bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrodeposited Co-Mo-P-TiO2 Composites for Hydrogen Evolution Reaction in an Alkaline Electrolyte
Authors: Wang Cheng , Podlaha Elizabeth J.
Published: December 2020

Aiming to improve the efficacy of earth abundant electrocatalysts for water splitting, novel Co-Mo-P-TiO2 composites were developed and the hydrogen evolution reaction (HER) characterized. The electrocatalytic performance was compared to electrodeposited Pt, Co, Co-Mo and Co-Mo-TiO2 thin films prepared galvanostatically onto rotating cylinder electrodes. The Co-Mo alloy and composites were prepared from a sulfate-citrate electrolyte with particles suspended in the electrolyte. Adding hypophosphite to the electrolyte resulted in a change of the Co:Mo composition ratio, decreasing Mo. The surface morphology was characterized by SEM, and deposit composition assessed by XRF and EDS. The electrochemical active surface area was characterized using a ferri/ferrocyanide redox reaction and by inspection of the limiting current. The HER activity was evaluated in a 1 M NaOH electrolyte at room temperature. The overpotential of the electrodeposited films at -10 mA/cm2 followed the order: Co-Mo-P-TiO2 > Pt > Co-Mo-TiO2 > Co-Mo > Co, where the alloys and composites had comparable Co:Mo composition ratio. There was some surface roughening due to the inclusion of the TiO2 particles, but the enhanced surface area was not significant enough to account for the large improvement of the HER, indicative of an energetic effect. The Tafel slopes of Co, Co-Mo and Co-Mo-TiO2 had similar values between 72-74 mV/dec. However, by adding phosphorus, the Co-Mo-P-TiO2 composites exhibited a favorably reduced Tafel slope to 62 mV/dec with low deposit concentration of P, 2.5 wt %. The exchange current density of Co-Mo was enhanced with TiO2, and further increased 3 times with added P in the deposit. Also, the Co-Mo-P-TiO2 composites underwent an ageing procedure for 48 hours that verified stability.
Pulsed Electrodeposition of Nanocatalysts for Energy Storage Applications: Mathematical Modeling and Experimental Studies
Authors: Karimi Shahram
Published: December 2020

With the growing demand for clean energy, the need for affordable, efficient energy storage technologies has never been more urgent. Pumped hydro and compressed air storage technologies have been widely used, but they are heavily dependent on location and are not considered to be universal solutions. Secondary batteries, including Li-ion and lead-acid batteries, have played a major role in storing excess electrical energy, but they suffer from high cost, performance degradation over time, and environmental issues during use and disposal. Metal-air batteries have experienced a renaissance on account of their acceptable energy density, superior cycleability, enhanced stability and cost benefits compared with other commercially available batteries. Despite these desirable properties, metal-air batteries suffer from a number of thermodynamics and kinetics hurdles that must be overcome, if their widespread deployment is desired. One of the major impediments to wide-scale commercialization of metal-air batteries continues to be their inferior capacity and cycle stability. Part of these issues can be ascribed to the shortcomings of the cathode materials and structures in general, and the inferiority of their catalyst layers in particular. It is well established that nano-structuring battery components would improve their short- and long-term performance by enhancing reaction kinetics.

Nanocatalysts such as transition metals, platinum and manganese dioxide were electrodeposited on a number of conductive substrates, including carbon paper, carbon cloth and titania nanotubes (TNTs) with high aspect ratios. Catalyst electrodeposition was performed utilizing pulsed current electrodeposition with different waveforms, low duty cycles, and high peak deposition current densities. All catalysts were characterized using microscopy, spectroscopy and electrochemical techniques. The presence of nanocatalysts were confirmed by SEM and XRD and were found to be 2-5 nm for platinum and 10-50 nm for nickel and oxides of manganese.

A mathematical model was developed to determine the roles of various deposition process parameters on the size and catalytic activity of the resulting nanocatalysts in different environments. The model is based on progressive nucleation and takes into account some key contributing factors towards growth current and, ultimately, nucleation, including diffusion, ohmic and charge transfer phenomena. A varying diffusion coefficient during electrodeposition was also considered and evaluated. Model predictions were confirmed by experimental measurements with emphasis on platinum and manganese dioxide nanocatalysts for use in PEM fuel cells and metal-air batteries, respectively.
(Electrodeposition Division Early Career Investigator Award Address) Metal Patterning by Electrodeposition: Local Bipolar Electrochemistry and Additive-Derived Electrode Bifurcation
Authors: Braun Trevor Michael
Published: December 2020

One of electrodeposition’s highest value applications is in manufacturing of electronic devices, ranging in scale from nanometer connections in integrated circuits up to millimeter scale features in printed circuit boards. The wide-range of feature geometries and substrate complexity (conducting, semiconducting, insulating, etc.) in this constantly evolving industry has driven extensive efforts to tailor both lateral and vertical material growth characteristics, diverging from more traditional electroplating applications focused on uniform films as applied to coatings. Like the electronics industry, techniques for 3D control of electrodeposition are consistently evolving. These methods include deposition through patterned masks (through-mask plating), use of sacrificial materials to form patterns (EFAB), localized electrodeposition using confined electrodes, and surface adsorbates that drive spatially-dependent active/passive regions through the coupling of local chemical and electrical gradients.

