Epitaxial Growth of Lattice-Mismatched Core-Shell TiO2 @MoS2 for Enhanced Lithium-Ion Storage

Anthracite-Derived Porous Carbon@MoS2 Heterostructure for Elevated Lithium Storage Regulated by the Middle TiO2 Layer

The rational design of MoS2/carbon composites have been widely used to improve the lithium storage capability. However, their deep applications remain a big challenge due to the slow electrochemical reaction kinetics of MoS2 and weak bonding between MoS2 and carbon substrates. In this work, anthracite-derived porous carbon (APC) is sequential coated by TiO2 nanoparticles and MoS2 nanosheets via a chemical activation and two-step hydrothermal method, forming the unique APC@TiO2@MoS2 ternary composite. The dynamic analysis, in-situ electrochemical impedance spectroscopy as well as theoretical calculation together demonstrate that this innovative design effectively improves the ion/electron transport behavior and alleviates the large volume expansion during cycles. Furthermore, the introduction of middle TiO2 layer in the composite significantly strengthens the mechanical stability of the entire electrode. As expected, the as-prepared APC@TiO2@MoS2 anode displays a high lithium storage capacity with a reversible capacity of 655.8 mAh g-1 after 150 cycles at 200 mA g-1, and robust cycle stability. Impressively, even at a high current density of 2 A g-1, the electrode maintains a superior reversible capacity of 597.7 mAh g-1 after 1100 cycles. This design highlights a feasibility for the development of low-cost anthracite-derived porous carbon-based electrodes.

Waxberry-like TiO2 with Synergistic Surface Modification of Pyrolytic Carbon Coating and Carbon Nanotubes as an Anode for Li-Ion Battery

Titanium dioxide (TiO2) as an anode material for lithium-ion batteries (LIBs) has the advantages of tiny volume expansion, high operating voltage, and outstanding safety performance. However, due to the low conductivity of TiO2 and the slow diffusion rate of lithium ions (Li+), it is limited in the application of LIBs. Therefore, waxberry-like TiO2 comodified by pyrolytic carbon coating and carbon nanotubes was prepared in this work. The waxberry-like TiO2 with nanorods on its surface shortens the diffusion distance of Li+. Carbon nanotubes and waxberry-like TiO2 are tightly combined through electrostatic assembly and form a cross-linked conductive network to provide more electron transmission paths. A thin layer of pyrolytic carbon wraps carbon nanotubes and waxberry-like TiO2, which enhance the conductivity of the composites and ensure the structural integrity of the materials throughout the cycling process. The experimental data revealed that the discharge-specific capacity of TiO2@CNT@C is 170.5 mAh g-1 after 3000 cycles at a large current density of 5 A g-1, and the discharge-specific capacity is still 143 mAh g-1 at the superhigh rate of 10 A g-1, which provides excellent rate performance and cyclic stability. The efficient dual-carbon modification strategy could potentially be extended to other materials.

Highly Stable CsPbBr3@MoS2 Nanostructures: Synthesis and Optoelectronic Properties Toward Implementation into Solar Cells

Halide perovskites (HPs) have gained significant interest in the scientific and technological sectors due to their unique optical, catalytic, and electrical characteristics. However, the HPs are prone to decomposition when exposed to air, oxygen, or heat. The instability of HP materials limits their commercialization, prompting significant efforts to address and overcome these limitations. Transition metal dichalcogenides, such as MoS2, are chemically stable and are suitable for electronic, optical, and catalytic applications. Moreover, it can be used as a protective media or shell for other nanoparticles. In this study, a novel CsPbBr3@MoS2 core-shell nanostructure (CS-NS) is successfully synthesized by enveloping CsPbBr3 within a MoS2 shell for the first time. Significant stability of CS-NSs dispersed in polar solvents for extended periods is also demonstrated. Remarkably, the hybrid CS-NS exhibits an absorption of MoS2 and quenching of the HP's photoluminescence, implying potential charge or energy transfer from HPs to MoS2. Using finite difference time domain simulations, it is found that the CS-NSs can be utilized to produce efficient solar cells. The addition of a MoS2 shell enhances the performance of CS-NS-based solar cells by 220% compared to their CsPbBr3 counterparts. The innovative CS-NS represents important progress in harnessing HPs for photovoltaic and optoelectronic applications.

