bluuebunny/crossref_metadata_2025_split huggingface dataset:
Examining the Charge Storage Mechanisms of Materials Used in Electrochemical Capacitors Using Electrochemical Impedance Spectroscopy
Authors: Donne Scott W , Dupont Madeleine F 
Published: February 2020

Electrochemical capacitors are a type of energy storage device which are characterised by their high specific energy, fast discharge rates and high cyclability. Electrochemical capacitors store energy in the electrical double layer which is formed at an electrode-electrolyte interface under an applied potential. These electrodes do not undergo any faradaic reactions and as a result, can charge and discharge very quickly and do not degrade significantly during cycling.
Pseudo-capacitors are a type of electrochemical capacitor in which the electrodes exhibit fast, highly reversible redox reactions in addition to double layer charging. This pseudo-capacitance increases the charge storage capabilities of these devices.
Electrodes used for electrochemical capacitors rely on high surface area materials to provide high capacitance, such as activated carbon. Whereas pseudo-capacitors utilise materials which can undergo fast redox reactions without causing any compositional or phase changes in the electrode, such as ruthenium dioxide and manganese dioxide.
Typically, electrochemical performance analysis of electrodes is conducted using potential sweep (cyclic voltammetry) or constant current charge discharge methods. These techniques provide a total capacitance for the electrode but do not allow for extensive analysis of the charge storage mechanisms. This is evident in the similar cycling behaviour of activated carbon, ruthenium dioxide and manganese dioxide, despite these materials having significantly different charge storage mechanisms.
In this work, these methods are used in conjunction with electrochemical impedance spectroscopy (EIS) to separate the capacitance arising from double layer charge storage compared to that stored through pseudo-capacitance. Three commonly used electrode materials were examined, each known to have different capacitance and charge storage mechanisms: (1) activated carbon, which has purely double layer capacitance in the order of ~150 F/g [1], (2) ruthenium dioxide, which exhibits pseudo-capacitance at the surface (due to its high conductivity) resulting in capacitance of ~900 F/g [2] and (3) manganese dioxide, which is reduced and oxidized throughout the bulk of the material leading to extremely high capacitance of 2000 F/g [3] (for electrodeposited thin films) and 260 F/g [4](for powdered electrodes).
1. Beguin, F. and E. Frackowiak, eds. Supercapacitors Materials, Systems, and Applications. ed. M. Lu2013, Wiley-VCH: Weinheim.
2. Long, J.W., et al., Langmuir, 15 (1999) 780-784.
3. Cross, A., et al., Journal of Power Sources, 196 (2011) 7847-7853.
4. Yang, X.-h., et al., Electrochimica Acta, 53 (2007) 752-757.
Formation of Aligned Nanoporous/Nanotubular Layers of Vanadium Oxy-Nitrides
Authors: Kirchgeorg Robin , Yang Yang , Hahn Robert , Schmuki P. 
Published: February 2020

This talk will present self-organized vanadium oxy-fluoride nanotubular layers grown by electrochemical anodization of vanadium in a [BF4]- electrolyte. In a thermal conversion of this amorphous VOxFy precursor structure in ammonia gas, aligned vanadium oxy-nitride (VOxNy) nanoporous/nanotubular layers could be formed. We established conditions to reach conversion of precursor structures to a well crystallized VOxNy nanotube structure, without the formation of any secondary phases or the collapse of the ordered morphology. The formed VON structures were investigated by SEM, EDX, XRD, XPS and electrochemical measurements for capacitor applications. The overall capacitance of the vanadium oxy-nitride structures showed a value of 250 F/g.
Reference:
Y. Yang, R. Kirchgeorg, R. Hahn, P. Schmuki Electrochemistry Communications, accepted
Electrochemical Characteristics of Cyclic Structure Additives in EDLCs
Authors: Park Soo-gil , Yi Hyeon-Seok , Choi Jin-Kwon , Yuk Young-Jae , Kim Han-Joo 
Published: February 2020

