bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials for ORR Electrocatalysis: Catalytic Center and Substrate Effects
Authors: Luo Yun , Sreekuttan M. Unni , Mora-Hernandez Juan Manuel , Alonso-Vante Nicolas
Published: February 2020

One of the most important challenges for polymer electrolyte membrane fuel cells (PEMFCs) in terms of facilitating its widespread commercial use is to improve the performance and durability of the electrocatalyst by developing novel catalysts (precious and non-precious catalytic centers) and support materials. One way to improve the oxygen reduction reaction (ORR) activity of Pt-based catalysts is to control Pt nanoparticles (Pt NPs) size, morphology and the dispersion onto substrates. Carbonyl chemical route for synthesizing Pt NPs facilitate a narrow particle size distributions (about 2-3 nm) [1], and homogeneous dispersion on different substrates [2,3]. A variety of carbon-based materials such as carbon nanotubes (CNT), graphite (HOPG), graphene, carbon nanohorns (CNH) and non-carbonaceous based materials, such as metal oxides (Titania, Yttria, Ceria, etc.,) [4,5] can be used as both catalyst and catalyst support materials. On the way to further explore the substrate effect on non-Pt electrocatalyst, CoSe2and CoO were supported on Carbon, CNH and nitrogen doped nanohorn (NCNH). The activity modulation in non-Pt catalysts was found to be strongly dependent on the morphology as well as the composition of substrate materials. The improved interaction of nitrogen species in NCNH and the metal centers modify the active reaction centers. This modified active reaction centers boost the catalytic activity with minimum overpotential for molecular oxygen reduction in alkaline medium (Figures 1a, b). Preliminary analysis indicates that this improved activity not only constrained in oxygen reduction but other catalytic reaction such as oxygen evolution reaction and hydrogen evolution reaction and further to an application on microfluidic fuel cells.

Acknowledgements

Authors acknowledge the partial support of the European Union’s Seventh Framework Programme (FP7/2007-2013) for the Fuel Cell and Hydrogen Joint Technology Initiative under grant agreement nr 303492 CathCat. SM U acknowledges the financial assistance through Raman-Charpak Fellowship, and JMMH acknowledges CONACyT fellowship.

[1] N. Alonso-Vante, Fuel Cell, 2006, 6, 182-189.

[2] J. Ma, A. S. Gago, W. Vogel, N. Alonso-Vante, Chemcatchem, 2013, 5, 701-705.

[3] L. Timperman, Y.J. Feng, W. Vogel, N. Alonso-Vante, Electrochimica Acta, 2010, 55, 7558-7563.

[4] Walter Vogel, Laure Timperman, Nicolas Alonso-Vante, Applied Catalysis A: General, 2010, 377, 167-173.

[5] C.Liu , Y.Wei and K.Wang, Chem.Comm., 2010, 46, 2483-2485.
Kinetics of Reaction with Oxygen of LnBa1-XSrxCo2-YFeyO6-δ (Ln - Selected Lanthanides) Oxides as Studied by Relaxation Methods
Authors: Swierczek Konrad , Zheng Kun , Klimkowicz Alicja
Published: February 2020

Kinetics of the reaction with oxygen of the oxides, during changes of the oxygen partial pressure in the surrounding atmosphere, can be studied by various relaxation methods (e.g. mass or electrical conductivity relaxation). These methods allow to determine chemical diffusion coefficient (D) and surface exchange coefficient (K), related to the mentioned reaction [1, 2]. Theoretical basis of relaxation methods relies on the solution combining first and second Fick’s law and flux density at the surface boundaries. Depending on the geometry of the actual sample (3D, disc-like, etc.), the respective solutions are different, however, simultaneous and reliable determination of both coefficients requires additional conduction to be filled: 0.03 ≤ l·K/D ≤ 30 [3]. In real cases, this may limit range of temperatures and oxygen partial pressures, at which such determination is possible. Also, it suggests the importance of the dimensional parameter l.

