| 1. |
- Sun, Jinhua, 1987, et al.
(author)
-
Critical Role of Functional Groups Containing N, S, and O on Graphene Surface for Stable and Fast Charging Li-S Batteries
- 2021
-
In: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 17:17
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Journal article (peer-reviewed)abstract
- Lithium‐sulfur (Li‐S) batteries are considered one of the most promising energy storage technologies, possibly replacing the state‐of‐the‐art lithium‐ion (Li‐ion) batteries owing to their high energy density, low cost, and eco‐compatibility. However, the migration of high‐order lithium polysulfides (LiPs) to the lithium surface and the sluggish electrochemical kinetics pose challenges to their commercialization. The interactions between the cathode and LiPs can be enhanced by the doping of the carbon host with heteroatoms, however with relatively low doping content (<10%) in the bulk of the carbon, which can hardly interact with LiPs at the host surface. In this study, the grafting of versatile functional groups with designable properties (e.g., catalytic effects) directly on the surface of the carbon host is proposed to enhance interactions with LiPs. As model systems, benzene groups containing N/O and S/O atoms are vertically grafted and uniformly distributed on the surface of expanded reduced graphene oxide, fostering a stable interface between the cathode and LiPs. The combination of experiments and density functional theory calculations demonstrate improvements in chemical interactions between graphene and LiPs, with an enhancement in the electrochemical kinetics, power, and energy densities.
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| 2. |
- Sun, Yue, et al.
(author)
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Surface chemistry and structure manipulation of graphene-related materials to address the challenges of electrochemical energy storage
- 2023
-
In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 59:18, s. 2571-2583
-
Journal article (peer-reviewed)abstract
- Energy storage devices are important components in portable electronics, electric vehicles, and the electrical distribution grid. Batteries and supercapacitors have achieved great success as the spearhead of electrochemical energy storage devices, but need to be further developed in order to meet the ever-increasing energy demands, especially attaining higher power and energy density, and longer cycling life. Rational design of electrode materials plays a critical role in developing energy storage systems with higher performance. Graphene, the well-known 2D allotrope of carbon, with a unique structure and excellent properties has been considered a “magic” material with its high energy storage capability, which can not only aid in addressing the issues of the state-of-the-art lithium-ion batteries and supercapacitors, but also be crucial in the so-called post Li-ion battery era covering different technologies, e.g., sodium ion batteries, lithium-sulfur batteries, structural batteries, and hybrid supercapacitors. In this feature article, we provide a comprehensive overview of the strategies developed in our research to create graphene-based composite electrodes with better ionic conductivity, electron mobility, specific surface area, mechanical properties, and device performance than state-of-the-art electrodes. We summarize the strategies of structure manipulation and surface modification with specific focus on tackling the existing challenges in electrodes for batteries and supercapacitors by exploiting the unique properties of graphene-related materials.
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| 3. |
- Berne, Olivier, et al.
(author)
-
PDRs4All : A JWST Early Release Science Program on Radiative Feedback from Massive Stars
- 2022
-
In: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 134:1035
-
Journal article (peer-reviewed)abstract
- Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1-3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb Space Telescope (JWST) will therefore arise in PDR emission. In this paper we present an Early Release Science program using the MIRI, NIRSpec, and NIRCam instruments dedicated to the observations of an emblematic and nearby PDR: the Orion Bar. These early JWST observations will provide template data sets designed to identify key PDR characteristics in JWST observations. These data will serve to benchmark PDR models and extend them into the JWST era. We also present the Science-Enabling products that we will provide to the community. These template data sets and Science-Enabling products will guide the preparation of future proposals on star-forming regions in our Galaxy and beyond and will facilitate data analysis and interpretation of forthcoming JWST observations.
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| 4. |
- Dong, Qibing, et al.
(author)
-
Regulating concentration of surface oxygen vacancies in Bi 2 MoO 6 /Bi-MOF for boosting photocatalytic ammonia synthesis
- 2024
-
In: Journal of Catalysis. - 0021-9517 .- 1090-2694. ; 433
-
Journal article (peer-reviewed)abstract
- Surface oxygen vacancies (OVs) engineering has been widely adopted as an effective strategy to enhance photocatalytic performance. At present, photocatalytic systems capable of precisely regulating surface OVs concentrations, which could help illuminate the effects of the surface OVs concentration on N2 fixation activity, are still scarce. Herein, bismuth-based metal organic framework (Bi-MOF) was loaded onto the surface of Bi2MoO6 (BMO) as an operable platform, and the OVs concentration in the Bi-MOF component of BMO/Bi-MOF could be regulated by reduction of bismuth ions therein. Experimental results confirm that optimum construction of OVs in the Bi-MOF promotes the photoelectrons transfer from BMO to Bi-MOF, facilitating the activation of N2 at OVs. Consequently, the optimized catalyst shows superior performance in NH3 production, which reaches 125.78 μmol h−1 g−1, 21.4 higher than that of BMO. This work underline the significance of regulating surface OVs concentration, providing inspiration for the development of efficient OVs-modified photocatalysts.
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| 5. |
- Gao, Mingming, et al.
(author)
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Engineered 2D MXene-based materials for advanced supercapacitors and micro-supercapacitors
- 2024
-
In: Materials Today. - 1369-7021 .- 1873-4103. ; 72, s. 318-358
-
Research review (peer-reviewed)abstract
- The class of two-dimensional transition metal carbides/nitrides/oxycarbides (known as MXenes) has shown great potential in energy storage applications due to their intrinsic layered structure, outstanding electrical conductivity, tunable surface chemistry, and unique physicochemical properties. This review summarizes the latest progresses of MXene-based materials for supercapacitors and micro-supercapacitors. First, state-of-the-art structural engineering strategies for the construction of novel MXene-based electrodes are highlighted, as the electrochemical performance of MXenes is influenced by their structure, such as interlayer spacing and surface functional group density. Furthermore, the charge storage mechanisms of MXene-based electrodes in different electrolytes are discussed to stimulate further design and development of tailored materials for high-performance devices. Moreover, different device fabrication technologies are summarized and the achievements of specific device geometries (e.g., fiber-shape, planar-type, and three-dimensional devices) containing MXene-based materials are critically reviewed. Finally, perspectives and outlook for the development of high-performance MXene-based electrodes in terms of material engineering, performance improvement and device innovation are provided, clearly indicating research directions for next-generation advanced energy storage devices.
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| 6. |
- Huang, Changjie, 1998, et al.
