bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bio-Polymer Derived Activated Carbons for Electrochemical Double Layer Capacitors
Authors: Chen Rong , Lipka Stephen M , Swartz Christopher R , Rogers Fon 
Published: February 2020

Electrochemical double layer capacitors (EDLCs), are energy storage devices featuring many advantages, including long cycle life, low internal resistance, and high power densities (i.e. fast charge/discharge rates). Due to these advantages EDLCs have drawn much attention recently, and have been applied to electric/hybrid vehicles, heavy-construction equipment, electronics, and grid utility storage. The most common electrode material for EDLCs is porous activated carbon with the advantages of low cost, abundant resources, and simple processing. In this present work, carbon materials for EDLCs were hydrothermally synthesized from low-cost bio-polymer precursors. Hydrothermal synthesis (HTS) uses simple equipment and runs under mild conditions; the process also uses environmentally friendly precursors and does not produce any hazardous waste. HTS provides a facile method for the development of inexpensive, high- performance carbon materials.
In this work, low cost precursors were obtained locally. The precursors were ground and mixed with DI water, and the solution was then sealed in a Teflon lined pressure vessel. The pressure vessel was heated to 200 °C for 24 hours. After the reactor cooled down, the as-synthesized carbons were harvested by filtration and dried in an oven at 120 °C overnight. The morphology of the as-synthesized carbons was characterized by scanning electron microscopy (SEM) as shown in Figure 1. The as-synthesized carbons went through a one-step activation, which increased the surface area to over 1000 m2/g, with 70% micro porosity. Electrodes were made, and tested in 1.8M TEMABF4in PC and 38% sulfuric acid. Cyclic voltammetry (CV) and galvanostatic charge-discharge tests were run on these activated carbons to study the electrochemical performance. The activated carbons showed very nice capacitor characteristics such as rectangular CV curves and very fast charge-discharge rates in both organic and aqueous electrolytes, as shown in Fig 2. The specific capacitance of these materials in organic electrolyte was ~90-120 F/g and had a volumetric capacitance of ~40-60 F/cc, while in aqueous electrolyte the gravimetric capacitance ranged from 180-200 F/g and 100-120 F/cc.
Supercapacitors Based on Mixture of Room Temperature Ionic Liquids Containing Specifically Adsorbed Iodide Anions
Authors: Thomberg Thomas , Tooming Tauno , Tõnurist Kerli , Siinor Liis , Jänes Alar , Lust Enn 
Published: February 2020

Applicability of room-temperature ionic liquids (RTILs) as electrolytes for electrical double layer capacitors (EDLCs), so-called supercapacitors and batteries has been discussed in many papers. RTILs have lower conductivity, higher viscosity and thus, narrower low temperature operation limit compared to aqueous and non-aqueous electrolytes. However, compared with volatile aqueous and organic electrolytes, RTILs are much safer in EDLCs applications. In order to improve the power and energy densities of EDLCs, various mixtures of ionic liquids have been investigated including systems of EMImBF4with EMImBr [1].
In the present studies 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) was chosen due to high bulk conductivity (k=13.6 mS cm-1). To increase the capacitance, EMImI was added because the noticeable increase in capacitance had been established within the potential region of I- ion specific adsorption for Bi(111)„ EMImBF4+ EMImI interface [2]. The electrochemical characteristics of this RTIL mixture have been characterized by cyclic voltammetry, electrochemical impedance spectroscopy, constant current charge/discharge and constant power discharge methods. Carbon used in these studies was synthesized from D-glucose by the hydrothermal carbonization method followed by additional pyrolysis and carbon dioxide activation steps (GDAC - D-glucose derived activated carbon) as described by Thomberg et al. [3].
Capacitance peaks in cyclic voltammetry curves (Fig. A) for EMImBF4 + EMImI mixture within the cell potential region from 0.8 to 1.2 V were established differently from the data for pure EMImBF4 and about 50% higher discharging charge Q values have been calculated at lower cell potential scan rate v≤10 mV s-1 in comparison with pure EMImBF4. According to the experimental energy and power relationships data, i. e Ragone plots (Fig. B), the addition of EMImI into EMImBF4increases noticeably the specific energy and specific power values of EDLC.

