Noble-Metal-Free Molybdenum Disulfide Cocatalyst for Photocatalytic Hydrogen Production

TiO2nanorod arrays/Ti3C2TxMXene nanosheet composites with efficient photocatalytic activity

Semiconductor photocatalysis holds significant promise in addressing both environmental and energy challenges. However, a major hurdle in photocatalytic processes remains the efficient separation of photoinduced charge carriers. In this study, TiO2nanorod arrays were employed by glancing angle deposition technique, onto which Ti3C2TxMXene was deposited through a spin-coating process. This hybrid approach aims to amplify the photocatalytic efficacy of TiO2nanorod arrays. Through photocurrent efficiency characterization testing, an optimal loading of TiO2/Ti3C2Txcomposites is identified. Remarkably, this composite exhibits a 40% increase in photocurrent density in comparison to pristine TiO2. This enhancement is attributed to the exceptional electrical conductivity and expansive specific surface area inherent to Ti3C2TxMXene. These attributes facilitate swift transport of photoinduced electrons, consequently refining the separation and migration of electron-hole pairs. The synergistic TiO2/Ti3C2Txcomposite showcases its potential across various domains including photoelectrochemical water splitting and diverse photocatalytic devices. As such, this composite material stands as a novel and promising entity for advancing photocatalytic applications. This study can offer an innovative approach for designing simple and efficient photocatalytic materials composed of MXene co-catalysts and TiO2for efficient water electrolysis on semiconductors.

MoS2-Based Nanocomposites for Photocatalytic Hydrogen Evolution and Carbon Dioxide Reduction

Photocatalysis is a facile and sustainable approach for energy conversion and environmental remediation by generating solar fuels from water splitting. Due to their two-dimensional (2D) layered structure and excellent physicochemical properties, molybdenum disulfide (MoS₂) has been effectively utilized in photocatalytic H₂ evolution reaction (HER) and CO₂ reduction. The photocatalytic efficiency of MoS₂ greatly depends on the active edge sites present in their layered structure. Modifications like reducing the layer numbers, creating defective structures, and adopting different morphologies produce more unsaturated S atoms as active edge sites. Hence, MoS₂ acts as a cocatalyst in nanocomposites/heterojunctions to facilitate the photogenerated electron transfer. This review highlights the role of MoS₂ as a cocatalyst for nanocomposites in H₂ evolution reaction and CO₂ reduction. The H₂ evolution activity has been described comprehensively as binary (with metal oxide, carbonaceous materials, metal sulfides, and metal-organic frameworks) and ternary composites of MoS₂. Photocatalytic CO₂ reduction is a more complex and challenging process that demands an efficient light-responsive semiconductor catalyst to tackle the thermodynamic and kinetic factors. Photocatalytic reduction of CO₂ using MoS₂ is an emerging topic and would be a cost-effective substitute for noble catalysts. Herein, we also exclusively envisioned the possibility of layered MoS₂ and its composites in this area. This review is expected to furnish an understanding of the diverse roles of MoS₂ in solar fuel generation, thus endorsing an interest in utilizing this unique layered structure to create nanostructures for future energy applications.

Regulating the charge carrier transport rate via bridging ternary heterojunctions to enable CdS nanorods' solar-driven hydrogen evolution

Solar-driven hydrogen generation using single-semiconductor photocatalysts for hydrogen evolution seems to be challenging due to their poor solar to fuel conversion efficiency because of their fast charge carrier recombination. The ternary heterostructure was prepared by an advanced approach to suppress the recombination of photogenerated charge carriers and has contributed a new platform for designing highly efficient photocatalytic systems. Herein, we fabricated a ternary heterojunction with ultrathin WS₂-SnS₂ nanosheets and CdS nanorods, and the photocatalytic activity was studied. The optimized CdS/SnS₂-WS₂ (6 wt%) nanostructures were found to be highly stable and exhibited the highest hydrogen evolution rate of 232.45 mmol g^-1 h^-1, which was almost 93-fold higher than that of the pristine CdS nanorods. Also, Density Functional Theory (DFT) calculations confirmed that the favorable band alignment for charge transport and superior catalytic activity of the newly fabricated ternary nanostructures make them a potential candidate for solar-driven hydrogen production.