(author)
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Binder assisted graphene derivatives as lubricants in copper: Improved tribological performance for industrial application
- 2024
-
In: iScience. - 2589-0042. ; 27:4
-
Journal article (peer-reviewed)abstract
- Originally derived from graphite, high-quality single-layer graphene is an excellent anti-wear and -friction additive in metal matrix. Here, the tribological performance of 3 different commercialized graphene derivatives (e.g., graphene oxide [GO], reduced graphene oxide [RGO], and graphene nanoplatelet [GNP]) as additives in a Cu matrix, were investigated from an industrial perspective. To increase the interaction of graphene derivatives with Cu particles, and addressing the aggregation problem of the graphene derivatives, different binders (polyvinyl alcohol [PVA] and cellulose nanocrystals [CNC]) were introduced into the system. Benefiting from such a strategy, a uniform distribution of the graphene derivatives in Cu matrix was achieved with graphene loading up to 5 wt %. After high-temperature sintering, the graphene is preserved and well distributed in the Cu matrix. It was found that the GNP-containing sample shows the most stable friction coefficient behavior. However, GO and RGO also improve the tribological performance of Cu under different circumstances.
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| 7. |
- Iakunkov, Artem, et al.
(author)
-
Gravimetric tank method to evaluate material-enhanced hydrogen storage by physisorbing materials
- 2018
-
In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 20:44, s. 27983-27991
-
Journal article (peer-reviewed)abstract
- The most common methods to evaluate hydrogen sorption (volumetric and gravimetric) require significant experience and expensive equipment for providing reproducible results. Both methods allow one to measure excess uptake values which are used to calculate the total amount of hydrogen stored inside of a tank as required for applications. Here we propose an easy to use and inexpensive alternative approach which allows one to evaluate directly the weight of hydrogen inside a material-filled test tank. The weight of the same tank filled with compressed hydrogen in the absence of loaded material is used as a reference. We argue that the only parameter which is of importance for hydrogen storage applications is by how much the material improves the total weight of hydrogen inside of the given volume compared to compressed gas. This parameter which we propose to name Gain includes both volumetric and gravimetric characterization of the material; it can be determined directly without knowing the skeletal volume of the material or excess sorption. The feasibility of the Gravimetric Tank (GT) method was tested using several common carbon and Metal Organic Framework (MOF) materials. The best Gain value of ∼12% was found for the Cu-BTC MOF which means that the tank completely filled with this material stores a 12% higher amount of hydrogen compared to H2 gas at the same P–Tconditions. The advantages of the GT method are its inexpensive design, extremely simple procedures and direct results in terms of tank capacity as required for industrial applications. The GT method could be proposed as a standard check for verification of the high hydrogen storage capacity of new materials. The GT method is expected to provide even better accuracy for evaluation of a material's performance for storage of denser gases like e.g. CO2 and CH4.
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| 8. |
- Iakunkov, Artem, et al.
(author)
-
Swelling of graphene oxide membranes in alcohols : effects of molecule size and air ageing
- 2019
-
In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7, s. 11331-11337
-
Journal article (peer-reviewed)abstract
- Swelling of Hummers graphene oxide (HGO) membranes in a set of progressively longer liquid alcohols (methanol to 1-nonanol) was studied using synchrotron radiation XRD after air ageing over prolonged periods of time. Both precursor graphite oxides and freshly prepared HGO membranes were found to swell in the whole set of nine liquid alcohols with an increase of interlayer spacing from ∼7 Å (solvent free) up to ∼26 Å (in 1-nonanol). A pronounced effect of ageing on swelling in alcohols was found for HGO membranes stored in air. The HGO membranes aged for 0.5–1.5 years show progressively slower swelling kinetics, a non-monotonic decrease of saturated swelling in some alcohols and complete disappearance of swelling for alcohol molecules larger than hexanol. Moreover, the HGO membranes stored under ambient conditions for 5 years showed a nearly complete absence of swelling in all alcohols but preserved swelling in water. In contrast, precursor graphite oxide powder showed unmodified swelling in alcohols even after 4 years of ageing. Since the swelling defines the size of permeation channels, the ageing effect is one of the important parameters which could explain the strong variation in reported filtration/separation properties of GO membranes. The time and conditions of air storage require standardization for better reproducibility of results related to performance of GO membranes in various applications. The ageing of GO membranes can be considered not only as a hindrance/degradation for certain applications, but also as a method to tune the swelling properties of HGO membranes for better selectivity in sorption of solvents and for achieving better selective permeability.
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| 9. |
- Iakunkov, Artem, et al.
(author)
-
Swelling of graphene oxide membranes in alcohols : effects of molecule size and air ageing
- 2019
-
In: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 7:18, s. 11331-11337
-
Journal article (peer-reviewed)abstract
- Swelling of Hummers graphene oxide (HGO) membranes in a set of progressively longer liquid alcohols (methanol to 1-nonanol) was studied using synchrotron radiation XRD after air ageing over prolonged periods of time. Both precursor graphite oxides and freshly prepared HGO membranes were found to swell in the whole set of nine liquid alcohols with an increase of interlayer spacing from approximate to 7 angstrom (solvent free) up to approximate to 26 angstrom (in 1-nonanol). A pronounced effect of ageing on swelling in alcohols was found for HGO membranes stored in air. The HGO membranes aged for 0.5-1.5 years show progressively slower swelling kinetics, a non-monotonic decrease of saturated swelling in some alcohols and complete disappearance of swelling for alcohol molecules larger than hexanol. Moreover, the HGO membranes stored under ambient conditions for 5 years showed a nearly complete absence of swelling in all alcohols but preserved swelling in water. In contrast, precursor graphite oxide powder showed unmodified swelling in alcohols even after 4 years of ageing. Since the swelling defines the size of permeation channels, the ageing effect is one of the important parameters which could explain the strong variation in reported filtration/separation properties of GO membranes. The time and conditions of air storage require standardization for better reproducibility of results related to performance of GO membranes in various applications. The ageing of GO membranes can be considered not only as a hindrance/degradation for certain applications, but also as a method to tune the swelling properties of HGO membranes for better selectivity in sorption of solvents and for achieving better selective permeability.
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| 10. |
- Iakunkov, Artem, et al.
(author)
-
Swelling of Ti3C2Tx mxene in water and methanol at extreme pressure conditions
- 2024
-
In: Advanced Science. - : John Wiley & Sons. - 2198-3844. ; 11:9
-
Journal article (peer-reviewed)abstract
- Pressure-induced swelling has been reported earlier for several hydrophilic layered materials. MXene Ti3C2Tx is also a hydrophilic layered material composed by 2D sheets but so far pressure-induced swelling is reported for this material only under conditions of shear stress at MPa pressures. Here, high-pressure experiments are performed with MXenes prepared by two methods known to provide “clay-like” materials. MXene synthesized by etching MAX phase with HCl+LiF demonstrates the effect of pressure-induced swelling at 0.2 GPa with the insertion of additional water layer. The transition is incomplete with two swollen phases (ambient with d(001) = 16.7Å and pressure-induced with d(001) = 19.2Å at 0.2 GPa) co-existing up to the pressure point of water solidification. Therefore, the swelling transition corresponds to change from two-layer water intercalation (2L-phase) to a never previously observed three-layer water intercalation (3L-phase) of MXene. Experiments with MXene prepared by LiCl+HF etching have not revealed pressure-induced swelling in liquid water. Both MXenes also show no anomalous compressibility in liquid methanol. The presence of pressure-induced swelling only in one of the MXenes indicates that the HCl+LiF synthesis method is likely to result in higher abundance of hydrophilic functional groups terminating 2D titanium carbide.