Acknowledgments

This work was supported by European Regional Development Fund Project 3.2.0501.10–0015 and Estonian Center of Excellence in Research Project 3.2.0101–0030 “High-technology Materials for Sustainable Development”.

References:

S. Yamazaki, T. Ito, M. Yamagata and M. Ishikawa, Electrochim. Acta.
86, 294 (2012).

L. Siinor, C. Siimenson, K. Lust and E. Lust, Electrochem. Commun., 35, 5 (2013).

T. Thomberg, T. Tooming, T. Romann, R. Palm, A. Jänes and E. Lust, J. Electrochem. Soc., 160(10), A1834 (2013).
Electrochemical Performances of Carbon Electrode Materials Depending on Electrode Density for Hybrid Capacitors
Authors: Yang Sunhye , Kim Ick-Jun , Park Jun-Woo , Yun Sungdo 
Published: February 2020

Supercapacitors are of practical interest owing to their high power electrical energy storage and exceptionally long cycle life. Also, it has been used and developed such as memory back up for electric home appliance and information transport devices, renewable energy and power assist for transportation and machinery, voltage sag and renewable energy sources for stable electric power. Significantly, electric double layer capacitor (EDLC) consist of stacked activated carbon shows superior high power characteristics whereas it has low energy density as a drawback. Therefore, hybrid capacitor is one of possible candidates and is developing for high energy density.
The hybrid capacitor is made up with activated carbon electrode for electric double layer capacity and anode for intercalation and de-intercalation of lithium ions. Although it shows inevitable increase of energy density [1-3], the total output power is lower than that the EDLC due to chemical reaction on the anode. To increase the power density, the decrease of intercalation length for low diffusion resistance is necessary. The hybridization of activated materials with carbon nanotubes, carbon nanofiber, and graphene is intriguing for the application of highly conductive cathode electrode.
Here, we introduce the preparation of carbon electrodes to enhance the output power on the anode without high-dimensional and high cost method. In general, high density electrode has high power characteristics because of low contact resistance. However, in this study, the decrease of electrode density can be increase dramatically the output power in the high current density. This result may give rise to the decrease of diffusion resistance due to the low electrode density and the stable surface electrolyte interface at the reacting surfaces.
Invited: Water Based AC/AC Supercapacitors Reaching the Performance of Systems in Organic Electrolyte
Authors: Béguin François , Frackowiak Elzbieta , Abbas Qamar 
Published: February 2020

It has been long time accepted that capacitors with activated carbon (AC) electrodes in aqueous electrolytes do not deliver a high energy due to their low voltage, e.g., 0.7 – 0.8 V in KOH and H2SO4. Recently, we have demonstrated that the voltage window can be dramatically enhanced by using salt solutions with pH close to 7 [1,2]. In that case, the over-potential for di-hydrogen evolution at the negative electrode is very high [3], and the voltage window can be extended up to 1.5 V with stainless steel current collectors [4]. In this presentation, we introduce a number of strategies to optimize the performance of these systems.
First, the corrosion of the positive current collector has been reduced by adding an inhibitor (sodium molybdate) to the electrolyte. Besides the capacitance of the positive electrode is slightly enhanced, allowing its maximum potential to be reduced. In these conditions, the system displays an excellent cyclability, up to 1.6 V, without remarkable oxidation of the positive AC electrode [4].
The second improvement is based on using the advantages of the pseudo-capacitance provided by the carbon/iodine interface, while keeping the large potential window allowed by alkali salt solutions. An AC/AC capacitor in the KI – Li2SO4 mixture displays capacitance values up to 400 F g-1 at voltage of 1.6 V [5]. These values lead to an energy density which is comparable to the one reached with the same carbon in Et4NBF4/acetonitrile at 2.3 V.
Finally, we have explored various routes to extend the operational temperature range to low values. We have designed a formulation of aqueous lithium sulfate electrolyte allowing the AC/AC capacitor system to operate down to -40°C with excellent charge propagation (Figure 1). At this temperature, the pseudo-faradic contribution due to hydrogen storage is kinetically blocked, and the system consequently works as a typical EDL one.
In summary, AC/AC capacitors in aqueous alkali sulfate solutions with appropriate additives are now able to reach the performance of organic systems, while using environmental friendly and cost effective components.