Introduction

Electrochemical double-layer capacitor (EDLC) is on a rise as a kind of Energy storage system (ESS), nowadays.[1] EDLCs work by physical charge and discharge electrons at double-layer (also known as Helmholtz layer). Therefore, EDLCs have high power density and long cycle life, but energy density is very low.[2] The internal structure of EDLCs are consist of cathodic/anodic electrode, electrolyte and separator for prevention of short. Among of them, electrolyte is influence at internal resistance of EDLCs. Because of electrolytes were composed solvent and electrolytic salts.[3] So, we need to consider characteristics of solvent and salts. Characteristics of electrolyte are those; electrical stability, ion conductivity, viscosity, high temperature work, cell application.[4] Before papers are almost suggest cyclic structure carbonate as additives in PC, EC or AN-based electrolyte like DEC, DMC, etc. But GBL and PC addition can affirmative affects ion conductivity and potential stability.
In this study, we experiment additives for electrolyte in EDLCs. Especially, we focused on the cyclic structure solvents addition. The additive was used Tetrahydrofuran(THF), γ-butyrolactone (GBL) and Propylene Carbonate(PC). Furthermore, we applied electrolyte samples to EDLC cell.

Experiment

First of all, 1M TEABF4 in PC as reference, THF and GBL is added at propylene carbonate 0 to 30% by volume. In this process, whole salt concentration kept as 1M. Each concentration of sample was 5% interval.
Next, we approach PC addition to 1M SBPBF4 in AN. PC addition experiment goes same condition with upper experiment(0~30%, 5% interval).
As Electrochemical properties, Ion Conductivity and LSV were accepted. Ion conductivity determines almost specification of electrolyte. LSV shows electrical stability. Apply to EDLC unit cell, those examine was measured; CV, impedance, charge/dis-charge

Result& Discussion

THF and GBL addition shows low viscosity than pristine PC. By using THF and GBL, PC-based electrolyte can decrease viscosity. But THF has not enough electrical stability. In LSV results, yield point was decreased by THF addition. Theoretically, boiling point of GBL is 206°C and flash point is over 80°C. So, GBL addition is enlarge non-flammable properties.
Ion conductivity was observed by impedance. To suggest colligate property, the temperature range set 20°C to 80°C, and the interval is 10°C. By measuring LSV, current plateau area was detected that the area is stable potential range. GBL and PC addition gives electrical stability to Cell application shows overall effects at the electrolyte in EDLCs.

References

[1] R. Ko¨tz a, M. Carlen, Electrochimica Acta 45 (2000) 2483–2498
[2] P. Sharma, T.S. Bhatti, Energy Conversion and Management 51 (2010) 2901–2912
[3] S. Takeuchi, K. Miyazaki, F. Sagane, T. Fukutsuka, S.K. Jeong, T. Abe, Electrochimica Acta 56 (2011) 10450– 10453
[4] A. Laheaar, H. Kurig, A. Janes, E. Lust , Electrochimica Acta 54 (2009) 4587–4594
In-Situ Atomic Force Microscopy Studies of Ti3C2: A Promising New Material for Electrochemical Capacitors
Authors: Black Jennifer , Beidaghi Majid , Kalinin Sergei V. , Gogotsi Yury , Balke Nina 
Published: February 2020

MXenes are a newly discovered class of two-dimensional materials prepared through extraction of metals such as Al from MAX phases, whose general formula is Mn+1AXn, where M is an early transition metal, A an A-group element, and X is carbon and/or nitrogen.[1-3] Ti3C2 is one member of this MXene family which is capable of capacitances of up to 350 F cm-3, making this an attractive material for electrochemical capacitors.[4] The high storage capacity of this material is attributed to rapid intercalation of electrolyte ions within the layered structure [Figure 1a]. In this work we use in-situ atomic force microscopy (AFM) to probe the macroscopic expansion of Ti3C2 during electrochemical cycling. The in-situ electrochemical AFM cell used for this study as well as the relative height change of a Ti3C2 electrode in 1 M KOH electrolyte are shown in Figures 1b and c. During negative polarization of the material K+ ions are incorporated into the Ti3C2 structure associated with a macroscopic expansion of the electrode. Studies are performed on various Ti3C2 electrodes in several electrolytes to determine the effect of different ions and electrode structure on the electrochemical behavior and observed strain response.
References:

Naguib, M.;Come, J.;Dyatkin, B.;Presser, V.;Taberna, P.-L.;Simon, P.;Barsoum, M. W.; Gogotsi, Y. MXene: a promising transition metal carbide anode for lithium-ion batteries. Electrochemistry Communications 2012, 16, 61-64.

