Fabrication of TiO 2 /MoS 2 Composite Photocatalyst and Its Photocatalytic Mechanism for Degradation of Methyl Orange under Visible Light

Designing a TiO2-MoO3-BMIMBr nanocomposite by a solvohydrothermal method using an ionic liquid aqueous mixture: an ultra high sensitive acetaminophen sensor

This study shows a simplistic, efficient procedure to synthesize TiO₂-MoO₃-BMIMBr nanocomposites. Powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy have all been used to completely analyse the materials. The detection of acetaminophen (AC) has been examined at a modified glassy carbon electrode with TiO₂-MoO₃-BMIMBr nanocomposites. Moreover, the electrochemical behavior of the nanocomposite modified electrode has been studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The linear response of AC was observed in the range 8.26-124.03 nM. The sensitivity and detection limits (S/N = 3) were found to be 1.16 μA L mol^-1 cm^-2 and 11.54 nM by CV and 24 μA L mol^-1 cm^-2 and 8.16 nM by DPV respectively.

Cost-Effective and Highly Efficient Manganese-Doped MoS2 Nanosheets as Visible-Light-Driven Photocatalysts for Wastewater Treatment

One of the main objectives in wastewater treatment and sustainable energy production is to find photocatalysts that are favorably efficient and cost-effective. Transition-metal dichalcogenides (TMDs) are promising photocatalytic materials; out of all, MoS₂ is extensively studied as a cocatalyst in the TMD library due to its exceptional photocatalytic activity for the degradation of organic dyes due to its distinctive morphology, adequate optical absorption, and rich active sites. However, sulfur ions on the active edges facilitate the catalytic activity of MoS₂. On the basal planes, sulfur ions are catalytically inactive. Injecting metal atoms into the MoS₂ lattice is a handy approach for triggering the surface of the basal planes and enriching catalytically active sites. Effective band gap engineering, sulfur edges, and improved optical absorption of Mn-doped MoS₂ nanostructures are promising for improving their charge separation and photostimulated dye degradation activity. The percentage of dye degradation of MB under visible-light irradiations was found to be 89.87 and 100% for pristine and 20% Mn-doped MoS₂ in 150 and 90 min, respectively. However, the degradation of MB dye was increased when the doping concentration in MoS₂ increased from 5 to 20%. The kinetic study showed that the first-order kinetic model described the photodegradation mechanism well. After four cycles, the 20% Mn-doped MoS₂ catalysts maintained comparable catalytic efficacy, indicating its excellent stability. The results demonstrated that the Mn-doped MoS₂ nanostructures exhibit exceptional visible-light-driven photocatalytic activity and could perform well as a catalyst for industrial wastewater treatment.

Biomolecule Protective and Photocatalytic Potential of Cellulose Supported MoS2/GO Nanocomposite

In the current study, cellulose/MoS2/GO nanocomposite has been synthesized by a hydrothermal method. Reports published regarding efficiency of Mo and graphene oxide-based nanocomposites for environmental remediation motivated to synthesize cellulose supported MoS2/GO nanocomposite. Formation of nanocomposite was initially confirmed by UV-visible and FTIR spectroscopic techniques. Particle size and morphology of the nanocomposite were assessed by scanning electron microscopy (SEM), and it was found having particle size ranging from 50 to 80 nm and heterogeneous structure. The XRD analysis also confirmed the structure of the nanocomposite having cellulose, MoS2, and GO. The synthesized nanocomposite was further tested for biomolecule protective potential employing different radical scavenging assays. Results of radical DPPH● (50%) and ABTS ●+ (51%) scavenging studies indicate that nanocomposites can be used as a biomolecule protective agent. In addition, nanocomposite was also evaluated for photocatalytic potential, and the results showed excellent photocatalytic properties for the degradation of 4-nitrophenol up to 75% and methylene blue and methyl orange up to 85% and 70%, respectively. So, this study confirmed that cellulose supported/stabilized MoS2/GO nanocomposite can be synthesized by an ecofriendly, cost-effective, and easy hydrothermal method having promising biomolecule protective and photocatalytic potential.