In this presentation, I will highlight recent advances in two of these areas: electrodeposition through confined electrodes and by influencing deposition kinetics with surface adsorbates. In the former, bipolar electrochemistry is combined with microjet electrodes to permit localized electrodeposition of a ‘pixel’ on a conductive surface without requiring electrical contact; patterns are produced by rastering the microjet similar to commercial 3D-printing methods. In the latter, electrolyte additives that inhibit deposition can induce spontaneous formation of spatially bifurcated active and passive regions; characteristics of the electrode topography, surface heterogeneity, and electro(chemical) transport through the cell determine the shape of 2D pattern formation. Electroanalytical measurements of these active/passive systems inform electrode shape-change models describing the interplay between transport and electrochemical kinetics. This fundamental insight permits control of an otherwise random bifurcation process that can be tailored for a variety of applications.
Electrodeposition of Cuprous Oxide on a Free-Standing Porous Cu Framework for Photoelectrochemical Water Splitting
Authors: Kurniawan Mario , Stich Michael , Marimon Mayra , Camargo Magali Karina , Peipmann Ralf , Hannappel Thomas , Bund Andreas
Published: December 2020

The use of hydrogen as a chemical fuel is an attractive and promising method as an alternative sustainable green energy carrier. The combination of direct sunlight and semiconductor photoelectrodes in a photo-electrochemical (PEC) cell can generate hydrogen by splitting water molecules into H2 and O2
1. Copper(I) oxide or Cuprous oxide (Cu2O) is a p-type semiconductor with a bandgap of ~2 eV which makes it suitable for solar visible light absorption and it possesses a suitable band position for water reduction to hydrogen in the PEC cell2. The focus here is to increase the surface area of Cu2O photocathode to improve the PEC water splitting performance. Using dynamic hydrogen-bubble assisted electrochemical deposition method, a highly porous Cu substrate was synthesized in an acid copper sulfate bath at current densities above -1 A/cm2. To obtain a free-standing porous copper framework the structure must be reinforced at a lower current density using the same acidic bath and was separated from the substrate via ultrasonication The Cu2O crystal was then deposited on the free-standing porous Cu framework from an alkaline copper bath. The photoelectrochemical analysis of Cu2O was performed using a solar simulator at 1.5 AM and it shows a significant improvement of the photocurrent in comparison to the planar sample.

M. Grätzel, Nature, 414, 338–344 (2001).

A. Paracchino, V. Laporte, K. Sivula, M. Grätzel, and E. Thimsen, Nat. Mater., 10, 456–461 (2011).

Figure 1
AuCu Catalysts with High Activity and Selectivity for Electrochemical Reduction of CO2 to CO
Authors: Han Gyeong Ho , Kim Junhyeong , Kim Hyunki , Hong Seokjin , Ahn Sang Hyun
Published: December 2020

As the extensive usage of fossil fuels, the concentration of CO2 in the atmosphere has increased, and global warming becomes a critical problem. Recently various studies have been conducted to reduce the concentration of CO2. One attractive method to solve this problem is the electrochemical reduction of CO2. It produces feedstocks and useful fuels of C1 chemistry, such as CO, CH4, CH3OH and HCOOH at room temperature and ambient pressure. Among the useful products, the CO is known to have the economic benefit because the market price of CO is higher than other products. However, the electrochemical reduction usually suffers from huge energy losses due to the high overpotential originated form chemical stability of CO2. Therefore, development of a highly active catalyst is essential. Currently, Au-based and Au-based bimetallic catalysts are commonly used to convert CO2. To obtain highly activity and selectivity, the various investigates are being conducted to control properties, which their morphology, size, composition, facets and oxidation states. In addition, these properties can effect intermediate adsorption, grain size and electrochemical surface area.

Herein, AuCu nanoparticles were directly fabricated on carbon paper substrate by using electrodeposition method. The electrodeposition parameters such as precursor concentration and deposition time were changed to control the morphology and composition of AuCu catalysts. The AuCu nanoparticles were used as cathode for electrochemical carbon dioxide conversion in 0.5 M KHCO3 in H-type cell which was separated by proton conducting membrane. At a certain condition, the CO Faradaic efficiency of ~80 % was achieved at a potential of -0.7 VRHE. Further post-treatments such as anodizing or annealing methods were performed to change the control properties of the catalyst. And then, modification on catalytic performance was observed.
Real-Time Analysis of a Single Secondary Particle Using an Electrochemical Modeling
Authors: Song Jihun , Park Joonam , PARK SUN HO , Lee Yong Min
Published: December 2020

Promising electrode active materials such as LiNiMnCoO2, LiNiCoAlO2 and LiFePO4 is made by a secondary particle containing millions of primary particles to improve its conductivity and diffusion. Therefore, design and analysis of the secondary particle are most important things to improve the performance of the active material so some groups are studying the intrinsic characteristics by a single particle measurement technique which cycle a half-cell of a single active material particle and lithium metal. With this method, we can calculate the diffusion coefficient, exchange current density

Nevertheless, it is almost impossible to see what happened inside the particle during cycling and it is hard to optimize particle design by this method to meet the required each condition including high power or long cycle life.

To overcome this situation, we developed a single particle model which can easily analyze inside of the particle as well as design the particle. To get the reliability of the model, we compared the experimental result by the single particle measurement technique and the simulation result. Using this model, we can estimate the real-time properties including distributions of lithiation, electric potential and overpotential inside the particle and concentration in a liquid phase.