Naguib, M.;Kurtoglu, M.;Presser, V.;Lu, J.;Niu, J.;Heon, M.;Hultman, L.;Gogotsi, Y.; Barsoum, M. W. Two-Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2. Advanced Materials 2011, 23, 4248-4253.

Naguib, M.;Mashtalir, O.;Carle, J.;Presser, V.;Lu, J.;Hultman, L.;Gogotsi, Y.; Barsoum, M. W. Two-Dimensional Transition Metal Carbides. ACS Nano 2012, 6, 1322-1331.

Lukatskaya, M. R.;Mashtalir, O.;Ren, C. E.;Dall’Agnese, Y.;Rozier, P.;Taberna, P. L.;Naguib, M.;Simon, P.;Barsoum, M. W.; Gogotsi, Y. Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide. Science 2013, 341, 1502-1505.

Figure 1: a) SEM image of Ti3C2 working electrode. b) Photograph of in-situ electrochemical AFM cell. c) Cyclic voltammogram of Ti3C2 working electrode in 1 M KOH electrolyte and corresponding relative height change measured using in-situ AFM.
High Voltage AC/AC Capacitors Using the Carbon/Iodine Interface in Ionic Liquid Electrolyte
Authors: Frackowiak Elzbieta , Béguin François , Skowron Piotr 
Published: February 2020

Lately we have demonstrated that huge pseudo-capacitive contributions can be originated from the electrolyte when using high surface area activated carbon electrodes, for example by using iodide based solutions in water [1]. Although the use of such concept allows very high capacitance values to be reached, the energy of the AC/AC capacitors based on these electrolytes is limited by the relatively low value of voltage inherent to use of water. Therefore, in this work, we have investigated the performance of the carbon/iodine interface in ionic liquid electrolytes, both protic (PIL) and aprotic (AIL).
The PILs selected were triethylammonium bis(tetrafluoromethylsulfonyl)imide [Et3NH]-[TFSI] and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide [Emim]-[FSI]. Organic iodides - triethylammonium iodide [Et3NH]-[I] and tetraethylammonium iodide [Et4N]-[I] at a concentration of 0.25 mol·L-1 and inorganic iodides (LiI and KI) at a concentration of 0.2 mol·L-1 were introduced in the ionic liquid. The electrochemical experiments as cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy were conducted using a two-electrode cell construction. In some experiments, a silver wire was added as pseudo-reference to monitor the potential of individual electrodes. Activated carbon (AC) activated by KOH (4:1) with high microporosity ( SBET = 2180 m2·g-1, Vmicro = 0.96 cm3·g-1, L0 = 1.55 nm) was used as working and counter electrode. Glass microfiber paper (Whatman) was utilized as separator.
Galvanostatic (0.2 A·g-1) cycling up to 1.8 V in two-electrode cell with reference electrode (Figure 1B) demonstrates a remarkable increase of capacitance when KI is added to [Et3NH]-[TFSI], from 122 to 184 F·g-1. The voltammograms of figure 1A show clearly that the increase of capacitance is caused by the positive electrode where faradaic processes occur. The capacitance values of the positive electrode for 0.25 mol·L-1 [Et3NH]-[I] and 0.2 mol·L-1 LiI dissolved in [Et3NH]-[TFSI] reached 199 and 238 F·g-1
, respectively; for the negative electrode the capacitance reached 163 and 121 F·g-1
, respectively. The addition of 0.2 mol·L-1 inorganic iodide to aprotic IL also enhanced the capacitance from 116 F·g-1 for the pure AIL to 129 and 153 F·g-1for the KI and LiI solutions, respectively. Regardless of the different type of iodide derivatives dissolved in IL medium, faradaic processes occur at the positive electrode greatly increasing the capacitance of the whole capacitor system. However, iodide solutions in PILs seem to be more effective than the AILs ones.