2D/1D MoS2 /TiO2 Heterostructure Photocatalyst with a Switchable CO2 Reduction Product

Regulating the transfer pathway of charge carriers in heterostructure photocatalysts is of great importance for selective CO₂ photoreduction. Herein, the charge transfer pathway and in turn the redox potential succeeded to regulate in 2D MoS₂ /1D TiO₂ heterostructure by varying the light wavelength range. Several in situ measurements and experiments confirm that charge transfer follows either an S-scheme mechanism under simulated solar irradiation or a heterojunction approach under visible light illumination, elucidating the switchable property of the MoS₂ /TiO₂ heterostructure. Replacing the simulated sunlight irradiation with the visible light illumination switches the photocatalytic CO₂ reduction product from CO to CH_4. ¹³ CO₂ isotope labeling confirms that CO₂ is the source of carbon for CH₄ and CO products. The photoelectrochemical H₂ generation further supports the switching property of MoS₂ /TiO₂ . Unlike previous studies, density functional theory calculations are used to investigate the band structure of Van der Waals MoS₂ /TiO₂ S scheme after contact, allowing to propose accurate charge transfer pathways, in which the theoretical results are well matched with the experimental results. This work opens the opportunity to develop photocatalysts with switchable charge transport and tunable redox potential for selective artificial photosynthesis.

Photocatalytic degradation of dye wastewater by stepwise assembling PVA aerogel/TiO2/MoS2/Au composites in visible light

A PVA aerogel/TiO₂/MoS₂/Au catalyst formed gradually using a hydrothermal method is used to degrade Rhodamine B. SEM and TEM results show that the composite presents a uniform and well-structured porous network structure, high specific surface area and large pore diameter were proved by the results of nitrogen adsorption measurement. UV-vis DRS and PL results indicate that the composite has a high absorption rate in the visible light range, and the recombination of photogenerated electron-hole pairs can be effectively inhibited because the composite material forms a heterojunction. In the photocatalytic degradation experiment of Rhodamine B, the composite material shows high photocatalytic performance, which can reach 86% in two hours of light. The photocatalysts supported by PVA are easy to recover and have high catalytic performance even after five recycles. The study shows that PVA/TiO₂/MoS₂/Au composite material has great potential to be used for the degradation of dye wastewater.

Titanium dioxide based nanocomposites - Current trends and emerging strategies for the photocatalytic degradation of ruinous environmental pollutants

Many ruinous pollutants are omnipresent in the environment and among them; pesticides are xenobiotic and pose to be a bio-recalcitrance. Their detrimental ecological and environmental impacts attract attention of environmental excerpts and the surge of stringent regulations have endows the need of a technically feasible treatment. This critical review emphasizes about the occurrence, abundance and fate of structurally distinct pesticides in different environment. The practiced remedial strategies and in particular, the advanced oxidation processes (AOPs) those utilize the photo-catalytic properties of nano-composites for the degradation of pollutants are critically discussed. Photo-catalytic degradation utilizes many composite materials at nano-scale level, wherein synthesis of nano-composites with appropriate precursors and other adjoining functional moieties are of prime importance. Therefore, suitable starter materials along with the reaction conditions are prerequisite for effectively tailoring the nano-composites. The aforementioned aspects and their customized applications are critically discussed. The associated challenges, opportunities and process economics of degradation using photo-catalytic AOP techniques are highlighted and in addition, the review tries to explain how best the photo-degradation can be a stand-alone tool with a societal importance. Conclusively, the future prospects for undertaking new researches in photo-catalytic breakdown of pollutants that can be judiciously sustainable.

