Co-reporter:Xiujuan Wang, Kai Chen, Gang Wang, Xiaojie Liu, and Hui Wang
ACS Nano November 28, 2017 Volume 11(Issue 11) pp:11602-11602
Publication Date(Web):October 19, 2017
DOI:10.1021/acsnano.7b06625
Transition metal phosphides have been extensively investigated owing to their high theoretical capacities and relatively low intercalation potentials vs Li/Li+, but their practical applications have been hindered by low electrical conductivity and dramatic volume variation during cycling. In this work, an interesting strategy for the rational design of graphene (GR) encapsulated with a hollow FeP@carbon nanocomposite (H-FeP@C@GR) via a combination of a hydrothermal route, a carbon-coating process, phosphidation treatment, and carbothermic reaction is reported. The hollow FeP (H-FeP) nanospheres shelled with thin carbon layers are wonderfully incorporated into the GR matrix, interconnecting to form a three-dimensional (3D) hierarchical architecture. Such a design offers distinct advantages for FeP-based anode materials for both lithium ion batteries (LIBs) and sodium ion batteries (SIBs). For example, the 3D omnibearing conductive networks from the GR skeleton and outer coating carbon can provide an open freeway for electron/ion transport, promoting the electrode reaction kinetics. In addition, the wrapping of an H-FeP nanosphere in a thin carbon layer enables the formation of a solid electrolyte interphase (SEI) on the carbon layer surface instead of on the individual H-FeP surface, preventing the continual re-forming of the SEI. When used as anode materials for LIBs and SIBs, H-FeP@C@GR exhibited excellent electrochemistry performances.Keywords: batteries; carbon coating; DFT calculations; FeP; graphene;
Co-reporter:Hanying Wang;Shenghua Ma;Qian Ma
Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 9) pp:6936-6949
Publication Date(Web):27 February 2017
DOI:10.1007/s10854-017-6394-8
In this study, the effects of Si/Pb ratio of Pb–Te–Si–O glasses on the electrical performance of multicrystalline Si solar cells were investigated. We first studied the relationship between the properties of glass frit (such as transition temperature (Tg), crystallization tendency, and aggressiveness) and the Si/Pb ratios. Then, the influence of glass frit Tg on the structure of the contact interface, quality of ohmic contacts, and solar cell electrical performance was investigated. The results showed that the cell based on glass frit produced at moderately low Tg, had smaller series resistance and higher photoelectric conversion efficiency than those based on lower Tg and higher Tg glass frits. The optimal glass frit Tg was 289.6 °C; glass frits can form dense and thick films, which can reduce the bulk resistance of the grid line. At the same time, glass frits can reduce the Ag crystallite size to prevent high junction leakage and shunting of shallow emitters, and probably increase the concentration of Ag crystallites and Ag colloids to help tunnel the thinner glass layer. This led to formation of good ohmic contacts and conductive chains. All these features contributed to reach the best values of photoelectric conversion efficiency (18.628%) and series resistance (0.0019 Ω).
Co-reporter:Shaobo Cai;Gang Wang;Man Jiang
Journal of Solid State Electrochemistry 2017 Volume 21( Issue 4) pp:1129-1136
Publication Date(Web):16 November 2016
DOI:10.1007/s10008-016-3414-1
In this study, we develop a simple template-free strategy to fabricate uniform porous CuCo2O4 hollow spheres. The shells of the as-synthesized CuCo2O4 hierarchical hollow nanostructures are composed of primary nanoparticle units, leading to a superior specific surface area of 51 m2 g−1. When applied in lithium ion batteries, the porous CuCo2O4 hollow spheres show excellent lithium storage performance, which could deliver a high specific capacity of 930 mAh g−1 after 150 cycles for half-cell and 660 mAh g−1 after 50 cycles for full cell. The good electrochemical properties of the as-synthesized porous CuCo2O4 hollow spheres can be attributed to their unique porous structure, which is beneficial for shorting lithium ion-electron transmission path and alleviating the structural strain of volume change.
Co-reporter:Beibei Wang, Yuan Xia, Gang Wang, Yixuan Zhou, Hui Wang
Chemical Engineering Journal 2017 Volume 309(Volume 309) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.cej.2016.10.073
•Macroporous carbon sheets-supported MoS2/C nanospheres were designed.•The composite exhibits superior sodium storage properties.•The high performance can be due to the unique structure and remarkable synergy.Core shell MoS2/C nanospheres embedded in foam-like interconnected macroporous carbon sheets composite were successfully fabricated by a facile glucose carbonization process. In this unique architecture, the interconnected void nanospheres produced by SiO2 nanopsheres homogeneously surround the core shell MoS2/C nanospheres. When evaluated an anode material for sodium-ion batteries, the as-synthesized porous carbon sheets supported core shell MoS2/C composite displays a discharge capacity of 523 mAh g−1 after 100 discharge/charge cycles at the current density of 0.1 A g−1. Moreover, the 300th discharge capacity at a higher current density of 1 A g−1 is 337 mAh g−1. The superior electrochemical performance of the porous carbon sheets supported core shell MoS2/C composite can be attributed to the supporting carbon sheets with an interconnected macroporous structure, uniform distribution of carbon coated MoS2 nanospheres in carbon matrix, high electronic conductivity, and thus leading to enhanced structural stability and cyclability of the anode material.
Co-reporter:Xing Zhang, Beibei Wang, Gang Wang, Xiaojie Liu, Hui Wang
Electrochimica Acta 2017 Volume 258(Volume 258) pp:
Publication Date(Web):20 December 2017
DOI:10.1016/j.electacta.2017.11.125
Metal sulfide composites have been regarded as a new class of the most promising anode materials for the both lithium ion batteries (LIBs) and sodium ion batteries (SIBs). However, their practical applications have been restricted by their relative poor cyclabilities and low rate performances. Herein, the numerous metal sulfides/graphene/carbon nanotubes (MxSy/GC) composites with a sandwiched architecture assembled by uniform MxSy nanoparticles anchored in the GC matrix are fabricated for high-performance LIBs/SIBs via a scalable calcination approach. As a result of the superiorities of small particle size, preferable structural flexibility and the sandwiched architecture, the as-prepared MxSy/GC composites exhibit a significant improvement in LIBs performance. Among them, the FeS/GC composite demonstrates excellent electrochemical performances in LIBs with favorable cycling stability, high specific capacity (∼870 mAh g−1 at 0.25 A g−1) and remarkable rate performance. When applied as an anode material for SIBs, the FeS/GC composite still exhibits a superior reversible capacity of 300 mAh g−1 at a current density of 0.1 A g−1 after 100 cycles.
Co-reporter:Qian Ma;Shenghua Ma;Jintao Bai
RSC Advances (2011-Present) 2017 vol. 7(Issue 75) pp:47500-47506
Publication Date(Web):2017/10/06
DOI:10.1039/C7RA07574J
Due to the demand for a new environmentally friendly silver front conductive paste, it is imperative for silicon solar cells to use nontoxic lead-free glass frits. In the present paper, three kinds of Bi–Te–B–Si–P–O lead-free glass frits with different mass fraction ratios of B2O3/SiO2 (10/4, 6/8, and 2/12) were prepared by a melt cooling route. First, we investigated that the effect of those B2O3/SiO2 ratios on the transition temperature (Tg) of glass frits, and their Tg were 311 °C, 347 °C, and 366 °C, respectively. Then, the influence of Tg on cross-sectional microstructures of the front-silver electrodes, the Ag crystallites distribution on Si substrate, and electrical performance were studied. The fabricated solar cell showed the lowest series resistance (0.0017 Ω) and the highest photoelectric conversion efficiency (18.260%) based on the glass frit Tg of 347 °C. This is because the dense thick-film Ag grid can reduce the bulk resistance of the grid line. Besides, the glass frit with the Tg of 347 °C could control the growth and homogeneous distribution of silver crystallites in the glass layer and silicon substrate, which contributed to forming good ohmic contacts and tunneling effect with enough energy photoelectrons. The result was compared with the solar cell fabricated with a classical Pb-based glass frit with the conversion efficiency (18.230%) using the same device configuration, which indicated the designed lead-free glass frit could be a suitable substitute for a Pb-based glass frit for preparing environmentally friendly front-side silver paste for crystalline silicon solar cells.
Co-reporter:Hanying Wang;Shenghua Ma;Meiling Zhang
Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 16) pp:11934-11949
Publication Date(Web):26 May 2017
DOI:10.1007/s10854-017-7003-6
In this paper, the influence of screen-printing technology, sintering temperature, and the belt speed of sintering furnace on electrical properties of solar cells were researched. It is found that the morphology and aspect ratio of grid line are strongly influenced by printing parameters including the snap-off distance, the squeegee pressure and the squeegee speed. A number of comparative experiments showed that the electrical performance of solar cells was the best when the snap-off distance is 1200 µm, the squeegee pressure is 75 N, and the squeegee speed is 220 mm/s. Meanwhile, the surface morphology of the front electrode grid line prepared with the above optimum technology parameter is smooth and dense, and possesses good aspect ratio. To better understand the contact quality, the influence of sintering peak temperature on the electrical performance of solar cells was deeply studied. The results show that when the peak temperature was 900 °C, the series resistance (Rs) possesses the minimum value and the open circuit voltage (Voc), fill factor (FF), and conversion efficiency (Eff) all possess the maximum values. The effect of belt speed of sintering furnace on the electrical performance of the cells was also investigated. It is found that the electrical performance parameters were the optimal at the belt speed of 245 in/min.
