29 results on '"Xiumei Geng"'
Search Results
2. Design and experimental study of a stepped magnetorheological damper with power generation
- Author
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Xiaolong Yang, Yingjie Chen, Xiumei Geng, and Haiyan Liu
- Abstract
Traditional vehicle suspension magnetorheological dampers have problems with low output damping force and require additional energy input to operate, to improve the performance of the vehicle suspension magnetorheological damper, in this paper we propose and investigate a stepped magnetorheological damper structure with power generation, and conducts structural design and magnetic circuit analysis. The effects of different currents, damping gaps, coil slot positions, and coil turns on the damping performance of the stepped magnetorheological damper with power generation are numerically studied. The magnetic circuit sensitivity analysis of the power generation structure and the magnetorheological damper structure is also performed. Experiments have verified the effects of different input excitations on damping and energy-feeding performance, and the results of numerical analysis have been verified. The results show that when the excitation coil is wound for 257 turns, the magnetic circuit requirements are met, and the maximum damping force of the proposed electromagnetic energy fed stepped magnetorheological damper can reach over 4500N, meeting the use requirements.
- Published
- 2023
3. Numerical and experimental investigation of a large gap convergent ferrofluid seal with the stepped pole piece
- Author
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Xiaolong Yang, Yang Liu, Xiumei Geng, Liping Jiang, and Decai Li
- Subjects
Condensed Matter Physics ,Instrumentation ,Surfaces, Coatings and Films - Published
- 2023
4. A new continuous-discrete particle filter for continuous-discrete nonlinear systems.
- Author
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Yuanqing Xia, Zhi-Hong Deng, Li Li 0050, and Xiumei Geng
- Published
- 2013
- Full Text
- View/download PDF
5. Versatile synthesis of molybdenum sulfide from confined spaces for efficient hydrogen evolution
- Author
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Wentao Liang, Hongli Zhu, Xiumei Geng, Liao Chen, and Lei Yang
- Subjects
Tafel equation ,Materials science ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Amorphous solid ,Fuel Technology ,Molybdenum sulfide ,Chemical engineering ,Specific surface area ,Hydrogen evolution ,Crystallite ,0210 nano-technology ,Confined space - Abstract
(Quasi-)Amorphous molybdenum sulfide (MoSx) materials with disulfide (S22−) units have superior catalytic activities for hydrogen evolution reaction. However, the structures of the materials are less investigated and diversified. Herein, we first develop a new ethanol-thermal method to prepare MoSx and further apply versatile confined growth treatment with low-cost filler crystallites to efficiently modify its structure and consequent performance. Expectedly, because the material is quasi-amorphous and very deformable, its morphology varies dramatically from granules to foam-like material with specific surface area increases from 22.53 m2/g to 76.24 m2/g under the restriction of confined spaces. Importantly, the amount of S22− units which are responsible for the distinction of MoSx increases as well. By virtue of the confined growth, the catalytic performance of the original material on hydrogen evolution is improved significantly. The over-potential required to obtain 10 mA cm−2 current decreases remarkably from 278 mV to 209 mV and the Tafel slope decreases from 160 mV/decade to 72 mV/decade after confined growth. Therefore, we have proposed an effective method to synthesize and promote the catalytic performance of MoSx.
- Published
- 2017
6. Free-standing porous carbon electrodes derived from wood for high-performance Li-O2 battery applications
- Author
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Yang Han, Dunwei Wang, Hongli Zhu, Jingru Luo, Qi Dong, Lei Yang, Vivek Vattipalli, Xiahui Yao, Liao Chen, Xiumei Geng, and Wei Fan
- Subjects
Battery (electricity) ,Materials science ,Heteroatom ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Overpotential ,010402 general chemistry ,01 natural sciences ,law.invention ,Catalysis ,law ,General Materials Science ,Electrical and Electronic Engineering ,technology, industry, and agriculture ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Cathode ,0104 chemical sciences ,Capacitor ,chemistry ,Chemical engineering ,Electrode ,0210 nano-technology ,Carbon - Abstract
Porous carbon materials are widely used in particulate forms for energy applications such as fuel cells, batteries, and (super) capacitors. To better hold the particles together, polymeric additives are utilized as binders, which not only increase the weight and volume of the devices, but also cause adverse side effects. We developed a wood-derived, free-standing porous carbon electrode and successfully applied it as a cathode in Li-O2 batteries. The spontaneously formed hierarchical porous structure exhibits good performance in facilitating the mass transport and hosting the discharge products of Li2O2. Heteroatom (N) doping further improves the catalytic activity of the carbon cathode with lower overpotential and higher capacity. Overall, the Li-O2 battery based on the new carbon cathode affords a stable energy efficiency of 65% and can be operated for 20 cycles at a discharge depth of 70%. The wood-derived free-standing carbon represents a new, unique structure for energy applications.