In this work we present results concerning simultaneous determination of D and K, measured by mass and electrical conductivity relaxation techniques for perovskite-type oxides with LnBa1-xSrxCo2-yFeyO6-δ (Ln - selected lanthanides) chemical formula. The measurements were performed at elevated temperatures (600-800 ºC) in a wide range of oxygen partial pressures. The obtained results were analyzed taking into account crystal structure and the oxygen content in the considered compounds at high temperatures. It allowed to determine the correlation between structural (radius of Ln cation, degree of unit cell distortion, metal-oxygen-metal angle, unit cell free volume) and transport properties (oxygen diffusion coefficient, surface exchange coefficient, ionic and electronic component of the electrical conductivity) in the considered LnBa1-xSrxCo2-yFeyO6-δ.

Acknowledgements

The project was funded by the National Science Centre Poland (NCN) on the basis of the decision number DEC-2012/05/E/ST5/03772.

References

[1] G. Xiao, Q. Liu, F. Zhao, L. Zhang, C. Xia, F. Chen, J. Electrochem. Soc. 158 (2011) B455.

[2] J.A. Lane, J.A. Kilner, Solid State Ionics, 136-137 (2000) 997.

[3] M.W. den Otter, H.J.M. Bouwmeester, B.A. Boukamp, H. Verweij, J. Electrochem. Soc. 148 (2001) J1.
Recent Progress in New Nanocatalysts for Oxygen Reduction Reaction
Authors: Guo Shaojun
Published: February 2020

The design of new functional nanomaterials for enhancing oxygen reduction reaction (ORR) is highly desirable for promoting the development of fuel cell and lithium air battery devices. In this seminar, I will focus on my recent advances in rational design and controlled synthesis of high-quality multicomponent nanocrystals for enhancing ORR. I will start with three examples on how to engineer FePt NWs, FePtPd/FePt core/shell NWs and graphene-FePt NPs composite for getting advanced Pt-based catalysts for ORR with extremely high activity and stability. After that, I will move to non-Pt catalysts such as graphene-Co/CoO NPs and M/CuPd NPs (M=Ag, Au), which exhibit comparable and even higher ORR activity and stability than commercial Pt catalyst.
Fabrication and Characterization of Conductive Transparent Film Based on Carbon Nanotube for Optoelectronic Devices
Authors: Abdel-Fattah Tarek M , Dushatinski Thomas
Published: February 2020

Optoelectronic devises are an integral part of our modern society. From the screens on our electronic computers to the solar panels that will hopefully replace fossil fuel sources, the need for theses devices and advancements for their sustainability and improved mass production is a large area of interest. A common component of all of these devices is a conductive and transparent cathode, usually transparent conducting oxides (TCOs). The downfall of TCOs is their degradation and incompatibility with progressive flexible substrates as their resistivity increases significantly with flexing and environmental exposure.

This study involved the fabrication and characterization of a multi-walled carbon nanotube (MWCNT) and sodium lauryl sulfate (SDS) composite deposited over polyethylene terephalate. The cathode materials have showndrastically effect of the performance of both organic and dye sensitized solar cells. The roughness of the films and electronic absorbance spectra are important as roughness increases the surface area over a two dimensional area and has shown to improve efficiency in solar cells. Also the absorbance spectrum of the film would need to be complementary to the photovoltaic material.

Figure 1: Electronic absorbance spectra of the MWCNT:SDS thin film that has been background corrected for PET.

Figure 1 shows the absorption spectra from both UV-Vis and IR ranges. The spectrum shows decreases in transmittance at 635 nm, 115 1nm, 1201 nm, 1223 nm, and 1630 nm. These absorbance peaks would not interfere with poly(3-hexylthiophene-2,5-diyl) (P3HT) that has a strong broad maxima at 525nm that extends between 400nm and 600nm [1]. The roughness (Ra) value of the MWCNT:SDS film is much greater at 21.8 nm as compared to 0.59 nm for unannealed ITO films [2].