Acknowledgements: The Foundation for Polish Science is acknowledged for supporting the ECOLCAP Project realized within the WELCOME Program, co-financed from European Union Regional Development Fund.

References

[1] L. Demarconnay, E. Raymundo-Piñero, F. Béguin, Electrochem Commun. 12 (2010) 1275
[2] K. Fic, G. Lota, M. Meller, E. Frąckowiak, Energy Environ. Sci 5 (2012) 5842
[3] Q. Gao, L. Demarconnay, E. Raymundo-Piñero, F. Béguin, Energy Environ. Sci. 5 (2012) 9611
[4] P. Ratajczak, K. Jurewicz, P. Skowron, Q. Abbas, F. Béguin, Electrochim Acta (2014) DOI. 10.1016/j.electacta.2014.02.140
[5] „High energy electrochemical capacitor in mixed aqueous electrolyte”, International application PCT/PL2014/050002, 20 january 2014.
BiFeO3 Thin Films Prepared by ALD
Authors: Akbashev Andrew R. , Spanier Jonathan E. 
Published: February 2020

Bismuth ferrite (BiFeO3) is one of the most technologically promising multiferroics with a simple perovskite structure and high ferroelectric and antiferromagnetic ordering temperatures. High-quality heteroepitaxial growth of BiFeO3 thin films has been demonstrated mainly by PLD, MBE, RF sputtering and MOCVD, almost of them requiring ultrahigh vacuum and thus are rather expensive, particularly when used on an industrial scale. In contrast, ALD is relatively inexpensive and can produce atomically smooth coverage on structures with extremely high aspect ratio. In this talk we will discuss the growth of BiFeO3 thin films by ALD and the influence of the growth parameters on the phase composition of the resulting films. Briefly, the amorphous films were first grown and analyzed on Si wafers, SrTiO3(001), Nb:SrTiO3(001) at 250 C. Next, ex situ annealing was performed at various temperatures to study the crystallization process. According to XRD analysis and TEM imaging, the ALD-grown BiFeO3 films demonstrated a high crystallinity and epitaxial quality. Piezoresponse force microscopy showed an expected response of the ferroelectric phase. The ALD growth of BiFeO3 will provide a new way of convenient, technologically-oriented and commercially realizable deposition of a promising multiferroic for nanoelectronic devices.
This work was supported by the NSF DMR under 1124696 and by the ARO under W911.
Design Considerations for ZnO Transistors Made Using Spatial ALD
Authors: Nelson Shelby F. , Ellinger Carolyn R. , Tutt Lee W. 
Published: February 2020