Edge Rich Ultrathin Layered MoS2 Nanostructures for Superior Visible Light Photocatalytic Activity

Nanostructures of layered 2D materials have been proven one of the significant recent trends for visible-light-driven photocatalysis because of their unique morphology, effective optical adsorption, and rich active sites. Herein, we synthesized ultrathin-layered MoS₂ nanoflowers and nanosheets with rich active sites by using a facile hydrothermal technique. The photocatalytic performance of the as-synthesized MoS₂ nanoflowers (NF) and nanosheets (NS) were investigated for the photodegradation of MB (methylene blue), MG (malachite Green), and RhB (rhodamine B) dye under visible light irradiations. Ultrathin-layered nanoflowers showed faster degradation (96% in 150 min) in RhB under visible light irradiation, probably due to a large number of active sites and high available surface area. The kinetic study demonstrated that the first-order kinetic model best explained the process of photodegradation. The MoS₂ nanoflowers catalysts has similar catalytic performance after four consecutive cyclic performances, demonstrating their good stability. The results showed that the MoS₂ nanoflowers have outstanding visible-light-driven photocatalytic activity and could be an effective catalyst for industrial wastewater treatment.

Hydrothermal Synthesis of 1T-MoS2/Pelagic Clay Composite and Its Application in the Catalytic Reduction of 4-Nitrophenol

Pelagic clay is an emerging marine resource with strong hydrophilicity, fine particles and a large specific surface area. In this work, a 1T-MoS2/pelagic clay composite was fabricated by hydrothermal synthesis. In the composite, 1T-MoS2 nanosheets are evenly dispersed on the surface of the clay minerals, significantly reducing the agglomeration of MoS2. Compared with pure 1T-MoS2, the 1T-MoS2 nanosheets generated on the surface of pelagic clay have significantly smaller lateral dimensions and thicknesses. Moreover, the specific surface area is much larger than that of the pure 1T-MoS2 nanosheets fabricated by the same method, indicating that the active sites of the MoS2 sheets are fully exposed. In addition, the composite exhibited excellent hydrophilicity, leading to a high dispersibility in aqueous solutions. In this work, the composite was used as a catalyst in the reduction of 4-nitrophenol (4-NP), and the conversion of 4-NP reached up to 96.7%. This result shows that the 1T-MoS2/pelagic clay composite is a promising catalyst in a variety of reactions.

UV SPECTROSCOPY AND KINETIC RESEARCH OF PHOTODEGRADATION OF METHYL ORANGE IN THE PRESENCE OF TITANIUM DIOXIDE AND β-CYCLODEXTRIN OR ITS DERIVATIVES

The research is devoted to the study of the effect of β-cyclodextrin (β-CD) and its derivatives on the photocatalytic degradation of methyl orange in aqueous solutions in the presence of titanium dioxide. It has been shown that the kinetics of photodegradation of methyl orange is more accurately described by the pseudo first order equation for all investigated pH values. In the presence of cyclodextrins β-CD and 2-hydroxypropyl-β-cyclodextrin, acceleration of photodegradation was observed only after 30 min of irradiation. As a result, the oxidation of hydroxyl groups of cyclodextrin occurred. A significant slowdown in photodestruction in the TiO2-β-CD sample during the first 45 min is explained by the formation of inclusion complexes of cyclodextrin with methyl orange, which prevented the destruction of dye. The use of the β-cyclodextrin, its derivatives and increasing the acidity of the medium accelerates the processes of photodestruction of methyl orange in distilled and natural waters. Methyl orange was decolorized for 20 – 25 min in solutions of all investigated cyclodextrin derivatives at pH 2.5. The destruction of methyl orange was most effective with the use of sulfobutyl ether β-CD. The bactericidal lamp (λ = 254 nm) allows to increase the rate of destruction during the irradiation process. Methyl orange discolored much faster under the action of a bactericidal lamp than using only ultraviolet lamps with λ = 365 nm. A slight slowdown in the decomposition process is observed after several irradiation cycles. This may be due to the influence of the formed products of destruction. However, under such conditions, the by-products of reactions decompose much faster. The use of cyclodextrins is possible without significant loss of efficiency up to 8 cycles.

