Enhanced field emission performance of gold nanoparticle decorated Bi2S3 nanoflowers

Au nanoparticles (NPs) are decorated on hydrothermally synthesized Bi2S3 nanorods (NRs) to enhance the field electron emission (FEE) performance as compared to bare Bi2S3 nanorods, resulting in reduction in turn-on field from 3.7 to 2.7 V μm-1 (at the current density of 1.0 μA cm-2) with significant increment in maximum emission current density from 138 to 604.8 μA cm-2 (at a field of 7.8 V μm-1) respectively. FESEM/TEM reveals that Bi2S3 nanoflowers are assembled from Bi2S3 NRs of a typical diameter of 120 ± 10 nm, and Au NPs of diameter about 5-10 nm are uniformly decorated onto the surface of NRs to form an Au/Bi2S3 composite. XRD analysis suggests that the as-synthesized product consists of orthorhombic Bi2S3 NRs decorated with face-centered cubic Au NPs. The XPS spectrum shows the elemental mapping of the as-synthesized Au/Bi2S3. Improvement in field emission properties is mainly attributed to a reduction in work function and increasing emitting sites due to Au NP decoration.

Step-Scheme Heterojunction between CdS Nanowires and Facet-Selective Assembly of MnOx-BiVO4 for an Efficient Visible-Light-Driven Overall Water Splitting

The spatial separation and transport of photogenerated charge carriers is crucial in building an efficient photocatalyst for solar energy conversion into chemical energy. A step-scheme CdS/MnO_x-BiVO₄ photocatalyst was synthesized by spatial deposition of MnO_x and one-dimensional (1D) CdS nanowires on a three-dimensional (3D) decahedron BiVO₄ surface. The photocatalytic activity of CdS/MnO_x-BiVO₄ for the overall water-splitting reaction was investigated without sacrificial reagent under visible light irradiation. The synthesized photocatalysts were thoroughly analyzed using high-end characterization techniques. The 5CdS/MnO_x-BiVO₄ exhibited the highest H₂ and O₂ production rates of 1.01 and 0.51 mmol g^-1 h^-1, respectively, with an apparent quantum yield of 11.3% in the absence of any sacrificial reagent. The excellent photoactivity is due to the presence of oxygen vacancies along with effective charge separation/transfer properties and strong interaction of cocatalysts (MnO_x and Pt) with the photocatalysts (BiVO₄ and CdS) in the 5CdS/MnO_x-BiVO₄ heterojunction. The significance of the presence of MnO_x and Pt cocatalysts on the selective facets of BiVO₄ for efficient overall water splitting reaction is highlighted in this work.

CdS decorated MnWO4 nanorod nanoheterostructures: a new 0D-1D hybrid system for enhanced photocatalytic hydrogen production under natural sunlight

Constructing a heterostructure is an effective strategy to reduce the electron-hole recombination rate, which enhances photocatalytic activity. Here, we report a facile hydrothermal method to grow CdS nanoparticles on MnWO4 nanorods and their photocatalytic hydrogen generation under solar light. A structural study shows the decoration of hexagonal CdS nanoparticles on monoclinic MnWO4. Morphological studies based on FE-TEM analysis confirm the sensitization of CdS nanoparticles (10 nm) on MnWO4 nanorods of diameter-35 nm with mean length ∼100 nm. The lower PL intensity of MnWO4 was observed with an increasing amount of CdS nanoparticles, which shows inhibition of the charge carrier recombination rate. A CdS@MnWO4 narrow band gap semiconductor was employed for photocatalytic hydrogen generation from water under solar light and the highest amount of hydrogen, i.e. 3218 μmol h-1 g-1, is obtained which is 21 times higher than that with pristine MnWO4. The enhanced photocatalytic activity is ascribed to the formation of a CdS@MnWO4 nanoheterostructure resulting in efficient spatial separation of photogenerated electron-hole pairs due to vacancy defects. More significantly, direct Z-scheme electron transfer from MnWO4 to CdS is responsible for the enhanced hydrogen evolution. This work signifies that a CdS decorated MnWO4 nanoheterostructure has the potential to improve the solar to direct fuel conversion efficiency.

Micro Flowers of SrS/Bi2S3 Nanocomposite and Its Field Emission Properties

The three-dimensional hierarchical SrS/Bi2S3 heterostructures were synthesized by a template-free single-step hydrothermal method. The structural and morphological studies revealed the formation of a single crystalline orthorhombic heterostructure with rod-like morphologies possessing a high aspect ratio. The field emission properties of SrS/Bi2S3 nanorods were investigated. J–E and the Fowler–Nordheim (F–N) plot, as well as long-term field emission (FE) stability, were studied. SrS/Bi2S3 nanoflowers have enhanced the FE properties more than the virgin Bi2S3. The observed values of the re-producible turn-on field for SrS/Bi2S3 defined to draw an emission current density of ca. 1 µA/cm2 were found to be ca. 2.50 V/µm, and of the threshold field to draw a current density of ca. 10 µA/cm2 were found to be ca. 3.00 V/µm (without visible light illumination). A maximum emission current density of ca. 527 μA/cm2 was drawn without light and a current density of ca. 1078 μA/cm2 with light, which is higher than that of pristine Bi2S3.