We have used spatial atomic layer deposition (SALD) to fabricate a variety of thin film transistors using zinc oxide as the semiconductor and aluminum oxide as the insulator. The conductive electrodes are formed either from aluminum-doped zinc oxide, or from thermally evaporated metals. Spatial ALD can be performed at atmospheric pressure, and can grow coatings very quickly. Deposition occurs without a requirement for valve timing, by moving the substrate relative to the precursors flowing from a coating head. The proximity of the substrate to the coating head is controlled via a gas bearing design – allowing SALD to operate with purge times that are equivalent to the precursor exposure times (sub-second) unlike traditional chamber-based systems.
In this talk we will discuss examples of thin film electronics with architectures that are enabled by ALD, with a particular focus on spatial ALD. We use the well known conformality of ALD to build self-aligned, sub-micron channel length, vertical transistors. The vertical transistor electrical performance is impressive compared to amorphous silicon TFTs, for example, yet the alignment tolerances inherent in the fabrication process are large.
Our second approach to fabricating devices uses selective area deposition, with inkjet-printed inhibitor, to pattern all the active layers. We build full transistors and circuits using one inhibitor ink, the SALD system, and an oxygen plasma to clean the substrate. Performance of the resulting transistors and circuits match photolithographically patterned ones.
Promoted Platinum Catalytic Activity and Thermal Stability with Nano-Scale Cobalt Oxide Coating via Atomic Layer Deposition
Authors: Cao Kun , Huang Bin , Zhang Yihang , Liu Xiao , Shan Bin , Chen Rong 
Published: February 2020

Platinum nanoparticles (NPs) play an important role in the catalytic conversion of automotive exhaust. The catalytic performance is closely related to the number of active sites. One drawback of platinum catalyst is its tendency towards sintering under high temperatures which may occur during high engine loads. Sintering of Pt NPs will cause larger particles formation and a decrease in the number of active sites. [1]

Many methods have been tried to form core shell structures to encapsulate the metal nanoparticles with porous materials to minimize sintering.[2] The nanoparticles with a protective shell show good sintering resistance.[3] However in some cases the catalysis performance decreases because the thick protective shell blocks the access of the reactants. New methods are needed to improve the controllability of the coating layer thickness and structure to stabilize the metal nanoparticles and at the same time maintain the catalysis performance. Atomic layer deposition (ALD) shows it unique advantages in sub-nanometer thin film thickness control due to the self-limiting growth nature.[4] Recent works encapsulate the palladium nanoparticles with porous Al2O3 through ALD that effectively prevents sintering and coking in the ethane oxidation reactions.[5]

Here we report the use of active oxide layer to coat the platinum NPs for CO oxidation. Our results indicate that with proper thickness control of the coating layer the catalysts have good thermal stability. At the same time the platinum and the active ingredients in the oxide layer may also form alloy particles, further promoting the total catalysis performance.
Reference
[1] M A Asoro, D Kovar, Y Shao-Horn, P J Ferreira, Nanotechnology 21 (2010)
[2] Zhao M, Sun L, Crooks RM, J. Am. Chem. Soc. 120 (1998)
[3] Z Ma, S. Brown, J.Y. Howe, S.H Overbury, S Dai, J. Phys. Chem. C 112 (2008)
[4] Riikka L. Puurunen, J. Appl. Phys. 97, 121301 (2005)
[5] Lu. J. L, Fu. B. S, Kung, M.C, J W Elam, P C Stair, Science 8, 2405 (2012)
Precursor Development and Application for Atomic Layer Deposition
Authors: Chung Taek-Mo 
Published: February 2020

As a promising technique for thin film growth, atomic layer deposition (ALD) has been widely applied in various fields of microelectronics such as semiconductor, dielectric materials, metal electrode, and transparent conductive oxide as well as energy, display, and biotechnology. In the areas of electronics, the ALD technique needs appropriate precursors which have high vapor pressure, comparatively low deposition temperature, high deposition rate, and chemically and thermally stable during transportation from canister to deposition chamber. In many cases, the conventional metal complexes have been applied as precursors in ALD process without tuning the improvement of the characteristics to be required in device manufacture.
We have focused on the development of the target-oriented suitable metal precursors on the molecular level design for thin film growth by ALD. During the new precursor development, we have succeeded in preparing the optimum compounds for ALD thin film technology. The metal precursors newly synthesized at KRICT have been successfully adapted to deposit metal and metal oxide thin films using ALD in our laboratory and other academic research groups. In this presentation we will talk about our research results of design and synthesis of new metal precursors and their application to electronic devices with ALD, specially focusing on the highly concentrated precursors in electronic device manufacture.
Development of Continuous and Ultrathin Pt Electrocatalysts Using Plasma-Assisted ALD
Authors: Clancey Joel W. , Cavanagh Andrew S. , Kukreja Ratandeep , Kongkanand Anusorn , George Steven M. 
Published: February 2020