Toxicity evaluation of bulk and nanosheet MoS2 catalysts using battery bioassays

Herein, the main aim is to study the influence of the materials' structural properties on their ecotoxicological properties. The acute toxicity of the bulk (molybdenum disulfide) MoS₂ and 2D nanosheet MoS₂ was investigated using organisms of four different taxonomic groups. Ultrasound-assisted liquid-phase exfoliation method was used for preparing 2D nanosheets from bulk MoS₂. Bulk and nanosheet MoS₂ were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analyses. The acute toxicity of the bulk and nanosheet MoS₂ catalysts was evaluated with four different bioassays using the test organisms Vibrio fischeri (a marine photobacterium), Pseudokirchnerialla subcapitata (a freshwater microalga), Daphnia magna (a freshwater crustacean) and the freshwater duckweed Spirodela polyrhiza. The toxic effect of the materials depended on their structural/size features and the type/sensitivity of the test organism. Generally speaking, bulk MoS₂ was more toxic than its nanosheet form. The freshwater crustacean Daphnia magna appeared to be the most suitable, easy-to-handle, and at the same time sensitive test organism for bulk and nanosheet MoS₂ among the tested organisms.

Symbiotic composite composed of MoS2 and pelagic clay with enhanced disinfection efficiency

Molybdenum disulfide (MoS2) has attracted increasing attention as a promising photocatalyst. In addition to its application in photocatalytic hydrogen production and pollutant degradation, MoS2 is also used in water disinfection. However, its poor disinfection performance limits its practical utility. Herein, we prepared a symbiotic composite composed of MoS2 and pelagic clay (MoS2/PC) as a photocatalyst for water disinfection. The composite achieved a high disinfection rate of 99.95% to Escherichia coli (E. coli) under visible light illumination, which is significantly higher than that of bulk MoS2 (61.87%). Characterization shows that abundant hydroxyl groups in illite/montmorillonite (I/M) formed during hydrothermal synthesis of MoS2, which contributed to the enhanced disinfection activity. Those hydroxyl groups can attract photogenerated holes through electrostatic attraction, and facilitate the separation of photogenerated charge carriers, thereby enhancing the disinfection activity. Moreover, the good hydrophilicity of pelagic clay improves the dispersity of MoS2 in water, which is beneficial for its utility in aqueous solutions. In addition, the symbiotic structure restricts the growth and aggregation of MoS2 nanosheets and shortens the diffusion distance of charge carriers to the material surface, further reducing the recombination of electrons and holes. This study provides a way to improve the disinfection activity of MoS2 and also sheds light on high value-added utilization of pelagic clay.

Synthesis and Characterization of Co-ZnO and Evaluation of Its Photocatalytic Activity for Photodegradation of Methyl Orange

Photocatalysis is one of the techniques used for the eradication of organic pollutants from wastewater. In this study, Co-ZnO was tested as a photocatalyst for the degradation of methyl orange under irradiation of visible light. Co-ZnO loaded with 5%, 10%, and 15% Co was prepared by the precipitation method. The advanced techniques including X-ray diffraction, X-ray photoelectron spectroscopy, diffuse reflectance UV-visible spectroscopy, photoelectrochemical measurements, temperature-programmed desorption, photoluminescence, and fluorescence spectroscopy related to OH^• measurements were used for characterization of prepared Co-ZnO. Experiments showed that 10% Co-ZnO was a highly efficient catalyst for the photodegradation of methyl orange as compared to ZnO. The enhanced photocatalytic activity of Co-ZnO is attributed to the implantation of Co which inhibits the electron-hole recombination. A 100 mg/L solution of methyl orange dye was completely degraded within 130 min. The reaction kinetics has been described in terms of the Eley-Rideal mechanism.