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| 11. |
- Jia, Pan, et al.
(author)
-
The combination of 2d layered graphene oxide and 3d porous cellulose heterogeneous membranes for nanofluidic osmotic power generation
- 2021
-
In: Molecules. - : MDPI AG. - 1420-3049 .- 1420-3049 .- 1431-5157. ; 26:17
-
Journal article (peer-reviewed)abstract
- Salinity gradient energy, as a type of blue energy, is a promising sustainable energy source. Its energy conversion efficiency is significantly determined by the selective membranes. Recently, nanofluidic membrane made by two-dimensional (2D) nanomaterials (e.g., graphene) with densely packed nanochannels has been considered as a high-efficient membrane in the osmotic power generation research field. Herein, the graphene oxide-cellulose acetate (GO–CA) heterogeneous membrane was assembled by combining a porous CA membrane and a layered GO membrane; the combination of 2D nanochannels and 3D porous structures make it show high surface-charge-governed property and excellent ion transport stability, resulting in an efficient osmotic power harvesting. A power density of about 0.13 W/m2 is achieved for the sea–river mimicking system and up to 0.55 W/m2 at a 500-fold salinity gradient. With different functions, the CA and GO membranes served as ion storage layer and ion selection layer, respectively. The GO–CA heterogeneous membrane open a promising avenue for fabrication of porous and layered platform for wide potential applications, such as sustainable power generation, water purification, and seawater desalination.
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| 12. |
- Klechikov, Alexey, et al.
(author)
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Graphene decorated with metal nanoparticles : Hydrogen sorption and related artefacts
- 2017
-
In: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 250, s. 27-34
-
Journal article (peer-reviewed)abstract
- Hydrogen sorption by reduced graphene oxides (r-GO) is not found to increase after decoration with Pd and Pt nanoparticles. Treatments of metal decorated samples using annealing under hydrogen or air were tested as a method to create additional pores by effects of r-GO etching around nanoparticles. Increase of Specific Surface Area (SSA) was observed for some air annealed r-GO samples. However, the same treatments applied to activated r-GO samples with microporous nature and higher surface area result in breakup of structure and dramatic decrease of SSA. Our experiments have not revealed effects which could be attributed to spillover in hydrogen sorption on Pd or Pt decorated graphene. However, we report irreversible chemisorption of hydrogen for some samples which can be mistakenly assigned to spillover if the experiments are incomplete.
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| 13. |
- Klechikov, Alexey, et al.
(author)
-
Graphite oxide swelling in molten sugar alcohols and their aqueous solutions
- 2018
-
In: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 140, s. 157-163
-
Journal article (peer-reviewed)abstract
- Graphite oxides (GO) are intercalated rapidly by one to several layers of solvent when immersed in liquid but the GO solvates are typically unstable on air due to solvent evaporation. Here we study swelling of GO in solvents (sugar alcohols) with melting temperature point above ambient. Using in situ synchrotron radiation XRD experiments we demonstrated GO swelling in molten xylitol and sorbitol. The expanded GO structure intercalated with one layer of xylitol or sorbitol is preserved upon solidification of melt and cooling back to ambient conditions. The structure of solid solvates of GO with xylitol and sorbitol is based on non-covalent interaction and pristine GO can be recovered by washing in water. Intercalation of xylitol and sorbitol into GO structure in aqueous solutions yields similar but less ordered structure of GO/sugar alcohol solid solvates. Very similar inter-layer distance was observed for GO intercalated by sugar alcohols in melt and for GO immersed in sugar solutions. This result shows that sugar alcohols penetrate into GO inter-layer space without hydration shell forming 2D layers with orientation parallel to graphene oxide sheets. Therefore, hydration diameter of molecules should not be considered as decisive factor for permeation through graphene oxide inter-layers in multilayered membranes.
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| 14. |
- Klechikov, Alexey, et al.
(author)
-
Multilayered intercalation of 1-octanol into Brodie graphite oxide
- 2017
-
In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 9:20, s. 6929-6936
-
Journal article (peer-reviewed)abstract
- Multilayered intercalation of 1-octanol into the structure of Brodie graphite oxide (B-GO) was studied as a function of temperature and pressure. Reversible phase transition with the addition/removal of one layer of 1-octanol was found at 265 K by means of X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The same transition was observed at ambient temperature upon a pressure increase above 0.6 GPa. This transition was interpreted as an incongruent melting of the low temperature/high pressure B-GO intercalated structure with five layers of 1-octanol parallel to GO sheets (L-solvate), resulting in the formation of a four-layered structure that is stable under ambient conditions (A-solvate). Vacuum heating allows the removal of 1-octanol from the A-solvate layer by layer, while distinct sets of (00 l) reflections are observed for three-, two-, and one-layered solvate phases. Step by step removal of the 1-octanol layers results in changes of distance between graphene oxide planes by similar to 4.5 angstrom. This experiment proved that both L- and A-solvates are structures with layers of 1-octanol parallel to GO planes. Unusual intercalation with up to five distinct layers of 1-octanol is remarkably different from the behaviour of small alcohol molecules (methanol and ethanol), which intercalate B-GO structure with only one layer under ambient conditions and a maximum of two layers at lower temperatures or higher pressures. The data presented in this study make it possible to rule out a change in the orientation of alcohol molecules from parallel to perpendicular to the GO planes, as suggested in the 1960s to explain larger expansion of the GO lattice due to swelling with larger alcohols.
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| 15. |
- Klechikov, Alexey, et al.
(author)
-
Swelling of Thin Graphene Oxide Films Studied by in Situ Neutron Reflectivity
- 2018
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:24, s. 13106-13116
-
Journal article (peer-reviewed)abstract
- Permeation of multilayered graphene oxide (GO) membranes by polar solvents is known to correlate with their swelling properties and amount of sorbed solvent. However, quantitative estimation of sorption using standard (e.g., gravimetric) methods is technically challenging for few nanometers thick GO membranes/films exposed to solvent vapors. Neutron reflectivity (NR) was used here to evaluate the amount of solvents intercalated into the film which consists of only ∼31.5 layers of GO. Analysis of NR data recorded from the GO film exposed to vapors of polar solvents provides information about change of film thickness due to swelling, amount of intercalated solvent, and selectivity in sorption of solvents from binary mixtures. A quantitative study of GO film sorption was performed for D2O, d-methanol, ethanol, dimethyl sulfoxide (DMSO), acetonitrile, dimethylformamide (DMF), and acetone. Using isotopic contrast, we estimated selectivity in sorption of ethanol/d-methanol mixtures by the GO film. Estimation of sorption selectivity was also performed for D2O/DMF, D2O/DMSO, and D2O/acetonitrile binary mixtures. Sorption of polar solvents was compared for the thin GO film, micrometer thick free standing GO membranes, and graphite oxide powders.