References

Boland, P.; Sunkavalli, S.S.; Chennuri, S.; Foe, K.; Abdel-Fattah, T.M.; Namkoong, G. Inversigation of structural, optical, and electrical properties of regioregular poly(3-hexylthiophene)/fullerene blend nanocomposites for organic solar cells. 2010. Thin Solid Films. 518 1728-1731.

Raoufi, D.; Kiasatpour, A.; Fallah, H.R.; Rozatian, A.S.H. Surface characterization and microstructure of ITO thin films at different annealing temperatures. 2007. Appl. Surf. Sci. 253 9085-9090.
Controllable Phosphorus Doped Graphene Field Effect Transistor Using Phosphosilicate-Glass Films
Authors: Yoon Jin-sang
Published: February 2020

Graphene consists of a single layer of sp2 hybridized carbon with atoms arranged in a honeycomb lattice. According to the valence and conduction bands touch at the Brillouin zone, graphene is a zero-band-gap semiconductor. To use graphene is semiconductor electronics, it is very important to open a band gap. Doping is an efficient way to tailor the electronics properties of pristine graphene. The dopant atoms can modify the electronic band structure of graphene, and open up a band gap. A few approaches have been developed recently for the doped graphene. Unfortunately, the previous methods are not controllable and simple to use in semiconductor business.

In this paper, Chemical n-type doping process of graphene using solid phase diffusion method of PSG (phosphosilicate glass) film is demonstrated. Figure 1 shows the doping process flow the graphene field effect transistor. PSG films were grown by CVD(Chemical vapor deposition) method on highly doped silicon wafer. In order to activate the dopants of the PSG films were annealed from 700°C to 900°C at intervals of 100(pre-annealing). The as-grown graphene layers were transferred on CVD grown 300 nm thick PSG film on heavily p-type Silicon substrate by a wet transfer technique. Dopants were diffused by annealing process to graphene on PSG films from 300°C to 500°C at intervals of 100°C. (post-annealing)

Both pristine and annealed graphene films were analyzed by raman and XPS(X-ray photoelectron spectroscopy). For electrical characterization, drain current-gate voltage(ID-VG) and drain–source voltage (VDS) bias of 1 V was applied to the FETs when measuring the ID–VG characteristic. Figure 2 shows the survey XPS spectrum of doped graphene samples. The atomic percentage of P in doped graphene increasing according to annealing temperature of the samples. According to these results, dopants were diffused on the surface of graphene. Figure 3 shows ID-VG characteristics of the FETs formed on the different graphene layers. Dirac point of the pristine graphene FET was observed at around +50 V since the pristine graphene generally serves as a p-type material in air because of unexpected impurity problems. However, Dirac points were respectively shifted from 21.5V to 0.5V after annealing treatment process, indicating that this n-type doping method using PSG annealed process successfully.

We developed graphene doping process with solid phase diffusion of PSG film which allows the control of Dirac point in graphene. The feasibility of the n-doping process for graphene-based electronic devices was successfully demonstrated in this paper by fabricating a MOS capacitor with n-channel FETs on annealed graphene. It is believed that can be expand the application, not only channel doping, but also reducing the contact resistance.
Study of Electrochemical Behavior of Hybrid Materials Based on GO/ PMo12/Conducting Polymer Obtained By Interfacial Polymerization
Authors: Baas-López José Martin , García- Chan Ceyli , Cuentas-Gallegos Ana Karina , Pacheco Daniella
Published: February 2020

In the search to find materials with high conductivity, high electrochemical stability, recently the graphene family is presented as one promising advanced material. Nevertheless, are existing different challenges for avoid the restacks between their sheets and presented a semiconducting behavior due to their interaction with the medium, etc. Is for this what hybrids materials based on graphene could also offer great advantages for different applications for energy as for example electrochemical capacitors, solar cells, etc.

