S.V. Prabhakar Vattikuti

Improved photocatalytic activity of MoS2 nanosheets decorated with SnO2 nanoparticles

MoS2 nanosheets decorated with SnO2 mesoporous nanoparticles were successfully prepared by a facile two-step method. The MoS2 nanosheets were pre-synthesized using a solvothermal method and then decorated with the SnO2 mesoporous nanoparticles through a wet chemical method. The nanocomposite was characterized with powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersed spectrometry (EDX), high-resolution transmission electron microscopy (HRTEM), thermal gravimetric and differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). SnO2 mesoporous nanoparticles can be selectively formed and attached to the peripheral surface of the layered MoS2, which was confirmed by FESEM and HRTEM. The photocatalytic activity of the nanocomposite was examined with Rhodamine B (RhB) in aqueous solution under UV light irradiation. The SnO2 nanoparticles remarkably suppressed the electron–hole recombination effect on the MoS2 photocatalyst and improved the photocatalytic activity compared to a pristine MoS2 catalyst. A higher rate of pollutant degradation was accomplished within 50 min that was three times higher than that of the pristine MoS2 catalyst.

Synthesis and characterization of molybdenum disulfide nanoflowers and nanosheets: nanotribology

This paper reports the solvothermal synthesis of MoS2 nanoflowers and nanosheets. The nanoflowers have a mean diameter of about 100 nm and were obtained using thioacetamide (C2H5NS) as a sulfur source. The few layered nanosheets were obtained using thiourea (CH4N2S) as a sulfur source. The obtained powders were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The lubricating effect of MoS2 nanoflowers and nanosheets were analyzed using four-ball test, the topography of the wear scar was analyzed using SEM, EDS, and 3D surface profilometry. The relationship between the tribological properties and morphology of the materials was determined. It is observed that the engine oil containing the MoS2 nanomaterials penetrated more easily into the interface space, and it formed a continuous film on the interface surface. The tribological performance showed that the synthesized nanosheets had superior antiwear and friction-reducing properties as a lubrication additive compared with nanoflowers. Also, the wear scar of balls lubricated with nanoflowers revealed a larger diameter compared to nanosheets. In conclusion, nanosheets dispensed in oil have better tribological performance compared to nanoflowers oil in terms of capability to reduce friction.

Hydrothermally synthesized highly dispersed Na2Ti3O7 nanotubes and their photocatalytic degradation and H2 evolution activity under UV and simulated solar light irradiation

Photocatalytic water splitting technologies are currently being considered for alternative energy sources. However, the strong demand for a high H2 production rate will present conflicting requirements of excellent photoactivity and low-cost photocatalysts. The first alternative may be abundant nanostructured titanate-related materials as a photocatalyst. Here, we report highly dispersed Na2Ti3O7 nanotubes synthesized via a facile hydrothermal route for photocatalytic degradation of Rhodamine B (RhB) and the water splitting under UV-visible light irradiation. Compared with commercial TiO2, the nanostructured Na2Ti3O7 demonstrated excellent photodegradation and water splitting performance, thus addressing the need for low-cost photocatalysts. The as-synthesized Na2Ti3O7 nanotubes exhibited desirable photodegradation, and rate of H2 production was 1,755 μmol·g−1·h−1 and 1,130 μmol·g−1·h−1 under UV and simulated solar light irradiation, respectively; the resulting as-synthesized Na2Ti3O7 nanotubes are active in UV light than that of visible light response.

Sacrificial-template-free synthesis of core-shell C@Bi 2 S 3 heterostructures for efficient supercapacitor and H 2 production applications

Core-shell heterostructures have attracted considerable attention owing to their unique properties and broad range of applications in lithium ion batteries, supercapacitors, and catalysis. Conversely, the effective synthesis of Bi2S3 nanorod core@ amorphous carbon shell heterostructure remains an important challenge. In this study, C@Bi2S3 core-shell heterostructures with enhanced supercapacitor performance were synthesized via sacrificial- template-free one-pot-synthesis method. The highest specific capacities of the C@Bi2S3 core shell was 333.43 F g−1 at a current density of 1 A g−1. Core-shell-structured C@Bi2S3 exhibits 1.86 times higher photocatalytic H2 production than the pristine Bi2S3 under simulated solar light irradiation. This core-shell feature of C@Bi2S3 provides efficient charge separation and transfer owing to the formed heterojunction and a short radial transfer path, thus efficiently diminishing the charge recombination; it also facilitates plenty of active sites for the hydrogen evolution reaction owing to its mesoporous nature. These outcomes will open opportunities for developing low-cost and noble-metal-free efficient electrode materials for water splitting and supercapacitor applications.

