In the present work, we developed a micellar system of milk protein-surfactant (SDS)-graphene to prepare the graphene-based aerogels via hydrothermal and freeze-drying method, in which the novel ...surface-property of aerogels can be tuned with the decreasing of micellar size in the colloid systems resulting the improved specific surface area. The milk protein also severed as green and sustainable sources to introduce nitrogen heteroatoms into the aerogels. Subsequently, the aerogels were further graphitized and activated to fabricate N-doped porous nanocarbon at 600 °C. The initial surface composition and structure of the aerogel, which was proved, has obvious impact on the final structure of the synthesized nanocarbon materials, and thus influence their electrochemical activity. The optimized nanocarbon materials (MGPC-5), with enhanced specific surface area, degree of graphitization, and nitrogen doping, exhibited excellent capacitance performance and stability in both three-electrode system (518.8 F/g at a current density of 0.1 A/g) and symmetrical electrode system (120.8 F/g at current density of 0.1 A/g and with ~95% capacitance retention after 5000 cycles of charging and discharging at 3 A/g) in KOH. The assembled supercapacitor also shows ideal capacitive properties in series and parallel configurations. Tested with a stable 1.6 V windows in Li2SO4 electrolyte, the symmetric supercapacitor cell exhibits a high energy density up to 36.7 W h/kg. The present work provides a feasible fabrication method for high-performance supercapacitor based on graphene and biomass derived carbon, the proposed surface-property regulation and supercapacitor performance improvement strategy may also shed light on other energy related materials or system.
Milk micelles serve as multifunctional biomass additives to compose with graphene oxide for fabrication of nitrogen doped porous nanocarbon materials. The supramolecular interactions between the two components provide effective ability in regulation of the surface and porous property and improvement of the supercapacitor performance of nanocarbons. Display omitted
Display omitted
► The effective diffusion coefficient is determined by the effective concentration difference across the dialysis membrane. ► The effective diffusion coefficient was affected by ionic ...strength, binding agent, ligands and Donnan potential. ► The determination of effective diffusion coefficient and its application should be in the same environment.
Cellulose acetate dialysis membrane (CDM) has been used in the diffusive gradients in thin films (DGT) technique, where accurate diffusion coefficients are essential for the assessment of the concentrations of labile metal in solution. Effective concentration difference model (ECDM), based on the assumption that the effective diffusion coefficient of metal ion in the dialysis membrane is determined by the effective concentration difference (Δ
C
e) across the dialysis membrane, is proposed and applied to study the effect of ionic strength, binding agent, ligands and Donnan potential on the effective diffusion coefficient. The effective diffusion coefficients of Cd
2+ through the dialysis membrane immersed in receptor solutions with binding agent were almost the same as those in receptor solutions without binding agent at higher ionic strengths (0.01–1
M) but much higher than those at lower ionic strengths (0.001–0.0001
M). The effective diffusion coefficients of Cd
2+ through the dialysis membrane immersed in deionized water receptor solutions with binding agent were not significantly different from those in synthetic receptor solutions (receptor solutions with various ionic strengths) with binding agent. The DGT-labile fractions were measured in synthetic solutions and natural waters, which indicated that the effective diffusion coefficients, through the dialysis membrane immersed in the deionized water solution with binding agent as receptor solution and in the spiked natural water as source solution, were more suitable for DGT application.
Reduced graphene oxide (rGO) covered sulfur loaded on carbon fibers have been fabricated by combinations of melt-flow and electrochemical coverage strategies. rGO layers can serve as conductive ...composite and protective layer to improve the specific capacity and cycling stability of S/carbon fiber based LSB.
Display omitted
•Carbon fibers and rGO as conductive components supply double transporting paths of electrons.•rGO as blocking layers inhibits the soluble sulfur diffusing into electrolyte.•rGO layers as another redepositing places increase the utilization of sulfur.
To improve the electrochemical performance of Li-S batteries, a cathodic material (rGO150/S/CF-75) was fabricated for Li-S batteries by adopting a melt-flow method to load sulfur on biomass-derived carbon fibers, then the reduced graphene oxide was electrochemically covered on the outside surface of the sulfur. The coverage of reduced graphite oxide layers endows the performance of S/CF-75 multiple improvements. The specific capacity of rGO150/S/CF-75 cathode delivers a specific capacity of 1451.4 mAh g−1 at 0.1 A g−1. The specific capacity of rGO150/S/CF-75 cathode can still maintain 537.3 mAh g−1 after 1000 cycles at 5 A g−1 (109 % capacity retention). The excellent performance of rGO150/S/CF-75 cathode is benefit from not only the conductive paths of reduced graphene oxide layers and protective function of reduced graphene oxide layers inhibiting that the soluble sulfur diffuse into bulk electrolyte, but also the redistribution of sulfur on conductive carbon components during the cycling process.