Band engineering enhances the electrochemical properties by constructing TiO2 NRs-MoS2 NSFs flexible electrode

Research and development of flexible electrodes with high performance are crucial to largely determine the performance of flexible lithium-ion batteries (FLIBs) to a large extent. In this work, a flexible anode (TiO2 NRs-MoS2 NSFs/CC) is rationally designed and successfully constructed, in which TiO2 nanorods arrays (NRs) vertically grown on CC as a supporting backbone for MoS2 nanosheets flowers (NSFs) to form a TiO2 NRs-MoS2 NSFs heterostructure. The backbone can not only serve as a mechanical support MoS2 and improve its electronic conductivity, but also limit the dissolution of polysulfides issue during cycling. The density functional theory (DFT) analysis manifests that the obvious interaction between O and S at the interface for the TiO2 NRs-MoS2 NSFs heterostructure changes the electronic structure and reduces the band gap of TiO2 NRs-MoS2 NSFs. The small band gap and high electron state at the Fermi level are both beneficial to the transport of electrons, enhancing the kinetics, and giving the long cycling stability at high density and excellent rate capacity. Furthermore, the assembled TiO2 NRs-MoS2 NSFs/CC//NCM622 full cell delivers superior rate capacity and good cycling stability. Meanwhile, the soft-packed cell shows good mechanical flexibility, which can be lighted up successfully and keep brightness when folding with different angles. This result illustrates that it is a highly potential strategy for constructing flexible electrodes with the controlled electronic structure through band engineering to not only improve the electrochemical performance, but also possibly meet the requirements of high-performance FLIBs.

In Situ Assembly of Well-Defined MoS2 Slabs on Shape-Tailored Anatase TiO2 Nanostructures: Heterojunctions Role in Phenol Photodegradation

MoS2/TiO2-based nanostructures have attracted extensive attention due to their high performance in many fields, including photocatalysis. In this contribution, MoS2 nanostructures were prepared via an in situ bottom-up approach at the surface of shape-controlled TiO2 nanoparticles (TiO2 nanosheets and bipyramids). Furthermore, a multi-technique approach by combining electron microscopy and spectroscopic methods was employed. More in detail, the morphology/structure and vibrational/optical properties of MoS2 slabs on TiO2 anatase bipyramidal nanoparticles, mainly exposing {101} facets, and on TiO2 anatase nanosheets exposing both {001} and {101} facets, still covered by MoS2, were compared. It was shown that unlike other widely used methods, the bottom-up approach enabled the atomic-level growth of well-defined MoS2 slabs on TiO2 nanostructures, thus aiming to achieve the most effective chemical interactions. In this regard, two kinds of synergistic heterojunctions, namely, crystal face heterojunctions between anatase TiO2 coexposed {101} and {001} facets and semiconductor heterojunctions between MoS2 and anatase TiO2 nanostructures, were considered to play a role in enhancing the photocatalytic activity, together with a proper ratio of (101), (001) coexposed surfaces.

Photoinduced Strong Metal-Support Interaction for Enhanced Catalysis

Strong metal-support interaction (SMSI) construction is a pivotal strategy to afford thermally robust nanocatalysts in industrial catalysis, but thermally induced reactions (>300 °C) in specific gaseous atmospheres are generally required in traditional procedures. In this work, a photochemistry-driven methodology was demonstrated for SMSI construction under ambient conditions. Encapsulation of Pd nanoparticles with a TiO_x overlayer, the presence of Ti³⁺ species, and suppression of CO adsorption were achieved upon UV irradiation. The key lies in the generation of separated photoinduced reductive electrons (e^-) and oxidative holes (h⁺), which subsequently trigger the formation of Ti³⁺ species/oxygen vacancies (O_v) and then interfacial Pd-O_v-Ti³⁺ sites, affording a Pd/TiO₂ SMSI with enhanced catalytic hydrogenation efficiency. The as-constructed SMSI layer was reversible, and the photodriven procedure could be extended to Pd/ZnO and Pt/TiO₂.

Design of double-shell TiO2@SnO2 nanotubes via atomic layer deposition for improved lithium storage

TiO₂@Void@SnO₂ nanotubes synthesized by atomic layer deposition (ALD) display high capacity for lithium storage.

Function and Application of Defect Chemistry in High-Capacity Electrode Materials for Li-Based Batteries

Current commercial Li-based batteries are approaching their energy density limitation, yet still cannot satisfy the energy density demand of the high-end devices. Hence, it is critical to developing advanced electrode materials with high specific capacity. However, these electrode materials are facing challenges of severe structural degradation and fast capacity fading. Among various strategies, constructing defects in electrode materials holds great promise in addressing these issues. Herein, we summarize a series of significant defect engineering in the high-capacity electrode materials for Li-based batteries. The detailed retrospective on defects specification, function mechanism, and corresponding application achievements on these electrodes are discussed from the view of point, line, planar, volume defects. Defect engineering can not only stabilize the structure and enhance electric/ionic conductivity, but also act as active sites to improve the ionic storage and bonding ability of electrode materials to Li metal. We hope this review can spark more perspectives on evaluating high-energy-density Li-based batteries.

