The composites of graphene nanosheets decorated by Pt nano clusters have been prepared via reduction of graphite oxide and H
2PtCl
6 in one pot. Electrochemical experiments show that the composites ...have superior catalytic performance toward methanol oxidation indicating the graphene may have a splendid future as catalysts carrier in electrocatalysis and fuel cell.
Graphene was synthesized chemically by Hummers and Offeman method and the graphene-modified electrode was applied in selective determination of dopamine with a linear range from 5
μM to 200
μM in a ...large excess of ascorbic acid. Selective detection was realized in completely eliminating ascorbic acid, different from the methods based on the potential separations. π–π stacking interaction between dopamine and graphene surface may accelerate the electron transfer whereas weaken the ascorbic acid oxidation on this graphene-modified electrode. The resulted graphene-modified electrode also showed a better performance than multi-walled carbon nanotubes-modified electrode. The phenomena were considered from the elusive two-dimensional structure and unique electronic properties of graphene.
This paper describes the preparation, characterization, and electrochemical properties of reduced graphene sheet films (rGSFs), investigating especially their electrochemical behavior for several ...redox systems and electrocatalytic properties towards oxygen and some small molecules. The reduced graphene sheets (rGSs) are produced in high yield by a soft chemistry route involving graphite oxidation, ultrasonic exfoliation, and chemical reduction. Transmission electron microscopy (TEM), X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy clearly demonstrate that graphene was successfully synthesized and modified at the surface of a glassy carbon electrode. Several redox species, such as Ru(NH3)63+/2+, Fe(CN)63−/4−, Fe3+/2+ and dopamine, are used to probe the electrochemical properties of these graphene films by using the cyclic voltammetry method. The rGSFs demonstrate fast electron‐transfer (ET) kinetics and possess excellent electrocatalytic activity toward oxygen reduction and certain biomolecules. In our opinion, this microstructural and electrochemical information can serve as an important benchmark for graphene‐based electrode performances.
Reduced graphene sheet films are shown to be advanced electrode materials that can easily be prepared by a chemical method. Their electrochemical and electrocatalytic properties amongst which are fast electron‐transfer kinetics and excellent activity for a variety of electroactive species are revealed. These studies aid in understanding the relationship between the structure and electrochemical properties of graphene‐based electrodes, suggesting promising applications in efficient biosensing, energy‐conversion, biomedical, and other electronic systems.
► Graphene nanosheets modified by KOH treatment were used as supercapacitor materials. ► Some oxygen-containing functional groups were introduced by KOH treatment. ► The KOH treatment led to the ...improved electrochemical performance of graphene nanosheets.
Chemical modification of graphene nanosheets by KOH was examined as a way to enhance the specific capacity of graphene nanosheets in supercapacitor. Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy were used to investigate the effects of the treatment on the surface of the graphene nanosheets. The specific capacitance of 136
F
g
−1 was obtained for KOH treated graphene by integration of the cyclic voltammogram, an increase of about 35% compared with that for the pristine graphene nanosheets.
In order to ameliorate the capacitance and energy density of supercapacitors in aqueous electrolytes, nitrogen- and phosphorus-codoped carbon microspheres/reduced graphene oxide nanocomposites are ...obtained by hydrothermal treatment of graphite oxide and N,P-doped carbon microsphere. The as-prepared nanocomposites display a high specific surface area of 604.3 m
2
g
−1
and hierarchical pore structure composed of micropores, mesopores, and macropores. N,P-codoped carbon microspheres/reduced graphene oxide are used as electrode materials in the redox electrolyte of H
2
SO
4
and KI aqueous solution, exhibiting a excellent capacitance performance of up to ~ 654 F g
−1
at 2 A g
−1
, corresponding to the energy density of 14.53 Wh kg
−1
at power density of 402 W kg
−1
. Even at a high current of 20 A g
−1
, the electrode can keep a capacitance of 318 F g
−1
, showing an energy density of 7 Wh kg
−1
at power density of 3984 W kg
−1
. This study indicates the potential of nitrogen- and phosphorus-codoped carbon microspheres/reduced graphene oxide in high energy density supercapacitor.
Silanization of magnetic ironoxide nanoparticles with (3-aminopropyl)triethoxylsilane (APTES) is reported. The kinetics of silanization toward saturation was investigated using different solvents ...including water, water/ethanol (1/1), and toluene/methanol (1/1) at different reaction temperature with different APTES loading. The nanoparticles were characterized by Fourier transform infrared spectroscopy, vibrating sample magnetometry, transmission electron microscopy, and thermal gravimetric analysis (TGA). Grafting density data based on TGA were used for the kinetic modeling. It is shown that initial silanization takes place very fast but the progress toward saturation is very slow, and the mechanism may involve adsorption, chemical sorption, and chemical diffusion processes. The highest equilibrium grafting density of 301 mg/g was yielded when using toluene/methanol mixture as the solvent at a reaction temperature of 70 °C.
Abstract
Asymmetric transmission in which wave energy propagates only in one direction attracts significant attention in various fields because of its rich physics and potential applications. In this ...work, we propose an elastic mode-converting metamaterial, which allows a
full-power
mode-converting transmission from longitudinal waves to transverse waves in the forward direction, while completely restricts the L wave transmission in the inverse direction. The metamaterial is designed by simply cutting two arrays of periodic silts on a matrix by exploring a straight design methodology, and thus very friendly for fabrication and application. Eigen-frequency analysis shows that the bilayer metamaterial exhibits two modes with significantly close natural frequencies around the working frequency, one for full-power mode-converting transmission, and the other for asymmetric transmission. Ultrasonic experiments are carried out to validate the proposed design. Our work offers a simple and efficient way for the realization of a complete one-way mode-converting transmission, and could be critically useful in designing diode-like meta-devices for novel wave manipulations.
► Achieving very small internal resistant and excellent electrochemical response. ► Unlimited in the working medium able to incorporate in. ► Much easier to scale up. ► Retaining virtually all ...capacitance after a month.
A novel method involving vacuum filtration deposition (VFD) of graphene suspension is developed in this study to fabricate graphene based nickel foam electrode for supercapacitor. Acid-treated graphene nanosheets in a suspension can be easily deposited in the pores of nickel foam in large quantity using this method, thus producing supercapacitors with large energy capacity. Structural and morphological characterizations of as prepared electrodes have been carried out using scan electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Electrochemical performance of as prepared electrode has also been investigated through cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge analyzer, in comparison with electrodes prepared via existing technique. Our results demonstrated that the new electrode, while achieving much greater energy capacity due to large active substance incorporated, still maintains a relatively high power density and a good cycle performance in 6M KOH electrolyte. Our results also demonstrated that a supercapacitor made of the existing electrophoretic deposition based electrodes will lose its entire capacitance after certain time period (20 days in our study); whereas the VFD based one retains virtually all its performance after the same period. The present study shows the potential application of this method for fabrication of supercapacitor with much improved energy capacity.
Dielectric ceramic capacitors, with the advantages of high power density, fast charge-discharge capability, excellent fatigue endurance, and good high temperature stability, have been acknowledged to ...be promising candidates for solid-state pulse power systems. This review investigates the energy storage performances of linear dielectric, relaxor ferroelectric, and antiferroelectric from the viewpoint of chemical modification, macro/microstructural design, and electrical property optimization. Research progress of ceramic bulks and films for Pb-based and/or Pb-free systems is summarized. Finally, we propose the perspectives on the development of energy storage ceramics for pulse power capacitors in the future.
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