bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Energy Hybrid Capacitor with Quinone-Grafted Negative Electrode in Neutral Aqueous Electrolyte
Authors: Babuchowska Paulina , Béguin François 
Published: February 2020

It is known from literature that the capacitance performance of activated carbons (AC) can be enhanced by faradaic contributions owing to surface functionalities. Although many papers report on chemical oxidation of ACs to reach such objective, this method is not selective and leads to the formation of an important proportion of useless surface functional groups. Such disadvantage can be circumvented by using diazonium salts to graft molecules with the desired functionality on carbon, e.g., quinone-type. The redox activity of these molecules grafted on ACs has been demonstrated in sulfuric acid and potassium hydroxide aqueous media [1]. However, the materials display poor stability in KOH, and H2SO4 corrodes all non-noble metal current collectors used to build electrochemical capacitors (ECs). The objective of this presentation is to demonstrate the activity of anthraquinone-grafted carbons in non-corrosive aqueous media, such as neutral electrolytes [2], and to apply these materials as negative electrode in a hybrid capacitor where the positive electrode is from MnO2.
Anthraquinone (AQ) moieties were chemically grafted on the surface of the activated carbon DLC Supra 30 from Norit (Supra), giving the Supra-AQ carbon. The surface oxygenated functionality of as-received and grafted carbons was characterized by temperature-programmed desorption (TPD), using a TG equipment coupled with a mass spectrometer (MS). The larger mass loss for Supra-AQ (13.6 wt.%), compared to the pristine Supra one (2.6 wt.%), mainly related to CO evolution, confirms surface functionalization by quinone. The electrochemical response of Supra-AQ has been studied in 0.4 mol L−
1 phosphate buffer (pH=7.2) in order to avoid the shift of the redox peaks related with pH change during the measurements. In addition to the capacitive current related with the EDL formation, the CVs of Supra-AQ display reversible redox peaks characteristic of the grafted AQ molecules. As a result of grafting AQ, the capacity increases from 47 mAh g−
1 for Supra to 72 mAh g−
1 for Supra-AQ. During floating at 1.8 V, the hybrid Supra-AQ/MnO2 cell demonstrated stable capacitance and resistance, with 70% higher energy density than a Supra/MnO2asymmetric capacitor.
[1] G. Pognon, T. Brousse, L. Demarconnay, D. Bélanger, J.
Power Sources196 (2011) 4117.
[2] Q. Abbas, P. Ratajczak, P. Babuchowska, A. Le Comte, D. Bélanger, T. Brousse, F. Béguin, J. Electrochem. Soc. 162 (2015) A5148.
Interconnected Carbon Nanostructures for High Performance Supercapacitor Applications
Authors: Kim Hyun-Kyung , Kamali Ali Reza , Kumar R Vasant , Fray Derek John 
Published: February 2020

Graphene has a two-dimensional honeycomb structure consisting of a single layer of carbon atoms with a sp2-bonding configuration and has recently attracted significant attention owing to its unique properties, which include an exceptionally high specific surface area and high electrical and thermal conductivities as well as mechanical and chemical stability. However, graphene sheets exhibit an extreme tendency to agglomerate or restack. This leads to a surface that is electrochemically less effective, low electrical conductivity, and an interlayer spacing that hinders access to electrolyte ions, thus limiting the use of the sheets in supercapacitor applications. Introducing carbonaceous materials such as metal oxide, carbon nanotubes (CNTs) between the graphene sheets is a viable strategy for preventing the sheets from agglomerating.
In this study, we report the scalable fabrication of a high-quality hierarchical interconnected carbon nanostructure, combining two-dimensional graphene nanosheets and one-dimensional graphene nanoscrolls from graphite by a simple hightemperature molten salt method. The electrode using the prepared material exhibited high reversible specific capacitance, excellent rate capability, and good cyclability because of their unique interconnected networks of carbon nanostructures with high electrochemically active surface area and high electrical conductivity.
More details on the synthetic procedure, electrochemical and structural properties will be presented at the meeting.
Preparation and Electrochemical Properties of the Pouch-Type Edlc
Authors: Kim Ick-Jun , Yang Sunhye , Lim Sang-Min , Koo Bo-Kun 
Published: February 2020