MoS2 and MoS2 Nanocomposites for Adsorption and Photodegradation of Water Pollutants: A Review

The need for fresh and conveniently treated water has become a major concern in recent years. Molybdenum disulfide (MoS₂) nanomaterials are attracting attention in various fields, such as energy, hydrogen production, and water decontamination. This review provides an overview of the recent developments in MoS₂-based nanomaterials for water treatment via adsorption and photodegradation. Primary attention is given to the structure, properties, and major methods for the synthesis and modification of MoS₂, aiming for efficient water-contaminant removal. The combination of MoS₂ with other components results in nanocomposites that can be separated easily or that present enhanced adsorptive and photocatalytic properties. The performance of these materials in the adsorption of heavy metal ions and organic contaminants, such as dyes and drugs, is reviewed. The review also summarizes current progress in the photocatalytic degradation of various water pollutants, using MoS₂-based nanomaterials under UV-VIS light irradiation. MoS₂-based materials showed good activity after several reuse cycles and in real water scenarios. Regarding the ecotoxicity of the MoS₂, the number of studies is still limited, and more work is needed to effectively evaluate the risks of using this nanomaterial in water treatment.

Molybdenum Disulfide-Based Nanomaterials for Visible-Light-Induced Photocatalysis

Visible-light-responsive photocatalytic materials have a multitude of important applications, ranging from energy conversion and storage to industrial waste treatment. Molybdenum disulfide (MoS₂) and its variants exhibit high photocatalytic activity under irradiation by visible light as well as good stability and recyclability, which are desirable for all photocatalytic applications. MoS₂-based materials have been widely applied in various fields such as wastewater treatment, environmental remediation, and organic transformation reactions because of their excellent physicochemical properties. The present review focuses on the fundamental properties of MoS₂, recent developments and remaining challenges, and key strategies for tackling issues related to the utilization of MoS₂ in photocatalysis. The application of MoS₂-based materials in visible-light-induced catalytic reactions for the treatment of diverse kinds of pollutants including industrial, environmental, pharmaceutical, and agricultural waste are also critically discussed. The review concludes by highlighting the prospects of MoS₂ for use in various established and emerging areas of photocatalysis.

The fabrication of graphitic carbon nitride hollow nanocages with semi-metal 1T' phase molybdenum disulfide as co-catalysts for excellent photocatalytic nitrogen fixation

Improving the efficiency of photogenerated carrier separation is essential for photocatalytic N₂ fixation. Herein, the 2D semi-metal 1T'-MoS₂ was uniformly distributed in g-C₃N₄ nanocages (CNNCs) by a hydrothermal method, and the 1T'-MoS₂/CNNC composite was obtained. 1T'-MoS₂ as a co-catalyst can promote the transfer of electrons, improve the separation efficiency of photogenerated carriers, and also increase the number of effective active sites. In addition, the unique nanocage morphology of CNNCs is conducive to the scattering and reflection of incident light and improves the light absorption capacity. Therefore, the optimized 1T'-MoS₂/CNNC composite (5 wt%) shows a significantly improved photocatalytic N₂ fixation rate (9.8 mmol L^-1 h^-1 g^-1) and good stability, which is significantly higher than pure CNNCs (2.9 mmol L^-1 h^-1 g^-1), Pt/CNNC (8.2 mmol L^-1 h^-1 g^-1) and Pt/g-C₃N₄ nanosheet (CNNS, 6.3 mmol L^-1 h^-1 g^-1). This work guides guidance for the design of green and efficient N₂ fixation photocatalysts.

Zn-doped SnS with sulfur vacancies for enhanced photocatalytic hydrogen evolution from water

Tin sulfide has attracted considerable attention due to its adjustable optoelectronic properties. However, few present pieces of literature focus on the photocatalytic water splitting performance of stannous sulfide (SnS), despite...