Co-reporter:Xiaojun Zhao, Gang Wang, Yixuan Zhou, Hui Wang
Energy 2017 Volume 118(Volume 118) pp:
Publication Date(Web):1 January 2017
DOI:10.1016/j.energy.2016.12.018
•The flexible free-standing CoSnO3/GN/GNTs papers are prepared by a two-step process.•The CoSnO3 nanoparticles are embedded homogenously into the 3D GN/GNTs scaffold.•The 3D GN/GNTs framework can accommodate the volume expansion of CoSnO3.•The free-standing CoSnO3/GN/GNTs papers exhibit superior electrochemical properties.A facile strategy is designed for the fabrication of flexible and free-standing ternary CoSnO3/graphene/carbon nanotubes (CoSnO3/GN/CNTs) composite papers through a simple filtration, followed by annealing process. The CoSnO3/GN/CNTs composite papers with high flexibility and tailorability can be easily fabricated. The CoSn(OH)6 nanoparticles/graphene oxide/carbon nanotubes (CoSn(OH)6/GO/CNTs) composite papers obtained by a simple filtration method are transformed into CoSnO3/GN/CNTs composite papers after a thermal treatment process. In this unique composite structure, CoSnO3 nanoparticles (nanocubes and nanoboxes) are embedded homogenously into the 3D framework of graphene and carbon nanotubes, respectively, in which offers not only a 3D conductive network and a dual restriction on the aggregation of CoSnO3 nanoparticles, but also accommodates the large volume expansion of CoSnO3 nanoparticles. When used directly as binder- and conductive agent-free anodes for lithium-ion batteries, the CoSnO3/GN/CNTs composite papers exhibit superb electrochemical properties including extraordinary reversible capacities, superior rate capabilities and stable cycle performances compared to CoSnO3 nanoparticles and GN/CNTs paper, suggesting a new pathway for the rational engineering of anode materials.
Co-reporter:Xing Zhang, Xiao Jie Liu, Gang Wang, Hui Wang
Journal of Colloid and Interface Science 2017 Volume 505(Volume 505) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.jcis.2017.05.028
A robust and interconnected three-dimensional (3D) aerogel consisting of CoS2 nanoparticles, graphene nanosheets (GNs) and carbon nanotubes (CNTs) is synthesized as an anode material (CoS2/GCAs) for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). With the introduction of CNTs, the isolated CoS2 nanoparticles as well as GNs are jointed closely and cross-linked to construct a 3D conductive network. Benefited from the advantages of the positive synergistic effects of the individual components, CoS2/GCAs composite exhibits excellent electrochemical performances. When used as an anode for LIBs, it possesses a high reversible capacity of 975 mAh g−1 after 100 cycles at 0.25 A g−1. Apart from that, it also manifests a superior cycling stability with capacity of 258 mAh g−1 after 100 cycles at 0.05 A g−1 for SIBs. As a result of the enhanced electrochemical performance, CoS2/GCAs composite with an interconnected architecture could be regarded as a promising candidate for LIBs/SIBs.CoS2/GCAs composite is synthesized by a facile hydrothermal method and delivers an outstanding electrochemical performance for LIBs/SIBs.Download high-res image (160KB)Download full-size image
Co-reporter:Feini Lin, Hui Wang, Gang Wang
Electrochimica Acta 2016 Volume 211() pp:207-216
Publication Date(Web):1 September 2016
DOI:10.1016/j.electacta.2016.05.195
A facile sacrificial-template method combined with a post annealing treatment was developed to synthesize uniform hollow polyhedral (cubic, octahedral and dodecahedral) NiO materials. The electrochemical and lithium-ion battery performances of the shape controlled hollow polyhedral NiO materials were examined, providing us with a description of the structure-performance correlations of hollow polyhedral anodes. The lithium-ion battery performance was found to be highly dependent on the hollow polyhedral NiO morphology. The hollow dodecahedral NiO (HD-NiO) electrode exhibited excellent cycling stability, high reversible capacity and good rate capacity compared to the other two NiO samples. At a current density of 0.1 A g−1, the hollow dodecahedral NiO electrode displayed an especially high capacity of 980 mAh g−1 after 100 cycles, which was much higher than that of the hollow cubic and octahedral NiO electrodes. Most important of all, when assembled with LiCoO2 to construct a full lithium-ion battery (HD-NiO//LiCoO2), the HD-NiO electrode exhibited a reversible capacity of 627 mAh g−1 at a current density of 0.1 A g−1 in the potential range of 1.0–3.8 V. These results clearly demonstrate that hollow polyhedral NiO has potential as an anode material in next generation lithium-ion battery systems with improved storage capacities.
Co-reporter:Yuan Xia, Beibei Wang, Xiaojun Zhao, Gang Wang, Hui Wang
Electrochimica Acta 2016 Volume 187() pp:55-64
Publication Date(Web):1 January 2016
DOI:10.1016/j.electacta.2015.11.047
In this work, a core-shell composite composed of MoS2 nanosheets grown on hollow carbon microspheres is synthesized by a hydrothermal and a subsequent annealing route. The result shows that well-graphitized hollow-carbon@highlycrystallineMoS2(HC@MoS2) was obtained after the four-step reaction. And it is found that the synthesized MoS2 is consist of 2H and 1T phases. The lithium storage property of the composite is investigated as an anode material for lithium-ion batteries. Benefited from the special morphology and structure, a stable capacity of 970 mAh g−1 for over 100 cycles at a current density of 0.25 A g−1 is realized on the material. Even at a high current density of 4 A g−1, a reversible capacity as high as 560 mAh g−1 is delivered. Moreover, the reasons for the excellent electrochemical performance of the material are explored and discussed in detail.
Co-reporter:Hanying Wang, Yuping Tai, Ruixiao Li, Hui Wang and Jintao Bai
RSC Advances 2016 vol. 6(Issue 34) pp:28289-28297
Publication Date(Web):10 Mar 2016
DOI:10.1039/C6RA00800C
In this paper, highly-dispersed spherical micron-sized (D50 = 2.94 μm) and submicron-sized (D50 = 0.59 μm) silver powders were prepared by a chemical reduction method. Hybrid silver powder was then synthesized by mixing the micron- and submicron-sized silver powders, and the mass percentages of submicron-sized silver powder in the hybrids were 0, 100, 5, 10, 15, and 20%. The tap density of the silver powders, cross-sectional and surface microstructures, and performance of cells designed using these silver powders were investigated. The results suggested that the mass ratio of hybrid silver powder had an important influence on the structure of the contact interface, the quality of the ohmic contacts, and the electrical performance of solar cells. The electrical performances of solar cells made with mixed silver powder were better than those made using pure micron- or submicron-sized silver powders. The optimal level of submicron-sized silver powder content was 15 wt%. This was because the surface morphology of the thick films prepared using this hybrid was smooth and dense, the layer had sufficient silver crystallites to increase the contact area fraction, and there was a thin glass layer to improve the probability of tunnelling from Ag crystallites to the Ag grid. This led to the formation of good ohmic contacts and conductive chains. As a result, this silver powder gave the best photoelectric conversion efficiency (18.282%) and series resistance (0.0019 Ω).
Co-reporter:Dr. Yuan Xia;Beibei Wang;Dr. Gang Wang;Xiaojie Liu; Hui Wang
ChemElectroChem 2016 Volume 3( Issue 2) pp:299-308
Publication Date(Web):
DOI:10.1002/celc.201500419
Abstract
Ni–Fe bimetallic oxide nanotubes with a hollow and porous structure were synthesized by using metal-organic framework (MOF) annealing processes. The Ni/Fe molar ratios in the binary metal oxide were rationally designed. Typically, Ni0.62Fe2.38O4 (called NFO-0.25) nanotubes with a tube shell of around 10 nm possess a specific surface area of 134.3 m2 g−1 and are composed of nanosized primary particles. The lithium-ion battery performance of the nanotube anode was evaluated by galvanostatic and rate cycling. In the half-cell, a high capacity of 1184 mA h g−1 for the NFO-0.25 anode was maintained at a current density of 0.25 A g−1 after 200 cycles. In addition, the NFO-0.25/LiCoO2 full-cell has a reversible charge capacity of about 94 mAh g−1 with a high coulombic efficiency at the same current density. The feature of hollow and porous structures remarkably buffers the volume variation, and provides more active sites for lithiation–delithiation reactions, resulting in excellent lithium-storage performance.
Co-reporter:Yuan Xia
Ionics 2016 Volume 22( Issue 2) pp:159-166
Publication Date(Web):2016 February
DOI:10.1007/s11581-015-1554-4
Different particle sizes of dodecahedron precursors are synthesized by controlling the polarity of the solution. Through the results of scanning electron microscope (SEM) images, it can be found that different particle sizes of precursors present obvious edge angles and their morphology can be well retained after annealing. X-ray diffraction (XRD) measurements suggest that the annealed polyhedral products are pure single-phase NiCo2O4. When tested as lithium-ion battery anode, 0.5 μm NiCo2O4 polyhedra exhibits a specific capacity of 1050 mAh g−1 at 0.1 C at the 60th cycle, which was higher than theoretical capacity of single metal oxide (NiO 718 mAh g−1 and Co3O4 890 mAh g−1). It also exhibits the highest rate capability with an average discharge capacity of 890, 700, 490, 330, and 300 mAh g−1 at 0.5, 2, 4, 8, and 10 C, respectively. Those advantages are attributed to that small-sized particle with great surface areas decrease the actual current density at the surface and inner of the prepared electrode.
Co-reporter:Xiaojun Zhao;Gang Wang
Journal of Nanoparticle Research 2016 Volume 18( Issue 10) pp:
Publication Date(Web):2016 October
DOI:10.1007/s11051-016-3511-1
MnO2 nanotubes/reduced graphene oxide (MnO2/RGO) membranes with different MnO2 contents are successfully synthesized by a facile two-step method including vacuum filtration and subsequent thermal reduction route. The MnO2 nanotubes obtained are 38 nm in diameter and homogeneously imbedded in RGO sheets as spacers. The synthesized MnO2/RGO membranes exhibit excellent mechanical flexibilities and free-standing properties. Using the membranes directly as anode materials for lithium batteries (LIBs), the membranes for half LIBs show superb cycling stabilities and rate performances. Importantly, the electrochemical performances of MnO2/RGO membranes show a strong dependence on the MnO2 nanotube contents in the hybrids. In addition, our results show that the hybrid membranes with 49.0 wt% MnO2 nanotube in half LIBs achieve a high reversible capacity of 1006.7 mAh g−1 after 100 cycles at a current density of 0.1 A g−1, which is higher lithium storage capacity than that of reported MnO2-carbon electrodes. Furthermore, the synthesized full cell (MnO2/RGO//LiCoO2) system also exhibit excellent electrochemical performances, which can be attributed to the unique microstructures of MnO2 and GRO, coupled with the strong synergistic interaction between MnO2 nanotubes and GRO sheets.