Long-term reliability and high power characteristic of the electric double layer capacitor (EDLC) is excellent but it is difficult to miniaturize due to the small energy density (about 5-6Wh / L). This low energy density makes it difficult to retrofit into a limited space in a car or transportation fields.
As a way to increase the energy density of the cylindrical EDLC in commercialization, some companies have developed a pouch type EDLC. The pouch type EDLC has an energy density of about twice the cylindrical EDLC, enabling the miniaturization of the module. However, the pouch-shaped EDLC is not a good long-term reliability due to the swelling phenomenon caused by the reaction between the electrolyte and the electrode.
In this study, as a way of solve the problem, we have investigated the effects of sheet-laminating electrode technology, positive/negative electrode mass ratio, electrolyte, assembly technologies and evaluation techniques on the electrochemical properties of the pouch type EDLC.
Cycling Performance of Ppy Derived Carbon Based Symmetric Supercapacitors in Aqueous Electrolyte
Authors: Bello Abdulhakeem , Barzegar Farshad , Madito Moshawe Jack , Momodu Damilola Yusuf , Khaleed Abubakar Abubakar , Masikhwa Tshifhiwa Moureen , Dangbegnon Julien Koudio , Manyala Ncholu 
Published: February 2020

Electrochemical capacitors (ECs) also known as supercapacitors have attracted significant interest for the development of next generation of energy storage systems. ECs are characterized by their high power density and low energy density when compared with batteries [1,2]. ECs are suitable for transient energy saving application such as energy capture during braking in vehicles, in construction equipment such as cranes and for opening of doors in the A380 Jumbo jet, portable and flexible electronics [1]. However, the performance of ECs devices for most of these applications is exclusively dependent on the physicochemical properties of the electrode materials. Electrode materials with diverse dimensionalities such as 1D, 2D and 3D nanostructures have been explored to improve supercapacitive properties by taking advantages of the unique ability of the different nanostructure for ion propagation and charge storage [3,4]. The stability of supercapacitors is a very important feature for characterization of ECs devices. The traditional method of evaluating the stability is via the constant current charge-discharge (CCCD) cycling over several thousands of cycles which in many cases does not show degradation to the ECs devices. As an alternative to this, voltage holding or floating test has been proposed as a reliable technique to test the stability of electrode materials [5,6]. Here we report on the performance (speciﬁc capacitance) of symmetric capacitors based on mesoporous PPY derived carbons and the stability of the symmetric capacitors based on voltage holding (floating conditions) operating in aqueous electrolytes evaluated by cyclic constant current charge-discharge tests. Variation in the speciﬁc capacitance values with the floating conditions shows a good cycling life performance in alkaline electrolyte for ~190 h with slight degradation observed after 140 h.

References

[1] Simon P, Gogotsi Y. Materials for electrochemical capacitors. Nat Mater 2008;7:845–54.
[2] Conway BE. Electrochemical Supercapacitors: Scientific Fundamentals and Technological Applications. Kluwer Academic/Plenum: New York; 1999.
[3] Simon P, Gogotsi Y. Capacitive energy storage in nanostructured carbon--electrolyte systems. Acc Chem Res 2012;46:1094–103.
[4] Yan J, Wang Q, Wei T, Fan ZJ. Recent Advances in Design and Fabrication of Electrochemical Supercapacitors with High Energy Densities. Adv Energy Mater 2014;4:43.
[5] Weingarth D, Noh H, Foelske-Schmitz A, Wokaun A, Kötz R. A reliable determination method of stability limits for electrochemical double layer capacitors. Electrochim Acta 2013;103:119–24.
[6] Weingarth D, Foelske-Schmitz A., Kötz R. Cycle versus voltage hold - Which is the better stability test for electrochemical double layer capacitors? J Power Sources 2013;225:84–8.
Reactor R&D: Effect of Plasma Additives on Endohedral Metallofullerene and Empty-Cage Fullerenes
Authors: Stevenson Steven , Budd Sarah K , Kime Brittany L 
Published: February 2020

Metallofullerenes encapsulating metallic nitride clusters represent exciting molecules for fundamental study and application development. Mixed-metal nitride clusters are also of interest due to their dissimilar metals. The first step in providing these endohedrals to the scientific community is their synthesis, such as in an electric-arc reactor. Our hypothesis is that we can tune the fullerene product distribution in soot by varying the chemicals that we add to cored graphite rods. In this presentation, our results will demonstrate that plasma additives do permit us to selectively make different types of fullerenes.
Thermal Conductivity of Ultrananocrystalline Diamond/Nonhydrogenated Amorphous Carbon Composite Films Prepared By Coaxial Arc Plasma Deposition
Authors: Takeichi Satoshi , Nishiyama Takashi , Kohno Masamichi , Takahashi Koji , Katamune Yuki , Yoshitake Tsuyoshi 
Published: February 2020