Challenges and prospects about the graphene role in the design of photoelectrodes for sunlight-driven water splitting

Graphene and its derivatives have emerged as potential materials for several technological applications including sunlight-driven water splitting reactions. This review critically addresses the latest achievements concerning the use of graphene as a player in the design of hybrid-photoelectrodes for photoelectrochemical cells. Insights about the charge carrier dynamics of graphene-based photocatalysts which include metal oxides and non-metal oxide semiconductors are also discussed. The concepts underpinning the continued progress in the field of graphene/photoelectrodes, including different graphene structures, architecture as well as the possible mechanisms for hydrogen and oxygen reactions are also presented. Despite several reports having demonstrated the potential of graphene-based photocatalysts, the achieved performance remains far from the targeted benchmark efficiency for commercial application. This review also highlights the challenges and opportunities related to graphene application in photoelectrochemical cells for future directions in the field.

Enhanced photocatalytic performance of rhodamine B and enrofloxacin by Pt loaded Bi4V2O11: boosted separation of charge carriers, additional superoxide radical production, and the photocatalytic mechanism

Photocatalytic performance is influenced by two contradictory factors, which are light absorption range and separation of charge carriers. Loading noble metals with nanosized interfacial contact is expected to improve the separation and transfer of photo-excited charge carriers while enlarging the light absorption range of the semiconductor photocatalyst. Therefore, it should be possible to improve the photocatalytic performance of pristine nontypical stoichiometric semiconductor photocatalysts by loading a specific noble metal. Herein, a series of novel Pt-Bi4V2O11 photocatalysts have been successfully prepared via a surface reduction technique. The crystal structure, morphology, and photocatalytic performance, as well as photo-electron properties of the as-synthesized samples were fully characterized. Moreover, the series of Pt-Bi4V2O11 samples were evaluated to remove typical organic pollutants, rhodamine B and enrofloxacin, from aqueous solutions. The photoluminescence, quenching experiments and the electron spin resonance technique were utilized to identify the effective radicals during the photocatalytic process and understand the photocatalytic mechanism. The photocatalytic performance of Pt-Bi4V2O11 was tremendously enhanced compared with pristine Bi4V2O11, and there was additional ˙O2- produced during the photocatalytic process. This study deeply investigated the relation between the separation of charge carriers and the light harvesting, and revealed a promising strategy for fabricating efficient photocatalysts for both dyes and antibiotics.

Impact of structure, doping and defect-engineering in 2D materials on CO2 capture and conversion

2D material based strategies for adsorption and conversion of CO2 to value-added products.

A novel ternary MQDs/NCDs/TiO2 nanocomposite that collaborates with activated persulfate for efficient RhB degradation under visible light irradiation

TiO₂ nanosheets modified with dual MQDs/NCD quantum dots not only promote light absorption capacity and electron–hole transport but also collaborate well with activated persulfate for pollutant degradation.

Liquid-phase exfoliated MoS2 nanosheets doped with p-type transition metals: a comparative analysis of photocatalytic and antimicrobial potential combined with density functional theory

MoS2 nanosheets were developed by undertaking the liquid-phase exfoliation of bulk counterparts. In order to enhance its photocatalytic properties, the host material was doped with p-type transition metals (i.e., Ag, Co, Bi, and Zr). The hydrothermal technique was used to produce samples doped with 7.5 wt% transition metals (TM). X-ray diffraction detected the existence of 2H-phase by mirroring its reflection at 2θ ∼ 14°, while the peak distribution revealed the degree of exfoliation in samples. Low PL intensities indicated a lower recombination of electron-hole pairs, as corroborated by a high degree of photocatalytic action. Raman analysis was undertaken to identify molecular vibrations. The A1g mode in Raman spectra consistently showed a blueshift in all samples and the E12g mode was only slightly affected, which is evidence of the p-type doping in the MoS2 nanosheets. In the XPS spectrum, two characteristic peaks of Mo 3d appeared at 229.87 and 233.03 eV assigned to Mo-3d5/2 and Mo-3d3/2, respectively. Furthermore, a microstructural examination with HR-TEM and FESEM divulged a thin-layered structure of MoS2 consisting of flat, gently curved or twisted nanosheets. Diverse morphologies were observed with a non-uniform distribution of the dopant. Photocatalytic action of the TM-doped products effectively degraded methylene blue (MB) concentrations of up to 94 percent (for Ag-MoS2). The synergistic effect of doped MoS2 nanosheets against S. aureus in comparison to E. coli bacteria was also evaluated. The efficacy % age improved from (0-31.7%) and (23.5-55.2%) against E. coli, and (0-34.2%) and (8.3-69.23%) against S. aureus. Moreover, results from first principles calculations indicate that substitutional doping of TM atoms is indeed advantageous. Theoretical calculations confirmed that doping with Ag, Co, Bi, and Zr leads to a decrease in the band gap to a certain degree, in which the conduction band edge shifts toward lower energy, while the valence band shifts closer to the high energy end. It can be concluded that Ag, Co, and Bi impurities can lead to beneficial p-type doping in MoS2 monolayered structures. With regards to doping with Zr, the acceptor levels are formed above the edge of the valence band, revealing an introduction of the p-type character.

