Search

In this paper, an effective strategy to fabricate mesoporous MoS 2(1-x) Se 2x composites supported on graphene sheets (meso-MoS 2(1-x) Se 2x /rGO) for use as anode materials for lithium ion batteries (LIBs) is reported. The meso-MoS 2(1-x) Se 2x /rGO composites possess a two-dimensional (2D) layered structure with well-defined mesoporosity and the MoS 2(1-x) Se 2x nanoparticles are perpendicularly grown on graphene sheets. Due to the merits of 2D layered structural configuration and sulfur-selenium coupled effect, the meso-MoS 2(1-x) Se 2x /rGO composites promise the enhanced electrochemical performance for LIBs. Introduction of Se may widen the spacing of the (002) crystal plane, as a result, rendering them more effective diffusion path for both Li + and e − during the charge and discharge process. More importantly, Se incorporation may further induce the transition of meso-MoS 2(1-x) Se 2x from 2H phase to more metallic 1 T phase. As such, the meso-MoS 1.12 Se 0.88 /rGO electrodes exhibit efficient rate capability and good cycling stability with an optimum capacity of 830 mA h g −1 at a current density of 100 mA g −1 for 150 th cycle. The meso-MoS 1.12 Se 0.88 /rGO electrode still keeps a capacity of 415.3 mA h g −1 even when the current density is 1000 mA g −1 making them promising for potential practical application. The novel synthetic strategy may be applicable to fabricate a large variety of 2D layered chalcogenide electrode materials for LIBs. [ABSTRACT FROM AUTHOR]

Owing to the faradaic oxidation and reduction reactions mainly taking place on surface, enlarging the specific surface of redox materials is one of the most effective ways to achieve excellent electrochemical performance. Here we report a binder-free three dimensional (3D) architecture electrode consisting of a graphene 3D network (G3DN) structure growing on flexible carbon paper (CP) by chemical vapor deposition and NiO nanoparticles growing on the G3DN by in-situ thermal decomposition for high rate battery and high-performance electrochemical capacitors. Such a nanostructure provides a large specific surface and fast electronic transmission channels. The unique structure design for this electrode enables outstanding performance, showing high specific capacity of 89.1 mAh cm −2 (119.2 mAh/g) at current density of 0.5 mA cm −2 (0.67 A/g) with the NiO loading of 0.7471 mg cm −2 . Meanwhile the electrode displays excellent rate capability and cycling stability, which keeps 85.48% of initial capacity after 3000 deep-discharge cycles. Furthermore, a solid-state symmetric electrochemical capacitor based on two NiO/G3DN/CP electrodes with an area of 4 cm 2 each is fabricated, and two pieces of them in series can light up 100 green LEDs for 2 min. The architecture of G3DN loaded with NiO might be generally applied to different kinds of nanomaterials for high-rate energy storage to improve their overall electrochemical performance. [ABSTRACT FROM AUTHOR]

Silicon has been recognized as the most promising anode material for high-capacity lithium ion batteries. However, its large volume variation during the charge-discharge process results in electrode pulverization and fast capacity loss on cycling. The paper reports a facile synthesis of phenylalanine-functionalized graphene quantum dots (PF-GQD) through the pyrolysis of citric acid and phenylalanine. The PF-GQD was coated on the surface of silicon nanoparticles (SiNP) and then treated by thermal annealing in Ar/H 2 to obtain PF-GQD@SiNP composite. The PF-GQD coating layer not only improves the electrical conductivity, but also effectively prevents the direct contact of silicon surface with the electrolyte molecules. The composite electrode exhibits an excellent electrochemical performance for lithium ion batteries. The specific capacity is 4066 mA h g −1 at 50 mA g −1 , 3796 mA h g −1 at 100 mA g −1 and 1820 mA h g −1 at 1000 mA g −1 . The capacity can remain 3068 mA h g −1 after 100 cycles at 100 mA g −1 . As a control sample, alanine-functionalized graphene quantum dots (AF-GQD) was also prepared and used for the fabrication of AF-GQD@SiNP composite. The result shows that the electrochemical performance of PF-GQD@SiNP is much better than that of AF-GQD@SiNP. The improvement is attributed to the benzene ring at the edge of graphene sheets. Its introduction creates a wider and finer energy level of electron and well-defined steric structure compared to AF-GQD, which further accelerates the electron transfer and electrolyte transport and leads to an improved electrochemical performance. In addition, the study also provides an economic, eco-friendly and facile method for the fabrication of silicon-based anode materials for next generation high-performance lithium ion batteries. [ABSTRACT FROM AUTHOR]