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| 16. |
- Mishukova, Viktoriia, et al.
(author)
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Microsupercapacitors Working at 250 °C
- 2023
-
In: Batteries & Supercaps. - : Wiley-VCH Verlagsgesellschaft. - 2566-6223.
-
Journal article (peer-reviewed)abstract
- The raised demand for portable electronics in high-temperature environments (>150 °C) stimulates the search for solutions to release the temperature constraints of power supply. All-solid-state microsupercapacitors (MSCs) are envisioned as promising on-chip power supply components, but at present, nearly none of them can work at temperature over 200 °C, mainly restricted by the electrolytes which possess either low thermal stability or incompatible fabrication process with on-chip integration. In this work, we have developed a novel process to fabricate highly thermally stable ionic liquid/ceramic composite electrolytes for on-chip integrated MSCs. Remarkably, the electrolytes enable MSCs with graphene-based electrodes to operate at temperatures as high as 250 °C with a high areal capacitance (~72 mF cm−2 at 5 mV s−1) and good cycling stability (70 % capacitance retention after 1000 cycles at 1.4 mA cm−2).
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| 17. |
- Nordenstrom, Andreas, et al.
(author)
-
Thermally reduced pillared GO with precisely defined slit pore size
- 2020
-
In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 10:12, s. 6831-6839
-
Journal article (peer-reviewed)abstract
- Graphene oxide (GO) pillared with tetrakis(4-aminophenyl)methane (TKAM) molecules shows a narrow distribution of pore size, relatively high specific surface area, but it is hydrophilic and electrically not conductive. Analysis of XRD, N-2 sorption, XPS, TGA and FTIR data proved that the pillared structure and relatively high surface area (similar to 350 m(2) g(-1)) are preserved even after thermal reduction of GO pillared with TKAM molecules. Unlike many other organic pillaring molecules, TKAM is stable at temperatures above the point of GO thermal reduction, as demonstrated by TGA. Therefore, gentle annealing results in the formation of reduced graphene oxide (rGO) pillared with TKAM molecules. The TKAM pillared reduced graphene oxide (PrGO/TKAM) is less hydrophilic as found using dynamic vapor sorption (DVS) and more electrically conductive compared to pillared GO, but preserves an increased interlayer-distance of about 12 angstrom (compared to similar to 7.5 angstrom in pristine GO). Thus we provide one of the first examples of porous rGO pillared with organic molecules and well-defined size of hydrophobic slit pores. Analysis of pore size distribution using nitrogen sorption isotherms demonstrates a single peak for pore size of similar to 7 angstrom, which makes PrGO/TKAM rather promising for membrane and molecular sieve applications.
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| 18. |
- Nordenström, Andreas, et al.
(author)
-
Thermally reduced pillared GO with precisely defined slit pore size
- 2020
-
In: RSC Advances. - 2046-2069. ; 10:12, s. 6831-6839
-
Journal article (peer-reviewed)abstract
- Graphene oxide (GO) pillared with tetrakis(4-aminophenyl)methane (TKAM) molecules shows a narrow distribution of pore size, relatively high specific surface area, but it is hydrophilic and electrically not conductive. Analysis of XRD, N2 sorption, XPS, TGA and FTIR data proved that the pillared structure and relatively high surface area (∼350 m2 g−1) are preserved even after thermal reduction of GO pillared with TKAM molecules. Unlike many other organic pillaring molecules, TKAM is stable at temperatures above the point of GO thermal reduction, as demonstrated by TGA. Therefore, gentle annealing results in the formation of reduced graphene oxide (rGO) pillared with TKAM molecules. The TKAM pillared reduced graphene oxide (PrGO/TKAM) is less hydrophilic as found using dynamic vapor sorption (DVS) and more electrically conductive compared to pillared GO, but preserves an increased interlayer-distance of about 12 Å (compared to ∼7.5 Å in pristine GO). Thus we provide one of the first examples of porous rGO pillared with organic molecules and well-defined size of hydrophobic slit pores. Analysis of pore size distribution using nitrogen sorption isotherms demonstrates a single peak for pore size of ∼7 Å, which makes PrGO/TKAM rather promising for membrane and molecular sieve applications.
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| 19. |
- Ou, Jinhua, et al.
(author)
-
Highly transparent nickel and iron sulfide on nitrogen-doped carbon films as counter electrodes for bifacial quantum dot sensitized solar cells
- 2019
-
In: Solar Energy. - : Pergamon Press. - 0038-092X .- 1471-1257. ; 193, s. 766-773
-
Journal article (peer-reviewed)abstract
- Semiconductors are widely used as counter electrodes in quantum dot-sensitized solar cells. However, many counter electrode materials have poor conductivity and require tedious post-treatment procedures. Here, our groups develop a highly transparent MS2@N-doped C film materials (M = Ni, Fe) derived from layer-by-layer self-assembly of a M-TCPP film as a counter electrode in bifacial CdS/CdSe quantum dot-sensitized solar cells. Devices based on the MS2@N-doped C films exhibited higher respective front- and reverse-side power conversion efficiencies (i.e., 4.57% and 3.98% for the NiS2@N-doped C film and 3.18% and 2.63% for the FeS2@N-doped C film) than those of Pt-based devices (2.39% and 1.74%). We attribute the outstanding catalytic activity and excellent stability of the MS2@N-doped C film materials to the homogeneous sulfides within the transparent nitrogen-doped C film, as confirmed by electrochemical analyses, including cycle voltammetry, impedance spectroscopy and Tafel-polarization measurements.
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| 20. |
- Poletti, Fabrizio, et al.