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] G. Lota, E. Frackowiak, Electrochem. Comm. 11 (2009) 87-90
Plasma Enhanced Atomic Layer Deposition on Powders
Authors: Rampelberg Geert , Longrie Delphine , Deduytsche Davy , Detavernier C. 
Published: February 2020

Surface engineering of micro- and nanoparticles is of great importance in fields such as catalysis, energy and sensing. For many of these applications particles are required with different bulk and surface properties. A popular technique to achieve this is to coat the particle surface with a nanometer thick layer. Only a few techniques have been explored for depositing such thin conformal coatings. Chemical vapor deposition (CVD) has been used extensively for this purpose, but suffers from a lot of disadvantages, such as imperfect control over layer thickness and uniformity of the coating over all individual particles, particle agglomeration and formation of additional undesired particles due to gas phase reactions between the CVD reactants. In contrast, atomic layer deposition (ALD) is known as a reliable technique for covering complex 3D objects with ultrathin conformal coatings. However, to perform ALD on large quantities of powders, the individual particles need to be fluidized or agitated. Fluidized bed reactors are most often used for ALD on particles, but this reactor concept does not seem to be compatible with plasma enhanced ALD, which is advantages for e.g. coating on temperature sensitive polymer particles or deposition of metals and metal nitrides.
In this work, a rotary reactor was used to agitate particles, enabling the deposition of conformal coatings by thermal and plasma-enhanced ALD. Particles ranging from nanometer size to millimeter size were successfully coated with layers of Al2O3, TiO2, AlN and TiN.[1]In-situ mass spectroscopy confirmed that ALD was performed by detecting the expected reaction products. By monitoring the formation of these reaction products over time, it was possible to optimize precursor and reactant usage, which is linearly dependent on the effective surface area of the particles. In the case of plasma enhanced ALD, in-situ optical emission spectroscopy confirmed the mass spectroscopy data. X-ray fluorescence revealed the expected linear relationship between the amount of ALD cycles and the deposited amount of material, while X-ray photo-electron spectroscopy was used to confirm the composition and purity of the coatings. Transmission electron spectroscopy finally showed that the individual particles were coated uniformly and conformally. Our results prove that the proposed rotary reactor enables conformal deposition on nano- and micropowders by thermal and plasma enhanced ALD. In this way, surface engineering of such particles can be achieved.

[1] D. Longrie et al., Surface & Coating Technology 213 (2013) 183-191
Growth of Al Doped ZnO Thin Films by Atomic Layer Deposition Process
Authors: Zhang Kai , Chen Xin , Lin Pengtao , Obulreddy Santosh Kumar Reddy , Baumgart Helmut 
Published: February 2020

ZnO is a transparent semiconductor with a wide and direct band gape of 3.37 eV, large excitonic binding energy of ~60 meV, high mechanical and thermal stabilities, and good electrical conductivity. Therefore, ZnO based materials are extensively investigated in spintronics, gas and biological sensors, solar cells, catalysts, electronics, piezoelectric devices and high-efficiency short-wavelength optoelectronic nanodevices. In solar cell application, especially Al doped ZnO (AZO) thin films have been extensively developed and investigated due to their low cost, high thermal stability, high optical transparency and high conductivity [1, 2 , 3].
Several methods have been applied to deposit ZnO thin films in the past, such as sol gel spin coating, magnetron sputtering, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). Among these, ALD is considered as a novel technique to deposit ZnO thin films, because it possesses self-limiting surface reactions in each ALD cycle, which consequently control the layer thickness with unprecedented atomic level precision, stoichiometry, composition, uniformity of large area and maintain excellent conformity of complex nanostructures. In addition, ALD process is able to introduce separately each precursor to react on the surface of the structure. The concentration of dopant in the ZnO films can be precisely controlled by the number of ALD cycles, so that the physical properties of AZO films, such as carrier density and conductivity, can be adjusted to meet the requirements of different applications.
In this study, Al doped ZnO thin films were deposited by the ALD technique with trimethylaluminium (TMA), diethylzinc (DEZ) and water vapor as aluminium, zinc and oxygen precursors, respectively. The films were grown in Savannah 100 cross-flow thermal ALD reactor. The growth temperature was maintained at 250 oC during the reaction. N2 was used as a carrier gas with a flow rate of 20 sccm. The ALD AZO films with various Al doping level were prepared by introducing TMA cycles once in every 30 pulses of DEZ and H2O injection.
The structural, optical and electrical properties of the AZO films prepared by using ALD processes were investigated. The crystal structure of ZnO was analyzed by X-ray diffraction (XRD). The AZO film surface morphology was inspected using a field emission scanning electron microscopy (FE-SEM). The surface roughness was analyzed by atomic force microscopy (AFM). The sheet resistivity of AZO films was determined by using four-point probe measurements. The optical reflection was carried out by UV-VIS-NIR spectrometer.
References:
P. Genevée, F. Donsanti, G. Renou, D. Lincot, Applied Surface Science 264, 464 (2013)

