Co-reporter:J.P. Cheng, L. Liu, K.Y. Ma, X. Wang, Q.Q. Li, J.S. Wu, F. Liu
Journal of Colloid and Interface Science 2017 Volume 486() pp:344-350
Publication Date(Web):15 January 2017
DOI:10.1016/j.jcis.2016.09.064
Supercapacitor with metal hydroxide nanosheets as electrode can have high capacitance. However, the cycling stability and high rate capacity is low due to the low electrical conductivity. Here, the exfoliated α-Co(OH)2 nanosheets with high capacitance has been assembled on few-layer graphene with high electric conductivity by a facile yet effective and scalable solution method. Exfoliated hydrotalcite-like α-Co(OH)2 nanosheets and few-layer graphene suspensions were prepared by a simple ultrasonication in formamide and N-methyl-2-pyrrolidone, respectively. Subsequently, a hybrid was made by self-assembly of α-Co(OH)2 and few-layer graphene when the two dispersions were mixed at room temperature. The hybrid material provided a high specific capacitance of 567.1 F/g at 1 A/g, while a better rate capability and better stability were achieved compared to that mad of pristine and single exfoliated α-Co(OH)2. When the hybrid nanocomposite was used as a positive electrode and activated carbon was applied as negative electrode to assembly an asymmetric capacitor, an energy density of 21.2 Wh/kg at a power density of 0.41 kW/kg within a potential of 1.65 V was delivered. The high electrochemical performance and facile solution-based synthesis method suggested that the hybrid of exfoliated α-Co(OH)2/few-layer graphene could be a potential electrode material for electrochemical capacitor.
Co-reporter:Song Hao Guo, Peng Wei Yuan, Jiao Wang, Wen Qiang Chen, Ke Yuan Ma, F. Liu, J.P. Cheng
Journal of Electroanalytical Chemistry 2017 Volume 807(Volume 807) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.jelechem.2017.11.009
•Copper cobalt carbonate hydroxide (CH) microspheres are synthesized by simple method.•The morphology, structure and electrochemical performances of Cu-Co CH are dominated by Cu/Co ratio.•The Cu-Co CH electrodes exhibit good capacitive performances.•The hybrid capacitor Cu-Co CH//AC shows extraordinary cycling stability.Copper cobalt carbonate hydroxide (Cu-Co CH) microspheres were synthesized as a pseudocapacitive electrode material via a simple one-step hydrothermal method. Morphological characterization of the Cu-Co CH microspheres was carried out by scanning electron microscopy and transmission electron microscopy, showing their dandelion-like structure with the size approximately 4–7 μm. The crystalline structure, morphology and electrochemical performances of Cu-Co CH materials could be readily dominated by the molar ratio of Cu to Co. Among various stoichiometries of Cu-Co CHs, sample Cu0.48Co1.52 CH delivered the highest specific capacitance of 397.3 F g− 1 at 1 A g− 1 with a good rate capability. Cu0.48Co1.52 CH electrode material also exhibited a remarkably excellent cycling stability, ~ 99% of initial capacitance retention even after 10,000 charge/discharge cycles at 2 A g− 1. An asymmetric energy storage device was assembled by using Cu0.48Co1.52 CH as positive electrode and activated carbon as negative electrode in 2 M KOH electrolyte. The hybrid capacitor device could deliver an energy density of 26.3 Wh kg− 1 at a power density of 400.2 W kg− 1, and remain 16.7 Wh kg− 1 at 8374.2 W kg− 1. Meanwhile, it also showed amazing stability with ~ 99% capacity retention after 10,000 cycles. Based on the above results, Cu-Co CH microspheres possessed practical application as electrode materials for electrochemical capacitors due to their good structural stability in KOH electrolyte.
Co-reporter:J. Wang, K.Y. Ma, J. Zhang, F. Liu, J.P. Cheng
Journal of Colloid and Interface Science 2017 Volume 507(Volume 507) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.jcis.2017.07.095
Hierarchical nickel sulfide (NiSx) hollow microspheres can be successfully synthesized with a template-free method using α-Ni(OH)2 microspheres as a precursor by calcination and sulfidation. The intermediate Ni hollow spheres, formed at different calcination temperatures (300 °C and 400 °C) under H2/N2 atmosphere, can be easily transformed into NiSx with similar morphology and mixed phases of Ni3S2 and NiS during the followed sulfidation process. The formation processes for the hollow structure of NiSx are also discussed in this work. Particularly, the NiSx prepared from Ni intermediate spheres at 300 °C show a high specific capacity of 153.6 mAh g−1 at 0.5 A g−1 at high mass loading due to its small crystal size, hierarchically porous structure and high electrical conductivity. A hybrid capacitor was assembled by using it as positive electrode and activated carbon as negative electrode to examine their practical applications in a full-cell configuration. The hybrid capacitor exhibited excellent comprehensive performances in 1.6 V. The hybrid capacitor also showed good cycling stability, with 81.25% of the initial specific capacitance after 1000 cycles at 2 A g−1. Above results indicate the great potential of the NiSx hollow spheres as a promising electrode material for supercapacitor applications.Download high-res image (104KB)Download full-size image
Co-reporter:M. Li, PengWei Yuan, SongHao Guo, F. Liu, J.P. Cheng
International Journal of Hydrogen Energy 2017 Volume 42, Issue 48(Volume 42, Issue 48) pp:
Publication Date(Web):30 November 2017
DOI:10.1016/j.ijhydene.2017.10.019
•Ni-Co and Ni-Mn LDHs coatings were deposited on the surface of SiO2 microspheres.•Porous Ni-Co and Ni-Mn LDHs microspheres with hollow cores were fabricated.•Ni-Co LDHs microspheres exhibited higher electrochemical performance than Ni-Mn LDHs.The development of electrode materials with hierarchically porous structure and high electrochemical stability is crucial for the electric energy density of supercapacitors. Hollow microspheres of Ni-Co layered double hydroxides (LDHs) and Ni-Mn LDHs are fabricated with a simple co-precipitation method at low temperature using SiO2 microspheres as a sacrifice template. The as-fabricated two LDH hollow microspheres possess a unique 3D architecture and exhibit high specific capacitance, as well as excellent rate and cycling performances as electrode materials of supercapacitors. A specific capacitance of 1766.4 F g−1 at 1 A g−1 is achieved for Ni-Co LDHs electrode, much higher than that of Ni-Mn LDHs. A hybrid capacitor composed of Ni-Co LDHs hollow spheres and activated carbon is fabricated and evaluated for practical application, providing an energy density of 44.3 Wh kg−1 at a power density of 0.425 kW kg−1. This study indicates that the hollow LDH microsphere prepared by our method is a promising material for supercapacitors.