Besides, we analyze the secondary particle with change of the particle design (solid volume fraction, primary particle size and secondary particle size)
A Rhombohedral Li2NaV2(PO4)3/C Nanoflake Cathode for Li-Ion Battery with High Rate Capability and Long Cycle Stability
Authors: Alfaruqi Muhammad Hilmy , Islam Saiful , Kim Seokhun , Park Sohyun , Kim Jaekook
Published: December 2020

Rhombohedral Li2NaV2(PO4)3 (LNVP) is an attractive cathode material for lithium-ion battery (LIB) application due to its single voltage plateau at 3.7 V that provides a constant output power. However, only view studies have reported rhombohedral (LNVP) cathode material because it requires a complex route to synthesize. Here, we propose a simple and low-cost pyro-synthesis strategy to develop a rhombohedral LNVP/C nanoflake electrode for useful LIB applications for the first time. When tested in lithium-ion cells, the rhombohedral LNVP/C demonstrated long cycle stability with 100% of the initial discharge capacity retained after 300 cycles. Under long-term cycling, the present cathode showed approximately 99% of Coulombic efficiency. Besides, the realization of specific capacities of 77 and 55 mAh g-1 at current densities as high as 6.4 and 12C, respectively, clearly demonstrates the decent rate capabilities of the prepared rhombohedral LNVP/C electrode. The present study proves to be useful for utilizing the pyro-synthesis process as a straightforward and cost-cutting approach not only to develop nanostructured rhombohedral LNVP/C but also other cathode materials for high performance LIB applications.
In-Plane Oriented Linear Assembly of Te Nanowires in Polydimethylsiloxane-Based Composite Film for the Enhancement of Piezoelectric Property
Authors: Cho Hong-Baek , Park Kee-Ryung , Lim Minseob , Song Yoseb , Choa Yong-Ho
Published: December 2020

Flexible piezoelectric materials are attractive as empowering devices in the field of sensors, actuators and energy harvesting. Herein, we fabricate a polymer-based nanocomposite with piezoelectric property by incorporation of tellurium (Te) nanowires. Firstly, large-scale selective synthesis of uniform single crystalline tellurium nanowires with a diameter of 150 nm av. and 10 μm av. in length, can be realized by a hydrothermal process. The Te nanowires with random distribution in pre-polymer of polydimethylsiloxane (PDMS) is relocated forming linearly aligned assembly controlled by application of external AC electric field. The aligned Te-PDMS at 0.5 wt% Te content gives a maximum output voltage of 13.9 V, which is 2.4-fold comparing corresponding film with random distribution. This work provides an effective alignment of nanofillers in a viscous polymer matrix and noble method to fabricate enhance piezoelectric composite film materials.
Combined Experimental and Multi-Scale Modeling Approach to the Development of Electrocatalysts with Improved CO2 Reduction Activity Towards C2+ Alcohols
Authors: Morales Guio Carlos Gilberto
Published: December 2020

The development of high performance catalysts for the production of fuels and chemical in electrochemical reactors call for a profound understanding of the processes occurring at multiple scales and emphasizes the importance of broadening catalyst design principles beyond the transition state theory to include fundamentals of mass and charge transport. The selective production of C2+ alcohols on cooper electrodes requires that multiple thermo-chemical and electro-chemical steps occur at the electrode-electrolyte interface at rates faster than those for the competing hydrogen and hydrocarbon evolution reactions. At the same time, the rates of most of these reactions are not only dependent on the intrinsic activity of copper, but are highly affected by the local environments that determine the rate of regeneration of reaction intermediates, the availability of proton sources for proton-electron coupled steps and the extend of the thermodynamic driving force for the formation of each of the multiple products.

In this talk, a mathematical model based on the Poisson-Nernst-Planck equation is presented that describes transport phenomena and ion migrations within an electrochemical cell. This models is shown as a valid tool for the rationalization of experimental observations and the normalization of experimental reaction rates to changes in the local concentration of species during electrocatalysis. Normalization of reaction rates to local changes in concentrations allows a better understanding of the nature of electrode/electrolyte interfaces during CO2 reduction to C2+ alcohols and the decoupling of mass transport effects and intrinsic kinetics. Charge transfer coefficients and pre-exponential factors are extracted from experimental data to describe the intrinsic activities of copper and other transition metal electrodes during the electrochemical reduction of CO2 to CO, alcohols and hydrocarbons. We demonstrate the rational application of this mathematical model in the design of more active and selective electrocatalyst for C2+ alcohol production by introducing cooperative catalysis schemes where gold nanoparticles generate high local concentrations of carbon monoxide intermediates on neighboring copper sites that catalyze the production of C2+ alcohols at higher rates than without gold. Electrode nanostructuring is also leveraged to create local environments withing electrode pores that increase the rate of C2+ alcohols formation. Finally, the extent to which these mathematical models could be used in the description and design of modular electrochemical reactors for practical applications is discussed to highlight challenges and opportunities of future electrocatalytic technologies for the production of C2+ alcohols from CO2.
Influence of Processing Route and Chemical Composition on Electrochemical Properties of High-Capacity Layered Oxide Cathodes
Authors: Fung Kenneth , Chang Chia Chin , Fung Kuan-Zong , Tsai Shu-Yi
Published: December 2020

To obtain high-capacity Li ion batteries; oxide cathodes with layered structure still remain the ones that provide high enough capacities. It is known that electrons and Li+ ions are being extracted simultaneously in the charging process. During high-voltage charging, more ionic/electronic defects formed in layered oxides will be created. Thus, their electrochemical and structural properties are strongly affected by the formation and/or elimination of these defects. Higher defect concentration, like Li vacancies, VLi’, tends to destabilize its crystal structure. As a result, the phase transformation may occur in the cycled cathode. Accordingly, the capacity fading was frequently observed in cycled layered cathode due to the phase-changing process. Moreover, the existing defects in layered oxides are typically determined by the condition of fabrication processes, for instance the dopants and oxygen partial pressure.