In this work was obtained hybrid materials based on GO/ PMo12/conducting polymer, conducting polymer/PMo12 andGO/ PMo12. The OG was obtained by Brodie method and thermally reduced. The method that was used for polymerization of monomers (pyrrole and aniline) was interfacial. For the cases of conductive polymer/PMo12, the ratio was 16.6% monomer and 83.4 % of PMo12 of weight while GO/ PMo12/conducting polymer this ration was of 10, 50 and 40% in weight, respectively.

All materials obtained were characterized by DRX, SEM, Raman and FTIR; and for evaluate their electrochemical behavior, the materials was deposited on cloth carbon and characterized by voltamperometry cyclic using a cell with three electrodes and H2SO4 1M at different scan rates; also was evaluated stability cyclic at 1000 cycles.
EIS Evaluation and Synthesis Nylon/Graphene Oxide Electrospun Composite Coating
Authors: Menchaca Carmina , García César , García Miguel Angel , Uruchurtu Jorge
Published: February 2020

Graphene has attracted strong scientific and technological interest in recent years, and. It has shown great promise in many applications because of its unique physicochemical properties: high surface area (theoretically 2630 m2/g for single-layer graphene), excellent thermal and electric conductivity, and strong mechanical strength. Many methods have been developed to produce graphene. In general, nylon 6-6 has excellent mechanical resistance due to the mutual attraction of their long chains and their crosslinking. Since nylon discovery, a great interest has been developed due to its technological importance, its commercial characteristic, and its complexity related to the morphological changes associated to its crystallinity, not only in solid state, but also in solution and under melting point conditions.

A possible application for nylon 6-6/graphene oxide composite film is as a anticorrosion coating on the stainless steel bipolar plate for PEMFC due to the possible decrease of aggressive species diffusion through the coating as well as facilitating the electron discharge of the cathodic reaction, therefore diminishing the metal degradation and eliminating the passive layer that causes unacceptable reduction in contact resistance and possible fouling of the catalyst and the ionomer.

Starting from exfoliated graphite, different treatments were tested in order to obtain the best graphite oxide conditions. These included: calcination in a muffle for two hours at 700 or 800 °C. After that, ultrasonic agitation for three hours in acidic, basic or peroxide solutions was performed. Afterwards, particles were rinsed, filtered and dried at ambient temperature. These samples were characterized under SEM and FTIR techniques. Electrochemical cells were prepared using porous silica or nylon films as substrate covered with graphite oxide for further oxidation and reduction by electrochemical procedures. Polarization curves were performed to determine the best oxidation/reduction potentials under different acidic, alkaline and peroxide solutions. The best oxidation condition was obtained in KOH and the best reduction in H2SO4solutions. With these results potentiostatic oxidation and reduction curves were applied to further oxidize carbon species and then, reduced them onto the porous silica or nylon surface forming the graphite film.

Keywords: nylon, grapheme, electrochemical, synthesis.

Presenting author’s email: cesar.garcia@uaem.mx
Invited: Controlled Growth of Hierarchical Metal Oxide Nanoarchitectures by an Atmospheric Pressure Micro-Afterglow
Authors: Gries Thomas , Altaweel Ayman , Kuete Saa Duclair , Belmonte Thierry
Published: February 2020

Metal oxide nanostructures with controlled shapes and size distribution have stimulated interest in fundamental scientific research owing to their morphology-dependent properties that offer potential wide-ranging applications. Plasma-assisted processing is one of the emerging processes used for the production of various metal oxide nanostructures [1]. In this study, we present an innovative strategy to synthesize different metal oxide nanostructures. This very simple process consists in exposing a metal surface directly to the afterglow of an argon-oxygen micro-plasma at atmospheric pressure [2].