Co-reporter:KeYuan Ma, Fu Liu, MeiBian Zhang, XiaoBin Zhang, J.P. Cheng
Electrochimica Acta 2017 Volume 225(Volume 225) pp:
Publication Date(Web):20 January 2017
DOI:10.1016/j.electacta.2016.12.163
•Co-Fe LDH@NiOcompositewithshell-corestructurewasdepositedonNifoam.•The shell-core structure will generate high resistance between the interface of core and shell.•Electrochemical performance of the hybrid was improved at a low current density.Hybrid materials with three-dimensional hierarchical architectures have drawn considerable attention in the field of energy storage and conversion owing to the improved electrolyte-accessible surface area and shortened ion transfer paths. In this work, a novel hierarchical Co-Fe LDH@NiO composite with shell-core rod arrays grown on the surface of Ni foam is presented for the use of electrode material without any organic binders and conductive agents. It is found that the expected good conductivity, large electrolyte-accessible surface area and sufficient active sites cannot be well achieved at the same time. Owing to the facile electrolyte diffusion paths and large exposed surface area, Co-Fe LDH@NiO with 46.06% Co-Fe LDH has a specific capacity of 361 C g−1 at 1 A g−1. However, at high current densities, its performance decreases quite dramatically due to the poor electrical conductivity of NiO support and the high interface contact resistance between NiO microrods and Co-Fe LDH nanosheets. The assembled hybrid supercapacitor based on Co-Fe LDH@NiO-Ni and activated carbon electrodes can deliver an energy density of 22 Wh kg−1 at the power density of 800 W kg−1, showing a promising potential in energy storage and conversion.
Co-reporter:KeYuan Ma, J.P. Cheng, Jing Zhang, Min Li, Fu Liu, XiaoBin Zhang
Electrochimica Acta 2016 Volume 198() pp:231-240
Publication Date(Web):20 April 2016
DOI:10.1016/j.electacta.2016.03.082
Co-Fe layered double hydroxides (LDHs) with different Co/(Fe2+, Fe3+) atomic ratios are fabricated via co-precipitation followed by an I2 partial oxidation process. The initial Co/Fe ratio in solution is changed in a wide range and has a significant influence on the phase and structure of the product. Structural analysis confirms that Co-Fe LDHs with four Co/Fe molar ratios (2.35, 1.07, 0.58 and 0.24) shows a typical hydrotalcite-like structure and layered plate-like morphology. A high Fe content will destroy the hydrotalcite structure and lead to the formation of magnetite particles. Electrochemical data demonstrate that the specific capacitance of Co-Fe LDHs is strongly dependent on Co/Fe ratio. The Co-Fe LDHs with a high Co/Fe ratio of 2.35 can deliver the highest capacitance of 728 F g−1 at 1 A g−1 among them and when assembled into asymmetric supercapacitor with activate carbon as negative material, it can exhibit an energy density of 27.3 Wh kg−1 at a power density of 823.5 W kg−1. The incorporation of Fe not only prevents the formation of β-Co(OH)2 but also delivers a high capacitance. But, too much Fe is not preferred because it will lead to unstable structures and poor electrochemical performance due to the generation of iron compounds.The incorporation of Fe2+/Fe3+ not only prevents the formation of β-Co(OH)2 but also delivers a higher capacitance even at a high Fe content. However, too high Fe content may destroy the layered structure of LDHs and lead to the decay of the electrochemical performances.
Co-reporter:M. Li, J.P. Cheng, J. Wang, F. Liu, X.B. Zhang
Electrochimica Acta 2016 Volume 206() pp:108-115
Publication Date(Web):10 July 2016
DOI:10.1016/j.electacta.2016.04.084
•Flower-like Ni-Mn LDH and Co-Mn LDH were synthesized by co-precipitation method.•Ni-Mn LDH and Co-Mn LDH are in-situ grown on the surface of reduced graphene oxide.•A high specific capacitance of 1635 F g−1 at 1 A g−1 is achieved for Ni-Mn LDH/rGO.Pure Ni-Mn layered double hydroxide (LDH), Co-Mn LDH with a flower-like morphology and sandwich-like Ni-Mn LDH/reduced graphene oxide (rGO), Co-Mn LDH/rGO hybrids are fabricated via a simple co-precipitation method. In the hybrids, Ni-Mn and Co-Mn hydroxide nanoflakes are tightly anchored on the both surfaces of rGO, leading to the composites with high specific surface areas. Electrochemical measurements prove that rGO can improve the capacitance and cyclic stability of the hybrid materials and that Ni-Mn LDH delivers a much higher specific capacitance but a worse cycling performance than Co-Mn LDH. A high specific capacitance of 1635 F g−1 at 1 A g−1 and a high rate retention of 71% at 10 A g−1 are achieved for Ni-Mn LDH/rGO. A hybrid capacitor with Ni-Mn LDH/rGO as positive electrode and activated carbon as negative electrode is assembled. It possesses a specific capacitance of 84.26 F g−1 at 1 A g−1 and an energy density of 33.8 Wh kg−1 within a potential window of 1.7 V.
Co-reporter:KeYuan Ma, WenJia Zhao, J.P. Cheng, Fu Liu, XiaoBin Zhang
Journal of Colloid and Interface Science 2016 Volume 468() pp:238-246
Publication Date(Web):15 April 2016
DOI:10.1016/j.jcis.2016.01.058
A novel hydrothermal process is demonstrated to prepare acetate anions intercalated α-Co(OH)2 that can be delaminated in water without any additional anion exchange processes. Positively charged Co(OH)2 nanosheets with lateral size of hundreds of nanometers and thickness less than 2 nm can be obtained by dispersing the as-obtained α-Co(OH)2 into water followed by sonication. The exfoliated Co(OH)2 nanosheets can be restacked into its original structure with different interlayer d-spacings. A flexible free-standing film with stacking Co(OH)2 nanosheets and graphene oxide (GO) layers can be obtained through flocculation of the Co(OH)2 nanosheets with GO nanosheets suspensions followed by a vacuum filtration, but the content of Co(OH)2 has to be kept under a low value so as to obtain films with flexible nature. Electrochemical tests show that this kind of film is not suitable to be used as electrode material for supercapacitor and lithium ion battery, because the content of active material is not high and the compacted junction between opposite charged nanosheets will prevent the electrolyte from diffusing into the interlayer space.Free-standing α-Co(OH)2/graphene oxide thin film was fabricated through delamination and reassembling of acetate anions intercalated α-Co(OH)2 and graphene oxide in water.