A technique for the selective measurement of diffusive gradients in thin-films (DGT) for free Cu2+ ions was developed using a 0.030 M solution of polyvinyl alcohol (PVA) as the liquid binding phase ...with the liquid-type DGT devices (PVA DGT). The PVA DGT had a substantial binding capacity at pH 5.6 − 8.6 and concentrations of competitive Na+ up to 0.7 M. The measurements of PVA DGT and cupric ion selective electrode (Cu-ISE) for free Cu2+ in synthetic river water (recovery = 97.51 ± 2.58% for PVA DGT and recovery = 98.25 ± 1.46% for Cu-ISE), in spiked river water (recovery = 24.99 ± 3.55% for PVA DGT and recovery = 26.32 ± 3.33% for Cu-ISE) and in spiked industrial wastewater (recovery = 4.21 ± 3.13% for PVA DGT and recovery = 5.10 ± 2.78% for Cu-ISE) were equivalent. The results showed that PVA DGT could measure selectively the free Cu2+ ion concentrations in water samples.
The paper presents a novel strategy for the fabrication of sandwich-like N, S co-doped graphene aerogels using π-π and H-bonding interactions between 2, 5-Dimercapto-1, 3, 4-thiadiazole (DMTD) and GO ...via hydrothermal method. The synergistic effect between N and S atoms plays key role to improve the supercapacitor performance of the fabricated graphene aerogel material.
Display omitted
•π-conjugated DMTD molecules are used as dopant precursors and pillared agents for the fabrication of NSGA.•NSGA delivers a high gravimetric specific capacitance of 321 F g−1 at a current density of 1 A g−1.•The π-conjugated and H-bonding interactions improve the accessible surface area of NSGA.•The synergistic effect of N andS and enhancement of surface area are the main reason in promoting the SC performance.
Rational constructing carbon electrode materials with heteroatoms (eg. N, S, B, F) and high surface area is essencial to the appealing performance of supercapacitor (SC). Here we present a novel fabrication strategy for sandwich-like N, S co-doped three-dimensional (3D) porous graphene aerogels (NSGAs) via one-pot hydrothermal method for high performance SCs materials. The unique advantage of the proposed synthesis strategy is the applications of 2, 5-Dimercapto-1, 3, 4-thiadiazole (DMTD) as bifunctional pillared agents and efficient dopant precursors. The planar DMTD molecules have shown strong supramolecular π-π and H-bonding interactions with graphene oxide (GO), thus avoiding the restacking of graphene sheets and enhancing the doping efficiency and amount of S atoms, which are beneficial to the SC performance of NSGA. The synthesized NSGA samples exhibit the atomic content of S up to 2.39 at.% with surface area at 366.0 m2 g−1, and display a maximum energy density of 10.52 W h kg−1 for assembled symmetric supercapacitor. The relatively high tandem device performance with a remarkable current response, even at 2000 mV s−1, reaches the top level for graphene-based SC system. The proposed simple fabrication strategy and attracting performance of NSGA material shed light on the potential practical applications of graphene-based material as SCs, and the observed structure-function relations also provides physical-chemical insight into the function principle of heteroatom doped graphene in SCs.
Display omitted
•Feasibility for sampling 4-chlorophenol by DGT technique was investigated.•A relationship between binding rate and diffusion rate in the DGT technique was deduced.•Nylon membrane as ...diffusion layer of the DGT technique.•Molecularly imprinted polymer as binding agent of the DGT technique.
For the first time, a diffusive gradients in thin films (DGT) device using molecularly imprinted polymer (MIP) as the binding agent and nylon membrane (NM) as the diffusive layer (NM-MIP-DGT) has been developed for sampling 4-chlorophenol (4-CP) in water. The MIP was prepared by precipitation polymerization with methacrylic acid as monomer and ethyleneglycoldimethacrylate as cross-linker. The diffusion coefficient of 4-CP through NM was obtained to be 0.788±0.040μcm2s−1 by diffusion cell method. The ratio was 1.01±0.05 (mean±standard deviation) for the concentration of 4-CP sampled by NM-MIP-DGT and analyzed by HPLC method to the total concentration of 4-CP in the synthetic solution where free 4-CP species dominated. The results showed that NM-MIP-DGT could sample 4-CP in synthetic solution accurately. The performance of NM-MIP-DGT for sampling 4-CP was independent of pH in the range of 3–7 and ionic strength in the range of 0.0001–0.1molL−1 NaCl solution. The concentration of free form of 4-CP sampled by NM-MIP-DGT decreased with the increasing concentration of dissolved organic carbon in different water samples due to the electrostatic interaction of natural organic compounds with 4-CP. 1.8mgL−1 of the free form of 4-CP was determined by HPLC which was sampled by NM-MIP-DGT in an intermediate untreated industrial effluent. The NM-MIP-DGT can be a potential passive tool for sampling the free form of 4-CP in water.