(author)
-
Continuous capillary-flow sensing of glucose and lactate in sweat with an electrochemical sensor based on functionalized graphene oxide
- 2021
-
In: Sensors and Actuators, B: Chemical. - : Elsevier BV. - 0925-4005. ; 344
-
Journal article (peer-reviewed)abstract
- We describe an electrochemical device for the simultaneous monitoring of glucose and lactate in sweat, based on enzymatic sensors exploiting capillary flow to induce continuous, stable sensing. The enzymes, namely glucose oxidase and lactate oxidase, were anchored to a graphene oxide and chitosan composite (GO-Ch) of original synthesis, to achieve stable deposition of the bioreceptors on the electrochemical platform. We tested both biosensors on a realistic device architecture: they were embedded in a nitrocellulose strip, to exploit capillary force to induce a continuous flux of sweat on the sensor platform, ensuring the constant renewal of sample. We could achieve good sensitivity at potentials close to zero by using Prussian Blue as redox mediator, thus avoiding interference from other chemical species present in the complex matrix. The sensing signal was stable and linear over two hours in a concentration range of glucose and lactate between the limit of quantification (32 and 68 nM, respectively) and the upper limit of linearity (3.8 and 50.0 mM, respectively). The device is simple, robust, stable, and can be easily worn without the direct contact of the active part with the skin, making it suitable for simultaneous monitoring of glucose and lactate in human sweat.
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| 21. |
- Rebrikova, Anastasiya T., et al.
(author)
-
Swollen Structures of Brodie Graphite Oxide as Solid Solvates
- 2020
-
In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:42, s. 23410-23418
-
Journal article (peer-reviewed)abstract
- Swelling of Brodie graphite oxide (B-GO) was studied for a series of normal alcohols from methanol to 1-nonanol. Isopiestic, X-ray diffraction (XRD), thermogravimetric, and differential scanning calorimetry data demonstrated that sorption of polar liquids into GO lamellas formed the set of regular swollen structures, simple binary "solid solvates", characterized by the distance between the GO planes and the value of sorption. Temperature-composition behavior of the swollen structures was adequately described by conventional binary phase diagrams. Phase transformation of the low-temperature swollen structure of B-GO with 1-nonanol gave a clear example of incongruent melting transition typical for the binary solvates. A discreet set of the interplane distances observed by XRD and the stepwise equilibrium desorption pointed to the layered arrangement of solvent molecules in the swollen structures. The swollen structures with one to five parallel layers were observed for a series of normal alcohols with B-GO. The average volume of one layer, 0.36 +/- 0.06 cm(3) g(-1) B-GO, was almost the same for rather different organic liquids and was possibly restricted by the internal geometry of B-GO. This internal volume available for the sorption of the first layer was reasonably estimated from geometrical parameters of B-GO.
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| 22. |
- Ren, Haitao, et al.
(author)
-
Facile synthesis of nitrogen, sulfur co-doped carbon quantum dots for selective detection of mercury (II)
- 2024
-
In: Environmental Chemistry Letters. - 1610-3653 .- 1610-3661. ; 22:1, s. 35-41
-
Journal article (peer-reviewed)abstract
- Developing carbon quantum dots with high throughput and quantum yields is important to boost their application in environmental detection. This study proposes nitrogen, sulfur co-doped carbon quantum dots as a fluorescent probe for mercury detection in an aqueous environment, which was synthesized by a facile and high-output tactic using methyl orange as a precursor for the first time. Results demonstrate that the obtained carbon quantum dots have a high selectivity, low detection limit of 237 nM, and fast response time, approximately 30 s, for trace mercury. The detection mechanism involves the synergistic action of static quenching, inner filter effect, and photo-induced electron transfer. Moreover, results show a high product yield (75.6%) and quantum yield (29.4%), which are higher compared to previous studies. These findings indicate that developed carbon quantum dots are promising sensing nanomaterials for mercury detection.
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| 23. |
- Sanchez, Jaime S., et al.
(author)
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Versatile electrochemical manufacturing of mixed metal sulfide/N-doped rGO composites as bifunctional catalysts for high power rechargeable Zn–air batteries
- 2024
-
In: Journal of Materials Chemistry A. - 2050-7488 .- 2050-7496. ; 12:20, s. 11945-11959
-
Journal article (peer-reviewed)abstract
- The development of rechargeable zinc–air batteries requires air cathodes capable of performing both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with high performance and an extended operational lifespan. Here, we present a cost-effective and versatile electrochemical method for the direct assembly of such electrocatalysts, consisting of nitrogen-doped reduced graphene oxide (NrGO) and mixed transition metal sulfides (NiCoMnSx or NCMS). To this end, we use a small electric bias to electro-deposit both NrGO and NCMS directly on conductive graphene foam, resulting in a perfect porous network and two interpenetrated paths for the easy transport of electrons and ions. The NCMS/ NrGO composite shows one of the highest limiting currents reported so far for a non-noble metal catalyst. Additionally, it exhibits outstanding bifunctional performance for the ORR/OER, superior to both mixed transition metal compounds and noble metals from previous reports. Thus, it serves as a highly efficient air cathode for practical zinc–air batteries featuring high power densities (124 mW cm−2) and long catalyst durability (1560 cycles, around 260 h). We attribute the excellent performance to the synergistic effect between hetero-structured metallic sites and nitrogen dopants. Our approach can be used for preparing efficient zinc–air cathodes on conductive 3D carbon substrates with arbitrary shapes and good performance.
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| 24. |
- Sanchez Sanchez, Jaime, 1990, et al.
(author)
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All-Electrochemical Nanofabrication of Stacked Ternary Metal Sulfide/Graphene Electrodes for High-Performance Alkaline Batteries
- 2022
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In: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 18
-
Journal article (peer-reviewed)abstract
- Energy-storage materials can be assembled directly on the electrodes of a battery using electrochemical methods, this allowing sequential deposition, high structural control, and low cost. Here, a two-step approach combining electrophoretic deposition (EPD) and cathodic electrodeposition (CED) is demonstrated to fabricate multilayer hierarchical electrodes of reduced graphene oxide (rGO) and mixed transition metal sulfides (NiCoMnSx). The process is performed directly on conductive electrodes applying a small electric bias to electro-deposit rGO and NiCoMnSx in alternated cycles, yielding an ideal porous network and a continuous path for transport of ions and electrons. A fully rechargeable alkaline battery (RAB) assembled with such electrodes gives maximum energy density of 97.2 Wh kg−1 and maximum power density of 3.1 kW kg−1, calculated on the total mass of active materials, and outstanding cycling stability (retention 72% after 7000 charge/discharge cycles at 10 A g−1). When the total electrode mass of the cell is considered, the authors achieve an unprecedented gravimetric energy density of 68.5 Wh kg−1, sevenfold higher than that of typical commercial supercapacitors, higher than that of Ni/Cd or lead–acid Batteries and similar to Ni–MH Batteries. The approach can be used to assemble multilayer composite structures on arbitrary electrode shapes.
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| 25. |
- Sanchez Sanchez, Jaime, 1990, et al.