Co-reporter:J.M. Xu, J.P. Cheng
Journal of Alloys and Compounds 2016 Volume 686() pp:753-768
Publication Date(Web):25 November 2016
DOI:10.1016/j.jallcom.2016.06.086
•Recent advances of Co3O4 as gas sensing materials are critically reviewed.•Different Co3O4 nanostructures from 0D particle to 3D architecture are included.•A wide variety of Co3O4-based composites as gas-sensor materials are discussed.As a p-type semiconductive material, Co3O4 has been widely studied as gas sensor materials, in addition to energy storage, catalyst and magnetic semiconductor. The gas sensors prepared using Co3O4 and its composites were reviewed in this work. Investigation has indicated that the gas sensing performances of Co3O4 micro-/nanostructures are strongly related to the surface area, porous nature and morphologies. Thus, the gas sensing properties of Co3O4 micro-/nanostructures will change with the tuned configurations. Hierarchically porous structures of Co3O4 usually exhibit a high response and low operating temperature to detect gases. In this review, attention is also focused on Co3O4-based composites, including Co3O4/inorganic metal oxides, Co3O4/carbon nanomaterials, Co3O4/polymers and Co3O4/noble metals, due to their unique effects on the final gas sensing application. The Co3O4 composites generally show higher gas response than single component due to the catalytic action or synergetic effects between the components. This paper has summarized an overview of the literature on gas sensing of Co3O4 and suggested potential directions for future progress.
Co-reporter:KeYuan Ma, J.P. Cheng, Fu Liu, XiaoBin Zhang
Journal of Alloys and Compounds 2016 Volume 679() pp:277-284
Publication Date(Web):15 September 2016
DOI:10.1016/j.jallcom.2016.04.059
•Co–Fe layered double hydroxides nanoplates are vertically anchored on the surfaces of carbon fibers.•Enhanced electrochemical performance is obtained from the fabricated hybrid material.•Co–Fe LDHs with carbon materials can deliver an improved capacitance for real applications.We demonstrate the fabrication of a core-shell structure composite of Co–Fe layered double hydroxides (LDHs) on the surface of carbon fiber cloth (CFC). The Co–Fe LDHs nanoplates are vertically anchored onto the surface of electrical conductive CFC via a simple hydrothermal process followed by an I2 oxidation process. The hexagonal Co–Fe LDHs nanoplates on the surfaces of carbon fibers form a porous network film. The carbon fibers with high conductivity can act as conductive cores to support a large number of Co–Fe LDHs nanoplates to deliver a high specific capacitance of 774 F g−1 at the current density of 1 A g−1. An assembled asymmetric capacitor by using Co–Fe LDHs-CFC as positive electrode material and activated carbon as negative electrode material can deliver an energy density of 16.1 Wh kg−1 at the power density of 399.7 W kg−1 with a good cycling stability. This study provides a way to combine Co–Fe LDHs with carbon materials to obtain a composite that can deliver an improved performance for electrochemical capacitor application.A core-shell (carbon fiber core-metal hydroxide shell) structure was fabricated by loading Co–Fe layered double hydroxides nanoplates onto electrical conductive carbon fiber cloth. The as-prepared hybrid material can deliver an enhanced specific capacitance of 774 F g−1 at 1 A g−1. Meanwhile, the assembled asymmetric capacitor by using Co–Fe LDHs-CFC as positive electrode material and activated carbon as negative electrode material can deliver an energy density of 16.1 Wh kg−1 at the power density of 399.7 W kg−1 with an excellent cycling stability.
Co-reporter:X.F. Gong, J.P. Cheng, K.Y. Ma, F. Liu, Li Zhang, XiaoBin Zhang
Materials Chemistry and Physics 2016 Volume 173() pp:317-324
Publication Date(Web):15 April 2016
DOI:10.1016/j.matchemphys.2016.02.018
•Ni–Co sulfide arrays are directly grown on Ni foam as supercapacitor electrodes.•The capacitance increases to 314% of the initial value in the first 5000 cycles.•Enlarging the potential range, the areal capacitance can further increase.The synthesis of NiCo2S4/Co9S8 nanorod arrays directly grown on Ni foam and its application as a supercapacitor electrode were investigated. The electrode demonstrated a superior electrochemical performance and its capacitance could increase to 314% of the initial value after 5000 cycles due to a progressive activation. The highest areal specific capacitance could be 8.08 F cm−2 and the corresponding mass specific capacitance was 2068 F g−1 at the current density of 5 mA cm−2. Even after 10,000 cycles, its areal specific capacitance could be still 5.53 F cm−2, 190% of the initial capacitance. When the current density was increased, the areal capacitance would decrease usually. Through increasing the anode voltage, the areal specific capacitance could increase. The combination of high electrical conductivity, porous structure and the synergic effects of nickel and cobalt, played significant roles to obtain supercapacitor electrodes with excellent performances.
Co-reporter:J. Zhang, F. Liu, J. P. Cheng, and X. B. Zhang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 32) pp:17630
Publication Date(Web):July 23, 2015
DOI:10.1021/acsami.5b04463
Nickel–cobalt oxides were prepared by coprecipitation of their hydroxides precursors and a following thermal treatment under a moderate temperature. The preformed nickel-cobalt bimetallic hydroxide exhibited a flower-like morphology with single crystalline nature and composed of many interconnected nanosheets. The ratio of Ni to Co in the oxides could easily be controlled by adjusting the composition of the original reactants for the preparation of hydroxide precursors. It was found that both the molecular ratio of Ni to Co and the annealing temperature had significant effects on their porous structure and electrochemical properties. The effect of the Ni/Co ratio on the pseudocapacitive properties of the binary oxide was investigated in this work. The binary metal oxide with the exact molar ratio of Ni:Co = 0.8:1 annealed at 300 °C, showing an optimum specific capacitance of 750 F/g. However, too high an annealing temperature would lead to a large crystal size, a low specific surface area, as well as a much lower pore volume. With the use of the binary metal oxide with Ni:Co = 0.8:1 and activated carbon as the positive and negative electrode, respectively, the assembled hybrid capacitor could exhibit a high-energy density of 34.9 Wh/kg at the power density of 875 W/kg and long cycling life (86.4% retention of the initial value after 10000 cycles).Keywords: hybrid capacitor; hydrothermal; nickel-cobalt oxides; porous structure; pseudocapacitive property
Co-reporter:Min Li, K.Y. Ma, J.P. Cheng, Danhui Lv, X.B. Zhang
Journal of Power Sources 2015 Volume 286() pp:438-444
Publication Date(Web):15 July 2015
DOI:10.1016/j.jpowsour.2015.04.013
•Ni–Co hydroxide nanoflakes are decorated on the surface of CNTs by a CBD method.•A high rate capability of 61% retention after a 70-fold increase in current densities is achieved.•The specific capacitance can maintain 77% of the initial value after 10,000 cycles.A carbon nanotubes (CNTs)-nickel–cobalt hydroxide nanoflake core–shell structure is designed and fabricated by a facile one-step chemical bath deposition method. Structure analysis confirms that the as-synthesized hydroxides are conformally coated on the surface of CNTs with a hydrotalcite structure. The incorporation of Co into nickel hydroxides can improve the electrical conductivity together with intercalated sulphate ions into the interlayer spacing to enlarge the lattice space, which further improves the rate capabilities and cycling stability. Electrochemical data demonstrates that the hybrid hydroxide with Ni–Co molar ratio of 1:2 exhibits a high specific capacitance of 1151 F g−1 at 1 A g−1 and an excellent high rate capability, with 61% retention after a 70-fold increase in current densities. Its specific capacitance can maintain 77% of the initial value after 10,000 cycles. The nickel–cobalt hydroxide nanoflakes-CNTs hybrid shows a great potential of being an electrode material for supercapacitors with its high specific capacitance, good rate capability and long-term cycling life.