Diamond possesses the highest thermal conductivity (2 × 103 Wm-1K-1) in all bulk materials, owing to low phonon scattering in diamond. Since phonon scattering is drastically enhanced by grain boundaries, the thermal conductivity of polycrystalline diamond films is strongly dependent on the grain size. The thermal conductivity of ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite (UNCD/a-C:H) films comprising a large number of UNCD grains with diameters of less than 10 nm and an a-C:H matrix have been prepared mainly by chemical vapor deposition (CVD). The highest thermal conductivity reported so far is 12 Wm-
1K-
1, which is comparable with that of sp3-rich non-hydrogenated amorphous carbon (a-C). It has been reported for a-C:H and UNCD/a-C:H films that the thermal conductivity is degraded by the incorporation of H atoms in the films.
Recently we have realized the formation of UNCD/a-C films comprising UNCD grains and an a-C matrix, by coaxial arc plasma deposition (CAPD). CAPD does not necessarily require a hydrogen atmosphere during the deposition for the formation of diamond grains. So far, the thermal conductivity of hydrogen-free UNCD/a-C films has never been studied because H atoms are unintentionally incorporated into the films from source gases in CVD. In this study, UNCD/a-C films were deposited under a base pressure, and the thermal conductivity of the films were measured for the first time to our knowledge.
UNCD/a-C films were deposited on n-Si substrates at base pressures of less than 10-4 Pa and the substrate temperature of 550 °C using coaxial arc plasma gun equipped with a graphite target. Mo films with the thickness of 80 nm were deposited on the UNCD/a-C films by sputtering for the TDTR. The thermal conductivity of the UNCD/a-C films was measured by a time-domain thermoreflactance (TDTR) technique.
The thermal conductivity of the UNCD/a-C films was estimated to be 23.7 Wm-
1K-
1 by TDTR. The thermal conductivity is evidently higher than that of UNCD/a-C:H prepared by CVD. Two reasons for it are supposed. One is that an a-C in UNCD/a-C is probably advantageous for thermal conduction as compared with an a-C:H in UNCD/a-C:H, since it has been reported for a-C:H that the thermal conductivity decreases with increasing hydrogen content in a-C:H. The other is that UNCD/a-C does not contain hydrogen atoms that prevent from phonon scattering, whereas the preferential existence of hydrogen atoms at grain boundaries between UNCD grains and those between UNCD grains and an a-C:H matrix enhances phonon scattering for UNCD/a-C:H films prepared by CVD, which results in a decrease in the thermal conductivity. Further details will be presented in the conference.
Field Emission from Titanium-Coated Carbon Nanotubes Grown on Micron-Sized Silicon Pillar Arrays
Authors: Uh Hyung Soo , Park Sangsik 
Published: February 2020

Carbon nanotubes (CNTs) have attracted great attention because of their unique physical properties such as high mechanical strength, thermal stability and electrical properties[1]. Because CNTs have high electron emission efficiency at low voltage due to their high aspect ratio, CNTs have been regarded as the most efficient electron emitter among various materials such as metal, semiconductor. However, the electric-field-screening effect of the dense CNTs and relatively high work function of CNTs (~ 5 eV) degrades the emission performance significantly[2,3]. CNTs grown on uneven substrate can reduce electric-field-screening effect and coating of CNTs with lower work function leads to enhanced field emission. In particular, it is reported that the coating Titanium (Ti) on CNTs affects the work function and the substantial change in surface morphology of CNTs most significantly[4].
In this paper, we report the combined effect of suppression of electric-field-screening and lower work function on field emission characteristics by Ti-coated CNTs on micron-sized silicon (Si) pillar arrays. Micron-sized Si pillar arrays are formed using conventional photolithography process including reactive ion etching by mixture gas of SF6 and Ar. CNTs are grown on Invar(52% Fe-42% Ni-6% Co alloy) catalyst using C2H2 as a source gas by inductively-coupled plasma-enhanced chemical vapor deposition. Then, Ti with 5 nm thickness is optionally coated on CNTs by sputtering method and field emission behaviors are investigated in a diode configuration in the vacuum of ~10-7 Torr.
Field enhancement factor for CNTs on Si pillar arrays was higher by 15% compared with that of CNTs on Si. The application of Ti on CNT surface reduced turn-on field by 30% further compared with that of pristine CNTs. In addition, coating of CNTs also improved emission stability by strengthening the adhesion between CNTs and substrate. We expect that the Ti-coated CNTs grown on micron-sized silicon pillar arrays can be excellent electron sources, providing a very stable current at very low ﬁelds by reduction of electric-field-screening effect and effective work function of emitters..

