Nanostructured Graphenes and Metal Oxides for Fuel Cell and Battery Applications

2013 ◽  
Vol 705 ◽  
pp. 126-131 ◽  
Author(s):  
Zhe Fei Li ◽  
Jian Xie ◽  
Lia Stanciu ◽  
Yang Ren
Keyword(s):  
Composite Material ◽  
Graphene Oxide ◽  
Fuel Cell ◽  
Metal Oxides ◽  
Surface Area ◽  
Current Density ◽  
Graphene Sheets ◽  
Nanoparticle Composites ◽  
A Current

Graphene/spacer nanoparticle composites were prepared by reducing graphene oxide with hydrazine in the presence of different contents of polyaniline nanoparticles. In-situ cryo-TEM image of GO-spacer solution shows that spacer nanoparticles are anchored on GO sheets. During the reduction, as-adsorbed spacer nanoparticles were sandwiched between layers of graphene. These spacer nanoparticles act as spacers to create gaps between neighboring graphene sheets, resulting in higher surface area. Graphene/spacer nanocomposites exhibited highest specific surface area of 1500 m2/g. Utilizing this composite material, a supercapacitor with specific capacitance of 267 F/g at a current density of 0.1 A/g was achieved.

Microstructure and Properties of Co@RGO/Cu Composites by One-Step In Situ Reduction Method

2020 ◽  
Vol 993 ◽  
pp. 646-653
Author(s):  
Shao Hui Liu ◽  
Yu Zhao ◽  
Xu Ran
Keyword(s):  
Composite Material ◽  
Graphene Oxide ◽  
Reduction Method ◽  
Pure Copper ◽  
Copper Matrix ◽  
Comprehensive Properties ◽  
Plasma Sintering ◽  
Reduced Graphene ◽  
One Step

In order to improve the interfacial bonding between graphene and copper and improve the dispersibility of graphene in the copper matrix, a novel method was used to prepare graphene. Firstly, graphene oxide (GO) was prepared by the modified Hummer's method, and then the reduced graphene oxide-supported cobalt nanoparticle composite powder (Co@RGO) was prepared by one-step in-situ reduction method. The fabricated materials were mixed with copper powder to obtain various volume fractions. The powder mixture was subjected to compression and discharge plasma sintering (SPS) to prepare a bulk copper-based composite material. The microstructure and its comprehensive properties were studied by SEM, TEM, XRD, FTIR and Raman. The results show that the agglomeration of graphene can be effectively inhibited after the cobalt nanoparticles supported on the graphene surface. The proper amount of Co@RGO could be uniformly dispersed in the copper matrix. The composite material showed a high electrical conductivity (>86% IACS), and the Vickers hardness also increased by about 30% compared with pure copper.

Formation of Buried Sio2 By High Dose Implantation of Oxygen at Room and Liquid Nitroeen Temperatures

1985 ◽  
Vol 53 ◽  
Author(s):  
F. Namavar ◽  
J. I. Budnick ◽  
F. H. Sanchez ◽  
H. C. Hayden
Keyword(s):  
Liquid Nitrogen ◽  
Current Density ◽  
Room Temperature ◽  
Rutherford Backscattering ◽  
High Dose ◽  
Crystalline Quartz ◽  
Oxygen Ions ◽  
High Dose Implantation ◽  
A Current

ABSTRACTWe have carried out a study to understand the mechanisms involved in the formation of buried SIO2 by high dose implantation of oxygen into Si targets. Oxygen ions were implanted at 150 keV with doses up to 2.5 X 1018 ions/cm2 and a current density of less than 10 μA/cm2 into Si 〈100〉 at room and liquid nitrogen temperatures. In-situ Rutherford backscattering (RBS) analysis clearly indicates the formation of uniform buried SIO2 for both room and liquid nitrogen temperatures for doses above 1.5 X 1018/cm2.Oxygen ions were implanted at room temperature into crystalline quartz to doses of about 1018 ions cm2 at 150 keV, with a current density of 〈10〉10 μA/cm2. The RBS spectra of the oxygen implanted quartz cannot be distinguished from those of unimplanted ones. Furthermore, Si ions were implanted into crystalline quartz at 80 keV and dose of 1 X 1017 Si/cm2, and a current aensity of about 1 μA/cm2. However, no signal from Si in excess of the SiO2 ratio could be observed. Our results obtained by RBS show that implantation of either Si+ or O into SiO2 under conditions stated above does not create a layer whose Si:O ratio differs measurably from that of SiO2.