Co-reporter:J. Zhang, J.P. Cheng, M. Li, L. Liu, F. Liu, X.B. Zhang
Journal of Electroanalytical Chemistry 2015 Volume 743() pp:38-45
Publication Date(Web):15 April 2015
DOI:10.1016/j.jelechem.2015.02.021
•Ni–Co binary hydroxides with hydrotalcite-like structure are synthesized by hydrothermal method.•The contents of Ni and Co in the binary hydroxides can be easily tuned.•With Ni increase, the hydroxides have a higher capacitance with a deteriorative rate capability.Nickel and cobalt binary hydroxides with hydrotalcite-like structure were successfully synthesized by a one-step hydrothermal method without any surfactants. The contents of Ni and Co in the binary hydroxides could be easily tuned by altering the molar ratio of metal salts in the reaction solution. Five typical hydroxides were prepared with different Ni–Co molar ratios of 1:0, 7:3, 5:5, 3:7 and 0:1. Structure analysis confirmed that the hydroxides formed as 3D microflowers in shape with a good hydrotalcite-like structure. The Ni–Co binary hydroxides showed significant improvement in specific capacitance compared to unary hydroxides due to their higher interlayer spacings and improved electrical conductivity. As the content of nickel increased, the hydroxides tended to have a higher specific capacitance with a gradually deteriorative rate capability. Electrochemical data demonstrated that the binary hydroxide with Ni–Co molar ratio of 7:3 could deliver the maximum specific capacitance of 1803.6 F g−1, while the binary hydroxide with Ni–Co molar ratio of 3:7 exhibited a high rate capability. An asymmetric capacitor using a typical binary hydroxide as positive material and activated carbon as negative material exhibited an excellent comprehensive performance. Our experimental results also gave a clue that the charge storage stability and rate capability of these hydroxides highly depend on their interlayer spacing.SEM and EDS mappings of a typical flower-like Ni–Co binary hydroxide particle.
Co-reporter:J.M. Xu, K.Y. Ma, J.P. Cheng
Journal of Alloys and Compounds 2015 Volume 653() pp:88-94
Publication Date(Web):25 December 2015
DOI:10.1016/j.jallcom.2015.08.258
•Ni(OH)2 nanosheet film is grown on nickel substrate by hydrothermal treatment.•Precise mass loading of Ni(OH)2 could be determined by thermogravimetric analysis.•Mass content of Ni(OH)2 film is related to the concentration of ferric nitrate.•Ni(OH)2 and NiO films grown on Ni foam can be used as electrodes directly.Nickel hydroxide nanosheet films are prepared via a hydrothermal treatment of nickel foam at a low temperature using Fe(NO3)3 as an oxidant without any templates and nickel salts. The as-formed Ni(OH)2 nanosheets are vertically self-grown on the Ni foam substrate. They are inter-connected and free-standing to form a homogeneously porous coating on the substrate with a thickness about 1 μm. The mass loading of Ni(OH)2 film on nickel foam can be precisely determined by thermogravimetric analysis on base of phase transformation from nickel hydroxide to oxide. The mass loading of Ni(OH)2 is strongly related with the concentration of Fe(NO3)3. The Ni(OH)2 film grown on nickel foam can directly serve as additive-free electrodes and display a much high specific capacitance, 1100 F g−1 at 0.5 A g−1, excellent rate-capability performance owing to fast electron and ion transport. The Ni(OH)2 film can transform into NiO by annealing under a moderate temperature. However, the NiO film shows a low specific capacitance of 79 F g−1 at 0.5 A g−1. The preparation method concerns limited chemicals and produces little residual, implying a green chemical process to fabricate Ni(OH)2 and NiO films on Ni substrate.
Co-reporter:Lan Liu;Ke-Yuan Ma;Fu Liu;Xiao-Bin Zhang ;J. P. Cheng
European Journal of Inorganic Chemistry 2015 Volume 2015( Issue 14) pp:2448-2456
Publication Date(Web):
DOI:10.1002/ejic.201500118
Abstract
α-Form CoxNi1–x hydroxides with different Co/Ni ratios were synthesized by a chemical co-precipitation method under mild conditions. The effects of Co/Ni ratio on the structure, morphology, and supercapacitive properties of α-form CoxNi1–x hydroxides were investigated in detail. α-Form CoxNi1–x hydroxides had structures similar to those of hydrotalcite and α-Co(OH)2, and they exhibited better electrochemical performance than α-Co(OH)2 on testing by XRD, FTIR, and electrochemical performance (when x ≠ 0). The highest specific capacitance at 1 A g–1 for α-form CoxNi1–x hydroxides (for x = 0.2) is 1696.7 F g–1. An asymmetric supercapacitor packaged with Co0.6Ni0.4 hydroxide and activated carbon as positive and negative material, respectively, had an energy density of 23.5 Wh kg–1 at a power density of 412.5 W kg–1.
Co-reporter:Min Li, Fu Liu, J.P. Cheng, J. Ying, X.B. Zhang
Journal of Alloys and Compounds 2015 Volume 635() pp:225-232
Publication Date(Web):25 June 2015
DOI:10.1016/j.jallcom.2015.02.130
•NiAl-LDH nanosheets are in situ grown on carbon nanotubes pre-coated by Al2O3.•NiAl-LDH/CNTs exhibits a specific capacitance of 1500 F g−1 at 1 A g−1 with a good cycling stability.•The NiAl-LDHs/CNTs//AC asymmetric supercapacitor shows a high electrochemical performance.Binary composite consisting of nickel aluminum-layered double hydroxides (LDHs) nanosheets and carbon nanotubes (CNTs) is fabricated by a solution method. The CNTs are pre-coated by γ-Al2O3. The structural characterization and morphological observation demonstrate that Ni–Al hydroxide crystals with hydrotalcite structure are in situ deposited on the surface of CNTs. The as-prepared binary composite combines the pseudo-capacitive of Ni–Al LDHs with double-layer capacitive of carbon nanotubes. CNTs can improve the electrical conductivity and decrease the electrochemical polarization of the composite. Electrochemical measurements of the Ni–Al LDHs/CNTs material show a much better electrochemical performance than pure Ni–Al LDHs. It can yield a high specific capacitance of 1500 F g−1 at 1 A g−1, with 70.3% retention at 10 A g−1 in 2 M KOH and a good cycling stability. An asymmetric capacitor is assembled with Ni–Al LDHs/CNTs as a positive electrode and activated carbon as the negative electrode. It can cycle reversibly in a potential window of 1.8 V, and exhibits a high specific capacitance of 115 F g−1 and a high energy density of 52 W h kg−1 at 1 A g−1 as well as an excellent cycling stability.