G. Luka, T. A. Krajewski, B. S. Witkowski, G. Wisz, I. S. Virt, E. Guziewicz, M. Godlewski, J. Mater. Sci: Mater. Electron 22, 1810 (2011)

J. W. Elam, D. Routkevitch, S. M. George, Journal of The Electrochemical Society, 150 (6) G339 (2003).
Design, Synthesis and ALD Assessment of Organometallic Precursors for Semiconductor Applications
Authors: Dussarrat Christian 
Published: February 2020

While transistors continue scaling in both density and performance and as technological improvements allows dramatic cost reduction, the utilization of most performing transistors also requires most effective interconnects. The delays in interconnects are increasingly contributing to the overall circuit delays in a severe manner as dimensions shrink. New challenges are thus arising in processes for scaling and integration needed to obtain the required performances, including the usage of novel architectures at a change of semiconductor nodes. For example, one announced the implementation of FinFET structures, with the usage of vertical transistors, at 22nm, and several other players will follow ; ST Microelectronics and associated partners were successful in the implementation of FDSOI technology.
The new associated manufacturing challenges, especially the needs to deposit more conformal metallic thin films, can be translated as new opportunities to introduce the usage of organometallic materials in electronic industry. In order to perform that transition effectively for all the stakeholders involved, synergetic interactions need to occur between the chemical solution supplier that provides a new organometallic molecule and the corresponding screening test results, the equipment manufacturers that adapt and fine tune the process to the specification to its reactor and the chip manufacturers that validate the process and work on integration aspects.
The Effect of SPA-SiO2 Tunnel Oxide Thickness for Metal-Insulator-Silicon Photoelectrochemical Cells
Authors: Scheuermann Andrew G. , Lu David Q. , Ito Toru , Chidsey Christopher E.D. , McIntyre Paul C. 
Published: February 2020

Photoelectrochemical cells are becoming increasingly attractive for the on-site production of clean chemicals and fuels, both as end-use products and as an integrated energy storage solution for mitigating the intermittency of solar radiation. One persistent challenge in this field is the difficulty of simultaneously achieving high photovoltaic efficiency and chemical stability of semiconductor photoelectrodes during water oxidation under wide-ranging pH conditions. Wide band gap semiconducting metal oxides are frequently stable under water oxidation conditions but have inherent photocurrent limitations. We have recently demonstrated that atomic layer deposition (ALD) of a thin and chemically-protective TiO2 layer can avoid oxidation of the surface of a silicon photoanode during long-duration oxygen evolution. Our initial work showed that it was possible to decouple efficient light absorption by the silicon anode from the oxygen evolution reaction (OER) occurring on the surface of a water oxidation catalyst layer by the presence of an interposed ALD-TiO2 layer. This conformal and pinhole-free oxide layer was found to be dense enough to block the solution from oxidizing the underlying semiconductor (greatly increasing its stability), but still thin enough to allow efficient hole transport between an n-type silicon substrate and the iridium OER catalyst [1]. In more recent work, we have showed that ALD-TiO2 could be used with a variety of other catalysts to produce efficient devices with more than 600mV of open circuit voltage, high saturation currents, and similar stability. In addition, by studying thicker ALD-TiO2 films, we found that protection could be increased with a minor increase in anode resistance. The additional resistance is associated with bulk conduction of electronic carriers through states in the TiO2 band-gap between the catalyst and anode [2]. Together, these findings indicate that atomic layer deposited coatings in metal-insulator-semiconductor (MIS) photoanodes serve as a general protection method for a variety of semiconductor-catalyst systems. In addition to summarizing prior reports and the most recent results on such MIS photoelectrodes, this presentation will touch on future directions for efficient artificial photosynthesis using ALD surface protection layers.
[1] YW Chen, J.D. Prange, et al. Nat. Mater. 2011, 10, 539-44.
[2] A.G. Scheuermann, et al. Energy Environ. Sci. 2013, 6, 2487 – 96.