- Published
- 2017
7. Bioinspired Ultrastable Lignin Cathode via Graphene Reconfiguration for Energy Storage
- Author
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Xiumei Geng, Li Jiao, Hongli Zhu, Lei Yang, Liming Zhang, Yelong Zhang, Jonathan Hamel, Nicola Giummarella, and Gunnar Henriksson
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Graphene ,General Chemical Engineering ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,Energy storage ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Pseudocapacitor ,Environmental Chemistry ,Lignin ,0210 nano-technology ,Dissolution - Abstract
Lignin extracted from trees is one of the most abundant biopolymers on Earth. Quinone, a substructure in lignin, can be used for energy storage via reversible redox reactions through absorbing and releasing electrons and protons. However, these efforts have encountered hindrances, such as short life cycle, low cycling efficiency, and a high self-discharge rate. All of these issues are related to electrode dissolution by electrolyte solvents and the insulating nature of lignin. Addressing these critical challenges, for the first time, we use a reconfigurable and hierarchical graphene cage to capture the lignin by mimicking the prey-trapping of venus flytraps. The reconfigurable graphene confines the lignin within the electrode to prevent dissolution, while acting as a three-dimensional current collector to provide efficient electron transport pathways during the electrochemical reaction. This bioinspired design enables the best cycling performance of lignin reported so far at 88% capacitance retention for ...
- Published
- 2017
8. Two-Dimensional Water-Coupled Metallic MoS2 with Nanochannels for Ultrafast Supercapacitors
- Author
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Yelong Zhang, Yang Han, Lei Yang, Jingxiao Li, Mourad Benamara, Liao Chen, Xiumei Geng, and Hongli Zhu
- Subjects
Horizontal scan rate ,Supercapacitor ,Materials science ,business.industry ,Mechanical Engineering ,Diffusion ,Bioengineering ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Capacitance ,Energy storage ,0104 chemical sciences ,Ion ,Electrical resistivity and conductivity ,Monolayer ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business - Abstract
MoS2 is a promising electrode material for energy storage. However, the intrinsic multilayer pure metallic MoS2 (M-MoS2) has not been investigated for use in supercapacitors. Here, an ultrafast rate supercapacitor with extraordinary capacitance using a multilayer M-MoS2–H2O system is first investigated. Intrinsic M-MoS2 with a monolayer of water molecules covering both sides of nanosheets is obtained through a hydrothermal method with water as solvent. The super electrical conductivity of the as-prepared pure M-MoS2 is beneficial to electron transport for high power supercapacitor. Meanwhile, nanochannels between the layers of M-MoS2–H2O with a distance of ∼1.18 nm are favorable for increasing the specific space for ion diffusion and enlarging the surface area for ion adsorption. By virtue of this, M-MoS2–H2O reaches a high capacitance of 380 F/g at a scan rate of 5 mV/s and still maintains 105 F/g at scan rate of 10 V/s. Furthermore, the specific capacitance of the symmetric supercapacitor based on M-MoS...
- Published
- 2017
9. Free standing three-dimensional nitrogen-doped carbon nanowire array for high-performance supercapacitors
- Author
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Hongli Zhu, Lifeng Chen, Xiumei Geng, Guiyin Xu, Jinpeng Han, and Hui Dou
- Subjects
Materials science ,General Chemical Engineering ,Nanowire ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,01 natural sciences ,Capacitance ,Industrial and Manufacturing Engineering ,law.invention ,chemistry.chemical_compound ,law ,Polyaniline ,Environmental Chemistry ,Supercapacitor ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Carbon nanotube quantum dot ,chemistry ,Chemical engineering ,Electrode ,0210 nano-technology ,Carbon - Abstract
Three-dimensional polyaniline nanowire arrays are vertically grown on free-standing acidized carbon nanotube paper, and further carbonized to nitrogen doped carbon for supercapacitor electrodes. The three-dimensional porous structure of the as-prepared nitrogen doped carbon can increase the specific surface area and benefit ion transport into the interior of the electrode materials. Nitrogen doping can effectively improve the wettability of the carbon surface in the electrolyte and enhance the specific capacitance by a pseudocapacitive effect. Thus, free-standing nitrogen doped carbon nanowires on conductive carbon nanotube paper show excellent electrochemical performance as a supercapacitor electrode material. At a current density of 2 A g −1 , the specific capacitance reaches 210 F g −1 with 94% capacitance retention after 10,000 cycles.