In situ topotactic synthesis of a porous network Zn2Ti3O8 platelike nanoarchitecture and its long-term cycle performance for a LIB anode

CrystEngComm ◽  
2018 ◽  
Vol 20 (45) ◽  
pp. 7329-7336 ◽  
Author(s):  
Xingang Kong ◽  
Xing Wang ◽  
Dingying Ma ◽  
Jianfeng Huang ◽  
Jiayin Li ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Exchange Reaction ◽  
Current Density ◽  
Cycle Performance ◽  
Porous Network ◽  
Ion Exchange Reaction ◽  
Topotactic Transformation ◽  
A Current

Porous network Zn2Ti3O8 platelike nanoarchitecture was prepared by an ion exchange reaction and further in situ topotactic transformation, and it exhibited an enhanced reversibility capacity of 408 mA h g−1 after 1000 cycles at a current density of 1 Ag−1.

On the Chemical Reduced Large Specific Surface Area Graphene Oxide and its Electrochemical Performances

2015 ◽  
Vol 723 ◽  
pp. 615-618
Author(s):  
Li Lai Liu ◽  
Hai Jiao Zhang ◽  
Shuang Li ◽  
Chao Yang ◽  
Pei Xia Yang
Keyword(s):  
Graphene Oxide ◽  
Current Density ◽  
High Current Density ◽  
Chemical Reduction ◽  
High Capacity ◽  
Lithium Ion ◽  
Expanded Graphite ◽  
Raw Material ◽  
Graphene Sheets ◽  
Electrochemical Performances

Graphene oxide is prepared by modified Hummers method with the expanded graphite prepared from large flake graphite as raw material. The large tracts of graphene sheets prepared by ascorbic acid chemical reduction of graphite oxide are characterized by scanning electron microscope and X-ray diffraction. The electrochemical performances of graphene sheets are studied successively. The results show that large tracts of graphene sheets as an anode for lithium-ion batteries exhibits a high capacity of 1693 mAh·g-1 after initial discharge at a current density of 100 mA·g-1 and remains 426 mAh·g-1 after 100 cycles. The graphene sheets show good cycling stability even at high current density. The reversible specific capacities remains 218 mAh g-1 at the current densities of 1000 mA g-1 after 100 cycles.

High Reversible Capacity of Nitrogen-Doped Graphene as an Anode Material for Lithium-Ion Batteries

2014 ◽  
Vol 1070-1072 ◽  
pp. 459-464
Author(s):  
Chang Jing Fu ◽  
Shuang Li ◽  
Qian Wang
Keyword(s):  
Graphene Oxide ◽  
Electron Microscope ◽  
Lithium Ion Batteries ◽  
Current Density ◽  
Lithium Ion ◽  
X Ray ◽  
Nitrogen Doped ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene ◽  
A Current

Nitrogen-doped graphene (N-rGO) was synthesized in the process of preparation of reduced graphene oxide from the expanded graphite through the improved Hummers’ method. The morphology, structure and composition of nitrogen-doped graphene oxide (GO) and N-rGO were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The nitrogen content of N-rGO was approximately 5 at.%. The electrochemical performances of N-rGO as anode materials for lithium-ion batteries were evaluated in coin-type cells versus metallic lithium. Results showed that the obtained N-rGO exhibited a higher reversible specific capacity of 519 mAh g-1 at a current density of 100 mA⋅g-1 and 207.5 mAh⋅g-1 at a current density of 2000 mA⋅g-1. The excellent cycling stability and high-rate capability of N-rGO as anodes of lithium-ion battery were attributed to the large number of surface defects caused by the nitrogen doping, which facilitates the fast transport of Li-ion and electron on the interface of electrolyte/electrode.