High-Performance Electrocatalytic Conversion of N2 to NH3 Using 1T-MoS2 Anchored on Ti3C2 MXene under Ambient Conditions

Herein, 1T-MoS₂ nanospots assembled on conductive Ti₃C₂ MXene (1T-MoS₂@Ti₃C₂) are first developed to regard as efficient electrocatalytic nitrogen fixation catalysts with high selectivity. The 1T-MoS₂@Ti₃C₂ composite exhibits outstanding NRR activity with a faradic efficiency (FE) of 10.94% and a NH₃ yield rate of 30.33 μg h^-1 mg^-1_cat. at -0.3 V versus RHE. Notably, the 1T-MoS₂@Ti₃C₂ composite displays excellent stability and durability during the recycling test. The outstanding NRR catalytic activity is primarily attributed to the synergy effect between 1T-MoS₂ and Ti₃C₂ MXene. In addition, the isotopic experiment confirms the synthesized NH₃ deriving from the conversion of the supplied nitrogen.

Preferentially oriented large antimony trisulfide single-crystalline cuboids grown on polycrystalline titania film for solar cells

Photovoltaic conversion of solar energy into electricity is an alternative way to use renewable energy for sustainable energy production. The great demand of low-cost and efficient solar cells inspires research on solution-processable light-harvesting materials. Antimony trisulfide (Sb2S3) is a promising light-harvester for photovoltaic purposes. Here we report on the in situ grown monolayer of preferentially oriented, large Sb2S3 single-crystalline cuboids on a polycrystalline titania (TiO2) nanoparticle film. A facile, oriented seed-assisted solution-processing method is used, providing the Sb2S3/TiO2-based bulk/nano-planar heterojunction with a preferred structure for efficient planar solar cells. An orientation-competing-epitaxial nucleation/growth mechanism is proposed for understanding the growth of the Sb2S3 single-crystalline cuboids. With an organic hole transporting material, the stable solar cell of the heterojunction yields a power conversion efficiency of 5.15% (certified as 5.12%). It is found that the [221]-oriented Sb2S3 cuboids provide highly effective charge transport channels inside the Sb2S3 layer.

The rational design of hierarchical MoS2 nanosheet hollow spheres sandwiched between carbon and TiO2@graphite as an improved anode for lithium-ion batteries

Molybdenum disulfide (MoS₂) shows high capacity but suffers from poor rate capability and rapid capacity decay, which greatly limit its practical applications in lithium-ion batteries. Herein, we successfully prepared MoS₂ nanosheet hollow spheres encapsulated into carbon and titanium dioxide@graphite, denoted as TiO₂@G@MoS₂@C, via hydrothermal and polymerization approaches. In this hierarchical architecture, the MoS₂ hollow sphere was sandwiched by graphite and an amorphous carbon shell; thus, TiO₂@G@MoS₂@C exhibited effectively enhanced electrical conductivity and withstood the volume changes; moreover, the aggregation and diffusion of the MoS₂ nanosheets were restricted; this advanced TiO₂@G@MoS₂@C fully combined the advantages of a three-dimensional architecture, hollow structure, carbon coating, and a mechanically robust TiO₂@graphite support, achieving improved specific capacity and long-term cycling stability. In addition, it exhibited the high reversible specific capacity of 823 mA h g^-1 at the current density of 0.1 A g^-1 after 100 cycles, retaining almost 88% of the initial reversible capacity with the high coulombic efficiency of 99%.

Controlled synthesis of hollow C@TiO2@MoS2 hierarchical nanospheres for high-performance lithium-ion batteries

In this manuscript, we utilize a facile and efficient step-by-step strategy to synthesize three-layered C@TiO2@MoS2 hierarchical nanocomposites. These novel hybrids serve as anode materials in lithium-ion batteries (LIBs). The designed structure, in which MoS2 nanosheets are uniformly grown on TiO2 coated carbon hollow spheres, can enhance the electrical conductivity of electrodes, shorten the diffusion length of Li+ ions, alleviate the expansion of electrode materials and provide more active sites for lithium ion storage. As anode materials for lithium-ion batteries (LIBs), the C@TiO2@MoS2 hierarchical nanocomposites exhibit a high initial specific capacity (1687 mA h g-1) and good cycling performance (993.2 mA h g-1 after 100 cycles at a current density of 0.2 A g-1). Furthermore, the C@TiO2@MoS2 electrode exhibits high rate capacities of 963, 860, 806, 743, 703, 664 and 633 mA h g-1 at different current densities of 200, 500, 1000, 2000, 3000, 4000 and 5000 mA h g-1, respectively. The electrochemical performances stated above prove that the as-prepared C@TiO2@MoS2 nanocomposites can be promising anode materials for high-performance lithium-ion batteries.

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.