- Published
- 2017
10. Metallic and highly conducting two-dimensional atomic arrays of sulfur enabled by molybdenum disulfide nanotemplate
- Author
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Mourad Benamara, Shuze Zhu, Ismail Bilgin, Jingxiao Li, Xiumei Geng, Yang Han, Hongli Zhu, and Liao Chen
- Subjects
0301 basic medicine ,Materials science ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Conductivity ,Metal ,03 medical and health sciences ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,Phase (matter) ,lcsh:TA401-492 ,General Materials Science ,Molybdenum disulfide ,lcsh:Computer software ,021001 nanoscience & nanotechnology ,Sulfur ,Computer Science Applications ,lcsh:QA76.75-76.765 ,030104 developmental biology ,chemistry ,Chemical engineering ,Mechanics of Materials ,Modeling and Simulation ,visual_art ,visual_art.visual_art_medium ,lcsh:Materials of engineering and construction. Mechanics of materials ,Density functional theory ,Selected area diffraction ,0210 nano-technology - Abstract
Element sulfur in nature is an insulating solid. While it has been tested that one-dimensional sulfur chain is metallic and conducting, the investigation on two-dimensional sulfur remains elusive. We report that molybdenum disulfide layers are able to serve as the nanotemplate to facilitate the formation of two-dimensional sulfur. Density functional theory calculations suggest that confined in-between layers of molybdenum disulfide, sulfur atoms are able to form two-dimensional triangular arrays that are highly metallic. As a result, these arrays contribute to the high conductivity and metallic phase of the hybrid structures of molybdenum disulfide layers and two-dimensional sulfur arrays. The experimentally measured conductivity of such hybrid structures reaches up to 223 S/m. Multiple experimental results, including X-ray photoelectron spectroscopy (XPS), transition electron microscope (TEM), selected area electron diffraction (SAED), agree with the computational insights. Due to the excellent conductivity, the current density is linearly proportional to the scan rate until 30,000 mV s−1 without the attendance of conductive additives. Using such hybrid structures as electrode, the two-electrode supercapacitor cells yield a power density of 106 Wh kg−1 and energy density ~47.5 Wh kg−1 in ionic liquid electrolytes. Our findings offer new insights into using two-dimensional materials and their Van der Waals heterostructures as nanotemplates to pattern foreign atoms for unprecedented material properties. Molybdenum disulfide (MoS2) layers can be used as templates for the formation of two-dimensional elemental sulfur. A team led by Hongli Zhu at Northeastern University used density functional theory calculations to show that the sulfur atoms sandwiched between MoS2 layers can arrange themselves into two-dimensional atomic layers, featuring a triangular array structure that results from the intrinsic triangular pattern of the parent sulfur atoms within MoS2. These arrays are metallic, and thus contribute to the metallic phase and associated conductivity of the resulting hybrid structure composed of alternating MoS2 layers and two-dimensional sulfur layers. The experimentally synthesized compounds show conductivity up to 223 S/m. This strategy may be used for engineering of two-dimensional material hybrids by means of nano-template patterns.
