaction sites of ZnIn₂S₄ nanosheet and accelerate the hole transfer process by simply depositing cobalt phosphate (CoH_xPO_y, noted as Co-Pi), a non-precious co-catalyst, on its basal plane. Theoretical calculations combined with comprehensive characterizations reveal that Zn vacancies induced deep local energy levels serve as hole trap states to pin the photogenerated holes on (001) surface of ZnIn₂S₄. Upon Co-Pi deposition, Co atoms preferentially bond with S atoms nearby the Zn vacancies of ZnIn₂S₄. Taking advantage of the formation of Co-S bonds, Co-Pi acts as a hole receptor to extract the trapped holes effectively. As the photocatalytic activity of ZnIn₂S₄ is caused by active S atoms on its edge side, deposition of Co-Pi on planar side of nanosheets helps electron-hole migration to different facets. As a result of inert facet activation and spatial carrier separation, Co-Pi/ZnIn₂S₄ exhibits a superior photocatalytic H₂ evolution rate of 10.19 mmol g^-1h^-1 under visible light, which is superior to most of reported ZnIn₂S₄-based photocatalysts. This work will provide novel insights into the activation of inert basal planes of two-dimensional photocatalysts.

ZnIn2 S4 -Based Photocatalysts for Energy and Environmental Applications

As a fascinating visible-light-responsive photocatalyst, zinc indium sulfide (ZnIn₂ S₄ ) has attracted extensive interdisciplinary interest and is expected to become a new research hotspot in the near future, due to its nontoxicity, suitable band gap, high physicochemical stability and durability, ease of synthesis, and appealing catalytic activity. This review provides an overview on the recent advances in ZnIn₂ S₄ -based photocatalysts. First, the crystal structures and band structures of ZnIn₂ S₄ are briefly introduced. Then, various modulation strategies of ZnIn₂ S₄ are outlined for better photocatalytic performance, which includes morphology and structure engineering, vacancy engineering, doping engineering, hydrogenation engineering, and the construction of ZnIn₂ S₄ -based composites. Thereafter, the potential applications in the energy and environmental area of ZnIn₂ S₄ -based photocatalysts are summarized. Finally, some personal perspectives about the promises and prospects of this emerging material are provided.

Constructing a 2D/2D heterojunction of MoSe2/ZnIn2S4 nanosheets for enhanced photocatalytic hydrogen evolution

2D/2D MoSe₂/ZnIn₂S₄ heterojunctions exhibit high photocatalytic activity owing to MoSe₂ as a cocatalyst, which provides more active sites, reducing the overpotential and the activation energy for water reduction.

Constructing CuNi dual active sites on ZnIn2S4 for highly photocatalytic hydrogen evolution

Novel CuNi bimetal-modified ZnIn₂S₄ photocatalysts with enhanced photocatalytic hydrogen evolution performance have been explored. The possible mechanism of the synergistic effect and spillover effect between Cu and Ni were proposed.

Enhanced visible-light-driven photocatalytic H2 production and Cr(vi) reduction of a ZnIn2S4/MoS2 heterojunction synthesized by the biomolecule-assisted microwave heating method

Photocatalytic applications of flower-like ZnIn₂S₄/MoS₂ composite, synthesized by biomolecule-assisted microwave heating method, in H₂ evolution and Cr(vi) reduction reactions.

The Effect of Cu and Ga Doped ZnIn2S4 under Visible Light on the High Generation of H2 Production

A Cu+ and Ga3+ co-doped ZnIn2S4 photocatalyst (Zn(1−2x)(CuGa)xIn2S4) with controlled band gap was prepared via a simple one-step solvothermal method. Zn(1−2x)(CuGa)xIn2S4 acted as an efficient photocatalyst for H2 evolution under visible light irradiation (λ > 420 nm; 4500 µW/cm2). The effects of the (Cu and Ga)/Zn molar ratios of Zn(1−2x)(CuGa)xIn2S4 on the crystal structure (hexagonal structure), morphology (microsphere-like flower), optical property (light harvesting activity and charge hole separation ability), and photocatalytic activity have been investigated in detail. The maximum H2 evolution rate (1650 µmol·h−1·g−1) was achieved over Zn0.84(CuGa)0.13In2S4, showing a 3.3 times higher rate than that of untreated ZnIn2S4. The bandgap energy of Zn(1−2x)(CuGa)xIn2S4 decreased from 2.67 to 1.90 eV as the amount of doping Cu+ and Ga3+ increased.