(author)
-
Electrophoretic coating of LiFePO4/Graphene oxide on carbon fibers as cathode electrodes for structural lithium ion batteries
- 2021
-
In: Composites Science and Technology. - : Elsevier BV. - 0266-3538. ; 208
-
Journal article (peer-reviewed)abstract
- Carbon fibers (CF), commonly used in the structure of airplanes or cars, can also work as conductive electrodes in “structural batteries” for distributed energy storage. To this aim CF should be chemically functionalized, which is challenging due to their complex geometry and surface. Here, we describe an “all-electrostatic” approach taking advantage of the intrinsic conductivity of CF to coat them with a cathode material composed of LiFePO4 blended with nanosheets of electrochemically exfoliated graphene oxide (EGO). We first achieve electrostatic selfassembly of the nanometric components at the nanoscale, then use Electrophoretic Deposition (EPD) to obtain a uniform, macroscale coating on the fibers. We achieve a LiFePO4 loading >90 wt% featuring good adhesion on the carbon fibers, low degradation upon battery cycling, low charge transfer resistance. The electrode composite outperforms similar state-of-the-art cathode materials when used in Half-Cell vs. Li. Full battery cells using coated CF as cathode and pristine CF as anode yield specific energy density of 222.14 Wh⋅kg? 1 and power density of 0.29 kW⋅kg? 1 with 88.1% capacity retention at 1 C over 300 cycles, compatible with industrial applications of this technique in composites production.
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| 26. |
- Storsjö, Tobias, et al.
(author)
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Elemental carbon - An efficient method to measure occupational exposure from materials in the graphene family
- 2024
-
In: NanoImpact. - 2452-0748. ; 33
-
Journal article (peer-reviewed)abstract
- Graphene is a 2D-material with many useful properties such as flexibility, elasticity, and conductivity among others. Graphene could therefore become a material used in many occupational fields in the future, which can give rise to occupational exposure. Today, exposure is unknown, due to the lack of efficient measuring techniques for occupational exposure to graphene. Readily available screening techniques for air sampling and -analysis are either nonspecific or nonquantitative. Quantifying materials from the broad graphene family by an easy-to-use method is important for the large-scale industrial application of graphene, especially when for the safety of working environment. Graphene consists primarily of elemental carbon, and the present study evaluates the organic carbon/elemental carbon (OC/EC)-technique for exposure assessment. The purpose of this work is to evaluate the OC/EC analysis technique as an efficient and easy-to-use method for quantification of occupational exposure to graphene. Methods that can identify graphene would be preferable for screening, but they are time consuming and semi-quantitative and therefore not suited for quantitative work environment assessments. The OC/EC-technique is a thermal optical analysis (TOA), that quantitively determines the amount of and distinguishes between two different types of carbon, organic and elemental. The technique is standardised, well-established and among other things used for diesel exposure measurements (ref standard). OC/EC could therefore be a feasible measuring technique to quantitively determine occupational exposure to graphene. The present evaluation of the technique provides an analytical method that works quantitatively for graphene, graphene oxide and reduced graphene oxide. Interestingly, the TOA technique makes it possible to distinguish between the three graphene forms used in this study. The technique was tested in an industrial setting and the outcome suggests that the technique is an efficient monitoring technique to be used in combination with characterisation techniques like for example Raman spectroscopy, scanning electron microscopy and atomic force microscopy.
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| 27. |
- Sun, Jinhua, et al.
(author)
-
A Molecular Pillar Approach To Grow Vertical Covalent Organic Framework Nanosheets on Graphene : Hybrid Materials for Energy Storage
- 2018
-
In: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 57:4, s. 1034-1038
-
Journal article (peer-reviewed)abstract
- Hybrid 2D–2D materials composed of perpendicularly oriented covalent organic frameworks (COFs) and graphene were prepared and tested for energy storage applications. Diboronic acid molecules covalently attached to graphene oxide (GO) were used as nucleation sites for directing vertical growth of COF-1 nanosheets (v-COF-GO). The hybrid material has a forest of COF-1 nanosheets with a thickness of 3 to 15 nm in edge-on orientation relative to GO. The reaction performed without molecular pillars resulted in uncontrollable growth of thick COF-1 platelets parallel to the surface of GO. The v-COF-GO was converted into a conductive carbon material preserving the nanostructure of precursor with ultrathin porous carbon nanosheets grafted to graphene in edge-on orientation. It was demonstrated as a high-performance electrode material for supercapacitors. The molecular pillar approach can be used for preparation of many other 2D-2D materials with control of their relative orientation.
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| 28. |
- Sun, Jinhua, 1987, et al.
(author)
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Controllable Coating Graphene Oxide and Silanes on Cu Particles as Dual Protection for Anticorrosion
- 2023
-
In: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 15:32, s. 38857-38866
-
Journal article (peer-reviewed)abstract
- Although two-dimensional nanosheets like graphene could be ideal atomic coatings to prevent corrosion, it is still controversial whether they are actually effective due to the presence of parasitic effects such as galvanic corrosion. Here, we reported a reduced graphene oxide (RGO) coating strategy to protect sintered Cu metal powders from corrosion by addressing the common galvanic corrosion issue of graphene. A layer of silane molecules, namely, (3-aminopropyl)triethoxysilane (APTES), is deposited between the surface of Cu particles and the graphene oxide (GO), acting as a primer to enhance adhesion and as an insulating interlayer to prevent the direct contact of the Cu with conductive RGO, mitigating the galvanic corrosion. Due to this core−shell coating, the RGO uniformly distributes in the Cu matrix after sintering, avoiding aggregation of RGO, which takes place in conventional GO-Cu composites. The dual coating of GO and silane results in bulk samples with improved anticorrosion properties, as demonstrated by galvanostatic polarization tests using Tafel analysis. Our development not only provides an efficient synthesis method to controllably coat GO on the surface of Cu but also suggests an alternative strategy to avoid the galvanic corrosion effect of graphene to improve the anticorrosion performance of metal.
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| 29. |
- Sun, Jinhua, 1987, et al.
(author)
-
Covalent Organic Framework (COF-1) under High Pressure
- 2020
-
In: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:3, s. 1087-1092
-
Journal article (peer-reviewed)abstract
- COF-1 has a structure with rigid 2D layers composed of benzene and B3O3 rings and weak van der Waals bonding between the layers. The as-synthesized COF-1 structure contains pores occupied by solvent molecules. A high surface area empty-pore structure is obtained after vacuum annealing. High-pressure XRD and Raman experiments with mesitylene-filled (COF-1-M) and empty-pore COF-1 demonstrate partial amorphization and collapse of the framework structure above 12–15 GPa. The ambient pressure structure of COF-1-M can be reversibly recovered after compression up to 10–15 GPa. Remarkable stability of highly porous COF-1 structure at pressures at least up to 10 GPa is found even for the empty-pore structure. The bulk modulus of the COF-1 structure (11.2(5) GPa) and linear incompressibilities (k[100]=111(5) GPa, k[001]=15.0(5) GPa) were evaluated from the analysis of XRD data and cross-checked against first-principles calculations. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 30. |
- Sun, Jinhua, et al.