- Published
- 2017
11. Batteries: Freestanding Metallic 1T MoS2 with Dual Ion Diffusion Paths as High Rate Anode for Sodium-Ion Batteries (Adv. Funct. Mater. 40/2017)
- Author
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Yucong Jiao, Lei Yang, Xiumei Geng, Hongli Zhu, Yang Han, and Alolika Mukhopadhyay
- Subjects
High rate ,Materials science ,Sodium ,chemistry.chemical_element ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Ion ,Anode ,Biomaterials ,Metal ,chemistry ,Chemical engineering ,visual_art ,Electrochemistry ,visual_art.visual_art_medium ,Diffusion (business) - Published
- 2017
12. Two-Dimensional Water-Coupled Metallic MoS
- Author
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Xiumei, Geng, Yelong, Zhang, Yang, Han, Jingxiao, Li, Lei, Yang, Mourad, Benamara, Liao, Chen, and Hongli, Zhu
- Abstract
MoS
- Published
- 2017
13. Three-Dimensional Structures of MoS2Nanosheets with Ultrahigh Hydrogen Evolution Reaction in Water Reduction
- Author
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Jingbiao Cui, Xiumei Geng, Matthew Brozak, Wei Wu, Johnathan C. Armstrong, Alaa A. Al-Hilo, Tar-Pin Chen, Ning Li, and Weiwei Sun
- Subjects
Materials science ,Graphene ,Inorganic chemistry ,chemistry.chemical_element ,Chemical vapor deposition ,Molybdate ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Catalysis ,law.invention ,Biomaterials ,chemistry.chemical_compound ,Nickel ,chemistry ,Molybdenum ,law ,Electrochemistry ,Hydrogen production ,Nanosheet - Abstract
The hydrogen evolution reaction in an alkaline environment using a non-precious catalyst with much greater efficiency represents a critical challenge in research. Here, a robust and highly active system for hydrogen evolution reaction in alkaline solution is reported by developing MoS2 nanosheet arrays vertically aligned on graphene-mediated 3D Ni networks. The catalytic activity of the 3D MoS2 nanostructures is found to increase by 2 orders of magnitude as compared to the Ni networks without MoS2. The MoS2 nanosheets vertically grow on the surface of graphene by employing tetrakis(diethylaminodithiocarbomato)molybdate(IV) as the molybdenum and sulfur source in a chemical vapor deposition process. The few-layer MoS2 nanosheets on 3D graphene/nickel structure can maximize the exposure of their edge sites at the atomic scale and present a superior catalysis activity for hydrogen production. In addition, the backbone structure facilitates as an excellent electrode for charge transport. This precious-metal-free and highly efficient active system enables prospective opportunities for using alkaline solution in industrial applications.
- Published
- 2014
14. High-Quality Graphene Sheets from Graphene Oxide Hot Pressing and Its Applications
- Author
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Jingbiao Cui and Xiumei Geng
- Subjects
Materials science ,Fabrication ,Quality (physics) ,Scale (ratio) ,Graphene ,law ,Intercalation (chemistry) ,Nanotechnology ,Graphite ,Graphene oxide paper ,law.invention - Published
- 2016
15. Layer-Controlled and Wafer-Scale Synthesis of Uniform and High-Quality Graphene Films on a Polycrystalline Nickel Catalyst
- Author
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Guo Yufen, Mengtao Sun, Youpin Gong, Guangtong Liu, Weiwei Li, Mingsheng Long, Xiumei Geng, Jianbao Xu, Xuemin Zhang, Xiaohui Cao, Li Lu, Liwei Liu, and Liqiong Wu
- Subjects
Materials science ,Hydrogen ,Graphene ,chemistry.chemical_element ,Nanotechnology ,Chemical vapor deposition ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Catalysis ,law.invention ,Biomaterials ,Carbon film ,chemistry ,Chemical engineering ,law ,Electrochemistry ,Wafer ,Layer (electronics) ,Sheet resistance - Abstract
Chemical vapor deposition (CVD) provides a synthesis route for large-area and high-quality graphene films. However, layer-controlled synthesis remains a great challenge on polycrystalline metallic films. Here, a facile and viable synthesis of layer-controlled and high-quality graphene films on wafer-scale Ni surface by the sequentially separated steps of gas carburization, hydrogen exposure, and segregation is developed. The layer numbers of graphene films with large domain sizes are controlled precisely at ambient pressure by modulating the simplified CVD process conditions and hydrogen exposure. The hydrogen exposure assisted with a Ni catalyst plays a critical role in promoting the preferential segregation through removing the carbon layers on the Ni surface and reducing carbon content in the Ni. Excellent electrical and transparent conductive performance, with a room-temperature mobility of ≈3000 cm 2 V −1 s −1 and a sheet resistance as low as ≈100 Ω per square at ≈90% transmittance, of the twisted few-layer grapheme films grown on the Ni catalyst is demonstrated.
- Published
- 2012
16. Electrical and Raman properties of p-type and n-type modified graphene by inorganic quantum dot and organic molecule modification
- Author
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Mengtao Sun, Liwei Liu, Yanxue Hou, Bin Dong, Xiumei Geng, and Yuanzuo Li
- Subjects
Materials science ,Condensed matter physics ,Graphene ,General Physics and Astronomy ,Tetracyanoethylene ,law.invention ,symbols.namesake ,chemistry.chemical_compound ,chemistry ,Quantum dot ,Chemical physics ,law ,symbols ,Molecule ,Raman spectroscopy ,Bilayer graphene ,Graphene nanoribbons ,Graphene oxide paper - Abstract
We obtained n-type and p-type modified graphene by mixing quantum dots and depositing electron-acceptor molecules on the surface of graphene, respectively. The electrical and optical properties of these two types of samples were measured. For n-type modified graphene, the electrons were transferred from quantum dots to graphene. The resistance of these quantum dots in modified n-type graphene is significantly smaller than that of pristine graphene. For p-type graphene, modified by electron-acceptor organic molecules of tetracyanoethylene (TCNE), electrons were transferred from graphene to TCNE molecules. The resistance of this molecular modified p-type graphene is about 10% larger than that of pristine graphene. The charge transfer effect on the optical properties of graphene was investigated with Raman spectra.