In this study, two well-known layered oxides with fixed 80% Ni in the transition metal ion layer, namely NMC 811 and LiNi0.8Co0.15Al0.05O2 (NCA), were investigated. Their minor elements/dopants Mn and Al may play an important role on affecting their defect chemistry as well as electrochemical properties. Thus, their electrical/electrochemical/structural properties are examined as a function of the minor dopants, Mn and Al. First, the electrical measurement of NMC 811 and LiNi0.8Co0.15Al0.05O2 are conducted. Assembled cells using above-mentioned cathode and Li anode with desired liquid electrolyte were tested and cycled. SEM and XRD analyses were conducted on assembled and cycled cells. The analysis and results are illustrated based on the chemical characteristics of doping ions and the electronic/ionic defects induced.
Shedding Light about the Role of Proton Intercalation in Layered Cathode Materials By Means of First Principle Computations
Authors: Posada Perez Sergio , Rignanese Gian-Marco , Hautier Geoffroy
Published: December 2020

Flammability, toxicity, and cost are only a few drawbacks about the use of organic liquid electrolytes. On the other hand, working in aqueous electrolyte would therefore be extremely beneficial especially to lower production cost and obtain higher safety and lower toxicity.

In contrast to organic electrolytes, where only the inserted metal ions can (de)intercalate in the electrode material, the use of aqueous electrolytes opens the possibility of proton co-insertion. But are protons able to intercalate in the electrodes? and if the answer is affirmative, which is the effect of proton intercalation in the battery performance?

Several (electro)chemical studies combined with first-principles computations have confirmed the easy protonation of layered electrodes at different ranges of pH values and this fact has been directly related with the detrimental in cathode materials. Nevertheless, several studies reported the excellent performance of layered LiCoO2 and LiCo1/3Ni1/3Mn1/3O2 as positive electrode -without coating- using neutral or basic salt in water electrolytes. Thus, it remains an open question: Why these layered cathode materials so prone to proton intercalation could perform as well in aqueous environment?

In this work, we use density functional computations to investigate the lithium/proton exchange in some well-known cathode materials. The analysis of the proton insertion mechanism has been carried out in the bulk and surfaces of these materials in order to demonstrated which specific chemical and structural features lead to electrochemically stable materials for aqueous batteries. To analyze the Li+/H+ exchange, several Li+/H+/vacancy orderings and arrangements were computed to study the phase stability at different pH values. This study provides fundamental investigations about the role of H-intercalation in the performance of aqueous battery operations.
(Invited) Imaging the Surface of a Polycrystalline Electrodeposited Cu Film in Real Time Using in-Situ High-Speed AFM
Authors: Koorikkat Aswathi , Payton Oliver D , Picco Loren , Schwarzacher Walther
Published: December 2020

High-speed AFM is capable of scan rates around 1000 times greater than a conventional AFM. When used to probe the electrodeposition process, this technique can deliver high resolution images of films grown at rates as high as 0.6 nm per second in-situ in real time. This opens practical polycrystalline thin film electrodeposition processes up to study. We present data for Cu films electrodeposited from an organic additive-free acid sulphate electrolyte that reveals in detail how the grain structure coarsens with increasing film thickness. We image grain structure coarsening arising both from differing vertical growth rates and from grains overgrowing their neighbours laterally. Geometric constraints require coarsening caused by the former to be accompanied by increasing surface gradients, and we have measured these. Rather than block growth, deposition is actually enhanced in the scanning region, presumably due to forced convection associated with movement of the tip.
Atomistic State of Hydrogen in Electrochemically Deposited Cu Films
Authors: Fukumuro Naoki , Tohda Kosuke , Yae Shinji
Published: December 2020

Electro and electroless deposition of Cu films are widely used in the print circuit boards production. These electrochemical Cu deposition process are accompanied with the simultaneous hydrogen evolution, and the hydrogen co-deposition sometimes causes the voids and blisters1). However, the detail mechanism of such hydrogen-induced phenomena have not been clarified. We previously reported that the primary cause of the room-temperature grain growth observed in electrodeposited Cu films was the formation of superabundant vacancies induced by the hydrogen co-deposition2). In this study, the atomistic state of hydrogen co-deposited in the Cu films obtained by electro and electroless deposition and the influence of hydrogen on the microstructure of Cu films were investigated.

Cu films were electrodeposited from six different baths (sulfate bath, additive-containing bath, chloride bath, pyrophosphate bath, EDA bath, and EDTA bath) and electrolessly deposited from an EDTA bath. The amount and atomistic state of hydrogen in the Cu films were analyzed by thermal desorption spectroscopy (TDS). The microstructural analysis of the Cu films was performed by X-ray diffraction (XRD) and transmission electron microscopy (TEM).