Facile synthesis and defect optimization of 2D-layered MoS2 on TiO2 heterostructure for industrial effluent, wastewater treatments

Current research is paying much attention to heterojunction nanostructures. Owing to its versatile characteristics such as stimulating morphology, affluent surface-oxygen-vacancies and chemical compositions for enhanced generation of reactive oxygen species. Herein, we report the hydrothermally synthesized TiO₂@MoS₂ heterojunction nanostructure for the effective production of photoinduced charge carriers to enhance the photocatalytic capability. XRD analysis illustrated the crystalline size of CTAB capped TiO₂, MoS₂@TiO₂ and L-Cysteine capped MoS₂@TiO₂ as 12.6, 11.7 and 10.2 nm, respectively. The bandgap of the samples analyzed by UV–Visible spectroscopy are 3.57, 3.66 and 3.94 eV. PL spectra of anatase phase titania shows the peaks present at and above 400 nm are ascribed to the defects in the crystalline structure in the form of oxygen vacancies. HRTEM reveals the existence of hexagonal layered MoS₂ formation on the spherical shaped TiO₂ nanoparticles at the interface. X-ray photoelectron spectroscopy recommends the chemical interactions between MoS₂ and TiO_2, specifically, oxygen vacancies. In addition, the electrochemical impedance spectroscopy studies observed that L-MT sample performed low charge transfer resistance (336.7 Ω cm²) that promotes the migration of electrons and interfacial charge separation. The photocatalytic performance is evaluated by quantifying the rate of Congo red dye degradation under visible light irradiation, and the decomposition efficiency was found to be 97%. The electron trapping recombination and plausible photocatalytic mechanism are also explored, and the reported work could be an excellent complement for industrial wastewater treatment.

Synthesis, Characterization and Photocatalytic Activity of MoS2/ZnSe Heterostructures for the Degradation of Levofloxacin

Antibiotics have been extensively used over the last few decades. Due to their extensive usage and persistence in the environment, they are considered as emergent pollutants. It is, therefore, important to synthesize new materials for efficient antibiotic degradation. Herein, we report the MoS2/ZnSe heterostructures prepared by a simple ultrasonication method. Heterostructures were prepared with different ratios of MoS2 and ZnSe, i.e., 1:3, 1:1 and 3:1. Characterization of the heterostructures was done by UV-vis diffused reflectance spectroscopy (UV-vis-DRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and photoluminescence (PL) techniques to understand the morphology and surface chemistry. The results show that an efficient interface was formed to harness the visible light and degrade levofloxacin, which was monitored by gradual decreases in the UV-vis absorbance signal of levofloxacin. Among the prepared heterostructures and their pure counter parts, MoS2/ZnSe 3:1 (3:1 MZ) showed a better degradation activity of 73.2% as compared to pure MoS2 (29%) and ZnSe (17.1%) in the presence of visible light in a time span of two hours. The reusability studies showed that the catalytic performance of 3:1 MZ did not decrease significantly after three cycles. Moreover, the morphology and the crystal structure also remained unchanged.

Optimization of Photogenerated Charge Carrier Lifetimes in ALD Grown TiO2 for Photonic Applications

Titanium dioxide (TiO₂) thin films are widely employed for photocatalytic and photovoltaic applications where the long lifetime of charge carriers is a paramount requirement for the device efficiency. To ensure the long lifetime, a high temperature treatment is used which restricts the applicability of TiO₂ in devices incorporating organic or polymer components. In this study, we exploited low temperature (100–150 °C) atomic layer deposition (ALD) of 30 nm TiO₂ thin films from tetrakis(dimethylamido)titanium. The deposition was followed by a heat treatment in air to find the minimum temperature requirements for the film fabrication without compromising the carrier lifetime. Femto-to nanosecond transient absorption spectroscopy was used to determine the lifetimes, and grazing incidence X-ray diffraction was employed for structural analysis. The optimal result was obtained for the TiO₂ thin films grown at 150 °C and heat-treated at as low as 300 °C. The deposited thin films were amorphous and crystallized into anatase phase upon heat treatment at 300–500 °C. The average carrier lifetime for amorphous TiO₂ is few picoseconds but increases to >400 ps upon crystallization at 500 °C. The samples deposited at 100 °C were also crystallized as anatase but the carrier lifetime was <100 ps.