Different metals are treated by the afterglow (Cu, Zn, Fe). For example in the case of copper, this flexible process makes it possible to design in a single treatment step, hierarchical nanostructures, which are not obtained by classical thermal oxidation like nanowalls or nanoflowers (figure 1). The growth mechanism is driven by stress-induced migration due to the development of stress gradients caused by the formation of copper oxide layers CuO and Cu2O. A specific study based on the local stress evolution measurement is proposed to determine accurately its influence on the growth of copper oxide nanostructures.

In this work, we present also the possibility to obtain the localized growth of ruthenium oxide nanostructures by applying the afterglow on a ruthenium substrate [3]. The mechanism is two-fold. First, a nanostructure made of lamellae covers the whole surface. Second, localized bunches of nanowires are distributed randomly, their growth being driven by the local stress that depends on the presence of emerging defects. We study also the influence of two alkali salts: NaCl and KCl. The presence of these crystals on the surface enhances the growth of nanowires all around them, created a circular area where nanowires are found (figure 2). The different existing growth models are considered to interpret these new results. This nanowire growth mechanism can be another important way to control the location of the metal oxide nanostructures.

Reference

[1] K. Ostrikov, U. Cvelbar, A. Murphy “Plasma nanoscience: setting directions, tackling grand challenges”, J. Phys. D: Appl. Phys. 44 (2011) 174001.

[2] G. Arnoult, R.P. Cardoso, T. Belmonte, G. Henrion “Flow transition in a small scale microwave plasma jet at atmospheric pressure”, Appl. Phys. Let. 93 (2008) 191507.

[3] D. Kuete Saa, R.P. Cardoso, F. Kosior, A. Altaweel, T. Gries, S. Laminsi, T. Belmonte “Growth of ruthenium dioxide nanostructures by micro-afterglow oxidation at atmospheric pressure”, Surf. & Coat. Technol. DOI: 10.1016/j.surfcoat.2013.10.040 (in press).
Invited: Scalable Production of Nanowire Arrays and Powders Using Plasmas
Authors: Sunkara Mahendra Kumar
Published: February 2020

This presentation will highlight our group’s efforts with various scalable methods for continuous manufacturing of nanowires powders and arrays with help of plasmas. These scalable methods can be categorized in to the following: (a) scalable production of nanowires of low-melting metal oxide nanowire powders; (b) scalable production of nanowire arrays and powders for titania and related oxides; and (c) low-temperature growth of nanowires of silicon and related materials.

Scalable production method for nanowires of low-melting metal oxides: A novel atmospheric microwave plasma reactor is designed to process about a kilogram of nanowires per day and has already been demonstrated for the synthesis of tin oxide, zinc oxide and aluminum oxide nanowires.1 The resulting nanowires are 50-100 nm in diameter and several microns long.

Scalable production of titania and related metal oxide nanowires: We report a new ultrafast (reaction time on the scale of a minute) gas-phase method for synthesizing highly crystalline TiO2 nanowires (NWs) using direct oxidation of either Ti metal (foils or powders) or spherical TiO2 powders using an atmospheric pressure microwave plasma reactor.2 The current state of the art methods involve long reaction time scales (~1 day) for synthesis of TiO2 NWs.

Low-temperature synthesis of nanowire arrays of silicon and related materials: This presentation will also highlight our recent experiments on the synthesis of silicon nanowire arrays at temperatures lower than 300 C.

This presentation will also highlight our efforts in utilizing the nanowire based materials toward various energy conversion and storage applications including dye sensitized solar cells, lithium ion batteries, and photoelectrochemical water splitting.

References:

V. Kumar, J-H. Kim, C. Pendyala, B. Chernomordik, and M.K. Sunkara, “Gas-Phase, Bulk Production of Metal Oxide Nanowires and Nanoparticles Using a Microwave Plasma Jet Reactor”, J. Phys. Chem. C., 112, 46, 17750-17754 (2008).