In the electrodeposited Cu films with high hydrogen concentrations (x = H/Cu = 5.4 ~ 98.2×10-4), the room-temperature grain growth proceeded with the desorption of hydrogen during 7 ~ 21 days after deposition2). A pronounced desorption peak at 600 ~ 700 K due to the break-up of vacancy-hydrogen clusters3) was observed in the thermal desorption spectra of hydrogen from these Cu films.

In the thermal desorption spectra of hydrogen from electrolessly deposited Cu films, a pronounced peak at around 420 K and a small peak at 600 ~ 700 K were observed and the hydrogen concentration was x = 13.6×10-3. From the XRD measurements, the lattice expansion of about 0.14% was observed in the as-deposited Cu films, which was reduced with the desorption of hydrogen at room temperature after 7 days. These results suggest that the desorption peak at 420 K may be assigned to the desorption of hydrogen from the regular interstitial sites. In the TEM images of these Cu films, many nano-voids distributed in the crystal grains were observed. We consider that the hydrogen molecules trapped in the nano-voids should be desorbed at high temperature above 900 K. The high-temperature TDS measurements will be performed.

References

1) T. Sharma, A. E. Landry, A. Leger, D. A. Brown, T. Bernhard, S. Zarwell, F. Brüning, and R. Brüning, Thin Solid Films, 666, 76 (2018).

2) N. Fukumuro, H. Yoshida, T. Yamazaki, Y. Fukai, and S. Yae, J. Japan. Inst. Met. Mater., 80, 736 (2016).

3) Y. Fukai, M. Mizutani, S. Yokota, M. Kanazawa, Y. Miura, and T. Watanabe, J. Alloy. Comp.,
356-357, 270 (2003).
Hydrogen in Electrolessly Deposited Ni/Au and Ni/Pd/Au Films
Authors: Yae Shinji , Oda Yukinori , Sagara Yusaku , Fukumuro Naoki
Published: December 2020

For the surface finishing of copper layer on printed circuit boards, autocatalytic electroless deposition of nickel-phosphorus alloy and immersion deposition of gold (ENIG, Ni-P/Au) or autocatalytic electroless deposition of Ni-P, palladium and immersion deposition of Au (ENEPIG, Ni-P/Pd/Au) are widely used. The Ni-P/Pd/Au surface finish is suitable not only for lead-free soldering but also for wire bonding [1]. For soldering, it was reported that hydrogen plasma improved bonding behavior and realized a flux-free process [2]. Electrochemically deposited metal films include hydrogen atoms. The hydrogen adsorbed in metal films causes various phenomena such as atomic diffusion, alloying, crystal growth, void formation. We have been investigating the atomistic state and behavior of hydrogen in electrodeposited metals by thermal desorption spectroscopy [3, 4]. In this study we measured changes in hydrogen amounts in the Ni-P/Au and Ni-P/Pd/Au surface finishes [5]. We used two different electroless Pd baths using formic acid (Ni-P/Pd/Au) and sodium phosphinate (Ni-P/Pd-P/Au) as reducing agents. The Ni-P films contained large amounts of diffusible hydrogen that desorbs at room temperature. During autocatalytic electroless deposition of Pd and Pd-P on Ni-P films, the greater part of the hydrogen in the Ni-P films desorbed. Although no hydrogen evolution accompanied immersion Au deposition, the hydrogen amounts in Ni-P/Au, Ni-P/Pd/Au, and Ni-P/Pd-P/Au films were much greater than in films without a Au layer. Moreover, at room temperature, they remained almost unchanged for one month after deposition, indicating that the thin Au layer (< 0.1 μm) prevents hydrogen desorption from the metal films. The high hydrogen concentration in Ni-P/Au films improved solder wettability.

[1] Y. Oda, M. Kiso, S. Kurosaka, A. Okada, K. Kitajima, and S. Hashimoto, Proc. Internal. Microelectronic and Packaging Soc., IMAPS (2008).

[2] T. Hagihara, T. Takeuchi, and Y. Ohno, Proc. 10th Electronics Packaging Technology Conf. (IEEE), 595 (2008).

[3] N. Fukumuro, S. Kojima, M. Fujino, Y. Mizuta, T. Maruo, S. Yae, and Y. Fukai, J. Alloy. Comp., 645, S404 (2015).

[4] N. Fukumuro, K. Tohda, and S. Yae, this symposium.

[5] Y. Oda, Y. Sagara, N. Fukumuro, and S. Yae, J. Surf. Finish. Soc. Jpn., 70, 163 (2019).
Hydrogen Generation from an Alkaline NaBH4 Solution Using Different Cobalt Catalysts
Authors: Sukackiene Zita , Balciunaite Aldona , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus
Published: December 2020

The effective Co, CoB and CoBM, where M = Mo, Zn, and Fe, catalysts have been deposited on the Cu surface by a simple electroless metal deposition method using morpholine borane as a reducing agent and used as catalysts for hydrogen generation from an alkaline NaBH4 solution. The catalytic activity of different cobalt alloys catalysts towards the hydrolysis of NaBH4 has been investigated by measuring the amount of generated hydrogen from an alkaline solution contained 5 wt. % NaBH4 and 0.4 wt. % NaOH. The rate of H2 generation has been measured at solution temperatures in the range from 298 to 318 K in order to determine the activation energy.