Co-reporter:Beibei Wang, Gang Wang and Hui Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 33) pp:17403-17411
Publication Date(Web):22 Jul 2015
DOI:10.1039/C5TA03929K
In this article, we demonstrate a general approach to grow Mo2C nanoparticles of 10–40 nm on a graphene (GR) support through a simple and environmentally friendly carburization process. The unique and special structural features of the Mo2C/GR hybrids including good structural robustness, small particle size and porous structure permit easy access for electrons and ions to the electrode/electrolyte, when the resulting materials are used as anode materials for lithium-ion batteries. Electrochemical tests indicate that the Mo2C/GR hybrids exhibit much better lithium storage properties than pure GR and bulk Mo2C electrodes. The enhanced electrochemical properties of the Mo2C/GR hybrids are mainly ascribed to the synergetic effects between Mo2C nanoparticles and the highly conductive GR support. The results clearly demonstrate that the Mo2C/GR hybrids have potential application as anode materials in high-performance energy storage devices.
Co-reporter:Beibei Wang, Gang Wang, Hui Wang
Electrochimica Acta 2015 Volume 156() pp:1-10
Publication Date(Web):20 February 2015
DOI:10.1016/j.electacta.2014.10.157
In this paper, a versatile facile route to synthesize mesoporous hollow-structured metal oxides is demonstrated using sulfonated polystyrene (SPS) microspheres as hard templates. SEM and TEM images show that the Fe2O3, Co3O4 and NiO hollow microspheres are self-assembled by nanorods, nanoparticles and nanosheets, respectively. Hollow and mesoporous structures not only provide enhanced mechanical stabilities to buffer the large volume changes during the charge/discharge processes, but also provide large specific areas for sufficient penetration of electrolyte, thus leading to an excellent cyclic stability and rate capability. As proofs-of-concepts, all of the hollow and mesoporous metal oxides (Fe2O3, Co3O4 and NiO) deliver high initial discharge capacities and good capacity retentions (>80%) after more than 100 cycles in half cells. Most important of all, these assembled full-cells (MxOy(M = Fe, Co, Ni)/LiCoO2) also delivere excellent electrochemical performances. This work clearly demonstrates that the MxOy(M = Fe, Co, Ni)/LiCoO2 configuration are promising alternative high power-density energy storage devices in the near future.
Co-reporter:Jinxing Wang, Gang Wang, Hui Wang
Electrochimica Acta 2015 Volume 182() pp:192-201
Publication Date(Web):10 November 2015
DOI:10.1016/j.electacta.2015.09.080
Free-standing, flexible, paper-like Fe2O3/graphene/carbon nanotubes (Fe2O3/GCNTs) ternary hybrid film with a three-dimensional hierarchical structure is synthesized through a simple filtration and a subsequent reduction process. The Fe2O3 particles are densely anchored onto the GCNTs conducting network, which serves as an ideal host for fast and efficient lithium storage. The layered GCNTs network not only withstands the huge stresses caused by Fe2O3 expansion/extraction but prevents the agglomeration of Fe2O3 upon continuous charging/discharging. The as-synthesized Fe2O3/GCNTs hybrid film is directly used as an anode for both half and full lithium-ion cells. Electrochemical measurement results indicate a high reversible capacity and a good rate capability can be realized on the hybrid when tested in half cell system. Furthermore, the prepared anode also shows favorable operation in full cell system comprising LiCoO2 cathode. These superior electrochemical performances of the hybrid film can be ascribed to the unique micro-structure, surface properties, and the strong synergistic effects among the individual component.
Co-reporter:Beibei Wang, Gang Wang, Zhengyuan Lv and Hui Wang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 40) pp:27109-27117
Publication Date(Web):09 Sep 2015
DOI:10.1039/C5CP04628A
In this article, we demonstrate a simple solvothermal method towards in situ growth of hierarchical CoFe2O4 nanoclusters on graphene aerogels (GAs). SEM and TEM results confirm that CoFe2O4 nanoclusters are well wrapped by the graphene skeleton. As an anode material for lithium-ion batteries, the CoFe2O4/GAs composite displays a stable cycling performance with a reversible capacity of over 100 discharge/charge cycles at the current density of 0.1 A g−1, considerably higher than that of CoFe2O4 nanoclusters. Moreover, the reversible capacity of the CoFe2O4/GAs composite exhibits 966 mA h g−1 after 300 cycles even at a high current density of 0.5 A g−1. Most important of all, a new CoFe2O4/GAs//LiCoO2 full cell was successfully assembled, and this exhibited excellent electrochemical performance. The superior electrochemical performance of the CoFe2O4/GAs composite in half and full cells can be attributed to the synergistic interaction between the uniform CoFe2O4 nanoclusters and GAs, the high electrical conductivity, and the three-dimensional hierarchically porous structure, which can not only facilitate the diffusion of Li ions and electrolyte into the electrodes, but also prevent volume expansion/contraction upon prolonged discharge/charge cycling.
Co-reporter:Yuan Xia, Beibei Wang, Gang Wang and Hui Wang
RSC Advances 2015 vol. 5(Issue 120) pp:98740-98746
Publication Date(Web):10 Nov 2015
DOI:10.1039/C5RA19155F
We report a simple route to synthesis nitrogen-doped mesoporous interlinked carbon/NiO nanosheet that consist of carbon nanosheets and monodisperse NiO nanoparticles embedded in them homogeneously. The nitrogen-doped mesoporous interlinked carbon/NiO nanosheet with carbon content of 46% was obtained through directly low temperature heat treatment of Ni-ZIF-8 with a rapid heating rate (5 °C min−1). During the heat treatment, a large number of mesoporous were formed in the product with the evaporation (or thermal decomposition) of the organic ligand. When tested as an anode for lithium ion batteries (LIBs), the unique structure of the mesoporous carbon/NiO nanosheet not only shortened electro- and iron-transport pathways but also accommodated the volume change during Li+ intercalation and deintercalation process, resulting in a reversible capacity of 627 mA h g−1 at 0.5 A g−1 after 300 cycles. Moreover, the as-assembled carbon/NiO nanosheet supercapacitor can also exhibit an excellent cycling performance (414 F g−1 at 5 A g−1) with 92.2% specific capacitance retention after 3000 cycles by combined the pseudocapacitive behavior of the NiO nanoparticles with the electric double-layer capacitors (EDLCs) of the nitrogen-doped mesoporous carbon.
Co-reporter:Jinxing Wang and Hui Wang
RSC Advances 2015 vol. 5(Issue 38) pp:30084-30091
Publication Date(Web):23 Mar 2015
DOI:10.1039/C5RA01533B
Free-standing reduced graphene oxide membranes (rGOMs) with different thicknesses and carbon contents are prepared via a simple, low cost, scalable, and eco-friendly two-step process. Scanning electron microscopy results show that rGOMs thicken with increasing GO solution concentration. The as-prepared free-standing rGOMs are directly used as anode materials for lithium-ion batteries without conducting additives or binders. The cycling performance and rate capability of the membrane electrodes are investigated and compared, and results indicate that not all of the synthesized rGOM anodes exhibit good lithium storage properties. Only those membranes with a coriaceous structure, approximately 2.5 μm thickness, and suitable reduction degree present high performance for reversible lithium storage. Reasons for these findings are also provided.
Co-reporter:Gang Wang, Hui Wang, Jintao Bai
Journal of Alloys and Compounds 2015 Volume 627() pp:174-181
Publication Date(Web):5 April 2015
DOI:10.1016/j.jallcom.2014.11.184
•MnFe2O4 spheres are prepared by a facile two-step route.•The MnFe2O4 spheres show excellent electrochemical properties in half cell system.•The integrity of MnFe2O4 electrode could be maintained after the rate test.•The MnFe2O4 anode works well in full cell system with LiCoO2 as cathode.A simple hydrothermal method combined with a post annealing treatment is developed to produce high crystallinity manganese ferrite (MnFe2O4) spheres. The lithium storage properties of the material as an anode in both half and full lithium-ion batteries are investigated. And the electrochemical behaviors of the electrode during lithiation and delithiation process are clarified. Benefited from its sphere-like morphology, the MnFe2O4 electrode exhibits better lithium storage exhibitions than commercial MnFe2O4 particles in half cell system. When assembled with LiCoO2 to construct a full lithium-ion battery (LiCoO2//MnFe2O4), the spheres could deliver a reversible capacity of higher than 600 mA h g−1 at a current density of 0.1 A g−1 in the potential range of 1.2–3.8 V. This work clearly demonstrates the possibility of using LiCoO2//MnFe2O4 configuration for practical high-performance lithium-ion batteries in the near future.
Co-reporter:Guanghui Yuan;Gang Wang;Jintao Bai
Journal of Solid State Electrochemistry 2015 Volume 19( Issue 4) pp:1143-1149
Publication Date(Web):2015 April
DOI:10.1007/s10008-014-2710-x
A hollow carbon microsphere (HC) material was synthesized by hydrothermal method, which could be used as a potential hard template. Active sulfur is encapsulated into the hollow carbon microspheres via simple impregnation and heat treatments to design a sulfur−hollow carbon microsphere (S−HC) composite with the novel yolk−shell structure. The hollow carbon shell, acts as a conductor to provide a highly conductivity and short Li+ diffusion distance, as well as absorbs polysulfides to improve the cycle ability of the S−HC composite in lithium sulfur (Li−S) batteries. The internal void space inside the shell can accommodate the volumetric expansion of sulfur during lithiation. The initial discharge capacity of S−HC cathode is as high as 1420 mA h g−1 at 0.1 C. After a 100 cycle stability test, the S−HC cathode exhibits still as high as 710 mA h g−1 at 0.2 C. Test results indicate that the S−HC composite is a promising host material for the sulfur cathode in the Li−S battery applications.