(author)
-
Exactly matched pore size for the intercalation of electrolyte ions determined using the tunable swelling of graphite oxide in supercapacitor electrodes
- 2018
-
In: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 10:45, s. 21386-21395
-
Journal article (peer-reviewed)abstract
- The intercalation of solvent molecules and ions into sub-nanometer-sized pores is one of the most disputed subjects in the electrochemical energy storage applications of porous materials. Here, we demonstrate that the temperature- and concentration-dependent swelling of graphite oxide (GO) can be used to determine the smallest pore size required for the intercalation of electrolyte ions into hydrophilic pores. The structure of Brodie graphite oxide (BGO) in acetonitrile can be temperature-switched between the ambient one-layer solvate with an interlayer distance of approximate to 8.9 angstrom and the two-layer solvate (approximate to 12.5 angstrom) at low temperature, thus providing slit pores of approximately 2.5 and 6 angstrom. Using in situ synchrotron radiation X-ray diffraction (XRD) and the temperature dependence of capacitance in supercapacitor devices, we found that solvated tetraethylammonium tetrafluoroborate (TEA-BF4) ions do not penetrate into both the 2.5 and 6 angstrom slit pores formed by BGO interlayers. However, increasing the electrolyte concentration results in the formation of a new phase at low temperature. This phase shows a distinct interlayer distance of approximate to 15-16.6 angstrom, which corresponds to the insertion of partly desolvated TEA-BF4 ions. Therefore, the remarkable ability of the GO structure to adopt variable interlayer distances allows for the determination of pore sizes that are optimal for solvated TEA-BF4 ions (about 9-10 angstrom). The intercalation of TEA-BF4 ions into the BGO structure is also detected as an anomaly in the temperature dependence of supercapacitor performance. The BGO structure remains to be expanded, even after the removal of acetonitrile, adopting an interlayer distance of approximate to 10 angstrom.
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| 31. |
- Sun, Jinhua, et al.
(author)
-
Porous graphite oxide pillared with tetrapod-shaped molecules
- 2017
-
In: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 120, s. 145-156
-
Journal article (peer-reviewed)abstract
- Porous pillared graphene oxide (GO) materials were prepared using solvothermal reaction of Hummers GO with solution of Tetrakis(4-aminophenyl)methane (TKAm) in methanol. The intercalation of TKAm molecules between individual GO sheets, performed under swelling condition, results in expansion of inter-layer distance of GO from ∼7.5 Å to 13-14 Å. Pillaring GO with bulky, rigid 3D shaped TKAm molecules could be an advantage for the preparation of stable pillared structures compared to e.g. aliphatic or aromatic diamines. Insertion of TKAm molecules into inter-layer space of GO results in formation of interconnected network of sub-nanometer slit pores. The expanded GO structure prepared with optimized GO/TKAm composition shows Specific Surface Area (SSA) up to 660 m2/g which is among the highest reported for GO materials pillared using organic spacers. Modelling of GO structures pillared with TKAm molecules shows that maximal SSA of about 2300 m2/g is theoretically possible for realistic concentration of pillaring molecules in GO interlayers. Hydrogen sorption by pillared GO/TKAm is found to follow standard correlation with SSA both at ambient and liquid nitrogen temperatures with highest uptakes of 1.66 wt% achieved at 77 K and 0.25 wt% at 295 K. Our theoretical simulations show that pillared GO structures do not provide improvement of hydrogen storage beyond well-established physisorption trends even for idealized materials with subnanometer pores and SSA of 2300–3700 m2/g.
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| 32. |
- Sun, Jinhua, et al.
(author)
-
Rational design of sulfur-containing composites for high-performance lithium-sulfur batteries
- 2019
-
In: APL Materials. - : AMER INST PHYSICS. - 2166-532X. ; 7:2
-
Journal article (peer-reviewed)abstract
- Sulfur has received considerable attention as a cathode material for lithium-sulfur (Li-S) batteries due to its high theoretical energy density (2567 W h kg(-1)), high earth abundance, and environmental benignity. However, the insulating nature of sulfur and the shuttle effect of soluble lithium polysulfides result in serious technical issues, such as low utilization rate of sulfur, reduced columbic efficiency, and poor cycling stability, which compromise the high theoretical performance of Li-S batteries. In the past years, various attempts have been made to achieve high specific capacity and reliable cycling stability of Li-S batteries. Incorporation of sulfur into functional host materials has been demonstrated to be effective to improve the electrochemical performance of sulfur-based cathodes via enhancing the electron and Li ion conductivities, immobilizing sulfur/lithium polysulfides in cathodes, and accommodating the volume changes in sulfur-based cathodes. Therefore, the rational design of sulfur-containing composites needs to be emphasized as key strategies to develop high-performance cathodes for Li-S batteries. In this perspective, after reviewing the achievements obtained in the design of sulfur-containing composites as cathodes for Li-S batteries, we propose the new issues that should be overcome to facilitate the practical application of Li-S batteries.
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| 33. |
- Sun, Jinhua, 1987, et al.
(author)
-
Real-time imaging of Na+ reversible intercalation in "Janus" graphene stacks for battery applications
- 2021
-
In: Science advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:22
-
Journal article (peer-reviewed)abstract
- Sodium, in contrast to other metals, cannot intercalate in graphite, hindering the use of this cheap, abundant element in rechargeable batteries. Here, we report a nanometric graphite-like anode for Na+ storage, formed by stacked graphene sheets functionalized only on one side, termed Janus graphene. The asymmetric functionalization allows reversible intercalation of Na+, as monitored by operando Raman spectroelectrochemistry and visualized by imaging ellipsometry. Our Janus graphene has uniform pore size, controllable functionalization density, and few edges; it can store Na+ differently from graphite and stacked graphene. Density functional theory calculations demonstrate that Na+ preferably rests close to -NH2 group forming synergic ionic bonds to graphene, making the interaction process energetically favorable. The estimated sodium storage up to C6.9Na is comparable to graphite for standard lithium ion batteries. Given such encouraging Na+ reversible intercalation behavior, our approach provides a way to design carbon-based materials for sodium ion batteries.
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| 34. |
- Xia, Zhenyuan, 1983, et al.