Direct electron-beam patterning of monolayer MoS2 with ice

Two-dimensional transition metal dichalcogenides (TMDCs) are considered strong competitors for next generation semiconductor materials. In this paper, we propose direct electron-beam patterning of monolayer MoS2 inspired by an emerging ice lithography technique. Compared to conventional resist-based nanofabrication, ice-assisted patterning is free of contaminations from polymer resist and allows in situ processing of MoS2. The effects of electron beam dose and energy are investigated and nanoribbons with width below 30 nm are attainable. This method is expected to be applicable also to other TMDCs, providing a promising alternative for nanofabrication of 2D material devices.

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.

Bridge engineering in photocatalysis and photoelectrocatalysis

Solar driven photocatalysis and photoelectrocatalysis have emerged as promising strategies for clean, low-cost, and environmental-friendly production of renewable energy and removal of pollutants. There are three crucial steps for the photocatalytic and photoelectrochemical (PEC) processes: light absorption, charge separation and transportation, and surface catalytic reactions. While significant achievement has been made in developing multiple-component photocatalysts to optimize the three steps for improved solar-to-chemical energy conversion efficiency, it remains challenging when weak interfacial contact between components/particles hinders charge transfer, restricts electron-hole separation and lowers the structural stability of catalysts. Moreover, owing to the mismatch of energy bands, an undesirable charge transfer direction leads to an adverse consequence. To tackle these challenges, bridges are implemented to smoothen the interfacial charge transfer, improve the stability of catalysts, mediate the charge transfer directions and improve the photocatalytic/PEC performance. In this review, we present the advances in bridge engineering in photocatalytic/PEC systems. Starting with the definition and classifications of bridges, we summarize the architectures of the reported bridged photocatalysts. Then we systematically discuss the insight into the roles and fundamental mechanisms of bridges in various photocatalytic/PEC systems and their contributions to activity enhancement in various reactions. Finally, the challenges and perspectives of bridged photocatalysts are featured.

2D MoS2 nanosheets on 1D anodic TiO2 nanotube layers: an efficient co-catalyst for liquid and gas phase photocatalysis

One-dimensional TiO₂ nanotube layers with different dimensions were homogeneously decorated with 2D MoS₂ nanosheets via atomic layer deposition and employed for liquid and gas phase photocatalysis. The 2D MoS₂ nanosheets revealed a high amount of exposed active edge sites and strongly enhanced the photocatalytic performance of TiO₂ nanotube layers.

Photocatalytic H2 Evolution on TiO2 Assembled with Ti3C2 MXene and Metallic 1T-WS2 as Co-catalysts

The biggest challenging issue in photocatalysis is efficient separation of the photoinduced carriers and the aggregation of photoexcited electrons on photocatalyst's surface. In this paper, we report that double metallic co-catalysts Ti3C2 MXene and metallic octahedral (1T) phase tungsten disulfide (WS2) act pathways transferring photoexcited electrons in assisting the photocatalytic H2 evolution. TiO2 nanosheets were in situ grown on highly conductive Ti3C2 MXenes and 1T-WS2 nanoparticles were then uniformly distributed on TiO2@Ti3C2 composite. Thus, a distinctive 1T-WS2@TiO2@Ti3C2 composite with double metallic co-catalysts was achieved, and the content of 1T phase reaches 73%. The photocatalytic H2 evolution performance of 1T-WS2@TiO2@Ti3C2 composite with an optimized 15 wt% WS2 ratio is nearly 50 times higher than that of TiO2 nanosheets because of conductive Ti3C2 MXene and 1T-WS2 resulting in the increase of electron transfer efficiency. Besides, the 1T-WS2 on the surface of TiO2@Ti3C2 composite enhances the Brunauer-Emmett-Teller surface area and boosts the density of active site.

