Search

A novel sandwiched gel polymer electrolyte (GPE) was prepared using a facile method as separator solely for rechargeable Lithium–Sulfur batteries. As a result of the strong physical shielding and chemical absorption of GPE, the separator can not only suppress shuttle effect in ether-based electrolyte, but also improve utilization of sulfur significantly resulting in a high capacity. The PVDF layers could absorb ether-based electrolyte largely and then enhance Li + transfer; the PMMA layer can be utilized to trap the dissolved polysulfides. Lithium–Sulfur batteries with the sandwiched GPE separator shows an encouraging electrochemical performance. A high initial discharge capacity of 1711.8 mAh g −1 is obtained, and the capacity retains at 1145.3 mAh g −1 after 50 cycles at 200 mA g −1 , which is higher than that of the cell with the commercial separator. These results indicate that the appropriate GPE separator is more suitable in Lithium−Sulfur batteries applications. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a novel and convenient electrochemical sensor based on stacked graphene nanofibers (SGNF) and gold nanoparticles (AuNPs) composite modified glassy carbon electrode (GCE) was developed for the determination of bisphenol A (BPA). The AuNPs/SGNF modified electrode showed an efficient electrocatalytic role for the oxidation of BPA, and the oxidation overpotentials of BPA were decreased significantly and the peak current increased greatly compared with bare GCE and other modified electrode. The transfer electron number (n) and the charge transfer coefficient (α) were calculated with the result as n =4, α =0.52 for BPA, which indicated the electrochemical oxidation of BPA on AuNPs/SGNF modified electrode was a four-electron and four-proton process. The effective surface areas of AuNPs/SGNF/GCE increased for about 1.7-fold larger than that of the bare GCE. In addition, the kinetic parameters of the modified electrode were calculated and the apparent heterogeneous electron transfer rate constant (k s) was 0.51s−1. Linear sweep voltammetry was applied as a sensitive analytical method for the determination of BPA and a good linear relationship between the peak current and BPA concentration was obtained in the range from 0.08 to 250μM with a detection limit of 3.5×10−8 M. The modified electrode exhibited a high sensitivity, long-term stability and remarkable reproducible analytical performance and was successfully applied for the determination of BPA in baby bottles with satisfying results. [Copyright &y& Elsevier]

Abstract: A graphene sheets (GS), ionic liquid (IL) and chitosan (CS) modified electrode was fabricated and the modified electrode displayed excellent electrochemical catalytic activities toward guanine and adenine. The transfer electron number (n) and the charge transfer coefficient (α) were calculated with the result as n =2, α =0.58 for guanine, and n =2, α =0.51 for adenine, which indicated the electrochemical oxidation of guanine and adenine on GS/IL/CS modified electrode was a two-electron and two-proton process. The oxidation overpotentials of guanine and adenine were decreased significantly compared with those obtained at the bare glassy carbon electrode and multi-walled carbon nanotubes modified electrode. The modified electrode exhibited good analytical performance and was successfully applied for individual and simultaneous determination of guanine and adenine. Low detection limits of 0.75μM for guanine and 0.45μM for adenine were obtained, with the linear calibration curves over the concentration range 2.5–150μM and 1.5–350μM, respectively. At the same time, the proposed method was successfully applied for the determination of guanine and adenine in denatured DNA samples with satisfying results. Moreover, the GS/IL/CS modified electrode exhibited good sensitivity, long-term stability and reproducibility for the determination of guanine and adenine. [Copyright &y& Elsevier]

It is highly desirable to improve the high voltage stabilities of cathode materials for Li-ion battery materials since it can deliver a higher reversible capacity at high cutoff voltage. Herein, we propose a novel facile strategy to generate La 2 O 3 -modified LiNi 1/3 Co 1/3 Mn 1/3 O 2 with superior electrochemical performance in the voltage range of 2.5–4.5 V via a solid-state method. It can be observed that La 2 O 3 -modified LiNi 1/3 Co 1/3 Mn 1/3 O 2 can greatly enhance the electrochemical performance due to the synergistic effect of ion doping and surface-modifying. La ions doping can alleviate the Li + /Ni 2+ mixing, and substantially enhance the structure stability of LiNi 1/3 Co 1/3 Mn 1/3 O 2 during charge/discharge cycles at high cutoff voltage. LaNi 0.4 Co 0.6 O 3 /LaMnO 3.26 spreading on the surface layer is very useful in improving the diffusion of Li + and inhibiting the particles from reacting with the electrolyte, enhancing the high voltage stabilities of the interface between electrode and electrolyte. The capacity retention of 0.7% (molar fraction) La 2 O 3 -modified LiNi 1/3 Co 1/3 Mn 1/3 O 2 is 79.0% after 300 cycles compared to 61.7% for bare LiNi 1/3 Co 1/3 Mn 1/3 O 2 . And its discharge capacity at 10 C is 141.7 mAh g −1 in the voltage range of 2.5–4.5 V, which is higher than those of other samples. This work not only offers a facile novel strategy to achieve superior electrochemical performances of cathode materials but also presents some new insights into the stabilization mechanism of modified cathode materials during charge/discharge cycles or long-term storage at high cutoff voltage. [ABSTRACT FROM AUTHOR]