References:
[1] M. S. Dresselhaus, G. Dresselhaus, P. Avouris, Carbon Nanotubes: Synthesis, Structure, and Application, Springer, Berlin (2001).
[2] M. Shiraishi, M. Ata, Carbon 39 (2001) 1913.
[3] L. Nilsson, O. Groening, C. Emmenegger, O. Kuettel, E. Schaller, L. Schlapbach, H. Kind, J. M. Bonard, K. Kern, Appl. Phys. Lett. 76 (2000) 2071.
[4] Y. Cho, C. Kim, H. Moon, Y. Choi, S. Park, C.K. Lee, S. Han, Nano Lett. 8 (2008) 81.

Figure 1
Observation of Ferromagnetic Semiconductor Behaviors from Graphene Doped with Manganese-Oxide By Electrochemical Method
Authors: Park Chang-Soo , Qiu Dongri , Shon Yoon , Kim Eun Kyu 
Published: February 2020

Ferromagnetic semiconductors have attracted much attention in the field of spintronic application, because future electronic devices will have a switchable magnetic ordering in semiconductors for exploiting spin rather than charge. The key importance of the magnetic semiconductor is the Curie temperature to maintain the ferromagnetic ordering at room temperature. A high Curie temperature above room temperature has been shown in carbon-based materials. Recently, graphene which is an atomically monolayer graphite, has been an important issue for future spin electronic devices due to the high mobility and superb material properties. Especially, a theoretical result showed that graphene with defects behaves like a diluted magnetic semiconductor (DMS). In general, sp2 hybridized carbon atoms in graphene have an unsaturated dangling bond, which induces various surface modifications. Therefore, doping onto graphene easily leads to modification of the electronic structure, magnetic property, and carrier density.
In this work, we report an electrochemical doping of manganese-oxide onto graphene, and also investigate the ferromagnetic semiconductor behavior from the manganese-oxide doped graphene. We have doped a manganese-oxide onto graphene by an electrochemical method. Graphene showed a clear ferromagnetic semiconductor behavior after doping of manganese-oxide. The manganese-oxide doped graphene has a coercive field (Hc) of 232 Oe at 10 K, and has the Curie temperature of 270 K from the temperature-dependent resistivity using transport measurement. The ferromagnetism of manganese-oxide doped graphene attributes to the double-exchange from the coexistence of Mn3+ and Mn4+ on the surface of graphene. In addition, the semiconducting behavior is caused by the formation of manganese-oxide on graphene.
Chemical Etching and Transfer for Fabrication of Transparent Graphene Electrodes
Authors: Ishihara Masatou , Okigawa Yuki , Yamada Takatoshi , Hasegawa Masataka 
Published: February 2020

Conventional transparent electrodes make use of indium tin oxide (ITO) and are commonly used in touch screens, ﬂat panel displays and solar cells. Nearly 90% of ITO film market is for the touch screen application, which is expected to grow more and more in the future. Graphene is potential candidates for transparent conductive films for electrical and optoelectronic devices and various other applications due to its high electrical conductivity, chemical and physical stability. High-quality graphene films have been synthesized by microwave plasma treatment of a copper substrate with Joule heating using low concentration carbon source.
The copper foils with A4 (211 mm X 297 mm) size are used as substrate. Few-layer graphene was deposited on the copper foil for a few minutes. The transfer of the graphene films to a desired target substrate is enabled by the wet-etching of the underlying copper foil. This is carried out by treating the film with an aqueous (NH4)2S2O8 solution after a support material is covered on the graphene/copper surface, in our case a surface protective sheet. The graphene/sheet film is placed on the 188-mm thick polyethylene terephthalate (PET) substrate (graphene facing the surface). The surface protective sheet is removed from a sheet/graphene/PET film. We measured the transmittance and sheet resistance of the graphene/PET by using a haze meter and a four probe method, respectively.
The transmittance was 96% (except PET substrate) and the sheet resistance was about 500 ohm. Subsequently, graphene/PET film was doped with gold (III) chloride solution to decrease its sheet resistance. After doping processes, the sheet resistance of the graphene/PET films decreases below 150 ohm.
Acknowledgment: This work is mainly based on results obtained from a project supported by
New Energy and Industrial Technology Development Organization (NEDO).
Graphene Based Electronic Textiles Fabricated with Natural Materials
Authors: Jeon Jun Woo , Han Songlee , Shin Dong Seok , Kim Byung Hoon 
Published: February 2020