A Critical Review on Enhancement of Photocatalytic Hydrogen Production by Molybdenum Disulfide: From Growth to Interfacial Activities

Ultrathin 2D molybdenum disulfide (MoS₂ ), which is the flagship of 2D transition-metal dichalcogenide nanomaterials, has drawn much attention in the last few years. 2D MoS₂ has been banked as an alternative to platinum for highly active hydrogen evolution reaction because of its low cost, high surface-to-volume ratio, and abundant active sites. However, when MoS₂ is used directly as a photocatalyst, contrary to public expectation, it still performs poorly due to lateral size, high recombination ratio of excitons, and low optical cross section. Besides, simply compositing MoS₂ as a cocatalyst with other semiconductors cannot satisfy the practical application, which stimulates the pursual of a comprehensive insight into recent advances in synthesis, properties, and enhanced hydrogen production of MoS₂ . Therefore, in this Review, emphasis is given to synthetic methods, phase transitions, tunable optical properties, and interfacial engineering of 2D MoS₂ . Abundant ways of band edge tuning, structural modification, and phase transition are addressed, which can generate the neoteric photocatalytic systems. Finally, the main challenges and opportunities with respect to MoS₂ being a cocatalyst and coherent light-matter interaction of MoS₂ in photocatalytic systems are proposed.

Photocatalytic Hydrogen Production: Role of Sacrificial Reagents on the Activity of Oxide, Carbon, and Sulfide Catalysts

Photocatalytic water splitting is a sustainable technology for the production of clean fuel in terms of hydrogen (H2). In the present study, hydrogen (H2) production efficiency of three promising photocatalysts (titania (TiO2-P25), graphitic carbon nitride (g-C3N4), and cadmium sulfide (CdS)) was evaluated in detail using various sacrificial agents. The effect of most commonly used sacrificial agents in the recent years, such as methanol, ethanol, isopropanol, ethylene glycol, glycerol, lactic acid, glucose, sodium sulfide, sodium sulfite, sodium sulfide/sodium sulfite mixture, and triethanolamine, were evaluated on TiO2-P25, g-C3N4, and CdS. H2 production experiments were carried out under simulated solar light irradiation in an immersion type photo-reactor. All the experiments were performed without any noble metal co-catalyst. Moreover, photolysis experiments were executed to study the H2 generation in the absence of a catalyst. The results were discussed specifically in terms of chemical reactions, pH of the reaction medium, hydroxyl groups, alpha hydrogen, and carbon chain length of sacrificial agents. The results revealed that glucose and glycerol are the most suitable sacrificial agents for an oxide photocatalyst. Triethanolamine is the ideal sacrificial agent for carbon and sulfide photocatalyst. A remarkable amount of H2 was produced from the photolysis of sodium sulfide and sodium sulfide/sodium sulfite mixture without any photocatalyst. The findings of this study would be highly beneficial for the selection of sacrificial agents for a particular photocatalyst.

Facile and Cost-Efficient Synthesis of Quasi-0D/2D ZnO/MoS2 Nanocomposites for Highly Enhanced Visible-Light-Driven Photocatalytic Degradation of Organic Pollutants and Antibiotics

Nanoscale transition-metal dichalcogenide materials showed promising potential for visible-light responsive photocatalysis. Here, we report our investigations on the synthesis of heterodimensional nanostructures of two-dimensional (2D) ultrathin MoS₂ nanosheets interspersed with ZnO nanoparticles by using a facile two-step method consisting of sonication-aided exfoliation technique followed by a wet chemical process. The photocatalytic activity of the nanocomposites was examined by studying the degradation of different organic dye pollutants and tetracycline, a common antibiotic, under visible-light irradiation. It is found that within 30 min more than 90 % of the model organic dye was photodegraded by the optimized quasi-0D/2D hybrid nanomaterial. The reaction rate of pollutant degradation is about five and eight times higher than those of the pristine MoS₂ naonosheets and P25 photocatalysts, respectively. The outstanding photocatalytic activity of the heterodimensional hybrids can be attributed to a few beneficial features from the synergetic effects. Most importantly, the intimate junction between ZnO and MoS₂ facilitates the separation of photogenerated carriers, leading to the enhancement of photocatalytic efficiency. A tentative photocatalytic degradation mechanism was proposed and tested. Overall, the present work provides valuable insights for the exploration of cost-effective nanoscale heterodimensional hybrids constructed from atomically thin layered materials.