Synthesis and structural characterization of Al 2 O 3 -coated MoS 2 spheres for photocatalysis applications

This paper reports the synthesis of novel monodisperse Al2O3-coated molybdenum disulfide nanospheres (i.e., core-shell structures) using a one-step facile hydrothermal method. XPS analysis confirmed the purity and stable structure of the Al2O3- coated MoS2 nanospheres. A possible growth mechanism of the core-shell structure is also reported, along with their influence on the photodegradation process of rhodamine B (RhB). The Al2O3-coated MoS2 nanospheres demonstrate good photocatalytic activity and chemical stability compared to MoS2 spheres. TG-DTA analysis provided insight into the decomposition process of the precursor solution and the stability of the nanoparticles. The enhanced photocatalytic activity makes the Al2O3-coated MoS2 nanospheres a promising candidate as a photocatalyst that could be used in place of traditional Al2O3/MoS2 photocatalyst for the removal of pollutants from waste water.

Heterostructured Nanomaterials: Latest Trends in Formation of Inorganic Heterostructures

Abstract This chapter discusses the underlying principles governing the synthesis procedures of heterostructured materials. The latest developments and prospective applications as an environmentally friendly technology are also summarized. The focus is mainly on the preparation of two dimensional binary heterostructured materials, which have a wide range of applications as photocatalysts. Other photocatalytic applications of heterostructured materials in hydrogen production, energy conversion, and storage are also discussed. We introduce the latest trends and advancements in various heterostructured nanomaterials, including core-shell, hollow-interior, and dendritic morphologies, as well as composite formation. Information is provided on the relationships of the physical and chemical effects with the properties of the heterostructured nanomaterials, along with a technical basis for successfully developing novel nanostructures with simple procedures and low cost.

Tiny MoO3 nanocrystals self-assembled on folded molybdenum disulfide nanosheets via a hydrothermal method for supercapacitor

ABSTRACT Coupling of two active semiconductors can easily lead to a deterioration of their intrinsic properties. In this work, tiny MoO3 nanocrystals were deposited on 3D MoS2 frameworks via a hydrothermal reaction, with heterostructures forming by oxygen-bonding interactions at their interface. When tested as a supercapacitor electrode, the MoS2/MoO3 heterostructure exhibited a high specific capacitance of 287.7 F g−1 at a current density of 1 A g−1, and a remarkable cycling stability after 1000 cycles at 1 A g−1 in an aqueous solution compared to pristine MoS2. The results thus reveal the superior properties of the MoS2/MoO3 heterostructure for supercapacitor electrode. GRAPHICAL ABSTRACT IMPACT STATEMENT We successfully synthesized tiny MoO3 nanocrystals deposited on 3D MoS2 frameworks via a self-assembly. The MoS2/MoO3 heterostructure exhibited a high specific capacitance and cycling stability compared to pristine MoS2.

Visible-Light-Driven Photocatalytic Activity of SnO2–ZnO Quantum Dots Anchored on g-C3N4 Nanosheets for Photocatalytic Pollutant Degradation and H2 Production

A zero-dimensional/two-dimensional heterostructure consists of binary SnO2–ZnO quantum dots (QDs) deposited on the surface of graphitic carbon nitride (g-C3N4) nanosheets. The so-called SnO2–ZnO QDs/g-C3N4 hybrid was successfully synthesized via an in situ co-pyrolysis approach to achieve efficient photoactivity for the degradation of pollutants and production of hydrogen (H2) under visible-light irradiation. High-resolution transmission electron microscopy images show the close contacts between SnO2–ZnO QDs with the g-C3N4 in the ternary SnO2–ZnO QDs/g-C3N4 hybrid. The optimized hybrid shows excellent photocatalytic efficiency, achieving 99% rhodamine B dye degradation in 60 min under visible-light irradiation. The enriched charge-carrier separation and transportation in the SnO2–ZnO QDs/g-C3N4 hybrid was determined based on electrochemical impedance and photocurrent analyses. This remarkable photoactivity is ascribed to the “smart” heterostructure, which yields numerous benefits, such as visible-light-driven fast electron and hole transfer, due to the strong interaction between the SnO2–ZnO QDs with the g-C3N4 matrix. In addition, the SnO2–ZnO QDs/g-C3N4 hybrid demonstrated a high rate of hydrogen production (13 673.61 μmol g–1), which is 1.06 and 2.27 times higher than that of the binary ZnO/g-C3N4 hybrid (12 785.54 μmol g–1) and pristine g-C3N4 photocatalyst (6017.72 μmol g–1). The synergistic effect of increased visible absorption and diminished recombination results in enhanced performance of the as-synthesized tin oxide- and zinc oxide-modified g-C3N4. We conclude that the present ternary SnO2–ZnO QDs/g-C3N4 hybrid is a promising electrode material for H2 production and photoelectrochemical cells.