Crystallization of TiO2-MoS2 Hybrid Material under Hydrothermal Treatment and Its Electrochemical Performance

Hydrothermal crystallization was used to synthesize an advanced hybrid system containing titania and molybdenum disulfide (with a TiO₂:MoS₂ molar ratio of 1:1). The way in which the conditions of hydrothermal treatment (180 and 200 °C) and thermal treatment (500 °C) affect the physicochemical properties of the products was determined. A physicochemical analysis of the fabricated materials included the determination of the microstructure and morphology (scanning and transmission electron microscopy—SEM and TEM), crystalline structure (X-ray diffraction method—XRD), chemical surface composition (energy dispersive X-ray spectroscopy—EDS) and parameters of the porous structure (low-temperature N₂ sorption), as well as the chemical surface concentration (X-ray photoelectron spectroscop—XPS). It is well known that lithium-ion batteries (LIBs) represent a renewable energy source and a type of energy storage device. The increased demand for energy means that new materials with higher energy and power densities continue to be the subject of investigation. The objective of this research was to obtain a new electrode (anode) component characterized by high work efficiency and good electrochemical properties. The synthesized TiO₂-MoS₂ material exhibited much better electrochemical stability than pure MoS₂ (commercial), but with a specific capacity ca. 630 mAh/g at a current density of 100 mA/g.

Design of a new electrochemical sensing system based on MoS2–TiO2/reduced graphene oxide nanocomposite for the detection of paracetamol

Synthetic route for the MoS₂–TiO₂/rGO nanocomposite and the electrode reaction for paracetamol.

Two-dimensional MoS2 nanosheet-modified oxygen defect-rich TiO2 nanoparticles for light emission and photocatalytic applications

MoS₂/TiO₂ nanohybrids efficiently decompose organic pollutants under sunlight due to the combined effects of defect creation and hetero-junction formation.

Insights into the TiO2-Based Photocatalytic Systems and Their Mechanisms

Photocatalysis is a multifunctional phenomenon that can be employed for energy applications such as H2 production, CO2 reduction into fuels, and environmental applications such as pollutant degradations, antibacterial disinfection, etc. In this direction, it is not an exaggerated fact that TiO2 is blooming in the field of photocatalysis, which is largely explored for various photocatalytic applications. The deeper understanding of TiO2 photocatalysis has led to the design of new photocatalytic materials with multiple functionalities. Accordingly, this paper exclusively reviews the recent developments in the modification of TiO2 photocatalyst towards the understanding of its photocatalytic mechanisms. These modifications generally involve the physical and chemical changes in TiO2 such as anisotropic structuring and integration with other metal oxides, plasmonic materials, carbon-based materials, etc. Such modifications essentially lead to the changes in the energy structure of TiO2 that largely boosts up the photocatalytic process via enhancing the band structure alignments, visible light absorption, carrier separation, and transportation in the system. For instance, the ability to align the band structure in TiO2 makes it suitable for multiple photocatalytic processes such as degradation of various pollutants, H2 production, CO2 conversion, etc. For these reasons, TiO2 can be realized as a prototypical photocatalyst, which paves ways to develop new photocatalytic materials in the field. In this context, this review paper sheds light into the emerging trends in TiO2 in terms of its modifications towards multifunctional photocatalytic applications.

Electronic and nanostructure engineering of bifunctional MoS2 towards exceptional visible-light photocatalytic CO2 reduction and pollutant degradation

With recently increasing environmental issues and foreseeable energy crisis, it is desirable to design cheap, efficient, and visible-light responsive nano-photocatalyst for CO₂ conversion and pollutant degradation. Herein, we report a flower-like of MoS₂-based hybrid photocatalyst with high efficiency through nanostructure and electronic structure engineering. Nanostructure control is used to fabricate MoS₂ in to flower-like nanosheets (NSs) with large surface active area. Then MoS₂ is coupled with conduction-band edge matched tin dioxide (SnO₂) and decorated with Ag nanoparticles for suitable work function to create a unique cascade band alignment electronic structure to facilitate photoexcited charge transfer. It is shown that the amount-optimized nanocomposite of SnO₂/Ag/MoS₂ exhibits exceptional visible-light photocatalytic activities for conversion of carbon dioxide (CO₂) to methane (CH₄), approximately one order of magnitude enhancement than original MoS₂ with the apparent quantum efficiency 2.38% at 420 nm. Similarly, the optimized sample also shows high activities for 2,4-diclorophenol, Methylene-Blue, Rhodamine-B and Methyl-Orange degradation as compared to pure MoS₂. It is clearly demonstrated through combination of hydroxyl radical evaluation, photoelectrochemical and electrochemical impedance, that the enhanced photoactivities are attributed to the increased specific surface area, optimized band alignment for charge transfer and suppressed recombination. Our current work provides feasible routes for further research.