Co-reporter:Yuping Tai, Guojun Zheng, Hui Wang, Jintao Bai
Journal of Photochemistry and Photobiology A: Chemistry 2015 Volumes 303–304() pp:80-85
Publication Date(Web):15 April–1 May 2015
DOI:10.1016/j.jphotochem.2015.02.009
•The spectra of Ce3+ in YAG lies in the strongest region of solar spectrum.•The NIR emission intensity of Nd3+ is much stronger than Yb3+ and has no CTS.•The two-pathway ET mechanism dominates the DC process.•YAG:0.01Ce3+, xNd3+ show high ETE and QE due to the ET mechanism.•YAG:0.01Ce3+, xNd3+ has potential application in c-Si solar cells.Near-infrared (NIR) quantum cutting involving the down-conversion of an absorbed visible photon to emission of two NIR photons was demonstrated in Y3Al5O12 (YAG):0.01Ce3+, xNd3+ (x = 0, 1, 2, 5, 10, 15 mol%) samples. The photoluminescence properties of samples in visible and NIR regions were investigated to verify the energy transfer (ET) from Ce3+ to Nd3+. Results indicated that Nd3+ emissions located at 1064 nm was efficiently enhanced with Nd3+ concentration increasing because of ET from Ce3+. Based on these results, a possible two-pathway ET mechanism from Ce3+ to Nd3+ was presented. The decay lifetimes of YAG:0.01Ce3+, xNd3+ were estimated further to confirm the ET from Ce3+ to Nd3+. Simultaneously, the energy transfer efficiency (ETE) and quantum efficiency (QE) of YAG:0.01Ce3+, xNd3+ samples have been calculated as high as 79.43% and 160.7%, respectively. On the basis of maximum ETE and QE, the conclusion was drawn that the optimum Nd3+ concentration is 10 mol% and distance between Y3+ ions was 0.3659 nm without concentration quenching.
Co-reporter:Xiujuan Wang;Gaohong Zhai
Ionics 2015 Volume 21( Issue 6) pp:1533-1538
Publication Date(Web):2015 June
DOI:10.1007/s11581-014-1313-y
Elastic hollow SnO2 microspheres are synthesized through a facile templating method. The obtained hollow microspheres have a size of 1–3 μm, which are assembled by lots of nanoparticles of ∼20 nm. The electrochemical performance of the spheres as anode materials for lithium–ion batteries is evaluated. Benefited from the intrinsic structure advantages, the hollow tin dioxide exhibits good electrochemical lithium storage performance with high specific capacity and excellent rate capability. The good electrochemical performance should be reasonably ascribed to the mesoporous and hollow structures, which guarantee vast lithium storage sites, fast lithium–ion insertion/deinsertion, and sufficient void space to buffer the volume expansion. Most importantly, our results provide a new route to prepare hollow SnO2 microspheres and can be applied generally to a wide range of materials.
Co-reporter:Beibei Wang, Gang Wang, Hui Wang
Materials Letters 2014 Volume 122() pp:186-189
Publication Date(Web):1 May 2014
DOI:10.1016/j.matlet.2014.02.004
•Co3O4 micro-rod arrays grown directly on Cu foil are prepared by a hydrothermal method.•The synthesized Co3O4 micro-rods are 1–2 μm in diameter and 25 μm in length.•Co3O4/Cu electrode shows excellent lithium storage properties.In this paper, we report the growth of Co3O4 micro-rod arrays on Cu substrate by a modified hydrothermal method. The obtained Co3O4/Cu shows that the formed Co3O4 micro-rods on Cu foil are 1–2 μm in diameter and 25 μm in length. When evaluated as electrode materials for lithium-ion batteries, the specific capacity of Co3O4/Cu materials remains over 0.8 mA h mg−1 after 50 cycles at 0.1 C. The superior electrochemical performance of the Co3O4/Cu electrode may be attributed to the close contact of Co3O4 micro-rod arrays on Cu substrate and the extra space between the neighboring arrays, which provide fast pathways and reduce volume expansion.
Co-reporter:Guojun Zheng;Yuping Tai
Journal of Materials Science: Materials in Electronics 2014 Volume 25( Issue 9) pp:3779-3786
Publication Date(Web):2014 September
DOI:10.1007/s10854-014-2089-6
In the present paper, many monocrystal silicon (Si) solar cells are produced by screen printing a front contact paste prepared with crystalline silver particles, a series of glass frits with the different lead oxide (PbO) contents in Pb–Te–B–O system glass, and an organic medium. Under scanning electron microscopy, the selective etching of cells screen-printed by pastes containing the glass frits of different PbO contents from low to high (37.2–52.5 mol%) reveals the corrosion degree of antireflection coating and the growth of silver crystallite microstructures on Si substrate. When the PbO content is 42.7 mol% in glass frits, the silver crystallites of optimal size were formed to make the conversion efficiency of cells best. By comparing the cross-section microstructures of solar cells, the different transition temperatures (Tg = 283–546 °C) of glass frits are found to have a substantial impact on wetting behavior during the firing cycle. When the glass Tg is medium (Tg = 393 °C), the optimal glass layer will be obtained to derive photoelectrons smoothly.
Co-reporter:Gang Wang, Hui Wang, Shaobo Cai, Jintao Bai, Zhaoyu Ren, Jinbo Bai
Journal of Power Sources 2013 Volume 239() pp:37-44
Publication Date(Web):1 October 2013
DOI:10.1016/j.jpowsour.2013.03.105
•Fe2O3@C/GNs hybrid material was constructed by a two step route.•Fe2O3@C/GNs electrode shows superior electrochemical performance.•The integrity of Fe2O3@C/GNs electrode is maintained during the continuous cycles.A hybrid material of carbon-coated Fe2O3 submicro-particles loaded on graphene nanosheets (Fe2O3@C/GNs) is prepared by a two step route including a hydrothermal and a subsequent glucose impregnation-pyrolysis process. The obtained material is composed of GNs and ∼400 nm size Fe2O3 particles coated by thin carbon layer with a thickness of 5 nm. As an anode material for lithium ion batteries, Fe2O3@C/GNs hybrid shows an improved electrochemical performance in the initial coulombic efficiency (71%), reversible capacity (900 mA h g−1 after 50 cycles at a current of 200 mA g−1) and capacity retention rate (82% after 50 cycles). This result is much better than the synthesized bare Fe2O3 and Fe2O3/GNs electrodes. In addition to the contribution of GNs, the carbon-coated layer around Fe2O3 particles is believed to be a key factor to improve the electrochemical performance of Fe2O3.
Co-reporter:Beibei Wang, Gang Wang, Zhaozhao Zheng, Hui Wang, Jintao Bai, Jinbo Bai
Electrochimica Acta 2013 Volume 106() pp:235-243
Publication Date(Web):1 September 2013
DOI:10.1016/j.electacta.2013.05.085
A hybrid material of carbon coated Fe3O4 (Fe3O4@C) is synthesized by chemical vapor deposition method using Fe2O3 as starting material and acetylene as carbon source. The obtained material is Fe3O4 spheres of ∼400 nm coated by thin carbon layer with a thickness of ∼10 nm. As an anode material for lithium ion batteries, Fe3O4@C shows an improved electrochemical performance in the reversible capacity and cycling stability, together with excellent rate capability. The performance is much better than the results obtained from bare Fe2O3 and commercial Fe3O4 of the same size. In addition to the comparison of electrochemical impedance spectra of the Fe2O3, Fe3O4 and Fe3O4@C electrodes before and after 50 charge/discharge cycles, a surface contrast of the three electrodes before and after cycling is systematically investigated to explore the influence of carbon layer on the electrochemical performance of the Fe3O4 spheres.
Co-reporter:Xiaoqing Su, Gang Wang, Weilong Li, Jinbo Bai, Hui Wang
Advanced Powder Technology 2013 Volume 24(Issue 1) pp:317-323
Publication Date(Web):January 2013
DOI:10.1016/j.apt.2012.08.003
Abstract
Graphene nano-sheets (GNs) with high quality were successfully synthesized in a Teflon-lined container through a low temperature expansion process. The influence factors of expansion temperature, expansion mode and reduction time on the morphology and structure of products have been systematically investigated, and an optimum experimental condition for the synthesis of GNs has been obtained. The results showed that the Teflon-lined container is an effective apparatus for preparing GNs at relative low temperature (<300 °C). The low temperature synthetic process is simple, inexpensive and easy to scale up in comparison with the traditional method which often consume more energy, use more complicated instruments, or more costly. The electrochemical properties of the as-synthesized products were investigated as anode materials for lithium ion batteries.
Co-reporter:Hui Wang, Qi-Chao Yang, and Li Li
Journal of Chemical & Engineering Data 2013 Volume 58(Issue 4) pp:1034-1038
Publication Date(Web):March 29, 2013
DOI:10.1021/je400052y
The solubility data of the quaternary system CsCl–TbCl3–HCl(∼7.6 mass %)–H2O at 298.2 K were determined, and the corresponding phase diagram according to central projection data on the trigonal basal face CsCl–TbCl3–H2O was plotted. The diagram includes three invariant points and four crystallization fields corresponding to CsCl, Cs5TbCl8·6H2O, Cs2TbCl5·6H2O, and TbCl3·6H2O. Two new solid-phase compounds of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O, which are congruently soluble in the system, were isolated and characterized by the methods of powder X-ray diffraction, thermogravimetric, and differential thermal analysis. The standard molar enthalpies of solution for the two compounds of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were measured to be (60.64 ± 0.28) and (14.08 ± 0.45) kJ·mol–1 by heat conduction microcalorimetry under the conditions of infinite dilution, and their standard molar enthalpies of formation were calculated to be −(5087.1 ± 1.7) kJ·mol–1 and −(3764.2 ± 1.0) kJ·mol–1. The fluorescence excitation and emission spectra of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were measured. The results show that upconversion spectra exhibit for Cs5TbCl8·6H2O at 500 nm and 545 nm and for Cs2TbCl5·6H2O at 495 nm and 545 nm excited at 750 nm, and the upconversion intensity increases with the increase of TbCl3 contents in CsCl.