Co-reporter:Xuefei Gong, J.P. Cheng, Fu Liu, Li Zhang, Xiaobin Zhang
Journal of Power Sources 2014 Volume 267() pp:610-616
Publication Date(Web):1 December 2014
DOI:10.1016/j.jpowsour.2014.05.120
•Nickel–Cobalt hydroxide microspheres were electrodeposited on NiCo2O4 nanowire arrays.•The electrode of 10 min electrodeposition delivered a high areal capacitance of 6 F cm−2.•The synergic effect of conductive NiCo2O4 nanowires and porous hydroxides is important.Nickel–Cobalt hydroxide microspheres are electrodepositioned on the films of NiCo2O4 nanowires grown on the current collector through a facile approach and the hierarchical structures are then investigated as an electrode material for high-performance supercapacitors. Owing to the superior electrical conductivity of NiCo2O4 nanowires, the porous structure of the (Ni–Co)(OH)2 microspheres and the synergic effect of the multi-components, the electrode can deliver a high areal capacitance of 6 F cm−2 and a corresponding specific capacitance of 1132 F g−1 at a current density of 2 mA cm−2, as well as a good rate capability (61.8% capacitance retention from 2 mA cm−2 to 50 mA cm−2), and excellent cycling stability (90% capacitance retention after 2000 cycles). The results suggest that our research opens up the possibility for the fabrication of high-performance energy-storage devices of binder-free electrodes.
Co-reporter:J. P. Cheng, J. Zhang and F. Liu
RSC Advances 2014 vol. 4(Issue 73) pp:38893-38917
Publication Date(Web):05 Aug 2014
DOI:10.1039/C4RA06738J
Electrochemical capacitors, also known as supercapacitors, are energy storage devices, characterized by rapid rates of charging and discharging and high power density. In recent years, electrochemical capacitors have attracted significant attention as ‘bridges’ for the power/energy gap between traditional capacitors and batteries/fuel cells. The integrated performance of an electrochemical capacitor is essentially determined by its electrode materials. This is a review of electrode materials for electrochemical capacitors, chiefly concerning transition metal hydroxides. In this work, we focused particularly on recently published reports using cheap metal hydroxides as electrode materials for electrochemical capacitors, based on classification of metal hydroxide by composition and microstructure. Some important experimental data on this issue are indicated and summarized. Furthermore, a brief discussion of future development, challenges, and opportunities in this area is also provided.
Co-reporter:J.P. Cheng, L. Liu, J. Zhang, F. Liu, X.B. Zhang
Journal of Electroanalytical Chemistry 2014 Volumes 722–723() pp:23-31
Publication Date(Web):1 May 2014
DOI:10.1016/j.jelechem.2014.03.019
•Co(OH)2 exhibits an improved rate capability and stability intercalated with nitrate and sulfate.•The morphology and structure of α-Co(OH)2 after 2000 cycles tests are well reserved.•The phase transition from α-Co(OH)2 to β-form leads to a dramatic decay in capacitance.Pure hexagonally layered α-Co(OH)2 powder is prepared in large quantity by precipitation method under mild conditions. Subsequently, anion-exchange reaction and aging treatment in alkaline medium are performed to find their influence on the microstructure and supercapacitive properties of α-Co(OH)2. Various inorganic anions are successfully intercalated into the interlayer gallery of α-Co(OH)2 with the morphology and structure reserved. While the α-Co(OH)2 transforms into other cobalt compounds by aging treatment 1 Mol L−1 KOH solution at room temperature. The effects of anion-exchange on the supercapacitive properties are evaluated by cyclic voltammetry and galvanostatic charge–discharge tests. The α-Co(OH)2 exhibits a high specific capacitance, good rate capability and improved stability after intercalation with nitrate and sulfate. The morphology and structure of α-Co(OH)2 after 2000 continuous charge–discharge tests in 1 Mol L−1 KOH electrolyte are also well maintained, indicating its excellent stability in charge–discharge tests. In contrary, the phase transitions from α-Co(OH)2 to β-form and other cobalt phases lead to a dramatic decrease in the specific capacitance, from 763.4 F g−1 to 25.9 F g−1.Graphical abstract
Co-reporter:B.B. Wang, X.X. Fu, F. Liu, S.L. Shi, J.P. Cheng, X.B. Zhang
Journal of Alloys and Compounds 2014 Volume 587() pp:82-89
Publication Date(Web):25 February 2014
DOI:10.1016/j.jallcom.2013.10.176
•Hollow SnO2/α-Fe2O3 core–shell nanofibers were synthesized by electrospun and hydrothermal.•Glacial acetic acid could adjust the nucleation site and density of α-FeOOH nanorods on SnO2.•SnO2/α-Fe2O3 nanofibers exhibited better gas sensing performance than α-Fe2O3 and SnO2 fibers.One dimensional hierarchically hollow SnO2/α-Fe2O3 core–shell nanofibers were synthesized by using electrospun SnO2 hollow nanofibers as core followed by the hydrothermal growth and calcination of α-FeOOH nanorods on the outer surface of SnO2 nanofibers. The control experiments indicated that glacial acetic acid introduced in the hydrothermal solution could adjust the nucleation site and density of α-FeOOH nanorods as well as prevent the formation of urchin-like α-FeOOH byproduct. The growth process of α-FeOOH nanorods on SnO2 hollow nanofibers was also investigated. The hierarchical SnO2/α-Fe2O3 hollow nanofibers were then fabricated as gas sensors for the investigation of gas sensing applications. By comparison of sensing properties, the response values of the sensors fabricated with hierarchical SnO2/α-Fe2O3 core–shell nanofibers toward 100 ppm acetone and ethanol could reach to be 30.363 and 20.370, respectively, exhibiting much better performance than those using urchin-like α-Fe2O3 nanostructures and pure SnO2 nanofibers. Meanwhile, the sensors based on hierarchical SnO2/α-Fe2O3 nanofibers also had shorter response and recovery times than those of α-Fe2O3 nanostructures. The synergetic effect of the composite of α-Fe2O3 and SnO2 together with unique hollow core–shell architectures are main contribution for the enhanced gas sensing properties.