It has been determined that the synthesized Co/Cu, CoB/Cu and CoBM (M=Mo,Zn,Fe)/Cu catalysts demonstrate the catalytic activity for the hydrolysis reaction of NaBH4. The lowest obtained activation energy of the hydrolysis reaction of NaBH4 has been 27 kJ mol-1 for the CoBMo/Cu catalyst. The hydrogen generation rate has been achieved 15.30 ml min-1 using the CoBMo/Cu catalyst at a temperature of 313 K and it increases ~3.5 times with the increase of temperature to 343 K. Moreover, the CoBMo/Cu catalyst shows a highest catalytic activity for hydrogen generation from the alkaline NaBH4 solution as compared with that for other Co/Cu, CoB/Cu, CoBZn/Cu, and CoBFe/Cu catalysts.
Electrorefining of Gallium Using Bipolar Electrodes and a β-Alumina Membrane
Authors: Kozin Valentin F. , Blyznyuk Antonina V. , Omel'chuk Anatolii A
Published: December 2020

A method for the refining of gallium, using bipolar gallium electrodes, in molten electrolytes containing its compounds with lower oxidation states has been developed. A gallium (I) - β –alumina membrane was used to separate the electrodes and bipolar electrodes. The effect of the electrolysis conditions on gallium transfer from the anode to the cathode through the gallium (I) - β –alumina membrane has been studied. It has been show that gallium refining in molten electrolytes allows one to obtain high-purity gallium with high current efficiency.
(Invited) Electroforming in Space and Ground Telescopes
Authors: Valsecchi Giuseppe , Banham Robert
Published: December 2020

In the last 25 years, electroforming process has been extensively optimised to produce grazing incidence optics for the X-ray space telescopes, enabling the renown observatories Beppo-SAX for the Italian Space Agency, SWIFT for NASA, XMM Newton for ESA, eROSITA for MPE.

These optics are made of thin Nickel mirrors that are grown by electroforming process in an electrolytic bath on a Gold coated mandrel.

Mandrels are manufactured in Aluminium alloy with NiP coating, which allows, after polishing to reach very smooth roughness in the order of 0.3 nm.

After separation of the mirror from the mandrel, Gold layer becomes the X-Ray optical reflecting coating, preserving the low roughness of the mandrel.

The Nickel Mirror shells are nested tightly in high-performance optical structures, the X ray telescope.

The electroforming cycle ranged between 40 and 100 hours, depending on the thickness of the mirrors, typically between 0.2 and 0.6 mm for the innermost and outermost shells, respectively. The average electroforming time is 65 hours per mirror, with 1 hour for assembly and preparation of the mandrel and 1 hour for separation after electroforming.

Electroforming has also been adopted for production of large reflector panels for sub-millimetre radio telescope applications. These are laminated panels made of electroformed Nickel skins bonded to an Aluminium honeycomb core over a precise mould, resulting in typical shape accuracy of 8 µm at only 10 kg/m² mass density.

Between 2006 and 2016, 3000 mirror panels for 25 antennas of the ALMA radio-telescope array of ESO and 1600 mirror panels for the 50-m diameter Large Millimetre Telescope (LMT) “Alfonso Serrano” of INAOE were designed, produced and tested.

Electroforming replica consists of the replication of mirror substrates from high precision mandrels by means of the electroforming process.

The mandrel is machined and polished to the shape accuracy and surface roughness requirements of the final mirror.

In the electroforming process, the mandrel is Gold-coated by e-beam evaporation and then immersed in the electrolytic bath. Nickel ions, deposit onto the Gold-coated mandrel creating a low-stress Nickel mirror.

Upon reaching the desired thickness, the mandrel is removed from the bath and the mirror is separated from the mandrel. In this process, the Gold layer is bonded to the mirror, creating an integrated reflective layer with the same roughness as the mandrel. The mandrel is then qualified for the next electroforming cycle, where another mirror is replicated from the same mandrel, and so on for the following cycles.

Process cycles, key inspection points, verification and testing as part of the production cycles will be described and presented.

Panoramic view of ALMA radio-telescopes. Photo courtesy of ESO.

Figure 1
Magnetic Fluids Assisted Electro-Leaching of Metals
Authors: Accogli Alessandra , Pesce Ruggiero , Magagnin Luca
Published: December 2020

In current research, micro and nanoparticulate electrode materials have taken their place because they offer a large internal surface area with respect to the macroscopic dimensions of such electrodes [1]. The nano-impact method is a powerful tool that enables the characterization of individual particulate nano-objects in solution and study of their reactivity [2]. A three electrodes setup system working as a standard electrochemical cell is typically used. Magnetite (Fe3O4) nanoparticles with the strongest saturation magnetization of all naturally occurring iron oxides, combined with properties such as low toxicity, good biocompatibility, high stability, and low production costs, have attracted a lot of interest [3]. There is also substantial interest in their use as magnetic fluids, in data storage, in catalysis, and as electrode materials.