Co-reporter:Zhan-Ping Qiao, Hai-quan Xie, Xin Chen, and Hui Wang
Journal of Chemical & Engineering Data 2013 Volume 58(Issue 11) pp:3125-3129
Publication Date(Web):September 26, 2013
DOI:10.1021/je4005867
Solubility was studied in the CsCl + YbCl3 + HCl + H2O quaternary system along the (∼11.3 %) HCl section at 298.2 K using the isothermal solubility method, and the corresponding phase diagram was plotted. The compositions of solid phases were determined by the Schreinemaker’s wet residues technique. The system was complicated with four equilibrium solid phases CsCl, Cs4YbCl7·4H2O, Cs2YbCl5·5H2O, and YbCl3·6H2O. The compound Cs4YbCl7·4H2O was incongruently soluble, and the compound Cs2YbCl5·5H2O was congruently soluble in the system. The new solid phase compounds were characterized by chemical analysis, X-ray diffraction (XRD), and thermogravimetric/differential thermogravimetric (TG-DTG) techniques. The standard molar enthalpies of solution of Cs4YbCl7·4H2O and Cs2YbCl5·5H2O in water were measured to be (18.19 ± 0.47) and (13.22 ± 0.27) kJ·mol–1 by microcalorimetry under the condition of infinite dilution, and their standard molar enthalpies of formation were determined as being – (4039.2 ± 2.2) kJ·mol–1 and – (3469.2 ± 1.3) kJ·mol–1, respectively.
Co-reporter:Shibo Zhou;Gang Wang;Yinzhi Xie;Jinbo Bai
Journal of Nanoparticle Research 2013 Volume 15( Issue 6) pp:
Publication Date(Web):2013 June
DOI:10.1007/s11051-013-1740-0
Carbon-coated Co3O4 microparticles (Co3O4@C) with dendrite-like morphology are prepared by a low-temperature hydrothermal method and subsequent C2H2 chemical vapor deposition (CVD) for the first time. The synthesized precursor Co3O4 has a size of 8–10 μm, which is assembled by lots of aligned Co3O4 wire with 4–5 μm in length. After carbon coating, Co3O4 microparticles were proved to be coated in amorphous carbon of ~10 nm. A plausible formation process of the dendrite-like Co3O4 and Co3O4@C is proposed based on the morphology and structure characterizations of the materials. As an anode material for lithium-ion batteries, the Co3O4@C composite electrode exhibits higher reversible capacity and better cycling performance than the unmodified Co3O4 electrode. The reversible capacity of the Co3O4@C composite after 40 cycles is 500 mAh g−1, much higher than that of Co3O4 (148 mAh g−1). Electrochemical impedance spectra and cyclic voltammogram indicate that the carbon layer coated on Co3O4 by CVD can improve the electrochemical activity and enhance the reversibility of Co3O4 during charge/discharge cycles.
Co-reporter:Zhao Liu, XueLiang Qi, Hui Wang
Advanced Powder Technology 2012 Volume 23(Issue 2) pp:250-255
Publication Date(Web):March 2012
DOI:10.1016/j.apt.2011.03.004
Abstract
Spherical and mono-disperse micro-silver powder, a kind of silver powder with controllable size and high tap density, was prepared by using silver nitrate as metal source, ascorbic acid as reducing agent and gum arabic as dispersant under traditional chemical reduction method. The result of SEM images shown the spherical and mono-disperse silver powder with average particle size of about 1–2 μm and narrow particle size distribution was obtained. By varying the concentration of the reactants, dosage of dispersant and the pH of the mixture solution of ascorbic acid and gum arabic, the silver particles showed different size, and different size distribution. It was also found that the morphology of silver particles could transform from sphere to polyhedron and the tap density of silver powder was increased with the prolonging of reactants mixing time.
Co-reporter:Gang Wang, Hui Wang, Weilong Li, Zhaoyu Ren, Jintao Bai, Jinbo Bai
Fuel Processing Technology 2011 Volume 92(Issue 3) pp:531-540
Publication Date(Web):March 2011
DOI:10.1016/j.fuproc.2010.11.008
Fe/Al2O3 catalysts with different Fe loadings (10–90 mol%) were prepared by hydrothermal method. Ethanol decomposition was studied over these Fe/Al2O3 catalysts at temperatures between 500 and 800 °C to produce hydrogen and multi-walled carbon nanotubes (MWCNTs) at the same time. The results showed that the catalytic activity and stability of Fe/Al2O3 depended strongly on the Fe loading and reaction temperature. The Fe(30 mol%)/Al2O3 and Fe(40 mol%)/Al2O3 were both the effective catalyst for ethanol decomposition into hydrogen and MWCNTs at 600 °C. Several reaction pathways were proposed to explain ethanol decomposition to produce hydrogen and carbon (including nanotube) at the same time.
Co-reporter:Gang Wang, Ting Liu, Yongjun Luo, Yan Zhao, Zhaoyu Ren, Jinbo Bai, Hui Wang
Journal of Alloys and Compounds 2011 Volume 509(Issue 24) pp:L216-L220
Publication Date(Web):16 June 2011
DOI:10.1016/j.jallcom.2011.03.151
The micro-sized sphere Fe2O3 particles doped with graphene nanosheets were prepared by a facile hydrothermal method. The obtained Fe2O3/graphene composite as the anode material for lithium ion batteries showed a high discharge capacity of 660 mAh g−1 during up to 100 cycles at the current density of 160 mA g−1 and good rate capability. The excellent electrochemical performance of the composite can be attributed to that graphene served as dispersing medium to prevent Fe2O3 microparticles from agglomeration and provide an excellent electronic conduction pathway.
Co-reporter:Lijuan Wan, Zhaoyu Ren, Hui Wang, Gang Wang, Xin Tong, Shuanghong Gao, Jintao Bai
Diamond and Related Materials 2011 Volume 20(5–6) pp:756-761
Publication Date(Web):May–June 2011
DOI:10.1016/j.diamond.2011.03.027
A facile and rapid approach was used for the fabrication of chemically derived graphene nanosheets based on the reduction of graphite oxide (GO) in tube furnace assembly at different temperatures. The morphologies, microstructures, specific surface areas and other features of GO and graphene nanosheets were characterized. Structure characterization indicates that the platelet thickness of graphene nanosheets obtained at 300 °C was 1.62 nm, which corresponds to an approximately 5 layers stacking of the monoatomic graphene nanosheets. Electrochemical performances of the as-prepared graphene nanosheets were performed, the result of which could prove the above observation that graphene nanosheets (5 layers) obtained at 300 °C actually displayed the most remarkable electrochemical performances: the first discharge and charge capacities of graphene nanosheets were as high as 2137 mAh/g and 994 mAh/g, respectively, and after 100 cycles graphene nanosheets still possessed a high capacity of 478 mAh/g.Graphene nanosheets obtained at 300 °C shows better electrochemical performances than those obtained at 600 and 800 °C.Research Highlights► With the temperature growing, the thickness of graphene sheets increased. ► With the temperature growing, the distance between neighboring layers decreased. ► Graphene sheets obtained at 300 °C shows the best electrochemical performances.
Co-reporter:Gang Wang, Ting Liu, Xiaoling Xie, Zhaoyu Ren, Jinbo Bai, Hui Wang
Materials Chemistry and Physics 2011 Volume 128(Issue 3) pp:336-340
Publication Date(Web):15 August 2011
DOI:10.1016/j.matchemphys.2011.03.049
Using hydrothermal method, Fe3O4/graphene nanocomposite is prepared by synthesizing Fe3O4 particles in graphene. The synthesized Fe3O4 is nano-sized sphere particles (100–200 nm) and uniformly distributed on the planes of graphene. Fe3O4/graphene nanocomposite as anode material for lithium ion batteries shows high reversible specific capacity of 771 mAh g−1 at 50th cycle and good rate capability. The excellent electrochemical performance of the nanocomposite can be attributed to the high surface area and good electronic conductivity of graphene. Due to the high surface area, graphene can prevent Fe3O4 nanoparticles from aggregating and provide enough space to buffer the volume change during the Li insertion/extraction processes in Fe3O4 nanoparticles.Highlights► Fe3O4 nanoparticles dispersed homogeneously on graphene nanosheets were synthesized by hydrothermal route. ► The Fe3O4/graphene nanocomposite as the anode material for lithium ion batteries showed a high reversible specific capacity of 771 mAh g−1 during up to 50 cycles and good rate capability. ► The simple and low-cost method provides a potential approach for fabricating other graphene based materials.
Co-reporter:Xin Tong, Hui Wang, Gang Wang, Lijuan Wan, Zhaoyu Ren, Jintao Bai, Jinbo Bai
Journal of Solid State Chemistry 2011 Volume 184(Issue 5) pp:982-989
Publication Date(Web):May 2011
DOI:10.1016/j.jssc.2011.03.004
High quality graphene sheets are synthesized through efficient oxidation process followed by rapid thermal expansion and reduction by H2. The number of graphene layers is controlled by tuning the oxidation degree of GOs. The higher the oxidation degree of GOs is getting, the fewer the numbers of graphene layers can be obtained. The material is characterized by elemental analysis, thermo-gravimetric analysis, scanning electron microscopy, atomic force microscopy, transmission electron microscopy and Fourier transform infrared spectroscopies. The obtained graphene sheets with single, triple and quintuplicate layers as anode materials exhibit a high reversible capacity of 1175, 1007, and 842 mA h g−1, respectively, which show that the graphene sheets with fewer layers have higher reversible capacity.Graphical abstractThe typical TEM images of the graphene sheets derived from GO3(a), GO2(b) and GO1(c).Highlights► With the oxidation degree of GO increasing, the numbers of graphene layers decreased. ► With the numbers of graphene layers decreasing, the reversible capacity improved. ► Graphene sheets with single-layer exhibit the best electrochemical performances.