The novelty of this paper is that we use 5-mercapto-3-phenyl-1,3,4-thiadiazole-2(3H) thione potassium salt (BII) as pillaring agent and dopant to synthesize 3D sulfur and nitrogen co-doped graphene ...aerogel (SNGA) as supercapacitor electrode materials. It is noteworthy that BII is a vertical bicyclic molecule with a special head-to-head non-planar structure effectively inhibiting the close stacking of graphene sheets during the self-assembly process. Therefore, SNGA4 synthesized under optimal condition obtains a larger specific surface area (410.2 m2 g−1). At the same time, BII with rich sulfur and nitrogen promote the doping amount of sulfur atoms at 3.71 at.% via the supramolecular interactions (π-π interaction and hydrogen bonding). Furthermore, this work gives us a deeper understanding of how to choose pillaring agents and dopants in the fabrication of high-performance graphene-based.
Display omitted
•A vertical bicyclic BII molecule are used as pillaring agent and dopant for 3D sulfur and nitrogen co-doped graphene aerogel (SNGA).•The π-π interaction and H-bonding between BII and GO promote the doping of sulfur and nitrogen atoms of SNGA.•SNGA shows a high specific capacitance of 399 F g−1 at a current density of 1 A g−1.•The head-to-head vertical non-planar structure gives the BII a more significant effect in preventing graphene stacking.
The two-dimensional (2D) graphene sheets can be self-assembled into three-dimensional (3D) graphene aerogels by a typical hydrothermal route to improve the supercapacitor performance in recent years. The novelty of this paper is that we use 5-mercapto-3-phenyl-1,3,4-thiadiazole-2(3H) thione potassium salt (BII) as pillaring agent and dopant to synthesize 3D sulfur and nitrogen co-doped graphene aerogel (SNGA) as supercapacitor electrode materials. It is noteworthy that BII is a vertical bicyclic molecule with a special head-to-head non-planar structure effectively inhibiting the close stacking of graphene sheets during the self-assembly process. Therefore, SNGA4 synthesized under optimal condition obtains a larger specific surface area (410.2 m2 g−1). At the same time, BII with rich sulfur and nitrogen promote the doping amount of sulfur atoms at 3.71 at.% via the supramolecular interactions (π-π interaction and hydrogen bonding). In the three-electrode configuration, the capacitance reached 399F g−1 (current density is 1 A g−1), and the energy density gained 11.36 Wh kg−1 in the assembled supercapacitor system. These results indicate the great potential of SNGA4 as an electrode material for supercapacitors. Furthermore, this work gives us a deeper understanding of how to choose pillaring agents and dopants in the fabrication of high-performance graphene-based supercapacitor electrodes.
Display omitted
•Graphene oxide sheets modulate ultramicroporous region of milk colloid-derived carbon.•Synergy of graphene oxide and metal oxide leads carbon to an advanced pore system.•Milk ...colloid-derived carbon shows excellent capacitance by synergetic modulation.
Biomass-derived carbon has great potential as electrode for supercapacitors or batteries, and the rational design and modulation of the porous structure is the key for advanced electro-chemical property. Herein, graphene oxide (GO) sheets and metal oxide particles templates were introduced for modulating the ultramicropores (less than 1 nm) and supermicropores/mesopores (∼ 2 nm) of porous carbon derived from milk colloid, aiming to exploring the potential of biomass-derived carbon as supercapacitor electrodes. Through the synergetic modulations of GO and metal oxide particles, the proposed supercapacitor materials (G-NP-MPC) exhibit high gravimetric (358.4 F/g)/areal (3.58 F/cm2)/volumetric capacitance (277.5 F/cm3) at mass loadings of 10 mg/cm2 in aqueous electrolyte, which accomplishes remarkable improvement of carbon directly derived from milk colloid (181.1 F/g, 1.81 F/cm2 and 140.3 F/cm3) without pore modulation. Apart from aqueous electrolyte, the symmetric supercapacitor (G-NP-MPC) also exhibits relatively high energy density (43.0 W h/kg at the power density of 300 W/kg) in organic electrolyte with the potential window of 3 V. This work amplifies the function of graphene oxide sheets and metal oxide, which can corporately tune the pore size distribution in a narrow scope for enhancing integrated capacitance of biomass-derived carbon.
PDF
