Search

Three-dimensional (3D) porous heterogeneous metallic nanomaterials hold remarkable competitiveness in electrocatalytic fields due to their flexible porous structure and the electronic effect between heteroatoms, but challenges in synthesis still remain. Here, we design a facile stepwise reduction method to successfully synthesize urchin-like Au/Pd nanobranches (NBs). In a one-pot synthesis, small Au nanoparticles were initially generated. Later, numerous Pd nanotwigs were epitaxially grown and interlaced on the Au seeds to create unique channels, forming an Au-core/Pd-branches structure eventually. The as-prepared Au/Pd NBs exhibit greatly improved activity and stability for alkaline oxygen reduction reaction (ORR) electrocatalysis compared to the commercial Pt/C, with mass activity (1.4 A mg–1) and specific activity (2.4 mA cm–2) increased by 8.8 and 8.9 times, respectively. The excellent ORR performances of Au/Pd NBs are mainly attributed to the optimized electronic structure, improved utilization of surface active sites, and accelerated mass and charge transfer, which derives from the strong ligand effect, as well as the abundant porous channels of the Au/Pd NBs structure. The controllable design and synthesis of 3D porous Pd-based nanomaterials sheds light on a gigantic potential for ORR electrocatalysis. [ABSTRACT FROM AUTHOR]

In the past decades, toxic gas emissions have increased significantly owing to the rapid growth of industry and road transportation. Therefore, monitoring major pollutants, such as NO2, is crucial to protecting human health. The 2D materials that contain numerous adsorption sites and exhibit ultrahigh chemical reactivity can be used as sensor materials to detect these toxic gases. Herein, highly uniform, large‐area carbon‐incorporating hierarchical MoS2 nanobranches are synthesized by metal–organic chemical vapor deposition (MOCVD). An in situ carbon‐incorporation method that uses the carbon impurity present in the precursor as the seed during the MOCVD process is employed to form a hierarchical structure containing abundant adsorption sites. A gas sensor based on the resulting C‐MoS2 nanobranches contains many edge sites exhibits high adsorption energy, and consequently, has high NO2 gas sensitivity. Hence, this hierarchical C‐MoS2 gas sensor shows excellent sensing properties, exhibiting a device response of 1.67 at an extremely low NO2 concentration (≈5 ppb). The limit of detection of the gas sensor for NO2 is calculated to be low (≈1.58 ppt), further confirming its exceptional performance. Thus, the hierarchical C‐MoS2 nanobranches deposited herein provide novel insights regarding the properties of 2D materials and are highly suited for fabricating high‐performance NO2 sensors.

In this paper, results from the fabrication and study of a piezoelectric microgenerator using nanobranched zinc oxide (ZnO) film grown on poly(3,4-ethylenedioxythiphene) doped with a sulfonate (PEDOT:PSS)-coated flexible substrate are presented. The aim of the study is to extract information about the electrical behavior of the harvester at different frequencies, temperatures, and positions, as related to the ZnO nanostructure, as well as to examine its piezoelectric response. Radiofrequency (RF) sputtering with oxygen deficit during growth on an amorphous sublayer was used to obtain the nanobranched structure. The microdevice was studied at frequencies ranging from 1 Hz to 1 MHz for temperatures in the range of -10 °C to 40 °C, in both a non-bended position, and a radius of curvature position bended to 12 mm. It was found that non-ordered ZnO nanoformations facilitate the dipoles' motion, thus leading to low dielectric losses of 10-3, and a higher relative permittivity of ϵr ~15, compared with typically known values. The losses increase with one order of magnitude at bending, but still remain low. Dielectric characteristics indicate that the favorable working range of the microgenerator is within the lower frequency region, from 10 Hz to 10 kHz. The results were confirmed by the measured open circuit voltage, which reaches approximately 1 V within this range, versus 300 mV out of the range. [ABSTRACT FROM AUTHOR]

In this paper, results from the fabrication and study of a piezoelectric microgenerator using nanobranched zinc oxide (ZnO) film grown on poly(3,4-ethylenedioxythiphene) doped with a sulfonate (PEDOT:PSS)-coated flexible substrate are presented. The aim of the study is to extract information about the electrical behavior of the harvester at different frequencies, temperatures, and positions, as related to the ZnO nanostructure, as well as to examine its piezoelectric response. Radiofrequency (RF) sputtering with oxygen deficit during growth on an amorphous sublayer was used to obtain the nanobranched structure. The microdevice was studied at frequencies ranging from 1 Hz to 1 MHz for temperatures in the range of −10 °C to 40 °C, in both a non-bended position, and a radius of curvature position bended to 12 mm. It was found that non-ordered ZnO nanoformations facilitate the dipoles’ motion, thus leading to low dielectric losses of 10−3, and a higher relative permittivity of εr ~15, compared with typically known values. The losses increase with one order of magnitude at bending, but still remain low. Dielectric characteristics indicate that the favorable working range of the microgenerator is within the lower frequency region, from 10 Hz to 10 kHz. The results were confirmed by the measured open circuit voltage, which reaches approximately 1 V within this range, versus 300 mV out of the range.