- Published
- 2011
17. Aqueous-Processable Noncovalent Chemically Converted Graphene-Quantum Dot Composites for Flexible and Transparent Optoelectronic Films
- Author
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Guosheng Cheng, Liwei Liu, Xiumei Geng, Rensheng Song, Hongxing Xu, Zhenghui Liu, Haijian Zhong, Liang Niu, Zhijun Zhang, Mengtao Sun, Guangtong Liu, Zhenyuan Xing, Lianfeng Sun, and Li Lu
- Subjects
Optics and Photonics ,Materials science ,Photochemistry ,Oxide ,law.invention ,chemistry.chemical_compound ,law ,Quantum Dots ,General Materials Science ,Graphite ,Composite material ,Thin film ,Nanocomposite ,Graphene ,business.industry ,Mechanical Engineering ,Photoconductivity ,Graphene quantum dot ,Carbon ,chemistry ,Mechanics of Materials ,Quantum dot ,Optoelectronics ,Electronics ,Crystallization ,business - Abstract
The preparation and optoelectronic response of flexible composites via non-covalent coupling of quantum dots to chemically converted graphene is presented. The photoincluced charge transfer is confirmed by photoconductivity measurements and the photosensitivity is improved with increasing loadings of quantum dots. This opens up a new effective route to form composites for future large-area flexible and transparent optoelectronic devices.
- Published
- 2010
18. Interface Strain Induced Hydrophobic Facet Suppression in Cellulose Nanocomposite Embedded with Highly Oxidized Monolayer Graphene Oxide
- Author
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Lei Yang, Liao Chen, Bedanga Sapkota, Xiumei Geng, Huijuan Zhao, Hongli Zhu, and Qian Mao
- Subjects
Materials science ,Nanocomposite ,Graphene ,Hydrogen bond ,Mechanical Engineering ,Oxide ,Nanotechnology ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,Molecular dynamics ,chemistry ,Mechanics of Materials ,law ,engineering ,Biopolymer ,Facet ,Cellulose ,0210 nano-technology - Abstract
In nature, cellulose is a unique lightweight biopolymer with outstanding mechanical and optical properties that is readily available. Rigorous investigations have been conducted to use cellulose as an ingredient in the advanced functional composite design. In this work, a hybrid film composed of homogeneous cellulose nanocrystals (CNC) and high oxidation graphene oxide (GO) is obtained by sufficient blending and vacuum filtration. For the first time through the X-ray diffraction (XRD) spectrum, the suppression of the originally ordered hydrophobic (200) facet of CNC is observed with increasing concentrations of GO. Further, the originally ordered hydrophilic (110)/(1-10) facets of CNC remain intact. Through systematic molecular dynamics simulations of a set of simplified CNC–GO sandwich structures, the mechanism behind this hydrophilic/hydrophobic facets manipulation is revealed. The strain induced by the hydrogen bonding between the CNC hydroxyl groups and the oxidation types on GO is the dominant reason to cause the suppression of the hydrophobic facet of CNC in CNC–GO hybrid film. This strain induced mechanism provides an understanding for intrinsically manipulating cellulose–matrix interface and potentially engineering the cellulose based nanocomposite material properties for future advanced materials development.
- Published
- 2017
19. Freestanding Metallic 1T MoS2 with Dual Ion Diffusion Paths as High Rate Anode for Sodium-Ion Batteries
- Author
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Xiumei Geng, Hongli Zhu, Yucong Jiao, Yang Han, Alolika Mukhopadhyay, and Lei Yang
- Subjects
Materials science ,Graphene ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Anode ,Ion ,law.invention ,Biomaterials ,chemistry ,Chemical engineering ,law ,Electrode ,Lithium ,0210 nano-technology - Abstract
This work studies for the first time the metallic 1T MoS2 sandwich grown on graphene tube as a freestanding intercalation anode for promising sodium-ion batteries (SIBs). Sodium is earth-abundant and readily accessible. Compared to lithium, the main challenge of sodium-ion batteries is its sluggish ion diffusion kinetic. The freestanding, porous, hollow structure of the electrode allows maximum electrolyte accessibility to benefit the transportation of Na+ ions. Meanwhile, the metallic MoS2 provides excellent electron conductivity. The obtained 1T MoS2 electrode exhibits excellent electrochemical performance: a high reversible capacity of 313 mAh g−1 at a current density of 0.05 A g−1 after 200 cycles and a high rate capability of 175 mAh g−1 at 2 A g−1. The underlying mechanism of high rate performance of 1T MoS2 for SIBs is the high electrical conductivity and excellent ion accessibility. This study sheds light on using the 1T MoS2 as a novel anode for SIBs.