Co-reporter:J.P. Cheng, B.B. Wang, M.G. Zhao, F. Liu, X.B. Zhang
Sensors and Actuators B: Chemical 2014 190() pp: 78-85
Publication Date(Web):
DOI:10.1016/j.snb.2013.08.098
Co-reporter:J.P. Cheng, J.H. Fang, M. Li, W.F. Zhang, F. Liu, X.B. Zhang
Electrochimica Acta 2013 Volume 114() pp:68-75
Publication Date(Web):30 December 2013
DOI:10.1016/j.electacta.2013.10.029
•CoAl layered double hydroxide nanosheet arrays are synthesized by hydrothermal method.•Pt films coated on surface of CoAl nanosheets facilitate fast electron transport.•CoAl LDH nanosheets coated with Pt film for 5 min have an excellent performance.Three-dimensional network of cobalt and aluminum layered double hydroxide (LDH) nanosheets was synthesized on nickel foam by a simple hydrothermal method. The CoAl-LDH nonosheets were subsequently coated by ion sputtering with thin layers of Pt films to facilitate fast electron transport between current collector and the CoAl-LDH active materials. The optimal thickness of the Pt film acquiring the best performance was identified by applying various sputtering time in controlled experiments. The supercapacitor built by the CoAl-LDH nanosheets coated with Pt film sputtered for 5 min has a high specific capacitance (734.4 F g−1 at 3 A g−1), excellent rate capability as well as cycling stability. Moreover, it showed a long life of 77% retention after 6000 cycles and its general morphology was preserved after the test. The synergetic affect of conductive layer of Pt films and CoAl-LDH on the improvement of electrochemical properties was discussed and this would provide a useful clue in designing novel and effective electrode materials for supercapacitors.Schematic illustration for the electron transport between the current collector and the active CoAl LDH arrays, where the yellow arrows indicate the high resistance of CoAl LDH, while the green arrows present the high conductivity of Pt films on LDH.
Co-reporter:J.P. Cheng, Q.L. Shou, J.S. Wu, F. Liu, Vinayak P. Dravid, X.B. Zhang
Journal of Electroanalytical Chemistry 2013 Volume 698() pp:1-8
Publication Date(Web):1 June 2013
DOI:10.1016/j.jelechem.2013.03.017
•Fe3O4/rGO composites were easily prepared by a two-step method.•The mass ratio of Fe3O4 to rGO in the composites could be carefully controlled in the first step.•The content of Fe3O4 had great effect on the microstructure and capacitance of the composites.Fe3O4/reduced graphene oxide (rGO) composites were prepared by a two-step method: solution precipitation followed by hydrogen reducing. The mass ratio of Fe3O4 to rGO in the composites could be carefully controlled in the first step. The structure and morphology of Fe3O4/rGO composites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The electrochemical properties of the composites as electrode of supercapacitors were investigated using cyclic voltammetry and galvanostatic charge–discharge tests. It was found that the mass ratio of Fe3O4 to rGO had great effects on the crystal size of Fe3O4, specific surface areas and pore volume, as well as the specific capacitance of the composites. The capacitance of the composite was higher than that of any individual component due to the synergetic effect between Fe3O4 and rGO. The composite exhibited an excellent cyclic stability and could maintain the initial capacity over 1000 cycles without any decay. This report provides useful clues in design and synthesis graphene-based composites for the applications as energy materials.
Co-reporter:Qing-Liang Shou;Ji-Peng Cheng;Ji-Hong Fang;Fei-Hong Lu;Jia-Jie Zhao;Xin-Yong Tao;Fu Liu;Xiao-Bin Zhang
Journal of Applied Polymer Science 2013 Volume 127( Issue 3) pp:1697-1702
Publication Date(Web):
DOI:10.1002/app.37876
Abstract
The composites composed of Poly (vinylidene fluoride), expanded graphite (EG), and carbon nanotubes (CNTs) have been prepared by solution mixing, followed by compression. The structure of the composites was examined with scanning electron microscope and their electrical and thermal properties were investigated. About 1.2 wt % content of CNTs could present a percolated network in the polymer matrix, characterized by the electrical conductivity. The incorporation of EG and CNTs in the polymer caused an enhancement in thermal conductivity for the composites. However, a hybrid of EG and CNTs as filler of the polymer yielded a further improvement in thermal conductivity as compared to single component filler. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Jihong Fang, Min Li, Qianqian Li, Weifeng Zhang, Qingliang Shou, Fu Liu, Xiaobin Zhang, Jipeng Cheng
Electrochimica Acta 2012 Volume 85() pp:248-255
Publication Date(Web):15 December 2012
DOI:10.1016/j.electacta.2012.08.078
A microwave-assisted reflux method was used to rapidly synthesize CoAl-layered double hydroxide (CoAl-LDH)/graphene oxide composite. In the synthetic procedure, graphite oxide (GO) was exfoliated to graphene oxide nanosheets in company with the in situ growth of CoAl-LDH. The as-prepared products showed lamellar structures. The aggregation of LDH was effectively prevented by the presence of graphene oxide nanosheets. Electrochemical performances were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. All the composites had higher rate capability than pure CoAl-LDH, maintaining about 80% of discharge capacitance when the current density increased from 1 A g−1 to 20 A g−1. A maximum specific capacitance of 772 F g−1 was obtained at 1 A g−1 in 6 M KOH solution for the composite containing 12.9% GO. Moreover, the composite exhibited excellent long cycle life with about 73% specific capacitance retained at 6 A g−1 after 10,000 cycles.Graphical abstractHighlights► CoAl-layered double hydroxide/graphene oxide powders as supercapacitor materials. ► The composite was synthesized via a microwave-assisted reflux method. ► The composite with 12.9% graphite oxide showed the maximum specific capacitance. ► The composite electrode exhibited excellent cycling stability.
Co-reporter:X. Chen, J. P. Cheng, Q. L. Shou, F. Liu and X. B. Zhang
CrystEngComm 2012 vol. 14(Issue 4) pp:1271-1276
Publication Date(Web):28 Nov 2011
DOI:10.1039/C1CE05943B
Mesoporous cobalt oxide micro-flowers have been synthesized by a simple, surfactant-free method without employing any templates. In this method, cobalt hydroxide micro-flowers were initially prepared in a solution medium. Subsequently, they were applied as a precursor of cobalt oxide by heat treatment, to transform into porous micro-flowers. The morphology of cobalt oxide retained that of its precursor. Experimental analysis confirmed that calcination temperature had great influence on the pore structure and crystal size. The average size of cobalt oxide crystals increased with increasing calcination temperature. Nitrogen adsorption/desorption data showed that the pore size increased and the BET surface area decreased with the gradual increase of calcination temperature. The electrochemical properties of the cobalt oxide were investigated by cyclic voltammetry measurements.