High cost of Pt prevents wide-spread application of fuel cell vehicles. Fine nanoparticles (3-5nm in diameter) are traditionally used in order to increase electrochemically active surface area. A continuous Pt film is more stable and has a 5-10 fold higher area-specific activity than Pt nanoparticles.1 This is only economically viable when the Pt film is less than ~3 nm thick.
Pt ALD usually yields Pt nanoparticles during initial film growth. We have shown earlier in work on flat substrates that tungsten, with a higher surface energy than platinum (3.5 J/m2 vs 2.5 J/m2), can serve as an adhesion layer to achieve Pt ALD films that are dense and continuous at thicknesses of ~1.5 nm.2,3

To fabricate a practical electrocatalyst we developed a plasma-assisted, open-ended rotary reactor to deposit W and Pt ALD films on the high surface area metal oxide particles. We also deposited the layers on 3M NSTF substrate, an oriented organic crystalline substrate.
Transmission electron microscopy (TEM) showed uniform and continuous ~3-5 nm Pt films on the TiO2 particles. The W ALD and Pt ALD films deposited on the 3M NSTF substrate were characterized using TEM with electron energy loss spectroscopy (EELS). The TEM-EELS analysis revealed W ALD and Pt ALD films with thicknesses of ~3 nm that were continuous and conformal on the high aspect ratio NSTF substrates. The production of these thin film on high surface area substrates demonstrates that it is possible to further reduce cost of fuel cell catalyst.

Acknowledgements

The authors thank Mark K. Debe, Edward M. Fischer, and Andrew Steinbach of 3M for providing non-platinized NSTF substrate. Thanks are also extended to Cristin Keary, Tom Moylan, and Peter Harvey for engineering support.

References

H. A. Gasteiger et al., Appl. Cat. B: Env. 56, 9 (2005).

L. Baker et al., Appl. Phys. Lett. 101, 111601 (2012).

US Patent 8,647,723.
Tuning Photoresponse of Ultrathin ZnO Films Using Few Angstrom Al2O3 Overlayers
Authors: Wu Fei , Myung Yoon , Banerjee Parag 
Published: February 2020

Ultra-thin ZnO films can be deposited with precise thickness control, good conformality and uniformity by atomic layer deposition (ALD). This strategy has been widely used in optical devices and solar cells.[i] However, ZnO with a thickness less than 10 nm – where surface effects dominate electronic transport properties, has been found to possess a high degree of electronic defects.[ii] These defects originate on the surface as unterminated, dangling bonds and degrade electronic and optoelectronic transport properties.[iii]
To understand the phenomena further, we report here temperature-based (80K-320K) conductance and photoresponse (Ion/Ioff) properties of 6.1 nm ZnO. Further, we track these parameters as a function of ALD Al2O3 ‘overlayers’ deposited on the same ZnO film. The temperature based Ion/Ioff is shown in Figure 1, left and the maximum Ion/Ioff is shown as a function of ALD Al2O3 overlayers in Figure 1, right. Based on these data, the Ion/Ioff ratio initially increases with the number of ALD Al2O3 layers and maximizes at 7 cycles of Al2O3 overlayer. It then decreases for additional ALD Al2O3 cycles. A maximum Ion/Ioff of 11.4x is obtained with 7 cycles of ALD Al2O3.
Activation energy (Ea) for conduction will be estimated using conductance vs. temperature curves.[iv] Accompanying data using XPS and photoluminescence will structurally probe the surface modification of the ZnO due to addition of the ALD Al2O3monolayers. These results lead to insights into the passivation mechanisms of ultrathin ZnO films with applications in a wide variety of electronic and optoelectronic devices.