(author)
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Electrochemical exfoliation of graphite in H 2 SO 4 , Li 2 SO 4 and NaClO 4 solutions monitored: In situ by Raman microscopy and spectroscopy
- 2021
-
In: Faraday Discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 227, s. 291-305
-
Journal article (peer-reviewed)abstract
- The electrochemical exfoliation of graphite is one of the cheapest and most tunable industrial techniques to produce graphene nanosheets with a tunable degree of oxidation and solubility. Anodic oxidation allows high-yield production of electrochemically exfoliated graphene oxide (EGO) in either acid or salt solutions, with the key role played by ions electrochemically driven in between the graphene sheets. This chemical intercalation is followed by a mesoscale mechanical exfoliation process, which is key for the high yield of the process, but which is still poorly understood. In this work, we use Raman spectroscopy to simultaneously monitor the intercalation and oxidation processes taking place on the surface of highly ordered pyrolytic graphite (HOPG) during electrochemical exfoliation. The mechanism of EGO formation in either acidic (0.5 M H2SO4) or neutral (0.5 M Li2SO4) electrolytes through blistering and cracking steps is discussed and described. This process is also compared to the non-destructive intercalation of graphite in an organic electrolyte (1 M NaClO4 in acetonitrile). The results obtained show how high exfoliation yield and low defectivity can be achieved by the combination of efficient, non-destructive intercalation followed by chemical decomposition of the intercalants and gas production.
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| 35. |
- Xia, Zhenyuan, 1983, et al.
(author)
-
Selective deposition of metal oxide nanoflakes on graphene electrodes to obtain high-performance asymmetric micro-supercapacitors
- 2021
-
In: Nanoscale. - 2040-3372 .- 2040-3364. ; 13:5, s. 3285-3294
-
Journal article (peer-reviewed)abstract
- To meet the charging market demands of portable microelectronics, there has been a growing interest in high performance and low-cost microscale energy storage devices with excellent flexibility and cycling durability. Herein, interdigitated all-solid-state flexible asymmetric micro-supercapacitors (A-MSCs) were fabricated by a facile pulse current deposition (PCD) approach. Mesoporous Fe2O3 and MnO2 nanoflakes were functionally coated by electrodeposition on inkjet-printed graphene patterns as negative and positive electrodes, respectively. Our PCD approach shows significantly improved adhesion of nanostructured metal oxide with crack-free and homogeneous features, as compared with other reported electrodeposition approaches. The as-fabricated Fe2O3/MnO2 A-MSCs deliver a high volumetric capacitance of 110.6 F cm(-3) at 5 mu A cm(-2) with a broad operation potential range of 1.6 V in neutral LiCl/PVA solid electrolyte. Furthermore, our A-MSC devices show a long cycle life with a high capacitance retention of 95.7% after 10 000 cycles at 100 mu A cm(-2). Considering its low cost and potential scalability to industrial levels, our PCD technique could be an efficient approach for the fabrication of high-performance MSC devices in the future.
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| 36. |
- Xia, Zhenyuan, et al.
(author)
-
Selective deposition of metal oxide nanoflakes on graphene electrodes to obtain high-performance asymmetric micro-supercapacitors
- 2021
-
In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 13:5, s. 3285-3294
-
Journal article (peer-reviewed)abstract
- To meet the charging market demands of portable microelectronics, there has been a growing interest in high performance and low-cost microscale energy storage devices with excellent flexibility and cycling durability. Herein, interdigitated all-solid-state flexible asymmetric micro-supercapacitors (A-MSCs) were fabricated by a facile pulse current deposition (PCD) approach. Mesoporous Fe2O3 and MnO2 nanoflakes were functionally coated by electrodeposition on inkjet-printed graphene patterns as negative and positive electrodes, respectively. Our PCD approach shows significantly improved adhesion of nanostructured metal oxide with crack-free and homogeneous features, as compared with other reported electrodeposition approaches. The as-fabricated Fe2O3/MnO2 A-MSCs deliver a high volumetric capacitance of 110.6 F cm(-3) at 5 mu A cm(-2) with a broad operation potential range of 1.6 V in neutral LiCl/PVA solid electrolyte. Furthermore, our A-MSC devices show a long cycle life with a high capacitance retention of 95.7% after 10 000 cycles at 100 mu A cm(-2). Considering its low cost and potential scalability to industrial levels, our PCD technique could be an efficient approach for the fabrication of high-performance MSC devices in the future.
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| 37. |
- Xiao, Linhong, et al.
(author)
-
Recent Advances in Polymer-Based Photothermal Materials for Biological Applications
- 2020
-
In: ACS Applied Polymer Materials. - : American Chemical Society (ACS). - 2637-6105. ; 2:10, s. 4273-4288
-
Research review (peer-reviewed)abstract
- The photothermal effect, which is a phenomenon of converting light energy into thermal energy using photothermal conversion materials, has recently attracted significant attention in biological applications because of the minimal invasiveness to healthy tissues, high specificity, and easy operation. Polymer-based photothermal materials have emerged as a promising category of photothermal agents in biological applications because they show superiorities in tailorable molecular structures, high photothermal conversion efficiencies, and excellent biocompatibility. In this Review, we summarize the recent progresses achieved in polymer-based photothermal materials for biological applications. To have a better understanding of the working mechanism and the design of polymer-based photothermal materials, this Review starts with the fundamental description of photothermal conversion mechanism of polymer-based photothermal materials. According to their structures and compositions, the polymer-based photothermal materials can be classified into three types: conjugated polymers, polymer-modified carbon nanomaterials, and polymer-modified metals and metal compounds. Then we present the recent advances of the polymer-based photothermal materials in a diversity of biological areas such as photothermal therapy and photothermal sterilization. In the last section, we summarize the critical existing issues in polymer-based photothermal materials for biological applications and propose some perspectives that are related to the design and synthesis of polymer-based photothermal materials for biological applications.
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| 38. |
- Zeng, Yeli, et al.
(author)
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Can the Shanghai LNG Price Index indicate Chinese market? : An econometric investigation using price discovery theory
- 2020
-
In: Frontiers in Energy. - : Springer Science and Business Media LLC. - 2095-1701 .- 2095-1698. ; 14:4, s. 726-739
-
Journal article (peer-reviewed)abstract
- China became the world’s second largest liquefied natural gas (LNG) importer in 2018 but has faced extremely high import costs due to a lack of bargaining power. Assessments of the Shanghai LNG Price Index, first released in 2015, are vital for improving the understanding of these cost dynamics. This paper, using the LNG price index data from the Shanghai Petroleum and Gas Exchange (SHPGX) coupled with domestic and international LNG prices from July 1, 2015 to December 31, 2018, estimates several econometric models to evaluate the long-term and short-term equilibriums of the Shanghai LNG Price Index, the responses to market information shocks and the leading or lagging relationships with LNG and alternative energy prices from other agencies. The results show that the LNG price index of the SHPGX has already exhibited a long-term equilibrium and short-term adjustment mechanisms to reflect the average price level and market movements, but the market information transparency and price discovery efficiency of the index are still inadequate. China’s LNG market is still relatively independent of other natural gas markets, and marketization reforms are under way in China. The influence of the SHPGX LNG price index on the trading decisions of market participants is expected to improve with further development of China’s LNG reforms, the formation of a natural gas entry-exit system, and the increasing liquidity of the hub.
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