Amorphous MoS2 decorated on uniform Cd0.8Zn0.2S microspheres with dramatically improved photocatalytic hydrogen evolution performance

A series of Cd_1−xZn_xS solid solutions and samples of amorphous MoS₂ decorated on Cd_1−xZn_xS microspheres were successfully prepared.

Tuning Band Alignments and Charge-Transport Properties through MoSe2 Bridging between MoS2 and Cadmium Sulfide for Enhanced Hydrogen Production

Transition-metal dichalcogenide materials play a major role in the state-of-the-art innovations for energy conversion because of potential applications resulting from their unique properties. These materials additionally show inordinate potential toward the progress of hygienic power sources to deal with increasing environmental disputes at the time of skyrocketing energy demands. Herein, we report earth-abundant, few-layered, MoSe₂-bridged MoS₂/cadmium sulfide (CdS) nanocomposites, which reduce photogenerated electron and hole recombination by effectively separating charge carriers to achieve a high photocatalytic efficiency. Accordingly, the MoSe₂-bridged MoS₂/CdS system produced effective hydrogen (193 μmol·h^-1) as that of water using lactic acid as a hole scavenger with the irradiation of solar light. The presence of few-layered MoSe₂ bridges in MoS₂/CdS successfully separates photogenerated charge carriers, thereby enhancing the shuttling of electrons on the surface to active edge sites. To the best of our knowledge, this few-layered MoSe₂-bridged MoS₂/CdS system exhibits the most effective concert among altogether-reported MoS₂-based CdS composites. Notably, these findings with ample prospective for the development of enormously real photocatalytic systems are due to their economically viable and extraordinary efficiency.

Light-assisted synthesis MoSx as a noble metal free cocatalyst formed heterojunction CdS/Co3O4 photocatalyst for visible light harvesting and spatial charge separation

In this paper, a novel photocatalyst with visible light harvesting and spatial charge separation is reported, in which cobalt oxide (acting as a hole trap) and molybdenum sulfide (acting as an electron trap) are assembled on the surface of cadmium sulfide nanorods. The MoSx/CdS/Co3O4 composite photocatalyst shows a high H2 evolution with a yield of 537.51 μmol in 5 h, which is 35.53 times greater than over pristine CdS (15.13 μmol). The detailed underlying reason was comprehensively studied and understood by means of SEM, TEM, XRD, XPS, UV-vis DRS, BET; in particular, investigation of their photoelectrochemical properties with photocurrent, voltammetric scanning, fluorescence spectra etc. The high photocurrent response, the lower overpotential (-0.37 V vs. SCE), the faster electron transfer rate constant (ket = 4.23 × 109 s-1) and the short fluorescence lifetime (0.457 ns) supported the efficient spatial charge transfer between CdS and MoSx as well as Co3O4. The simultaneous loading of bicocatalysts can significantly improve the photo-induced spatial charge separation of CdS because MoSx nanoparticles act as an electron trap to rapidly transfer electrons from CdS while Co3O4 acts as a hole trap to quickly transfer holes, enhancing its photocatalytic performance as well.

Ultrathin layered MoS2 nanosheets with rich active sites for enhanced visible light photocatalytic activity

Edge-rich active sites of ultrathin layered molybdenum disulphide (MoS₂) nanosheets were synthesized by a hydrothermal method. The effect of pH on the formation of MoS₂ nanosheets and their photocatalytic response have been investigated. Structural and elemental analysis confirm the presence of S–Mo–S in the composition. Morphological analysis confirms the presence of ultrathin layered nanosheets with a sheet thickness of 10–28 nm at pH 1. The interplanar spacing of MoS₂ layers is in good agreement with the X-ray diffraction and high-resolution transmission electron microscopy results. A comparative study of the photocatalytic performance for the degradation of methylene blue (MB) and rhodamine B (RhB) by ultrathin layered MoS₂ under visible light irradiation was performed. The photocatalytic activity of the edge-rich ultrathin layered nanosheets showed a fast response time of 36 min with the degradation rate of 95.3% of MB and 41.1% of RhB. The photocatalytic degradation of MB was superior to that of RhB because of the excellent adsorption of MB than that of RhB. Photogenerated superoxide radicals were the key active species for the decomposition of organic compounds present in water, as evidenced by scavenger studies.

Edge-rich active sites of ultrathin layered molybdenum disulphide (MoS₂) nanosheets were synthesized by a hydrothermal method.