Co-reporter:J.P. Cheng, X. Chen, Jin-Song Wu, F. Liu, X.B. Zhang and Vinayak P. Dravid
CrystEngComm 2012 vol. 14(Issue 20) pp:6702-6709
Publication Date(Web):11 Jul 2012
DOI:10.1039/C2CE26057C
We synthesized porous Co3O4 with different hierarchical morphologies and studied the effects on their capacitor properties when they were used as electrode materials. By employing ammonia as the source of the hydroxide anion (OH−), an effective and robust precipitation route, free of surfactants, was developed to synthesize cobalt hydroxides with different hierarchical structures. When ammonia was used, the insufficient OH− supply could tune the formation of cobalt hydroxide to have different hierarchical structures. The (0001) cobalt hydroxide nanosheet is found to be the first product in the nucleation stage, and the basic building block for the hierarchical structures. Three types of anions were tested: the chloride (Cl−) anion prompted the formation of large plates with a similar aspect ratio to the basic building block; the nitrate (NO3−) anion formed large plates at the beginning, but this soon led to the formation of nanocolumn structures with a high aspect ratio; and the acetate (C2H3OO−) anion led to the formation of a flower-shaped hierarchical morphology with stacking of curved (0001) cobalt hydroxide nanosheets. Subsequent calcination transformed the cobalt hydroxides into porous cobalt oxide while the hierarchical morphology remained the same. Cobalt oxides with such complex hierarchical structures have a better capacitor performance, with higher specific capacitance, than Co3O4 nanoparticles. Among them, the Co3O4 hierarchical structure made with the nitrate anion shows the highest capacitance. The mechanism for forming the different hierarchical structures is discussed based on an electron microscopy investigation.
Co-reporter:Weifeng Zhang, Fu Liu, Qianqian Li, Qingliang Shou, Jipeng Cheng, Li Zhang, Bradley J. Nelson and Xiaobin Zhang
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 47) pp:16331-16337
Publication Date(Web):19 Oct 2012
DOI:10.1039/C2CP43673F
A method for producing nanocomposites of transition metal oxides A3O4 (where A represents Mn, Fe or Co) and graphene nanosheets (GNS) is presented. The reduction of graphene oxide (GO) and the formation of A3O4 nanoparticles (NPs) were carried out simultaneously during the reaction. The electrochemical properties of A3O4–GNS nanocomposites as electrode materials for supercapacitors are investigated by cyclic voltammetry and galvanostatic charge–discharge tests. The as-prepared Mn3O4–GNS, Fe3O4–GNS and Co3O4–GNS nanocomposites exhibit large specific capacitance (708, 358 and 240 F g−1, respectively), high energy density (20, 10 and 7 W h kg−1, respectively) and good electrochemical stability (retention of 73%, 67.8% and 95.8%, respectively, after 1000 charge–discharge cycles). The excellent electrochemical performance of the A3O4–graphene nanocomposites indicates great potential in the application in commercial supercapacitors.
Co-reporter:Qingliang Shou, Jipeng Cheng, Li Zhang, Bradley J. Nelson, Xiaobin Zhang
Journal of Solid State Chemistry 2012 Volume 185() pp:191-197
Publication Date(Web):January 2012
DOI:10.1016/j.jssc.2011.11.020
We report a one-step synthesis of a nanocomposite of goethite (α-FeOOH) nanorods and reduced graphene oxide (RGO) using a solution method in which ferrous cations serve as a reducing agent of graphite oxide (GO) to graphene and a precursor to grow goethite nanorods. As-prepared goethite nanorods have an average length of 200 nm and a diameter of 30 nm and are densely attached on both sides of the RGO sheets. The electrochemical properties of the nanocomposite were characterized by cyclic voltammetry (CV) and chronopotentiometry (CP) charge–discharge tests. The results showed that goethite/RGO composites have a high electrochemical capacitance of 165.5 F g−1 with an excellent recycling capability making the material promising for electrochemical capacitors.Graphical abstractThe reduced graphene oxide sheets are decorated with goethite nanorods. The as-prepared composite exhibits a high electrochemical capacitance with good recycling capability, which is promising for supercapacitor applications.Highlights► Ferrous ions act as reductant of graphite oxide and precursor of goethite nanorods. ► Goethite nanorods are attached on both sides of the reduced graphene oxide sheets. ► Composite exhibits a high specific capacitance and a good recycling capability. ► Composite is promising for supercapacitor applications.
Co-reporter:J.P. Cheng, R. Ma, D. Shi, F. Liu, X.B. Zhang
Ultrasonics Sonochemistry 2011 Volume 18(Issue 5) pp:1038-1042
Publication Date(Web):September 2011
DOI:10.1016/j.ultsonch.2010.12.008
Two-dimensional plate-like Fe3O4 nanocrystals were synthesized by a facile method using ultrasonic irradiation in aqueous solution at low temperature without protection from oxygen. The crystals were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier Transform infrared spectroscopy. The products subjected to ultrasound showed a two-dimensional morphology. The results obtained indicate that the morphologies of the magnetite crystals depend more on the ultrasonic irradiation than on the growth temperature. The thickness and width of the crystals increased with increasing temperature of the reaction medium. In addition, the magnetic hysteresis loop of the magnetite nanoplates was obtained at room temperature.Research highlights► Magnetite nanoplates were prepared by adding ferrous salt into alkali solution under ultrasonic irradiation at low temperature. ► The size of Fe3O4 nanoplates was influenced by the reaction temperature. ► The reported method is easily performed without severe conditions.
Co-reporter:J.P. Cheng, X. Chen, R. Ma, F. Liu, X.B. Zhang
Materials Characterization 2011 Volume 62(Issue 8) pp:775-780
Publication Date(Web):August 2011
DOI:10.1016/j.matchar.2011.05.008
Flower-like Co3O4 hierarchical microspheres composed of self-assembled porous nanoplates have been prepared by a two-step method without employing templates. The first step involves the synthesis of flower-like Co(OH)2 microspheres by a solution route at low temperatures. The second step includes the calcination of the as-prepared Co(OH)2 microspheres at 200 °C for 1 h, causing their decomposition to form porous Co3O4 microspheres without destruction of their original morphology. The samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffractormeter and Fourier transform infrared spectroscope. Some experimental factors including solution temperature and surfactant on the morphologies of the final products have been investigated. The magnetic properties of Co3O4 microspheres were also investigated.Flower-like Co3O4 microspheres are composed of self-assembled nanoplates and these nanoplates appear to be closely packed in the microspheres. These nanoplates consist of a large number of nanocrystallites less than 5 nm in size with a porous structure, in which the connection between nanocrystallites is random.Research Highlights► Flower-like Co3O4 hierarchical microspheres composed of self-assembled porous nanoplates have been prepared by a two-step method without employing templates. ► Layered Co(OH)2 microspheres were prepared with an appropriate approach under low temperatures for 1 h reaction. ► Calcination caused Co(OH)2 decomposition to form porous Co3O4 microspheres without destruction of their original morphology.