Co-reporter:Changhua Su;Xiaojie Liu
Crystal Research and Technology 2011 Volume 46( Issue 2) pp:209-214
Publication Date(Web):
DOI:10.1002/crat.201000642
Abstract
Monodispersed and single-crystalline hematite (α-Fe2O3) cubes have been successfully prepared by a template-free hydrothermal synthetic route with FeCl3 and CH3COONH4. The influences of the reactant concentration, reaction temperature, and reaction time on the crystal growth were systematically investigated. The results show that the monodisperse hematite cubes with high crystalline and narrow size distribution could be fabricated at the hydrothermal temperature of 160 °C for 24 h while the concentrations of FeCl3 and CH3COONH4 were in the range of 0.03-0.5 M and 0.05-0.1 M, respectively. In addition, the formation mechanism of hematite cube is also proposed, where the CH3COONH4 plays a role of shape controller in the formation of cube hematite structure. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Co-reporter:Xiaojie Liu, Hui Wang, Changhua Su, Pengwei Zhang, Jinbo Bai
Journal of Colloid and Interface Science 2010 Volume 351(Issue 2) pp:427-432
Publication Date(Web):15 November 2010
DOI:10.1016/j.jcis.2010.08.017
In this paper, the microspherical Fe2O3 was successfully obtained by calcining the FeCO3 sphere prepared by a hydrothermal route. The sphere morphology perfectly remained after the calcination of FeCO3 but the diameter of sphere decreased in a certain degree from 70–100 μm to 50–70 μm, which might be due to some loss of quantity during the calcination (FeCO3–Fe2O3). The sphere was solid and highly densified. At the same time, the effects of factors influencing the formation of FeCO3, such as PVP, reaction temperature were investigated. The simple formation process of FeCO3 was also proposed as follows: Fe2+ produced by the reduction of Fe3+ reacted with CO32- released from the decomposition of urea to form FeCO3 nanoparticle. Then, the formed nanoparticles aggregated together to produce sphere structure via oriented attachment. With the reaction time increasing, the sphere became solidness and densification.Graphical abstractMicrospherical Fe2O3 with diameter size of 50–70 μm was obtained by calcining the FeCO3 microsphere prepared by a hydrothermal route.Research highlights► The microspherical Fe2O3 was successfully obtained. ► The simple formation process of FeCO3 was proposed. ► PVP and reaction temperature played important roles.
Co-reporter:Hui Wang, Jian Wang, Zhong Fang, Xiaofang Wang, Huaiyu Bu
International Journal of Hydrogen Energy 2010 Volume 35(Issue 15) pp:8303-8309
Publication Date(Web):August 2010
DOI:10.1016/j.ijhydene.2009.12.012
A series of batch experiments were conducted to investigate the effects of the HCl-pretreated concentrations, enzyme hydrolysis time and temperature, the cellulase dosage, the ultrasonic time and the fermentation substrate concentration on hydrogen (H2) production from the anaerobic fermentation of apple pomace (AP). The natural mixed microorganisms from river sludge was used as the seed after being boiled for 15 min. A maximum cumulative H2 yield (CHYm) of 134.04 ml/g total solid (TS) and an average H2 production rate (AHPR) of 12.00 ml/g TS/h were obtained from the fermentation of the enzyme-hydrolyzed AAP (a AP soaked with 6% ammonia liquor for 24 h) at the substrate concentration of 15 g/L. The optimal enzyme hydrolysis conditions were proposed as follows: AAP with a cellulase dosage of 12.5 mg/g TS at the hydrolysis substrate concentration of 20 g/L after the ultrasonic irradiation for 20 min was hydrolyzed by the enzyme catalysis at 45 °C and initial pH 5.0 for 48 h.
Co-reporter:Yu Wang, Hui Wang, Xiaoqiong Feng, Xiaofang Wang, Jianxin Huang
International Journal of Hydrogen Energy 2010 Volume 35(Issue 7) pp:3092-3099
Publication Date(Web):April 2010
DOI:10.1016/j.ijhydene.2009.07.024
An anaerobic fermentation process to produce hydrogen from cornstalk wastes was systematically investigated in this work. Batch experiments numbered series I, II and III were designed to investigate the effects of acid pretreatment, enzymatic hydrolysis (enzymatic temperature, enzymatic time and enzymatic pH) on hydrogen production by using the natural sludge as inoculant. A maximum cumulative H2 yield of 126.22 ml g−1-CS (Cornstalk, or 146.94 ml g−1-TS, Total Solid) and an average H2 production rate of 9.58 ml g−1-CS h−1 were obtained from fermentation cornstalk with a concentration of 20 g/L and an initial pH of 7.0 at 36 °C through an optimal pretreatment process. The optimal process was that the substrate was soaked with an HCl concentration of 0.6 wt% at 90 °C for 2 h, and subsequently enzymatic hydrolysis for 72 h at 50 °C and pH 4.8 before fermentation. The biogas consisted of only H2 and CO2. In addition, the fermentation system was the typical ethanol-type fermentation according to ethanol and acetate as the main liquid by-products.
Co-reporter:Xiaoqiong Feng, Hui Wang, Yu Wang, Xiaofang Wang, Jianxin Huang
International Journal of Hydrogen Energy 2010 Volume 35(Issue 7) pp:3058-3064
Publication Date(Web):April 2010
DOI:10.1016/j.ijhydene.2009.07.015
The biological hydrogen (bio-H2) production from apple pomace (AP) by fermentation using natural mixed microorganisms in batch process was studied under various experimental conditions. The river sludge was used as a seed after being boiled for 15 min. The results show that the optimal pretreatment for AP was to soak it in the ammonia liquor of 6% for 24 h at room temperature. An optimal fermentation condition for bio-H2 production was proposed that the pretreated AP at 37 °C, the initial pH of 7.0 and the fermentation concentration of 15 g/l could produce a maximum cumulative H2 yield (CHYm) of 101.08 ml/g total solid (TS) with an average H2 production rate (AHPR) of 8.08 ml/g TS/h. During the conversion of AP into H2, acetic acid, ethanol, propionic acid and butyric acid were main liquid end-products.
Co-reporter:Xiaojie Liu, Hui Wang
Journal of Solid State Chemistry 2010 Volume 183(Issue 5) pp:1075-1082
Publication Date(Web):May 2010
DOI:10.1016/j.jssc.2010.03.017
Iron oxide modified with single- or double-metal additives (Cr, Ni, Zr, Ag, Mo, Mo–Cr, Mo–Ni, Mo–Zr and Mo–Ag), which can store and supply pure hydrogen by reduction of iron oxide with hydrogen and subsequent oxidation of reduced iron oxide with steam (Fe3O4 (initial Fe2O3)+4H2↔3Fe+4H2O), were prepared by impregnation. Effects of various metal additives in the samples on hydrogen production were investigated by the above-repeated redox. All the samples with Mo additive exhibited a better redox performance than those without Mo, and the Mo–Zr additive in iron oxide was the best effective one enhancing hydrogen production from water decomposition. For Fe2O3–Mo–Zr, the average H2 production temperature could be significantly decreased to 276 °C, the average H2 formation rate could be increased to 360.9–461.1 μmol min−1 Fe-g−1 at operating temperature of 300 °C and the average storage capacity was up to 4.73 wt% in four cycles, an amount close to the IEA target.Mo+Zr additive has the best modified effect on improving the redox performances of Fe2O3:H2 producing temperature of 276 °C and hydrogen storage capacity of 4.73 wt%.
Co-reporter:Jinxiang Diao, Hui Wang, Weilong Li, Gang Wang, Zhaoyu Ren, Jinbo Bai
Physica E: Low-dimensional Systems and Nanostructures 2010 Volume 42(Issue 9) pp:2280-2284
Publication Date(Web):July 2010
DOI:10.1016/j.physe.2010.05.006
A series of C-supported Co catalysts (Co(2, 5 and 8 wt%)/C) were prepared by impregnation. The effects of Co loading amounts and reaction temperature on ethanol decomposition to produce hydrogen and carbon nanotubes (CNTs) were investigated systematically. The results indicate that Co/C was quite an active catalyst for the co-production of hydrogen and CNTs at a relatively low temperature of 500 °C. Of all the catalysts, Co(5 wt%)/C was the most effective one based on the high hydrogen yield (88%) and CNT quality (being of relatively higher purity and lower defects). Besides H2, CO, CH4 and CO2 were also produced and the selectivity of the gas was in the order H2>CO>CO2>CH4.
Co-reporter:Wang Hui, Feng Xiaoqiong, Wang Xiaofang, Cheng Sanping, Gao Shengli
International Journal of Hydrogen Energy 2008 Volume 33(Issue 23) pp:7122-7128
Publication Date(Web):December 2008
DOI:10.1016/j.ijhydene.2008.09.017
Pure hydrogen can be stored and supplied directly to polymer electrolyte fuel cell by the redox of iron oxide: Fe3O4 + 4H2 → 3Fe + 4H2O and 4H2O + 3Fe → Fe3O4 + 4H2. Four bimetal-modified samples were prepared by impregnation. The hydrogen storage properties of the samples were investigated. The result shows that the Fe2O3–Mo–Al sample presented the most excellent catalytic activity and cyclic stability. H2 forming temperature and H2 forming rate could be surprisingly decreased and enhanced, respectively. The average H2 forming temperature at the rate of 250 μmol min−1·Fe-g−1 for Fe2O3–Mo–Al in the first 4 cycles could be decreased from 469 °C before the addition of Mo–Al to 273 °C after the addition of Mo–Al. The reason for it may be that the Mo–Al additive in the sample can prevent from the sintering of the particles and accelerate the H2O decomposition due to Mo taking part in the redox reaction. The average storage capacity of Fe2O3–Mo–Al was up to 4.68 wt%.
Co-reporter:Zhi Li, Hui Wang, Zongxun Tang, Xiaofang Wang, Jinbo Bai
International Journal of Hydrogen Energy 2008 Volume 33(Issue 24) pp:7413-7418
Publication Date(Web):December 2008
DOI:10.1016/j.ijhydene.2008.09.048
A series of batch experiments were conducted to investigate the effects of pH and glucose concentrations on biological hydrogen production by using the natural sludge obtained from the bed of a local river as inoculant. Batch experiments numbered series I and II were designed at an initial and constant pH of 5.0–7.0 with 1.0 increment and four different glucose concentrations (5.0, 7.5, 10 and 20 g glucose/L). The results showed that the optimal condition for anaerobic fermentative hydrogen production is 7.5 g glucose/L and constant pH 6.0 with a maximum H2 production rate of 0.22 mol H2 mol−1 glucose h−1, a cumulative H2 yield of 1.83 mol H2 mol−1 glucose and a H2 percentage of 63 in biogas.