- Published
- 2017
20. 2D Water-Coupled Metallic MoS2 with Nanochannels for Ultrafast Supercapacitor
- Author
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Hongli Zhu and Xiumei Geng
- Abstract
MoS2 is a promising electrode material for energy storage. However, the metallic, intrinsic multilayer, and pure MoS2 (M-MoS2) has not been investigated for use in supercapacitors. Here, an ultrafast rate supercapacitor with extraordinary capacitance using a multilayer M-MoS2-H2O system is first investigated. Intrinsic M-MoS2 with a monolayer of water molecules covering both sides of nanosheets is obtained through a hydrothermal method with water as solvent. The super conductivity of the as-prepared pure M-MoS2 is beneficial to electron transport for high power supercapacitor. Meanwhile, nanochannels between the layers of M-MoS2-H2O with a distance of ~1.18 nm are favorable for increasing the specific space for ion diffusion and enlarging the surface area for ion adsorption. By virtue of this, M-MoS2-H2O reaches a high capacitance of 380 F/g at a scan rate of 5 mV/s and still maintains 105 F/g at scan rate of 10 V/s. Furthermore, the specific capacitance of the symmetric supercapacitor based on M-MoS2-H2O electrodes retain a value as high as 249 F/g under 50 mV/s. These findings suggest that multilayered M-MoS2-H2O system with ion accessible large nanochannels and efficient charge transport provide an efficient energy storage strategy for ultrafast supercapacitors.
- Published
- 2017
21. High-Density Three-Dimension Graphene Macroscopic Objects for High-Capacity Removal of Heavy Metal Ions
- Author
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Weiwei Li, Guo Yufen, Youpin Gong, Wei Xiangfei, Mingsheng Long, Xiumei Geng, Chao Zhu, Liwei Liu, Liao Shutian, Jianbao Xu, Qiu Shengqiang, Mengtao Sun, Mingliang Chen, Liqiong Wu, and Song Gao
- Subjects
Multidisciplinary ,Aqueous solution ,Materials science ,Graphene ,Metal ions in aqueous solution ,Chemical vapor deposition ,Electrolyte ,Bioinformatics ,Article ,law.invention ,Adsorption ,Chemical engineering ,law ,Specific surface area ,Electrode - Abstract
The chemical vapor deposition (CVD) fabrication of high-density three-dimension graphene macroscopic objects (3D-GMOs) with a relatively low porosity has not yet been realized, although they are desirable for applications in which high mechanical and electrical properties are required. Here, we explore a method to rapidly prepare the high-density 3D-GMOs using nickel chloride hexahydrate (NiCl2·6H2O) as a catalyst precursor by CVD process at atmospheric pressure. Further, the free-standing 3D-GMOs are employed as electrolytic electrodes to remove various heavy metal ions. The robust 3D structure, high conductivity (~12 S/cm) and large specific surface area (~560 m2/g) enable ultra-high electrical adsorption capacities (Cd2+ ~ 434 mg/g, Pb2+ ~ 882 mg/g, Ni2+ ~ 1,683 mg/g, Cu2+ ~ 3,820 mg/g) from aqueous solutions and fast desorption. The current work has significance in the studies of both the fabrication of high-density 3D-GMOs and the removal of heavy metal ions.
- Published
- 2013
22. Electronic transport properties of graphene nanoribbon arrays fabricated by unzipping aligned nanotubes
- Author
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Song Gao, Youpin Gong, Mengtao Sun, Li Lu, Wei Xiangfei, Mingsheng Long, Xiumei Geng, Guangtong Liu, Liwei Liu, Changli Yang, and Chao Zhu
- Subjects
Materials science ,Graphene ,business.industry ,Biasing ,Nanotechnology ,Carbon nanotube ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Gate voltage ,Electronic, Optical and Magnetic Materials ,law.invention ,Differential conductance ,symbols.namesake ,law ,Luttinger liquid ,symbols ,Optoelectronics ,business ,Raman spectroscopy ,Saturation (magnetic) - Abstract
We report on the electronic transport of graphene nanoribbon (GNR) arrays fabricated by a chemical unzipping of well-aligned single-walled carbon nanotubes. The high quality of narrow GNRs is implied by the existence of high-field current saturation and the relatively low intensity of disorder peak in parallel polarized Raman spectra. We find the zero-bias anomaly and the power-law behavior in differential conductance as a function of bias voltage and temperature in the one-dimensional GNRs, which can be well described as Luttinger liquid. Furthermore, this Luttinger-liquid behavior can be tuned by changing the gate voltage.