Abstract: Hierarchical SnO2 core–shell nanobranches are produced by thermal oxidization of hierarchical SnO nanobranches that are synthesized using a vapor transport method. The SnO nanobranches with a single crystalline tetragonal structure were heat-treated at 923K in an ambient atmosphere and completely transformed to hierarchical SnO2 nanobranches with an orthorhombic crystal structure. The SnO2 nanobranches of a polymorphism have a core–shell structure in which SnO2 phase (P212121) is formed in the core and SnO2 phase (Pbcn) at the shell. The electrochemical capacitive properties of the SnO2 nanobranches are evaluated by cyclic voltammograms and galvanostatic charge–discharge measurements. Results show that the hierarchical SnO2 nanobranches have an excellent pseudocapacitive performance, i.e., the maximum specific capacitance of 40.5μF/cm2 and long-term cycling stability up to 1000 cycles with the 8.9% loss of maximum specific capacitance. [Copyright &y& Elsevier]

Abstract: Nanobranched TiO2 nanotubes (TONTs) were synthesized by a sol–gel dipping method for the formation of seed layer, followed by a solution-phase deposition process. The different concentrations of seed solution influence the density of nanobranches on the top surface of TONT, achieving complete surface coverage of nanobranches in 10 mM TiCl4 seed solution relative to 5 mM TiCl4 seed solution. With a control sample of bare TONT, the nanobranched TONTs were explored as a photoanode for dye-sensitized solar cells (DSSCs). In the 5 mM TiCl4 seed solution, the nanotree-shaped branches were sporadically formed on the top surface of TONT, with little effect on the photocurrent-voltage (J–V) properties, while in the 10 mM TiCl4 seed solution, J sc and fill factor increased, which may have been on account of the increased surface area and light scattering effect from rutile nanobranches, whereas the fill factor may be also increased by the electron transport property, leading to the degraded charge recombination. Accordingly, the nanobranched TONT showed 33% improved efficiency compared to bare TONT. [Copyright &y& Elsevier]

Short-range order sodium dodecyl sulfate (SDS)-bound micelles and long-range order poly(vinylpyrrolidone) (PVP)-SDS supramolecular assemblies in PVP-SDS aqueous solution illustrate the potential template application in directing hierarchical assembly of inorganic nanostructure. In this paper, ginger-like Au nanobranches with equivalent circle diameter around 50 nm were prepared in PVP-SDS aqueous solution under microwave irradiation through a one-pot, facile, rapid, and morphology-controlled synthesis route. Based on the experimental results, the possible growth mechanism of the ginger-like gold nanobranches is inferred to be a template-mediated and microwave-assisted hierarchical assembly via the unique co-effect of PVP-SDS soft template and microwave irradiation. At first, the precursors AuCl surrounding the SDS-bound micelles were rapidly reduced to Au by sodium citrate assisted by microwave irradiation and simultaneously assembled into abundant Au nanocrystals with diameters around 10 nm according to the bound micelle templates. And then several tiny Au nanocrystals linked by PVP chains within a limited space were instantly mediated by the long-range order PVP-SDS supramolecular assemblies to fabricate into polycrystal ginger-like Au nanobranches. X-ray diffraction (XRD) pattern indicates that the Au nanobranches are face-centered cubic phase, which is verified by high-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) pattern. [ABSTRACT FROM AUTHOR]

Palladium-based catalyst represents one of the most promising candidates among all non-platinum oxygen reduction reaction (ORR) catalysts. However, it is still challenging to precisely engineering their morphology and composition. Herein, highly branched core-shell PdCu@Pd nanocrystals have been fabricated via a simple one-pot synthesis that co-directed by hydrogen gas and halide ions. Such unique PdCu@Pd nanocrystals exhibit prominent ORR activity, durability and methanol-tolerance in alkaline media owing to their core-shell composition, highly-branched structure and defect-rich surface. This work elucidates a facile strategy to design highly branched core-shell nanomaterials, shedding light on the exploration and optimization of novel non-platinum ORR catalysts. A facile method for one-pot synthesis of Defect-rich PdCu@Pd Core-shell Nanobranches is developed. The as-made catalyst shows superior activity, durability and methanol-tolerance towards oxygen reduction reaction. Image 1 [ABSTRACT FROM AUTHOR]