Defect-Induced Epitaxial Growth for Efficient Solar Hydrogen Production

Epitaxial growth suffers from the mismatches in lattice and dangling bonds arising from different crystal structures or unit cell parameters. Here, we demonstrate the epitaxial growth of 2D MoS₂ ribbon on 1D CdS nanowires (NWs) via surface and subsurface defects. The interstitial Cd⁰ in the (12̅10) crystal plane of the [0001]-oriented CdS NWs are found to serve as nucleation sites for interatomically bonded [001]-oriented MoS₂, where the perfect lattice match (∼99.7%) between the (101̅1) plane of CdS and the (002)-faceted in-plane MoS₂ result in coaxial MoS₂ ribbon/CdS NWs heterojunction. The coaxial but heterotropic epitaxial MoS₂ ribbon on the surface of CdS NWs induces delocalized interface states that facilitate charge transport and the reduced surface state. A less than 5-fold ribbon width of MoS₂ as hydrogen evolution cocatalyst exhibits a ∼10-fold H₂ evolution enhancement than state of the art Pt in an acidic electrolyte, and apparent quantum yields of 79.7% at 420 nm, 53.1% at 450 nm, and 9.67% at 520 nm, respectively.

Carbon Domains on MoS2/TiO2 System via Catalytic Acetylene Oligomerization: Synthesis, Structure, and Surface Properties

Carbon domains have been obtained at the surface of a MoS2/TiO2 (Evonik, P25) system via oligomerization and cyclotrimerization reactions involved in the interaction of the photoactive material with acetylene. Firstly, MoS2 nanosheets have been synthesized at the surface of TiO2, via sulfidation of a molybdenum oxide precursor with H2S (bottom-up method). Secondly, the morphology and the structure, the optical and the vibrational properties of the obtained materials, for each step of the synthesis procedure, have been investigated by microscopy and spectroscopy methods. In particular, transmission electron microscopy images provide a simple tool to highlight the effectiveness of the sulfidation process, thus showing 1L, 2L, and stacked MoS2 nanosheets anchored to the surface of TiO2 nanoparticles. Lastly, in-situ FTIR spectroscopy investigation gives insights into the nature of the oligomerized species, showing that the formation of both polyenic and aromatic systems can be taken into account, being their formation promoted by both Ti and Mo catalytic sites. This finding gives an opportunity for the assembly of extended polyenic, polyaromatic, or mixed domains firmly attached at the surface of photoactive materials. The presented approach, somehow different from the carbon adding or doping processes of TiO2, is of potential interest for the advanced green chemistry and energy conversion/transport applications.

Rational Design of Three-Layered TiO2 @Carbon@MoS2 Hierarchical Nanotubes for Enhanced Lithium Storage

Here we demonstrate the rational design and synthesis of three-layered TiO₂ @carbon@MoS₂ hierarchical nanotubes for anode applications in lithium-ion batteries (LIBs). Through an efficient step-by-step strategy, ultrathin MoS₂ nanosheets are grown on nitrogen-doped carbon (NC) coated TiO₂ nanotubes to achieve the TiO₂ @NC@MoS₂ tubular nanostructures. This smart design can effectively shorten the diffusion length of Li⁺ ions, increase electric conductivity of the electrode, relax volume variation of electrode materials upon cycling, and provide more active sites for electrochemical reactions. Owing to these structural and compositional features, the hierarchical TiO₂ @NC@MoS₂ nanotubes manifest remarkable lithium storage performance with good rate capability and long cycle life.

Plasmon-Enhanced Photoelectrochemical Current and Hydrogen Production of (MoS2-TiO2)/Au Hybrids

Three component hybrid (MoS₂-TiO₂)/Au substrate is fabricated by loading plasmonic Au nanorods on the MoS₂ nanosheets coated TiO₂ nanorod arrays. It is used for photoelectrochemical (PEC) cell and photocatalyst for hydrogen generation. Owing to the charge transfer between the MoS₂-TiO₂ hetero-structure, the PEC current density and hydrogen generation of TiO₂ nanoarrays are enhanced 2.8 and 2.6 times. The broadband photochemical properties are further enhanced after Au nanorods loading. The plasmon resonance of Au nanorods provides more effective light-harvesting, induces hot-electron injection, and accelerates photo-excited charges separation. The results have suggested a route to construct nanohybrid by combining one-dimensional arrays and two-dimensional nanosheets, meanwhile have successfully utilized plasmonic nanorods as a sensitizer to improve the photochemical properties of the semiconductor nanocomposite.

Co9 S8 /MoS2 Yolk-Shell Spheres for Advanced Li/Na Storage

Uniform sized Co₉ S₈ /MoS₂ yolk-shell spheres with an average diameter of about 500 nm have been synthesized by a facile route. When evaluated as anodes for lithium-ion and sodium-ion batteries, these Co₉ S₈ /MoS₂ yolk-shell spheres show high specific capacities, excellent rate capabilities, and good cycling stability.