V. Kumar, J-H. Kim, J.B. Jasinski, E.L. Clark, and M.K. Sunkara, “Alkali assisted, atmospheric plasma production titania nanowire powders and arrays”, Crystal Growth and Design, 11 (7), 2913 (2011).
High Quality Inductively Coupled Plasma Chemical Vapor Deposited SiOxNy Gas Barrier Films for OLED Display
Authors: Bang S-H , Suk Jae-Ho , Choi Dio , Kim Kunsu , Hwang Nong M
Published: February 2020

SiOxNy thin films were synthesized on polyethylene terephthalate (PET) substrate at low temperature (~40°C) by inductively coupled plasma chemical vapor deposition (ICP- CVD) system. Details of the RF power, gas ratio (Si, N2, O2, Ar, H2), and film thickness effects on the SiOxNy/PET film properties in terms of deposition rate, chemical composition, water vapor transmittance rate (WVTR), transmittance, refractive index, surface morphologies, defect, and residual stress were described. When the RF power increased from 500W to 1200W, the deposition rate and surface roughness increased while WVTR decreased to a value near 0.008g/m2/day which is very good WVTR property as a single inorganic barrier thin films. A lower WVTR value can be achieved under a barrier thickness of 300nm.
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.
A Low-Cost Substrate-Integrated Lead-Carbon Hybrid Ultracapacitor with an Organic Metal
Authors: Banerjee Anjan , Shukla Ashok Kumar
Published: February 2020

A cost-effective substrate-integrated lead-carbon hybrid ultracapacitor using an organic metal is developed and performance tested. The hybrid ultracapacitor employs flexible exfoliated graphite sheets as negative plate current-collectors that are coated amperometrically with a thin layer of organic metal, namely poly-aniline; the latter providing good adhesivity to activated carbon layer that is pasted on to it for realizing an electrical-double-layer capacitor. The positive plate comprises the conventional lead sheet that is converted electrochemically into a substrate-integrated lead-oxide electrode.1 12V substrate-integrated lead-carbon hybrid ultracapacitor both in absorbent-glass-mat and polymeric silica gel electrolyte configurations are developed and performance tested. It is possible to realize 12V lead-carbon hybrid ultracapacitors both in absorbent-glass-mat and silica gel configurations with capacitance values of ~200 F and ~300 F, respectively, with faradaic efficiency value of ~ 90 % and cycle-life in excess of 100000 cycles. The effective cost of these ultracapacitors is estimated to be about US$ 4-5 Wh-1 as compared to US$20-30 Wh-1 for presently available commercial ultracapacitors. The performance-test data for 12V devices are summarized in Table 1. The galvanostatic discharge data and pulse cycle-life testing data for the substrate-integrated lead-carbon hybrid ultracapacitor are shown in Figures 1 and 2, respectively.2

Reference

A. Banerjee, M. K. Ravikumar, A. Jalajakshi, P. S. Kumar, S. A. Gaffoor, and A. K. Shukla, J. Chem. Sci., 124, 747 (2012).

A. K. Shukla and A. Banerjee, Indian Patent Application No. 1454/CHE/2014, dated 19/03/2014.
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.
Multiscale Simulations of ALD in Cross Flow Reactors
Authors: Yanguas-Gil Angel , Libera Joseph A. , Elam J. W.
Published: February 2020

