Carbon-based nanocomposites have developed as the most promising and emerging materials in nanoscience and technology during the last several years. They are microscopic materials that range in size from 1 to 100 nanometers. They may be distinguished from bulk materials by their size, shape, increased surface-to-volume ratio, and unique physical and chemical characteristics. Carbon nanocomposite matrixes are often created by combining more than two distinct solid phase types. The nanocomposites that were constructed exhibit unique properties, such as significantly enhanced toughness, mechanical strength, and thermal/electrochemical conductivity. As a result of these advantages, nanocomposites have been used in a variety of applications, including catalysts, electrochemical sensors, biosensors, and energy storage devices, among others. This study focuses on the usage of several forms of carbon nanomaterials, such as carbon aerogels, carbon nanofibers, graphene, carbon nanotubes, and fullerenes, in the development of hydrogen fuel cells. These fuel cells have been successfully employed in numerous commercial sectors in recent years, notably in the car industry, due to their cost-effectiveness, eco-friendliness, and long-cyclic durability. Further; we discuss the principles, reaction mechanisms, and cyclic stability of the fuel cells and also new strategies and future challenges related to the development of viable fuel cells. 相似文献
High‐surface‐area, guava‐leaf‐derived, heteroatom‐containing activated carbon (GHAC) materials were synthesized by means of a facile chemical activation method with KOH as activating agent and exploited as catalyst supports to disperse nickel oxide (NiO) nanocrystals (average size (2.0±0.1) nm) through a hydrothermal process. The textural and structural properties of these GHAC/NiO nanocomposites were characterized by various physicochemical techniques, namely, field‐emission SEM, high‐resolution TEM, elemental analysis, X‐ray diffraction, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and Raman spectroscopy. The as‐synthesized GHAC/NiO nanocomposites were employed as binder‐free electrodes, which exhibited high specific capacitance (up to 461 F g?1 at a current density of 2.3 A g?1) and remarkable cycling stability, which may be attributed to the unique properties of GHAC and excellent electrochemical activity of the highly dispersed NiO nanocrystals. 相似文献
We present a review of theoretical and experimental results for tunable microwave band-stop filters, band-pass filters, phase shifters, and a signal to noise enhancer, all based on a microstrip geometry and using a variety of magnetic thin films and layered structures. These devices are compatible in size and growth process with on-chip high-frequency electronics. For devices based on metallic ferromagnetic films of Fe and Permalloy, the operational frequency ranges from 5 to 35 GHz for external fields below 5 kOe. For the band-stop filters, we observed power attenuation up to ∼100 dB/cm, and an insertion loss on the order of ∼2-3 dB, for both Permalloy and Fe-based structures. We also explore the use of thin films of hexagonal ferrites, antiferromagnets, and liquid crystals, and show that useful devices can be constructed with films less than one 1 μm in thickness. 相似文献
This present investigation focused on novel p-type bismuth ferrite (BiFeO3)/n-type tin sulfide (SnS2) heterostructure photocatalyst has been favorably attained via a facile two-step process followed by co-precipitation approach for enhances the photocatalytic activity through the degradation of Methylene Blue (MB) and Rhodamine B (RhB) organic dyes under visible-light illumination. Structural, optical, and photocatalytic behavior of the prepared BiFeO3 and BiFeO3/SnS2 photocatalysts are carefully explored. The photocatalytic efficiency of BiFeO3/SnS2 nanocatalyst was calculated to be 83%, 78% for MB and RhB, respectively, within 120 min illumination whereas the pure BiFeO3 nanoparticle was 58% and 56% for MB and RhB. This prominent enhancement of visible light photocatalytic activity can be ascribed to the separation as well as the transfer of photogenerated charge carriers, successful exploitation of visible light absorption and donates the enlarged number of photocatalytic active sites by the formation of BiFeO3/SnS2 p-n heterojunction.
Chicken feather‐derived high‐surface‐area porous activated carbon (CFAC) material was prepared using chemical activation. A new composite composed of Ru‐Pd nanoparticles supported on CFAC (Ru‐Pd@CFAC) has been prepared by microwave‐thermal reduction in the presence of the support. Characterization by XRD, Raman, BET, FE‐SEM/TEM, FT‐IR, TGA, XPS, HAADF‐STEM‐EDS, H2‐chemisorption, H2‐TPR, and ICP‐AES was used to analyze the catalyst. This catalyst is found to be efficient for the reduction of hexavalent chromium (CrVI), potassium ferricyanide (K3[Fe(CN)6]), 4‐nitrophenol (4‐NP), and pendimethalin (PDM), at room temperature, and remains stable, even after several repeated runs. Moreover, it showed excellent catalytic activity compared with the monometallic counterparts. 相似文献
The present work describes, for the first time, in situ electrochemical preparation of dendrimer-encapsulated Cu nanoparticles
using a self-assembled monolayer of fourth-generation amine-terminated polyamidoamine (PAMAM) dendrimer as the template. Atomic
force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) studies of the modified surface confirmed the presence of
Cu nanoparticles entrapped in dendrimer film. Au electrode modified with a monolayer of the dendrimer enables preconcentration
and subsequent voltammetric detection of Cu2+ at picomolar concentrations. Further, Cu nanoparticles in the dendrimer monolayer could be electrochemically derivatised
to Cu hexacyanoferrate, which exhibits specific crystal planes, unlike the random distribution of crystal planes in bulk-formed
Cu hexacyanoferrate, which is another catalytically active material for sensor applications.
Figure Electrochemical preparation of copper–dendrimer nanocomposite 相似文献