High-performance carbon-based electronic textiles have recently been considered as the potential components for low-cost, multifunctional flexible and wearable electronics. Although many promising results have been reported to fabricate carbon textiles, they are not adoptable to the current textile industry, such as, nylon, cotton, polyester, and silk due to their chemical stability. Here, we report a facile way to prepare fully conductive, flexible, and stable reduced graphene oxide (RGO)-based textiles from yarns to fabrics using electrostatic interaction and hydrogen bonding.
The electronic textiles using graphene oxide (GO) was fabricated by two methods. First the currently used textiles such as nylon, cotton, and polyester were functionalized with bovine serum albumin (BSA) by soaking 0.5 wt% BSA solution for 10 min a room temperature. The prepared BSA-coated textiles were immersed in 1.0 mg/ml GO solution with mild shaking. As a result, GO-wrapped textiles were obtained. In order to endow the conducting property in these textiles, the GO-wrapped textiles were reduced by hydroiodic acid or thermal treatment. After reduction process, the conductivity reached up to 10 S/cm, which can light a LED lamp. This conducting textile fabricated with cotton, polyester, and nylon can be achieved by BSA through the hydrogen bonding between the protein (BSA) and graphene oxide. Using this property, we also synthesized the electronic textiles with cocoon silk and spider web. Since they already have proteins, the electronic textiles was fabricated without BSA, which was produced by simply dipping the silk and spider web into the GO solution. Its conductivity is comparable to that with BSA. These electronic textiles exhibit excellent electromechanical stability under severe mechanical deformation and a large number of repetitive bending cycles.

Figure 1
The Role of Graphene Nanostructures on Colloidal Quantum Dot Photovoltaic Devices
Authors: Tavakoli Mohammadmahdi , Tavakoli Razieh , Simchi Abdolreza , Fan Zhiyong 
Published: February 2020

PbS quantum dots (QDs) have received considerable attention in the past decade due to their low-cast solution processing, bandgap tenability by control the size, and multiexciton generation make them particularly attractive as an active absorbing layer in optoelectronic devices such as solar cells. Recently, combining semiconductor quantum dots and graphene are a new strategy to improve the optoelectronic properties of photovoltaics devices. Herein, we have reviewed our recent works which are expolred the role of graphene as a passivation agent on the surface of PbS QDs and an interface layer between the electron transfer layer and absorber layer. First, we have demonstrated that the graphene can wrap the surface of PbS QDs and passivate the deep trap states by using a novel solution proces. Simulation by density functional theory of a prototypical model of a non-stoichiometric Pb-rich core (400 atoms) coated by graphene (20 atoms for each graphene sheet) indicates the possibility of surface passivation of (111) planes of PbS with graphene resulting in a decrease in trap states and recombination sites. The graphene coating of the PbS quantum dots decrease the exciton lifetime up to 0.78 µs as compared to 1.2 µs for the oleic acid passivated PbS quantum dots due to the fast extraction of carriers. We have employed PbS/graphene as well as Cd-doped PbS/graphene quantum dots as active layers of bulk heterojunction solar cells, and achieved solar power conversion efficiencies of 3.6% and 4.1%, respectively. In addition to the surface passivation role, a thin layer of graphene as an interface layer can increase the performance of PbS QDs device due to the improvement of carriers transfer and enhancement of current density. In our work, a simple and novel method is employed to synthesize a new structure of graphene, i.e. hollow graphene. In this regards., ZnO-Graphene QDs nanocomposite synthesized by a solution method and then ZnO QDs were dissolved from the structure using an acidic solution to obtain hollow graphene. Afterward, this structure was utilized in PbS QDs solar cell in order to improve the carriers transport. It is shown that holow graphene electrodes enhance electron extraction, yielding 30% improvement in performance compared with conventional device.

Figure 1