- Published
- 2013
23. Interlayer catalytic exfoliation realizing scalable production of large-size pristine few-layer graphene
- Author
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Liwei Liu, Qiu Shengqiang, Weiwei Li, Mingsheng Long, Xiumei Geng, Liqiong Wu, Dongfang Li, Guo Yufen, Chao Zhu, Youpin Gong, Wei Xiangfei, Song Gao, Gebo Pan, Mengtao Sun, and Mingliang Chen
- Subjects
Multidisciplinary ,Materials science ,Graphene ,Intercalation (chemistry) ,Oxide ,Graphite oxide ,Nanotechnology ,Exfoliation joint ,Article ,Catalysis ,law.invention ,Crystal ,chemistry.chemical_compound ,chemistry ,law ,Graphite - Abstract
Mass production of reduced graphene oxide and graphene nanoplatelets has recently been achieved. However, a great challenge still remains in realizing large-quantity and high-quality production of large-size thin few-layer graphene (FLG). Here, we create a novel route to solve the issue by employing one-time-only interlayer catalytic exfoliation (ICE) of salt-intercalated graphite. The typical FLG with a large lateral size of tens of microns and a thickness less than 2 nm have been obtained by a mild and durative ICE. The high-quality graphene layers preserve intact basal crystal planes owing to avoidance of the degradation reaction during both intercalation and ICE. Furthermore, we reveal that the high-quality FLG ensures a remarkable lithium-storage stability (>1,000 cycles) and a large reversible specific capacity (>600 mAh g−1). This simple and scalable technique acquiring high-quality FLG offers considerable potential for future realistic applications.
- Published
- 2013
- Full Text
- View/download PDF
24. Reduced graphene oxide electrically contacted graphene sensor for highly sensitive nitric oxide detection
- Author
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Weiwei Li, Guosheng Cheng, Jianbao Xu, Guo Yufen, Liwei Liu, Xiumei Geng, Youpin Gong, Jizan Rong, Mengtao Sun, Xuemin Zhang, Peng Li, and Liqiong Wu
- Subjects
Materials science ,Graphene ,General Engineering ,Oxide ,General Physics and Astronomy ,Nanotechnology ,Chemical vapor deposition ,Dielectrophoresis ,Highly sensitive ,law.invention ,Nitric oxide ,chemistry.chemical_compound ,chemistry ,law ,Electrode ,General Materials Science ,Graphene oxide paper - Abstract
We develop graphene-based devices fabricated by alternating current dielectrophoresis (ac-DEP) for highly sensitive nitric oxide (NO) gas detection. The novel device comprises the sensitive channels of palladium-decorated reduced graphene oxide (Pd-RGO) and the electrodes covered with chemical vapor deposition (CVD)-grown graphene. The highly sensitive, recoverable, and reliable detection of NO gas ranging from 2 to 420 ppb with response time of several hundred seconds has been achieved at room temperature. The facile and scalable route for high performance suggests a promising application of graphene devices toward the human exhaled NO and environmental pollutant detections.
- Published
- 2011
25. InN nanowire transistors: Growth, electronics & photonics
- Author
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Jia Chen, Xiumei Geng, Haibin Liu, and Guosheng Cheng
- Subjects
Indium nitride ,Materials science ,business.industry ,Band gap ,Transistor ,Nanowire ,Nitride ,law.invention ,chemistry.chemical_compound ,Nanolithography ,chemistry ,Nanoelectronics ,law ,Optoelectronics ,Photonics ,business - Abstract
Semiconducting group-III nitrides have been the focus of intense research in recent years because of their excellent inherent electronic and optoelectronic properties. In particular, indium nitride (InN) has attracted much attention due to the lowest effective electron mass among all the III-nitride compounds, potentially leading to a high mobility. Optically, it was reported that InN has an unexpectedly low band gap of around 0.7–0.9 eV at room temperature, i.e., emitting in a wavelength of 1–2µm, a range widely used by the telecommunication industry.