In this paper, reduced carboxylic graphene/palladium nanoparticles (rGN-COOH/PdNPs) modified ultramicroelectrode array (UMEA) was investigated and applied in electrochemical determination of biochemical oxygen demand (BOD). The UMEAs were fabricated by micro electro-mechanical system technique. The sensitive film of rGN-COOH/PdNPs was prepared by self-assembling of carboxylic graphene (GN-COOH), electroreducing the GN-COOH and electrodepositing the palladium nanoparticles on UMEA. This modification method is suitable to UMEA, which can immobilize the sensitive film on the designed sites and maintain the unique characteristics of UMEA. Compared with the sensitive film of GN-COOH, rGN-COOH and PdNPs, the sensitive film of rGN-COOH/PdNPs showed satisfied electroreduction performance to dissolved oxygen (DO). A BOD microsensor was fabricated based on the rGN-COOH/PdNPs modified UMEA. A good linear range from 1 to 30 mg/L for BOD determination was displayed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, graphene-modified Li3V2(PO4)3 composites have been developed as Li-ion battery cathode materials with high specific capacity and excellent cycling stability. The composites are prepared by spray–drying process using graphene oxide nanosheet and citric acid as carbon source. X-ray diffraction patterns demonstrate that the as-prepared samples are well crystallized with orderly monoclinic structures. SEM and TEM images reveal that the 3D network graphene and Li3V2(PO4)3 primary nanoparticles interlace with each other. The citric acid-derived amorphous carbon species interrupt the stacking of graphene sheets and minimize in-plane anisotropy of electronic migration within graphene layers, which would facilitate fast electron migration and Li+ diffusion throughout the micro-sized spherical secondary particles. The discharge capacity of the composite could respectively achieve 131.4 and 181.5mAhg−1 in the voltage range 3.0–4.3V and 3.0–4.8V at 0.1C discharge rate, which almost reach the theoretical capacity of the cathode material. Both of them nearly showed no capacity decay at 0.1C charging and discharging rate after long cycles. [Copyright &y& Elsevier]

Abstract: This paper describes a new signal amplification strategy based on ionic liquid-doped chitosan film as a matrix and Au nanoparticle decorated graphene nanosheets (AuNP–graphene) as labels for the sensitivity improvement of an electrochemical immunosensor. At first, an ionic liquid was doped into ferrocene-branched chitosan film to obtain a novel redox composite, which was employed as an antibody immobilization matrix due to its better biocompatibility and higher electron transfer mobility. Then, the AuNP–graphene were prepared by a one-pot method in a aqueous-phase synthesis and were provided with a large surface area and multiple binding sites to allow high accessibility for the immobilization of secondary antibody (Ab2) and horseradish peroxidase (HRP). Based on the sandwich immunoassay format, the electrochemical signal could be amplified and adequately achieved, according to the catalytic reaction of the carried HRP towards the reduction of H2O2 with the aid of the IL and ferrocene synergistic effect. Using Immunoglobulin G (IgG) as a protein model, a good and repeatable linear relationship was found between the electrical signal outputs and human IgG concentration on a logarithm scale for a wide range of 2.0×10−10 to 5.0×10−7 g/mL, with a detection limit of 50pg/mL. In conclusion, the use of ionic liquid-doped chitosan redox film and AuNP–graphene greatly enhances the electrochemical signal and shows high sensitivity. [Copyright &y& Elsevier]