Two of the biggest challenges in reactor-scale simulations of ALD processes are our lack of knowledge on the mechanistic details of surface chemistry and the need to integrate reactor scale and feature scales in the simulations. In order to assist our process development and scale up we have developed a multiscale simulation code that allows us to study the impact of surface chemistry on the coating of large area substrates with high surface area/high aspect-ratio features. Our code, based on open-source libraries, takes advantage of the ALD surface chemistry to achieve an extremely efficient two-way coupling between reactor and feature length scales, and it can provide simulated quartz crystal microbalance and mass spectrometry data at any point of the reactor. By combining experimental surface characterization with simple analysis of growth profiles in a tubular cross flow reactor, we are able to extract a minimal set of reactions to effectively model the surface chemistry, including the presence of spurious CVD. These reactions are then used as an input for the large-scale 3D simulations. In this work, we will focus on two aspects of the problem: the impact of non-ideal surface chemistry and the role of reactor geometry in the coating of both planar and high surface area substrates. Finally, we will discuss the impact of moving substrates characteristic of roll-to-roll processes.
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.
Mechanical/Structural Properties of ALD Zirconium Oxide (ZrO2) Thin Films for High-Tech Applications
Authors: Mamun M A , Baumgart Helmut , Elmustafa A A
Published: February 2020

Among the transition metal oxides, zirconium oxide (zirconia) is considered the most extensively studied because of its remarkable properties such as high melting point, resistance against oxidation, and high refractive index [1-3]. Monoclinic crystal structure exists at room temperature and in the temperature range of up to 1170 °C whereas in the temperature range of 1170-2370 °C the dominant crystal structure is tetragonal. As the temperature increases above 2370 and up to 2680 °C, the crystal structure becomes cubic. Due to these various properties, zirconium oxides have been used in protective coatings, optical devices, laser mirrors, biomedical and in microelectronic applications. ZrO2is being used in artificial hip joints replacement due to its high hardness and excellent mechanical properties and in dental implants due to its exceptional resistance to bacterial infection. ZrO2 films of 200, 300, and 500, cycles were deposited on p-type Si (100) substrate using Atomic layer deposition (ALD) technique. The 300 ALD cycle samples were further annealed at 600 °C. We tested these films for structural, surface morphology, and nanomechanical properties using nanoindentation. The structural and surface properties were explored using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). We discuss the influence of the deposition technique on the structure and properties of the films citing the superiority of the ALD technique that is particularly used in the fabrication of the films that are presented in this study. The nanoindentation results indicate that the films become consistently softer as the number of cycles increase and the film thickness grow larger, Figure 1. Additionally, further annealing of the films enhanced the hardness and fracture toughness of the films. Figure 2 depicts radial cracks of shorter length of the annealed sample (left) compared to the other one (right) under the same applied stress.

References

J. Ciosek, W. Paszkowicz, P. Pankowski, J. Firak, U. Stanislawek, Z. Patron, Vacuum 72 (2004) 135.

Meriani S, editor. Proceedings of the InternationalConference Zirconia ’88. Advances in Zirconia Science and Technology. New York: Elsevier; 1989.

Venkataraj S, Kappertz O, Weis H, Drese R, Jayavel R, Wuttig M. J Appl Phys 2002;92(7):3599–607.
Thin-film Deposition of Silicon Nitrides and Oxides from Trihydridosilanes
Authors: Arkles Barry , Pan Youlin , Kaloyeros Alain
Published: February 2020

MOCVD of trihydridosilanes provides a route for generating self-assembled monolayers on metal substrates. Under mild conditions, trihydridosilanes interact with a variety of clean, hydrogenated and fresh metal and metalloid surfaces, including titanium, silicon and gold.1 In contrast, monohydridosilanes appear to have minimal interaction. All classes of hydridosilanes have minimal interaction with anhydrous oxide surfaces. A proposed mechanism for the initial steps of deposition involves the dissociative adsorption of the silanes with the formation of hydrogen, followed by topmost atom layer insertion and concomitant surface reconstruction. New alpha, omega bis(trihydrido)silane precursors are also described which offer the ability for dipodal substrate interaction. Alpha, omega trihydridosilane terminated oligopermethylsilanes with the potential to form molecular wires are presented.2

1 B. Arkles, Y.Pan, Y. Kim, E. Eisenbraun, C. Miller, A. Kaloyeros, J. Adhesion Science and Technology, 2014, 2012, 41.

2 B. Arkles, Y. Pan, G. Larson, US Pat. 8,575,381, 2013.