Metal-complex chromophores for solar hydrogen generation

Solar H₂ generation from water has been intensively investigated as a clean method to convert solar energy into hydrogen fuel. During the past few decades, many studies have demonstrated that metal complexes can act as efficient photoactive materials for photocatalytic H₂ production. Here, we review the recent progress in the application of metal-complex chromophores to solar-to-H₂ conversion, including metal-complex photosensitizers and supramolecular photocatalysts. A brief overview of the fundamental principles of photocatalytic H₂ production is given. Then, different metal-complex photosensitizers and supramolecular photocatalysts are introduced in detail, and the most important factors that strictly determine their photocatalytic performance are also discussed. Finally, we illustrate some challenges and opportunities for future research in this promising area.

Group 6 transition metal dichalcogenide nanomaterials: synthesis, applications and future perspectives

Group 6 transition metal dichalcogenides (G6-TMDs), most notably MoS₂, MoSe₂, MoTe₂, WS₂ and WSe₂, constitute an important class of materials with a layered crystal structure. Various types of G6-TMD nanomaterials, such as nanosheets, nanotubes and quantum dot nano-objects and flower-like nanostructures, have been synthesized. High thermodynamic stability under ambient conditions, even in atomically thin form, made nanosheets of these inorganic semiconductors a valuable asset in the existing library of two-dimensional (2D) materials, along with the well-known semimetallic graphene and insulating hexagonal boron nitride. G6-TMDs generally possess an appropriate bandgap (1-2 eV) which is tunable by size and dimensionality and changes from indirect to direct in monolayer nanosheets, intriguing for (opto)electronic, sensing, and solar energy harvesting applications. Moreover, rich intercalation chemistry and abundance of catalytically active edge sites make them promising for fabrication of novel energy storage devices and advanced catalysts. In this review, we provide an overview on all aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials in a comprehensive yet concise treatment. Particular emphasis is placed on establishing a linkage between the features of production methods and the specific needs of rapidly growing applications of G6-TMDs to develop a production-application selection guide. Based on this selection guide, a framework is suggested for future research on how to bridge existing knowledge gaps and improve current production methods towards technological application of G6-TMD nanomaterials.

Multidirectional-charge-transfer urchin-type Mo-doped W18O49 nanostructures on CdS nanorods for enhanced photocatalytic hydrogen evolution

The urchin shaped Mo doped W₁₈O₄₉ greatly enhances the charge transfer and photocatalytic efficiencies.

Noble metal nanostructure-decorated molybdenum disulfide nanocomposites: synthesis and applications

Noble metal nanostructure-decorated MoS₂ nanocomposites have been used in sensors, catalysts, antibacterial materials and batteries due to their excellent properties.

4,4′,4′′-Triaminotriphenylamine-based porous polyimide as a visible-light-driven photocatalyst

A novel polyimide photocatalyst was fabricated by a low-temperature condensation method and its photocatalytic mechanism was discussed.

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.

Heterogeneous Nanostructure Based on 1T-Phase MoS2 for Enhanced Electrocatalytic Hydrogen Evolution

As an electrocatalyst, conventional 2H-phase MoS₂ suffers from limited active sites and inherently low electroconductivity. Phase transitions from 2H to 1T have been proposed as an effective strategy for optimization of the catalytic activity. However, complicated chemical exfoliation is generally involved. Here, MoS₂ heterogeneous-phase nanosheets with a 1T phase (1T/2H-MoS₂) generated in situ were prepared through a facile hydrothermal method. The locally introduced 1T-phase MoS₂ can not only contribute more active sites but also markedly promote the electronic conductivity. Because of this unique structure, the as-synthesized 1T/2H-MoS₂ nanosheets exhibit remarkable performance for the hydrogen evolution reaction with a small overpotential of 220 mV at 10 mA/cm², a small Tafel slope of 61 mV/decade, and robust stability. This work facilitates the development of a two-dimensional heterogeneous nanostructure with enhanced applications.