Dynamic Behavior and In-Situ Diagnostics of PEFCs

2006 ◽  
Author(s):  
Kaspar Andreas Friedrich ◽  
Till Kaz ◽  
Stefan Scho¨nbauer ◽  
Heinz Sander
Keyword(s):  
Fuel Cell ◽  
Density Distribution ◽  
Current Density ◽  
Single Cells ◽  
Current Density Distribution ◽  
Bipolar Plate ◽  
Life Cycles ◽  
Operating Conditions ◽  
Bipolar Plates

During fuel cell operation the electrochemical activity often is not homogenous over the electrode area. This may be caused by an non-uniform water content in the membrane, an inhomogeneous temperature distribution, and reactant gradients in the cell. Consequently a variation of the current density over the cell area occurs which tends to result in inferior performance. For in situ measurements of the current density distribution in fuel cell stacks a segmented bipolar plate was developed. The segmented bipolar plate was first tested in single cells with stack endplates to verify the function of all components. The tests showed that the measurement tool works very reliable and accurate. The insight in an operating fuel cell stack via current density distribution measurement is very helpful to investigate interactions between cells. Results can be used to validate models and to optimise stack components, e.g. flow field and manifold design, as well as to detect the best stack operating conditions. By applying segmented bipolar plates as sensor plates for stack system controls an improved performance, safe operation and longer life cycles can be achieved. The developed segmented bipolar plates with integrated current sensors were used to assemble a short stack consisting of 3 cells; each of them having an active area of 25cm2 divided into 49 segments. The design of the bipolar plate proofed very suitable for easy assembling of single cells and stacks. First measurement results show that different current distributions can appear in the cells and these can vary from cell to cell, depending on the operating conditions of the stack. Electrical coupling between the cells was investigated and found to be only marginal for the assembly used.

Analysis of Single PEM Fuel Cell Performances Based on Current Density Distribution Measurement

2005 ◽  
Vol 3 (3) ◽  
pp. 351-357 ◽  
Author(s):  
P. C. Ghosh ◽  
T. Wüster ◽  
H. Dohle ◽  
N. Kimiaie ◽  
J. Mergel ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Density Distribution ◽  
Current Density ◽  
Operating Temperature ◽  
Current Density Distribution ◽  
Polymer Electrolyte Fuel Cells ◽  
Operating Conditions ◽  
Cathode Side ◽  
Gas Pressures

A new in situ measurement method of mapping the current density distribution in polymer electrolyte fuel cells (PEFC) is used to analyze the performance of a fuel cell under different operating conditions. The present method is useful in investigating the current density distribution in a single cell as well as a stack, which carries the information about the local reactant activity over the electrode area. It was found that the current density close to the gas inlets is strongly influenced by the reactants' relative humidity. The performance close to the gas outlets is greatly influenced by the inlet gas pressures and the stoichiometry factors of the reactant gases, mainly on the cathode side. It was also observed that the performance of the fuel cell drops with the increase in operating temperature if the reactant gases are not sufficiently humidified.

scholarly journals Enhancement of the electro-activated persulfate process in dye removal using graphene oxide nanoparticle

2021 ◽  
Author(s):  
Bita Ayati ◽  
Zeinab Ghorbani
Keyword(s):  
Graphene Oxide ◽  
Current Density ◽  
Dye Removal ◽  
Electrochemical Process ◽  
Sodium Persulfate ◽  
Sulfate Concentration ◽  
Oxide Nanoparticle ◽  
Acid Blue ◽  
A Current ◽  
Activated Persulfate

Abstract This study aimed to improve the speed of the electrochemical process by graphene oxide nanoparticle as a current accelerator in Acid Blue 25 removal from aqueous solutions. To do so, the effect of different parameters including pH, dye concentration, sodium persulfate concentration, the ratio of sodium persulfate to iron (II) sulfate concentration, current density, and the distance between electrodes was investigated on dye removal. Under optimal conditions of pH = 5, dye concentration = 200 mg/L, sodium persulfate concentration = 500 mg/L, iron (II) sulfate concentration = 100 mg/L, current density = 16.67 mA/cm2, and electrode distance = 2 cm, 95% of dye was removed after 60 minutes in the electro-activated persulfate process; while the modified electro-activated persulfate process achieved 95% dye removal after only 40 minutes under the same conditions. This system was able to remove 90% of dye after 60 minutes at a higher concentration (300 mg/L). Also, the modified electro-activated persulfate process obtained the removal of 80% of COD, and 54% of TOC after 180 minutes in the mentioned conditions, for the dye concentration of 300 mg/L.

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