Co-reporter:J. P. Cheng;R. Ma;X. Chen;D. Shi;F. Liu ;X. B. Zhang
Crystal Research and Technology 2011 Volume 46( Issue 7) pp:723-730
Publication Date(Web):
DOI:10.1002/crat.201100144
Abstract
Two-dimensional plate-like Fe3O4 nanocrystals and nanoparticles could be synthesized by a simple one-step sonochemical method through ultrasonic irradiation in reverse co-precipitation solution at low temperature. This technique provided a facile and rapid way to prepare Fe3O4nanocrystals with different morphology and size. Magnetite nanoplates were synthesized with only ferrous salt adding into alkali solution, and adding ferric ions with low molar ratio in the metal salts solution would lead to the formation of very small magnetite nanoparticles (∼10 nm). The size of as-prepared magnetite nanoparticles increased with increasing reaction temperature and showed narrow size distribution, the standard deviation less than 2 nm. This investigation indicated that ferric ions had significant influence on the morphology of Fe3O4 nanocrystals. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Co-reporter:J.P. Cheng, X.B. Zhang, G.F. Yi, Y. Ye, M.S. Xia
Journal of Alloys and Compounds 2008 Volume 455(1–2) pp:5-9
Publication Date(Web):8 May 2008
DOI:10.1016/j.jallcom.2007.01.014
The present work describes a procedure for the preparation of iron oxide and carbide nanoparticles in carbon nanotube (CNT) matrix using the wet impregnation method and subsequent heat treatment in different atmosphere. In this way, two specific composites were produced with magnetite and cementite phase particles dispersed in CNTs, respectively, and cementite particles were encapsulated in graphene shells. As-prepared nanoparticles were all single crystalline and characterized by transmission electron microscopy (TEM), high-resolution TEM and X-ray diffraction. The magnetic properties of the resultant products were studied using vibrating sample magnetometer at room temperature.
Co-reporter:J.P. Cheng, X.B. Zhang, Y. Ye
Journal of Materials Processing Technology 2008 Volume 206(1–3) pp:180-183
Publication Date(Web):12 September 2008
DOI:10.1016/j.jmatprotec.2007.12.009
Multi-walled carbon nanotubes were decorated with nickel cations after nitric acid oxidization and the resultant product was calcined in an inert atmosphere. The samples were characterized by transmission electron microscopy and X-ray diffraction. The nickel oxide nanoparticles were initially dispersed on the external surfaces of carbon nanotubes. Continuous calcination in an inert atmosphere caused the reduction of nickel oxide nanocrystals to metallic nickel nanoparticles, where carbon nanotubes functioned as reducing agent. The metallic nickel nanoparticles were deposited on the surface of nanotubes and they could be used as catalyst in homogeneous or heterogeneous reactions.
Co-reporter:J.P. Cheng, Jiao Wang, Q.Q. Li, H.G. Liu, Y. Li
Journal of Industrial and Engineering Chemistry (25 December 2016) Volume 44() pp:1-22
Publication Date(Web):25 December 2016
DOI:10.1016/j.jiec.2016.08.008
SnO2 has been extensively investigated and used to detect a variety of gases for practical application. SnO2 nanomaterials with different morphologies and spatial assemblies have been fabricated in the last few years in order to improve the gas sensing performances. Meanwhile, many reports on the fabrication and gas sensing research using SnO2-based composites have been also published recently. In this work, we reviewed the recent developments of conductivity type of gas sensors for various SnO2-based composites, including SnO2/inorganic metal oxide, SnO2/carbon nanomaterials, SnO2/noble metals, SnO2/polymer, and SnO2/other materials in the last five years. Most of reports demonstrated that using a composite the properties of the gas sensing material could be greatly improved, such as high sensitivity, low working temperature, quick response, excellent stability or low detection limit. Each component had its unique effect to influence the sensing properties of the composite. The possible development directions were also discussed.Download high-res image (103KB)Download full-size image
Co-reporter:M. Li, F. Liu, X. B. Zhang and J. P. Cheng
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 43) pp:NaN30078-30078
Publication Date(Web):2016/10/06
DOI:10.1039/C6CP05119G
A variety of carbon materials varying from 0D to 2D, i.e. 0D nanoparticles, 1D carbon nanotubes (CNTs) and 2D reduced graphene oxide (rGO) are selected to in situ combine with Ni–Mn layered double hydroxide (LDH) to prepare electrode materials for supercapacitors. Through a simple solution method, hierarchical Ni–Mn LDH/carbon composites can be easily fabricated. A comparative study is carried out on the sandwich-like LDH/rGO, flower-like LDH/carbon black, turbostratic-structured LDH/CNTs and ternary LDH/CNTs/rGO for their structure, morphology, porous properties and electrochemical performances. The results show that the ternary Ni–Mn LDH/CNTs/rGO composite yields the highest specific capacitance of 1268 F g−1 in 2 M KOH electrolyte and a long lifespan, exhibiting great potential for supercapacitor applications. Meanwhile, investigation on the influence of the cation species of MOH (M = Li+, Na+ or K+) and the alkali concentration of the KOH electrolyte illustrates that increasing the concentration of the KOH electrolyte can benefit the capacitive performance of the electrode and that NaOH shows great advantages as an electrolyte for the Ni–Mn LDH/CNTs/rGO electrode due to its high capacitance and small resistance.
Co-reporter:Weifeng Zhang, Fu Liu, Qianqian Li, Qingliang Shou, Jipeng Cheng, Li Zhang, Bradley J. Nelson and Xiaobin Zhang
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 47) pp:NaN16337-16337
Publication Date(Web):2012/10/19
DOI:10.1039/C2CP43673F
A method for producing nanocomposites of transition metal oxides A3O4 (where A represents Mn, Fe or Co) and graphene nanosheets (GNS) is presented. The reduction of graphene oxide (GO) and the formation of A3O4 nanoparticles (NPs) were carried out simultaneously during the reaction. The electrochemical properties of A3O4–GNS nanocomposites as electrode materials for supercapacitors are investigated by cyclic voltammetry and galvanostatic charge–discharge tests. The as-prepared Mn3O4–GNS, Fe3O4–GNS and Co3O4–GNS nanocomposites exhibit large specific capacitance (708, 358 and 240 F g−1, respectively), high energy density (20, 10 and 7 W h kg−1, respectively) and good electrochemical stability (retention of 73%, 67.8% and 95.8%, respectively, after 1000 charge–discharge cycles). The excellent electrochemical performance of the A3O4–graphene nanocomposites indicates great potential in the application in commercial supercapacitors.
![Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]](http://img.cochemist.com/ccimg/138200/138184-36-8.png)
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