One-Step Low Temperature Hydrothermal Synthesis of Flexible TiO₂/PVDF@MoS₂ Core-Shell Heterostructured Fibers for Visible-Light-Driven Photocatalysis and Self-Cleaning

Novel flexible and recyclable core-shell heterostructured fibers based on cauliflower-like MoS₂ and TiO₂/PVDF fibers have been designed through one-step hydrothermal treatment based on electrospun tetrabutyl orthotitanate (TBOT)/PVDF fibers. The low hydrothermal temperature avoids the high temperature process and keeps the flexibility of the as-synthesized materials. The formation mechanism of the resultant product is discussed in detail. The composite of MoS₂ not only expands the light harvesting window to include visible light, but also increases the separation efficiency of photo-generated electrons and holes. The as-prepared product has proven to possess excellent and stable photocatalytic activity in the degradation of Rhodamine B and levofloxacin hydrochloride under visible light irradiation. In addition, the TiO₂/PVDF@MoS₂ core-shell heterostructured fibers exhibit self-cleaning property to dye droplets under visible light irradiation. Meanwhile, due to its hydrophobicity, the resultant product can automatically remove dust on its surface under the rolling condition of droplets. Hence, the as-prepared product cannot only degrade the contaminated compounds on the surface of the material, but also reduce the maintenance cost of the material due to its self-cleaning performance. Therefore, the as-prepared product possesses potential applications in degradation of organic pollutants and water treatment, which makes it a prospective material in the field of environmental treatment.

Revealing the role of the 1T phase on the adsorption of organic dyes on MoS2 nanosheets

Herein, different phases of MoS₂ nanosheets were synthesized, characterized and tested for dye removal from water. The influence of the MoS₂ phases as well as the 1T concentration on the adsorption performance of organic dyes MO, RhB and MB was deeply investigated. The results revealed that the 1T-rich MoS₂ nanosheets have superior adsorption performance compared to other 2H and 3R phases. The kinetic results of the adsorption process demonstrate that the experimental data followed the pseudo-second order equation. Meanwhile, the adsorption of dyes over the obtained materials was fitted with several isotherm models. The Langmuir model gives the best fitting to the experimental data with maximum a adsorption capacity of 787 mg g⁻¹. The obtained capacity is significantly higher than that of all previous reports for similar MoS₂ materials. Computational studies of the 2H and 1T/2H-MoS₂ phases showed that the structural defects present at the 1T/2H grain boundaries enhance the binding of hydroxide and carboxyl groups to the MoS₂ surface which in turn increase the adsorption properties of the 1T/2H-MoS₂ phase.

The high adsorption capacity of dyes onto the 1T-rich MoS₂ samples is due to the strong binding between the hydroxide/carboxyl groups and the 1T active sites. The capacity can be tuned by controlling the ratio between 1T and 2H phases of MoS₂ nanosheets.