Co-reporter:Hui Wang;Xian-Sheng Wang;Xin-Zhi Wang;Xiao-Fang Wang;Fa-Xin Dong;Qi-Zhen Shi
Chinese Journal of Chemistry 2007 Volume 25(Issue 7) pp:
Publication Date(Web):16 JUL 2007
DOI:10.1002/cjoc.200790171
Modified iron oxide, a new material for hydrogen storage and supply to polymer electrolyte fuel cell (PEFC), was prepared by impregnating Fe or Fe2O3 powder with an aqueous solution containing metal cation additives (Al, Cr, Ni, Co, Zr and Mo). Hydrogen storage properties of the samples were investigated. The results show that both Fe and Fe2O3 powder with additive Mo presented excellent catalytic activity and cyclic stability, and their hydrogen producing temperature could be surprisingly decreased. The temperature of forming hydrogen for the Fe2O3-Mo at the rate of 250 µmol·min−1·Fe-g−1 could be dramatically decreased from 527 °C before addition of Mo to 283 °C after addition of Mo in the fourth cycle. The cause for it was probably related to preventing the sinter of the sample particles. In addition, hydrogen storage capacity of the Fe2O3-Mo can reach w=4.5% (72 kg H2/m3), close to International Energy Agency (IEA) criterion. These show the value of practical application of the Fe2O3-Mo as the promising hydrogen storage material.
Co-reporter:Hui Wang, Haifeng Yang, Wang Chuang, Xinquan Ran, Qizhen Shi, Zhenyi Wen
Journal of Molecular Graphics and Modelling 2007 Volume 25(Issue 6) pp:824-830
Publication Date(Web):March 2007
DOI:10.1016/j.jmgm.2006.08.003
Based on the experiments, the UAM1 method was adopted to investigate benzene condensation of an important intermediate and the molecule growing mechanism during the cyclohexane pyrolysis process. The conclusions were drawn as follows: (1) from the viewpoint of thermodynamics, the condensation of benzene and C4H5 is a spontaneous reaction and the rising temperature will increase the spontaneous tendency of the reaction. (2) From the viewpoint of kinetic, the condensation of benzene and C4H5 is a two-step reaction. The rate-determining step is step 2 of hydrogen removal from intermediate C10H10 (I1) with the activation energy of 350.61 kJ/mol below 1473 K while the rate-determining step is step 1 that free radical C4H5 attacks benzene to form intermediate C10H10 (I1) with the activation energy ΔE0≠θ=31.74 kJ/mol above 1473 K. (3) The space structure, electronic structure and thermodynamics parameters of molecular reaction of dense-ring aromatizing compounds can be used to replace the resonance energy and free valence to judge the activation of thermodynamic reaction of compounds. And (4) the analysis of the space structure, electronic structure and thermodynamic parameters show that the growing process of molecules with benzene used as initial reactants becomes more easier as the multi-ring aromatizing molecular system increases.
Co-reporter:Wang Hui, Sakae Takenaka, Kiyoshi Otsuka
International Journal of Hydrogen Energy 2006 Volume 31(Issue 12) pp:1732-1746
Publication Date(Web):September 2006
DOI:10.1016/j.ijhydene.2005.12.010
Pure hydrogen can be chemically stored and supplied directly to PEFC via the redox of modified fumed-Fe-dust obtained from steel company: storage of H2:Fe3O4+4H2→3Fe+4H2OH2:Fe3O4+4H2→3Fe+4H2O or Fe2O3(initialstate)+3H2→2Fe+3H2O; recovery of H2:3Fe+4H2O→Fe3O4+4H2H2:3Fe+4H2O→Fe3O4+4H2. Modified fumed-Fe-dust with various metal additives has been prepared by impregnating metal cations of Cr, Al, Zr, Mo, Mo–Al, Mo–Ti, Mo–Zr, Mo–Ce, Mo–Rh, Mo–Ni or Mo–Cu. The reduction of the oxidized fumed-Fe-dust (denoted as FeOxFeOx) with and without additives and the performances of formation H2 of the reduced FeOxFeOx-dust have been mainly investigated. The results show that: (1) among the metal additives tested, Mo was the most effective element to enhance the rate of H2 produced in the oxidation with H2O as well as cyclic stability in repeated redox cycles for oxidized fumed-Fe-dust at low temperature 354 °C; (2) the state of additive Mo in oxidized FeOxFeOx was suggested to be the chemical composition of 2FeO·MoO22FeO·MoO2 based on the result of XRD spectra; (3) the sintering of the particles was one of the factors effecting on the catalytic activity and cycling stability of the modified FeOxFeOx, but what kinds of metal additives to be added in FeOxFeOx must be much more important for the sample to promote catalytic activity and keep cyclic stability effective.
Co-reporter:Hui Wang;Jin-Xia Duan;Xin-Quan Ran;Shi-Yang Gao
Chinese Journal of Chemistry 2004 Volume 22(Issue 10) pp:
Publication Date(Web):26 AUG 2010
DOI:10.1002/cjoc.20040221014
The equilibrium solubility of one CsCl-YCl3-H2O ternary section of CsCl-YCl3-9.5%HCl-H2O quaternary system at T=298.15 K was investigated by the physico-chemical analysis method and the corresponding phase diagram was plotted. The crystallization of two new double salts Cs4YCl7·10H2O (4:1 type) and Cs3Y2Cl9·14H2O (3:2 type) was successful and they were obtained from the complicated system directly. Both were identified and characterized by X-ray, thermal analysis method of TG-DTG, DSC. The fluorescence experiments show that up-conversion phenomenon does not exist in compounds Cs4YCl7·10H2O and Cs3Y2Cl9·14H2O.
Co-reporter:Hui Wang, Haifeng Yang, Xinquan Ran, Qizhen Shi, Zhenyi Wen
Journal of Molecular Structure: THEOCHEM 2004 Volume 710(1–3) pp:179-191
Publication Date(Web):26 November 2004
DOI:10.1016/j.theochem.2004.03.046
The pyrolysis mechanism of important intermediate 1-hexene of carbon matrix precursor cyclohexane was studied theoretically. Possible reaction paths were designed based on the potential surface scan and electron structure of the initial C–C bond breaking reactions. Thermodynamic and kinetic parameters of the possible reaction paths were computed by UB3LYP/6-31+G* at different temperature ranges. The results show that 1-hexene pyrolyzes at 873 K. When below 1273 K, the major reaction paths are those that produce C3H4, and above 1273 K, the major reaction paths are those that produce C3H3 from the viewpoint of thermodynamics. From the viewpoint of kinetics, the major product is C3H3, it results from the pyrolysis reaction of 1-hexene cracking bond C3–C4 and generating C3H5 and C3H7 with the activation energy ΔE0≠θ=296.32 kJ/mol. Kinetic results also show that product C3H4 accompany simultaneously, which is the side reaction starting from the pyrolysis of 1-hexene forming C4H7 and C2H5 with the activation energy of 356.73 kJ/mol. When reaching 1473 K, the rate constant of the rate-determining steps of these two reaction paths do not show much difference, which means both the reaction paths exist in the pyrolysis process at the high temperature. The above results are basically in accordance with mass spectrum analysis and far more specific.
Co-reporter:Hui Wang;Jin-Xia Duan;Xin-Quan Ran;Shi-Yang Gao
Chinese Journal of Chemistry 2002 Volume 20(Issue 9) pp:
Publication Date(Web):26 AUG 2010
DOI:10.1002/cjoc.20020200920
The equilibrium solubility of CsCl-CeCl3-HCl (11%)-H2O quaternary system at 25 °C has been determined by the physic-chemical analysis method, and the phase diagram was plotted. Two new double salts 3CsCl · CeCl3 · 3H2O and CsCl · CeCl3 · 4H2O obtained from the complicated system were identified and characterized by XRD, TG-DTA, DSC, UV and fluorescence spectroscopy. Studies on the fluorescence excitation and emission show that 3CsCl · CeCl3 · 3H2O and CsCl · CeCl3 · 4H2O have upconversion luminescence of infrared-visible range, and the upconversion emission intensity increases with the increase of ratio of CeCl3 in CsCl.
Co-reporter:Hui Wang, Haifeng Yang, Xinquan Ran, Zhenyi Wen, Qizhen Shi
Journal of Molecular Structure: THEOCHEM 2002 Volume 581(1–3) pp:1-9
Publication Date(Web):5 April 2002
DOI:10.1016/S0166-1280(01)00726-6
The thermodynamic and kinetic research of the pyrolysis mechanism of toluene was investigated for different reaction temperatures 298, 773, 843, 963, 1073, and 1223 K by using the UB3LYP/3-21G∗ method. The results show that when the pyrolysis temperature of toluene is lower than 963 K, the main reaction path supported by thermodynamics is the path producing benzyl, and the yield of the resulting bitoluene by combining benzyl is higher than that of the resulting bibenzene. When the temperature is higher than 963 K, the thermodynamic calculation result tends to support the reaction path that produces phenyl and methyl radicals, and the yield of producing bibenzene by radical reaction is found to be higher than that of producing bitoluene. When the pyrolysis temperature of toluene is lower than 1223 K the main reaction path supported by kinetics is the reaction generating benzyl. The reaction is completed via two steps and the activation energy of the rate-control step is and the reaction rate of bitoluene production by radical is faster than that of producing bibenzene; when the temperature is higher than 1223 K, the main reaction path is the reaction that produces both phenyl and methyl radicals, with an activation energy of In this case, the reaction rate of bibenzene production undergoing radical combining is faster than that of bitoluene production. This mechanism is in accordance with the experiments.