• Hetero-phase hybridization strengthens internal electric field. • Covalent interaction creates nucleation sites and stabilizes the hybrids. • In-situ growth of MOF on Co 2 (OH) 2 CO 3 eliminates self-aggregation. • Controlled synthesis of the heterostructure with MWCNTs aid produces synergistic effect. • The integrated electrode delivers superior rate performance at high current density. In this work, bimetallic nickel-cobalt based metal organic framework (MOF) is in-situ grown on 2D laminar Co 2 (OH) 2 CO 3 with multi-walled carbon nanotubes (MWCNTs) aid to form nanoflower-like hierarchical porous heterogeneous structure for advanced supercapacitor application. Benefitting from the low crystal surface energy of Co 2 (OH) 2 CO 3 , its intersection and connection with MOF generate convenient electron path and open channel for ionic transmission, and large contact area. The high aromaticity of MWCNTs slows down destruction for MOF structure from water molecule through providing hydrophobic environment, guaranteeing stable presence of the resulting composite in aqueous electrolyte. The synergistic effect of Ni/Co with high redox activity in bimetallic NiCo-MOF provides rapid and multiple redox reactions for enhanced capacitance. Taking full advantage of promising merits of individual components, the optimized NiCo MOF-Co 2 (OH) 2 CO 3 nanosheet-MWCNT 30 (NCM-NS-CNT 30) composite under MWCNT dosage of 30 mg delivers greatly enhanced specific capacitance (1773 F g−1 at 1 A g−1) and obviously improved rate performance (96.5 % retention at 10 A g−1). Based on it, the fabricated hybrid supercapacitor (HSC) NCM-NS-CNT 30 //AC presents comparatively good energy density (30.625 Wh Kg−1), superior to most recently reported Ni, Co-based supercapacitors. [Display omitted] [ABSTRACT FROM AUTHOR]

• A hollow structure PZ-20 was prepared by controlling the ligand exchange time. • Hollow structure r-NiCo 2 S 4 with sulfur vacancies for more active sites and redox reactions was synthesized. • The fabricated structure exhibited an ultra-high specific capacitance. • The assembled device presented an high energy density of 43.80 Wh·kg−1 under 800 W·kg−1. Defect and hollow structure on transition metal sulfides can produce abundant active sites and shorten electron/ion diffusion paths, improving the conductivity of electrochemically active materials. In this study, an effective strategy was proposed for preparing r-NiCo 2 S 4 electrode materials with sulfur vacancies and hollow structures and resulted excellent electrochemical performance through ligand exchange followed chemical reduction. Due to the unique structure, the prepared r-NiCo 2 S 4 electrode exhibited excellent specific capacitance (1406.4 F g−1 at 1 A g−1) and rate capacity (90.03%). Additionally, a hybrid supercapacitor r-NiCo 2 S 4 //AC HSC was assembled using r-NiCo 2 S 4 as the positive electrode and AC as the negative electrode. It presented an excellent energy density of 43.8 Wh kg−1 under 800 W kg−1 and cycling performance with 93.93% capacity retention after 10,000 cycles at 5 A g−1. This study provided a simple strategy for design and optimization of electrode materials with a unique hollow structure and sulfur vacancies. [ABSTRACT FROM AUTHOR]

A novel acetylene black/sulfur@graphene composite (AB/S@G) with unique three-dimensional sandwich structure was successfully prepared via an in situ sulfur deposition strategy and self-assembly. Acetylene black as conductive carbon skeleton and graphene nanosheets as physical shields played an extremely important role for improving the electrochemical performances of the AB/S@G cathode. Compared with the AB/S cathode, the AB/S@G cathode with a sulfur content of 54 wt% exhibited a high utilization of sulfur, an enhanced cyclical stability, and an excellent rate capability. The AB/S@G cathode came true a high sulfur utilization of 95.73% after undergoing a high initial discharge capacity of 1603.5 mAh g −1 at a current density of 200 mA g −1 , much higher than that (71.78%) of the AB/S cathode. The excellent electrochemical performances were principally attributed to the combined effect of graphene nanosheets and acetylene black, which provided an improved electrical conductivity for the sulfur cathode, effective restraining for soluble polysulfides, and powerful buffer for the volume changes of sulfur during cycling. [ABSTRACT FROM AUTHOR]

A disposable biosensor for determination of hydrogen peroxide (H2O2) based on Fe3O4–Au magnetic nanoparticles coated horseradish peroxidase (HRP) and graphene sheets (GS)–Nafion film modified screen-printed carbon electrode (SPCE) was fabricated. To construct the H2O2 biosensor, GS–Nafion solution was first dropped onto the surface of SPCE. Subsequently, the biocomposites of Fe3O4–Au magnetic nanoparticles coated HRP were adsorbed on the surface with the aid of an external magnetic field to fabricate the SPCE|GS–Nafion/Fe3O4–Au-HRP electrode. X-ray powder diffractometer (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry(i–t curve) were employed to study the synthesis of GS, the construction processes and electrochemical properties of the biosensor. Under optimized experimental conditions, CV demonstrated that the direct electron transfer (DET) of HRP was realized. The biosensor had an excellent performance in terms of electrocatalytic reduction toward H2O2. The linear response of the biosensor to H2O2 was in the concentration range of 2.0×10−5 mol/L to 2.5×10−3 mol/L (R =0.9994) with a detection limit of 1.2×10−5 mol/L (S/N=3). The proposed electrochemical biosensor was sensitive, rapid, disposable with low cost, fewer sample volume, easy preparation and strong anti-interference, which showed great promise for screen-determination of trace H2O2 in real samples. [ABSTRACT FROM AUTHOR]