A comparative study on the photocatalytic degradation of organic dyes using hybridized 1T/2H, 1T/3R and 2H MoS2 nano-sheets

MoS2 is a very attractive material and has been well studied for potential applications in various areas. However, due to the wide variety of factors affecting the molecular and electronic structure of MoS2, several contradictory reports about the adsorptive and photocatalytic properties of such materials have been published. In most of these reports, the effect of the actual phase of the materials on the properties was neglected. Here, different phases of MoS2 nanosheets (1T/2H, 1T/3R and 2H) have been obtained using the hydrothermal method with different Mo : S molar ratios and different autoclave filling ratios. The obtained materials have been thoroughly characterized using Raman, UV-vis, powder XRD, SEM, TEM and XPS measurements in order to accurately identify the existing phases in each material. A comparative study of the photocatalytic organic dye degradation efficiency under white light irradiation has been conducted using methyl orange to correlate the different activity of each material to the respective phase composition. The results indicate a much higher performance of the 1T/2H phase compared to the 2H and 3R phases. Detailed computational studies of the different phases revealed the emergence of mid-gap states upon introducing 1T sites into the 2H lattice. This leads to the improvement of the photocatalytic activity of 1T/2H compared to the other prepared materials.

Preparation of MoS2/TiO2 based nanocomposites for photocatalysis and rechargeable batteries: progress, challenges, and perspective

The rapidly increasing severity of the energy crisis and environmental degradation are stimulating the rapid development of photocatalysts and rechargeable lithium/sodium ion batteries. In particular, MoS₂/TiO₂ based nanocomposites show great potential and have been widely studied in the areas of both photocatalysis and rechargeable lithium/sodium ion batteries due to their superior combination properties. In addition to the low-cost, abundance, and high chemical stability of both MoS₂ and TiO₂, MoS₂/TiO₂ composites also show complementary advantages. These include the strong optical absorption of TiO₂vs. the high catalytic activity of MoS₂, which is promising for photocatalysis; and excellent safety and superior structural stability of TiO₂vs. the high theoretic specific capacity and unique layered structure of MoS₂, thus, these composites are exciting as anode materials. In this review, we first summarize the recent progress in MoS₂/TiO₂-based nanomaterials for applications in photocatalysis and rechargeable batteries. We highlight the synthesis, structure and mechanism of MoS₂/TiO₂-based nanomaterials. Then, advancements and strategies for improving the performance of these composites in photocatalytic degradation, hydrogen evolution, CO₂ reduction, LIBs and SIBs are critically discussed. Finally, perspectives on existing challenges and probable opportunities for future exploration of MoS₂/TiO₂-based composites towards photocatalysis and rechargeable batteries are presented. We believe the present review would provide enriched information for a deeper understanding of MoS₂/TiO₂ composites and open avenues for the rational design of MoS₂/TiO₂ based composites for energy and environment-related applications.

Combination of mesoporous titanium dioxide with MoS2 nanosheets for high photocatalytic activity

This study presents a facile approach for the preparation of MoS2 nanosheet decorated by porous titanium dioxide with effective photocatalytic activity. Mesoporous titanium dioxide nanostructures first synthesized by a hydrothermal process using titanium (III) chloride and then the MoS2/TiO2 were prepared through mixing of MoS2 nanosheet with mesoporous titanium dioxide under ultrasonic irradiation. The synthesized nanocomposite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET) analysis. The results showed that the nanocomposite has mesoporous structure with specific surface area of 176.4 m2/g and pore diameter of 20 nm. The as-prepared MoS2/TiO2 nanocomposites exhibited outstanding photocatalytic activity for dye degradation under sunlight irradiation, which could be attributed to synergistic effect between the molybdenum disulfide nanosheet and mesoporous titanium dioxide. The photocatalytic performance achieved is about 2.2 times higher than that of mesoporous TiO2 alone. It is believed that the extended light absorption ability and the large specific surface area of the 2D MoS2 nanosheets in the nanocomposite, leading to the enhanced photocatalytic degradation activity.

Highly efficient visible-light photocatalytic activity of MoS2–TiO2 mixtures hybrid photocatalyst and functional properties

2D-layered molybdenum disulfide (MoS₂) and MoS₂/TiO₂ nanocomposite were synthesized by a hydrothermal method.

Insights into enhanced visible-light photocatalytic activity of C60 modified g-C3N4 hybrids: the role of nitrogen

Unsaturated N₂ atoms in the interfaces play a major role in promoting the photocatalytic performance of C₆₀ modified g-C₃N₄ hybrids.