In this work, magnetite micro and nanoparticles have been synthetized by chemical precipitation method in presence of surfactants or functional organic polymer. The use of surfactants to stabilize these synthesized nanoparticles is crucial, as Fe3O4 nanoparticles have high surface energies and tend to aggregate. Magnetic fluids constituted by dispersed functionalized magnetite particles are used as particulate electrode in different fluids and characterized into a three electrodes cell in order to evaluate their electrochemical behavior. A deeper understanding of the particulate electrode has been performed in situ on supported particles through electrochemical AFM/STM measurements, highlighting the behavior of the single aggregate. Together with the charge transfer characterization as a function of particles size and concentration, functionalization and fluid composition, practical applications of the particulate electrodes will be presented. Specifically, the use of particulate electrodes in the electrochemical metal recovery, showing the ions adsorption properties of magnetite particles as a function of surface functionalization and their electrochemical reduction at the magnetic fluid/current collector interphase will be discussed for specific systems, e.g. copper and lithium.

1.V. Noack, H. Weller, A. Eychmu1ller, J. Phys. Chem. B, 106 (2002) 8514-8523

2. S.V Sokolov et al., Phys.Chem.Chem.Phys., 19 (2017) 28

3. K. Murugappan, ChemElectroChem, 1 (2014) 1211 – 1218
Disordered Cubic Spinel Structure in the Delithiated Li2MnO3 revealed By Difference Pair Distribution Function Analysis
Authors: Oishi Masatsugu , Shimoda Keiji , Ohara Koji , Kawaguchi Tomoya , Uchimoto Yoshiharu
Published: December 2020

An archetypical Li-rich layered oxide, Li2MnO3, shows a large initial charge capacity of ~350 mAh g-1 with little oxidation of the constituent Mn ions, yet, the crystal structure of delithiated Li2MnO3 is still unclarified because the structural disorder induced by the considerable Li extraction makes the analysis challenging. We have performed X-ray pair distribution function (PDF) analysis in combination with the X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to reveal the disordered crystalline structure of the electrochemically delithiated Li2MnO3. The XRPD and TEM analyses clarified the formation of a low-crystallinity phase in the light of the average structure. The XAS and PDF analyses revealed that the MnO6–based framework was rearranged with maintaining the MnO6 octahedral coordination after the initial charge. The difference pair distribution function (d-PDF) technique was therefore employed to extract the structural information of the low-crystallinity disordered phase. The delithiated phase was found to have a structure similar to the cubic spinel, LiMn2O4, rather than that of delithiated LiMn2O4 (l-MnO2). In addition, the middle-range order of the delithiated phase deteriorated after the charge, indicating a decrease of coherent domain size to a single nm order. The composite structure formed after the first charge, therefore, consists of the disordered cubic spinel structure and unreacted Li2MnO3. The formation of the composite structure “activates” the electrode material structurally and eventually induces characteristic large capacity of this material.
Impact of Annealing Time on Lithium Local Environment of LiMn0.5Ni0.5O2: DFT-Supported 6 Li Solid-State NMR Study
Authors: Shin Woochul , Vu Anh , Garcia Juan , Ji Xiulei , Iddir Hakim , Dogan Fulya
Published: December 2020

To quench the thirst of ever-increasing demand for high energy and low-Co lithium-ion batteries (LIB), LiMn0.5Ni0.5O2 has received considerable attention as a promising alternative cathode. However, it has been plagued by the structural failure driven by the irreversible phase change upon subsequent cycling and the structural degradation caused by the unavoidable Li/Ni exchange.[i] This brings the importance of understanding the relation with lithium local environments and domains on overall electrochemical properties of materials.

In this study, we have focused on two different samples, prepared by different annealing times (150 vs. 15 hours) to elucidate the change of local lithium surroundings and its sensitivity to the annealing time. We use a combination of 6Li solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR)[ii] and density functional theory (DFT)[iii] techniques to illuminate the impact of annealing time to the local lithium environment of LiMn0.5Ni0.5O2. Examination of NMR spectra reveals peak shift and intensity change, which is scrutinized by the assistance of DFT that is capable of deconvoluting the NMR spectra and obtain the corresponding local lithium environment. We compare the NMR spectra of the previously reported transition metal arrangements such as a zigzag, row, and honeycomb structures and describe the influence of Li/Ni exchange on the shape of the spectra. Overall, we combine the various computed-NMR spectra that show in close proximity to the experimental spectra, which provides new insights to understand the correlation between annealing time and local lithium environment for a promising LIB cathode design.

[i] Ceder, G. et al., Phase Transitions in the LiNi0.5Mn0.5O2 System, Chem. Mater. 2007, 19, 7, 1790–1800

[ii] Grey, C. P. et al., NMR Studies of Cathode Materials for Lithium-Ion Rechargeable Batteries, Chem. Rev. 2004, 104, 4493−4512

[iii] Casas-Cabanas, M. et al., DFT-Assisted Solid-State NMR Characterization of Defects in Li2MnO3, Inorg. Chem. 2019, 58, 8347−8356
Local Electrochemical Impedance Spectroscopy: Towards an Improvement in the Low Frequency Domain
Authors: Pereira Gomes Maurilio , Costa Isolda , Pebere Nadine , Rossi Jesualdo Luis , Turmine Mireille , Vivier Vincent
Published: December 2020

The ability to probe surface reactivity at the local scale has led to a new understanding of the electrochemical reactivity in relation to the surface microstructure. Among the various techniques developed in recent years, local electrochemical impedance spectroscopy (LEIS) takes advantage of using a transient approach to locally characterize a stationary electrochemical system without the need to add any redox mediator in solution. The principle of LEIS was pioneering by Isaacs et al. [1, 2]. The local current density, , is obtained from the local potential difference in solution, , measured with a probe which consisted in three reference microelectrodes positioned close to the interface of interest, as depicted in Fig. 1.