Co-reporter:Hui Wang, Haifeng Yang, Xinquan Ran, Qizhen Shi, Zhenyi Wen
Journal of Molecular Structure: THEOCHEM 2002 Volume 581(1–3) pp:187-194
Publication Date(Web):5 April 2002
DOI:10.1016/S0166-1280(01)00757-6
Pyrolysis process of important intermediate 1,3-butadiene from the pyrolysis of cyclohexane was studied theoretically. Standard enthalpy changes for the two possible pyrolysis reaction paths were computed by UB3LYP/3-21G∗, UB3LYP/6-31G∗, UB3LYP/6-31+G∗ and UB3LYP/6-311+G∗. Thermodynamic and kinetic computation for the reaction paths at different temperature ranges was pursued by UB3LYP/6-31+G∗ because of its accuracy. The results show that (1) the pyrolysis temperature of 1,3-butadiene is above 1173 K, main products are C2 and C4 species, and the possibility of getting C2 species is more; (2) at a temperature range of 298–1473 K, the reaction path 2 that starts with the broken C–H bond and produce C4 species which is feasible from the viewpoint of thermodynamics; (3) the reaction path 1 that starts with the broken C–C bond and produce C2 species which is feasible from the viewpoint of kinetics, and the reaction activation energy of the rate-determining step for path 1 is 452.60 kJ/mol; (4) with increasing temperature, the rate constant of the rate-determining steps of the two reaction paths are nearer to each other, which means that both the reaction paths exist in the pyrolysis process. The above results are basically in accordance with the mass spectrum analysis of 1,3-butadiene, and is far more specific than experimental result.
Co-reporter:Gang Wang, Jianhua Wang, Hui Wang, Jintao Bai
Journal of Environmental Chemical Engineering (September 2014) Volume 2(Issue 3) pp:1588-1595
Publication Date(Web):1 September 2014
DOI:10.1016/j.jece.2014.05.021
Catalytic decomposition of ethanol over a molybdenum modified Fe/MgO catalyst to synthesize carbon nanotubes and hydrogen-rich gas is evaluated at temperatures between 600 and 900 °C. The results show that molybdenum modified Fe/MgO is an effective catalyst for the production of single-walled carbon nanotubes and hydrogen at 800 °C. According to the gaseous and solid products obtained, the reaction pathways for ethanol decomposition are suggested. Catalytic activities and stabilities of Fe/MgO and molybdenum modified Fe/MgO catalysts on ethanol decomposition are compared. The results show that the catalytic performance for the production of carbon nanotubes and hydrogen from ethanol decomposition can be improved significantly after the modification of molybdenum.
Co-reporter:Ruihao Chen, Yinzhi Xie, Yaqian Zhou, Jianhua Wang, Hui Wang
Journal of Energy Chemistry (March 2014) Volume 23(Issue 2) pp:244-250
Publication Date(Web):1 March 2014
DOI:10.1016/S2095-4956(14)60142-X
A series of molybdenum modified Ni/MgO catalysts (Ni-Mo/MgO) with different loading ratios of Ni : Mo were prepared by impregnation method. Ethanol decomposition to co-produce multi-walled carbon nanotubes and hydrogen-rich gas at temperatures of 600–800 °C was investigated over the synthesized Ni-Mo/MgO catalysts. The results showed that the catalytic activity depended strongly on the reaction temperature and loading ratio of Ni : Mo. According to the gaseous and solid products obtained, the reaction pathways for ethanol decomposition were suggested.Catalytic decomposition of ethanol over a molybdenum modified Ni/MgO catalyst to produce hydrogen and multi-walled carbon nanotubes simultaneously has been realized successfully.Download full-size image
Co-reporter:Xiujuan Wang, Xiaojie Liu, Gang Wang, Yixuan Zhou, Hui Wang
Journal of Power Sources (28 February 2017) Volume 342() pp:105-115
Publication Date(Web):28 February 2017
DOI:10.1016/j.jpowsour.2016.12.025
Co-reporter:Yingdi Lv, Hui Wang, Xiaofang Wang, Jinbo Bai
Journal of Crystal Growth (15 June 2009) Volume 311(Issue 13) pp:3445-3450
Publication Date(Web):15 June 2009
DOI:10.1016/j.jcrysgro.2009.03.046
Monodisperse Fe3O4 microspheres assembled by a number of nanosize tetrahedron subunits have been selectively synthesized through the hydrothermal process. The synthesized Fe3O4 microspheres have good dispersibility. The subunits made up of microspheres were uniform in size and like-tetrahedron in shape. The average diameter of each Fe3O4 microsphere is about 50–55 μm. The length of each edge of tetrahedron is about 100 nm. A series of experiments had been carried out to investigate the effect of reductant, precipitator and reaction time on the formation of Fe3O4 microsphere and tetrahedron subunits. The results show that ascorbic acid as reductant and urea as precipitator supplied a relatively steady environment during the synthesis process and led to the formations of Fe3O4 tetrahedron subunit and monodisperse Fe3O4 microspheres. As the reaction time increased from 3 to 24 h, the Fe3O4 microspheres tended towards dispersion and becoming large in size from 10–20 to 50–55 μm, and the subunits formed Fe3O4 microspheres that varied from spheroid to tetrahedron and from a small nanoparticle (20–30 nm) to a large one (90–110 nm). A reasonable explanation for the formations of the Fe3O4 microsphere and the tetrahedron subunit was proposed through Ostwald ripening and the attachment growth mechanism, respectively.
Co-reporter:Xing Zhang, Hui Wang, Gang Wang
Journal of Colloid and Interface Science (15 April 2017) Volume 492() pp:
Publication Date(Web):15 April 2017
DOI:10.1016/j.jcis.2016.12.071
In order to improve the conductivity and electrochemical activity, Co9S8 nanoparticles anchored in three-dimensional carbon nanosheet networks (3D Co9S8@CNNs) are fabricated by a simple strategy with the assistance of NaCl. Combining the advantages of nanoscale and porous structure, 3D Co9S8@CNNs can retard the aggregation of Co9S8 nanoparticles, provide abundant electrochemical active sites, as well as accommodate the mechanical stress during the cycling of lithium ion batteries (LIBs) or sodium ion batteries (SIBs). Thus, when evaluated as an anode for LIBs, the as-prepared 3D Co9S8@CNNs electrode exhibits outstanding electrochemical performance with a high reversible capacity of 935 mAh g−1 after 200 cycles at 0.25 A g−1. As for SIBs, it also delivers superior cycling stability with a capacity of 249 mAh g−1 after 50 cycles at 0.1 A g−1. These results demonstrate that 3D Co9S8@CNNs composite has potential to be utilized as an anode material for LIBs/SIBs with enhanced electrochemical performance.3D Co9S8@CNNs composite is successfully fabricated by a simple route and delivers outstanding electrochemical performance for LIBs/SIBs.
Co-reporter:Xiujuan Wang, Xiaojie Liu, Gang Wang, Yuan Xia and Hui Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 47) pp:NaN18542-18542
Publication Date(Web):2016/10/27
DOI:10.1039/C6TA07452A
Here we report a simple but effective method to fill carbon nanotube (CNT) channels with a dense distribution of Fe3O4 nanoparticles, to produce Fe3O4@CNT. The resulting novel heterogeneous nanostructure displayed multiple attractive features as an anode material in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). For example, this nanostructure displayed voids that apparently effectively prevented active material from aggregating and helped to accommodate their volumetric expansion during the cycling process. In addition, most solid electrolyte interphases (SEIs) formed on the surfaces of the CNT shells instead of on individual Fe3O4 nanoparticles, limiting the amount of SEIs and increasing the stability of the Fe3O4 nanoparticles. As a result, when tested for LIBs, the Fe3O4@CNT nanocomposite exhibited an excellent rate capacity and cycling performance in half and full cells. A high reversible capacity of 720 mA h g−1 was obtained after 200 cycles at 1 A g−1, and when the current density was increased to 8 A g−1, the specific capacity was 400 mA h g−1. As for SIBs, a specific capacity of 377 mA h g−1 at 0.1 A g−1 was achieved after 300 cycles. The facile synthetic route and unique nanostructure design may be extended to high-performance anode materials for LIBs and SIBs.
Co-reporter:Beibei Wang, Gang Wang and Hui Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 33) pp:NaN17411-17411
Publication Date(Web):2015/07/22
DOI:10.1039/C5TA03929K
In this article, we demonstrate a general approach to grow Mo2C nanoparticles of 10–40 nm on a graphene (GR) support through a simple and environmentally friendly carburization process. The unique and special structural features of the Mo2C/GR hybrids including good structural robustness, small particle size and porous structure permit easy access for electrons and ions to the electrode/electrolyte, when the resulting materials are used as anode materials for lithium-ion batteries. Electrochemical tests indicate that the Mo2C/GR hybrids exhibit much better lithium storage properties than pure GR and bulk Mo2C electrodes. The enhanced electrochemical properties of the Mo2C/GR hybrids are mainly ascribed to the synergetic effects between Mo2C nanoparticles and the highly conductive GR support. The results clearly demonstrate that the Mo2C/GR hybrids have potential application as anode materials in high-performance energy storage devices.
Co-reporter:Beibei Wang, Gang Wang, Zhengyuan Lv and Hui Wang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 40) pp:NaN27117-27117
Publication Date(Web):2015/09/09
DOI:10.1039/C5CP04628A
In this article, we demonstrate a simple solvothermal method towards in situ growth of hierarchical CoFe2O4 nanoclusters on graphene aerogels (GAs). SEM and TEM results confirm that CoFe2O4 nanoclusters are well wrapped by the graphene skeleton. As an anode material for lithium-ion batteries, the CoFe2O4/GAs composite displays a stable cycling performance with a reversible capacity of over 100 discharge/charge cycles at the current density of 0.1 A g−1, considerably higher than that of CoFe2O4 nanoclusters. Moreover, the reversible capacity of the CoFe2O4/GAs composite exhibits 966 mA h g−1 after 300 cycles even at a high current density of 0.5 A g−1. Most important of all, a new CoFe2O4/GAs//LiCoO2 full cell was successfully assembled, and this exhibited excellent electrochemical performance. The superior electrochemical performance of the CoFe2O4/GAs composite in half and full cells can be attributed to the synergistic interaction between the uniform CoFe2O4 nanoclusters and GAs, the high electrical conductivity, and the three-dimensional hierarchically porous structure, which can not only facilitate the diffusion of Li ions and electrolyte into the electrodes, but also prevent volume expansion/contraction upon prolonged discharge/charge cycling.
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