- Published
- 2010
26. [Determination of amino acids in Isatis indigotica Fort by reversed-phase high performance liquid chromatography with pre-column derivatization]
- Author
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Shaohui, Wan, Hao, Yang, and Xiumei, Geng
- Subjects
Proline ,Glutamic Acid ,Dinitrofluorobenzene ,Amino Acids ,Isatis ,Arginine ,Chromatography, High Pressure Liquid - Abstract
A reversed-phase high performance liquid chromatographic method with pre-column derivatization for the determination of amino acids, which were known as the characteristic constituents of Isatis indigotica Fort was established. The amino acids in alkalescence were derivatized with 2, 4-dinitro-fluorobenzene (DNFB). A reproducible method for simultaneous qualitative analysis of glutamic acid (Glu), argirine (Arg) and proline (Pro) and quantitative analysis of Arg and Pro in Isatis indigotica Fort has been established. NaAc buffer (pH 6.4) acetonitrile (85:15, v/v) as mobile phase and a Sinochrom ODS-BP column were used. The detector was operated at 360 nm. The linear regressions of the standard curves were determined for Arg and for Pro. The method was carried out over the range of 0. 627 - 5.016 microg for Arg and 0. 874 - 7.000 microg for Pro. The recoveries were 98.5% and 98.4% with the relative standard deviations of 2.5% and 2.3% for Arg and Pro respectively. The results indicate that among the three amino acids in Isatis indigotica Fort, Arg content was the highest, Pro the second and Glu the lowest. The method has good accuracy and repeatability and it can be used for the quality control of Isatis indigotica Fort.
- Published
- 2005
27. Two-Dimensional Water-Coupled Metallic MoS2 with Nanochannels for Ultrafast Supercapacitors.
- Author
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Xiumei Geng, Yelong Zhang, Yang Han, Jingxiao Li, Lei Yang, Benamara, Mourad, Liao Chen, and Hongli Zhu
- Subjects
- *
SUPERCAPACITORS , *MOLYBDENUM , *ENERGY storage , *ELECTRIC capacity , *ELECTRIC conductivity , *ELECTRON transport - Abstract
MoS2 is a promising electrode material for energy storage. However, the intrinsic multilayer pure metallic MoS2 (M-MoS2) has not been investigated for use in supercapacitors. Here, an ultrafast rate supercapacitor with extraordinary capacitance using a multilayer M-MoS2-H2O system is first investigated. Intrinsic M-MoS2 with a monolayer of water molecules covering both sides of nanosheets is obtained through a hydrothermal method with water as solvent. The super electrical conductivity of the as-prepared pure M-MoS2 is beneficial to electron transport for high power supercapacitor. Meanwhile, nanochannels between the layers of M-MoS2-H2O with a distance of ∼1.18 nm are favorable for increasing the specific space for ion diffusion and enlarging the surface area for ion adsorption. By virtue of this, M-MoS2-H2O reaches a high capacitance of 380 F/g at a scan rate of 5 mV/s and still maintains 105 F/g at scan rate of 10 V/s. Furthermore, the specific capacitance of the symmetric supercapacitor based on M-MoS2-H2O electrodes retain a value as high as 249 F/g under 50 mV/s. These findings suggest that multilayered M-MoS2-H2O system with ion accessible large nanochannels and efficient charge transport provide an efficient energy storage strategy for ultrafast supercapacitors. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
28. InN nanowire transistors: Growth, electronics & photonics.
- Author
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Guosheng Cheng, Haibin Liu, Xiumei Geng, and Jia Chen
- Published
- 2010
- Full Text
- View/download PDF
29. Electronic transport properties of graphene nanoribbon arrays fabricated by unzipping aligned nanotubes.
- Author
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Youpin Gong, Mingsheng Long, Guangtong Liu, Song Gao, Chao Zhu, Xiangfei Wei, Xiumei Geng, Mengtao Sun, Changli Yang, Li Lu, and Liwei Liu
- Subjects
- *
ELECTRIC properties , *NANORIBBONS , *GRAPHENE , *CARBON nanotubes , *RAMAN spectra - Abstract
We report on the electronic transport of graphene nanoribbon (GNR) arrays fabricated by a chemical unzipping of well-aligned single-walled carbon nanotubes. The high quality of narrow GNRs is implied by the existence of high-field current saturation and the relatively low intensity of disorder peak in parallel polarized Raman spectra. We find the zero-bias anomaly and the power-law behavior in differential conductance as a function of bias voltage and temperature in the one-dimensional GNRs, which can be well described as Luttinger liquid. Furthermore, this Luttinger-liquid behavior can be tuned by changing the gate voltage. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
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