Whatever the mode of operation, the spatial resolution of the technique is governed by the following parameters [3, 4]:

- The diameter of each microelectrode used for sensing the local potential in solution;

- The distance between the two potential microprobes (the smaller the distance, the smaller the potential difference) [5];

- The distance between the dual probe and the substrate is an important parameter to be considered. Due to the potential distribution in the electrochemical cell, the difference in potential to be measured will be smaller if the probe is positioned far from the substrate. This may result in difficulties in measuring properly LEIS response in the low frequency domain, as regularly encounter, for instance, in coating degradation application.

In the present work, we reported a new experimental setup that allows the measurement of local electrochemical impedance response of an interface in a wide frequency range, including the low frequency domain which is discussed. Proofs of concept with model systems, as well as passive materials and coatings are presented.

Keywords:Local electrochemical impedance spectroscopy; low frequency measurements; electrochemical instrumentation; micro-electrochemistry.

References

[1] R.S. Lillard, P.J. Moran, H.S. Isaacs, A novel method for generating quantitative local electrochemical impedance spectroscopy, J. Electrochem. Soc., 139 (1992) 1007-1012.

[2] F. Zou, D. Thierry, H.S. Isaacs, A high-resolution probe for localized electrochemical impedance spectroscopy measurements, J. Electrochem. Soc., 144 (1997) 1957-1965.

[3] V.M.-W. Huang, S.-L. Wu, M.E. Orazem, N. Pebere, B. Tribollet, V. Vivier, Local electrochemical impedance spectroscopy: A review and some recent developments, Electrochim. Acta, 56 (2011) 8048-8057.

[4] O. Gharbi, K. Ngo, M. Turmine, V. Vivier, Local electrochemical impedance spectroscopy: A window into heterogeneous interfaces, Current Opinion in Electrochemistry, 20 (2020) 1-7.

[5] C.P.d. Abreu, C.M.d. Assis, P.H. Suegama, I. Costa, M. Keddam, H.G. de Melo, V. Vivier, Influence of probe size for local electrochemical impedance measurements, Electrochim. Acta, 233 (2017) 256-261.

Figure 1
Welcome Remarks - F02: Advances in Application and Theory of Electrochemical Impedance Spectroscopy
Authors: Orazem Mark E.
Published: December 2020

Welcome to F02: Advances in Application and Theory of Electrochemical Impedance Spectroscopy! Take a moment to listen to welcome remarks from the lead organizer, Mark Orazem.
Challenges in Moving to Multiscale Battery Models - Where Electrochemistrymeets and demands more from Math
Authors: Shah Krishna , Subramaniam Akshay , Mishra Lubhani , Jang Taejin , Bazant Martin , Braatz Richard , Subramanian Venkat R.
Published: December 2020

As lithium-metal and lithium-sulfur batteries are receiving great attention being among the most promising candidates for next-generation batteries in transportation applications, there has been significant recent interest in studying their multiscale characteristics. Multiple studies have conveyed the importance of microscale effects, pressure effects, and morphology changes for these batteries, especially for batteries with lithium metal as the anode. Advances in computing power make researchers believe that the detailed multiscale models can be efficiently simulated to arrive at the insights for the degradation and performance loss; however, this is not true and special attention needs to be paid to local singularities, boundary layers, moving boundaries, etc. This work presents 2D examples that illustrate the importance of grid convergence studies, provides well-defined detailed models to test the efficiency of numerical schemes, and discusses the associated simulation challenges. Perspective on important numerical aspects for robustness and efficiency, and recommendations on the possible best practices for studies involving multiscale modeling are also discussed.
A Comprehensive Studies on the Performance of a LiNi0.6Mn0.2Co0.2O2 Cathode Using a Physics-Based Model
Authors: Ansah Solomon , Hyun Hyejeong , Shin Namsoo , Lee Jong-Sook , Lim Jongwoo , Cho Hoon-Hwe
Published: December 2020

The gradual growth of the Li metal anode in lithium-ion batteries (LIBs) due to their high theoretical energy density has made it become the future of the battery fraternity replacing graphite anode. Notwithstanding, the cathode material, layered lithium transition metal oxides (particularly NMC – LiNixCoyMnzO2), plays an important role because of it’s potential to improve the overall energy density, lifetime and safety of the cell. For this reason, we present physics-based models developed with COMSOL Multiphysics that describe the effect of the structural properties of the positive electrode, which is LiNi0.6Mn0.2Co0.2O2 (NMC 622), on the performance of the Li metal cell. The models include charge conservation in the solid and electrolyte phase, mass conservation in the solid phase and electrolyte phase and the electrochemical kinetics generated at the interfaces between the solid phase and the electrolyte. The results from the models are validated with experimental data and there was a good agreement between them. The validated models are then employed to investigate the effects of particle size and porosity of the NMC 622 on the performance of the Li metal battery. The understanding of this study can be employed to potentially predict optimized structural parameters for Li metal battery depending on the desired applications.