Figure 1. Left - The Ion/Ioff vs. temperature (left) and, Right - The maximum Ion/Ioff plotted with number of ALD Al2O3 cycles. (*Ion/Ioffis defined by the light conductance over the dark conductance.)

[i] a) Lee, D.-J., Kim, H.-M., Kwon, J.-Y., Choi, H., Kim, S.-H., Kim, K.-B. Adv. Funct. Mater. 2011, 21, 448-455. b) Wang, J.-C., Weng, W.-T., Tsai, M.-Y., Lee, M.-K., Lee, M.-k., Horng, S.-F. Perng, T.-P., Kei, C.-C., Yu, C.-C. Meng, H.-F. J. Mater. Chem. 2010, 20, 862-866.
[ii] a) Cheun, H., Fuentes-Hernandez, C., Zhou, Y., Potscavage, W. J., Kim, S.-J., Shim, J., Dindar, A., Kippelen, B. J. Phys. Chem. C 2010, 114, 20713-20718. b) Na, J.-S., Scarel, G., Parsons, G. N. J. Phys. Chem. C 2010, 114, 383-388.
[iii] Cheun, H., Fuentes-Hernandez, C., Zhou, Y., Potscavage, W. J., Kim, S.-J., Shim, J., Dindar, A., Kippelen, B. J. Phys. Chem. C 2010, 114, 20713-20718.
[iv] Wu, F., Tian, L., Kanjolia, R., Singamaneni, S., Banerjee, P. ACS Appl. Mater. Interfaces, 2013, 5, 7693-7697.
Plasmonics and Metamaterials with Transparent Conducting Oxides
Authors: Abb Martina , Wang Yudong , Traviss D , Bruck R , de Groot C. H. , Chong Harold , Sepulveda Borja , Muskens Otto L. 
Published: February 2020

With the maturation of the field of plasmonics, there is an increasing interest to develop new materials for plasmonics and field-enhanced spectroscopy. In particular, the combination with complementary functionalities, such as active control, is of importance. Metal oxides form an interesting materials platform with many applications in catalysis, chemical sensing, transparent conductors or heat reflective coatings.
Here, I will present our recent results on the use of highly conductive metal oxides such as indium-tin-oxide (ITO) and aluminium-doped ZnO (AZO) in active plasmonics and metamaterials [1-4]. We can define three windows of operation for these materials, corresponding to the regimes of dielectric [1,2], metallic [3], and epsilon-near zero [4] response. By combining metal oxides with plasmonic materials such as gold and silver, we explore new types of hybrid response with the potential of electrical and picosecond optical control of plasmon resonances [1]. This includes combination of lithographically defined plasmonic nanostructures with coatings obtained using atomic layer deposition (ALD) [2].
Further in the mid infrared spectral range, the plasmonic response of highly doped metal oxides can be used for spectroscopic characterization of molecular species using Surface Enhanced Infrared Absorption [3]. We have developed new methods for the fabrication of metal oxide antennas and have demonstrated their use as plasmonic devices for infrared molecular fingerprinting. Finally, an intermediate regime is explored where the ITO permittivity approaches zero and the optical response is governed by superluminal group velocity enabling new plasmonic modes with large nonlinearity [4].

[1] M. Abb, Y. Wang, P. Albella, C. H. de Groot, J. Aizpurua, O. L. Muskens, ACS Nano 6, 6462 (2012)

[2] M. Abb, B. Sepulveda, H. M. H. Chong, O. L. Muskens, J. Opt. 14, 114007 (2012)

[3] M. Abb, Y. Wang, N. Papasimakis, C. H. de Groot, O. L. Muskens, Nano Lett 14, 346 (2014)

[4] D. Traviss, R. Bruck, B. Mills, M. Abb, O. L. Muskens, Appl. Phys. Lett. 102, 121112 (2013)