bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Behavior of Tris(2,2'-bipyridine)Cobalt Complex in Some Ionic Liquids
Authors: Katayama Yasushi , Nakayama Shota , Tachikawa Naoki , Yoshii Kazuki 
Published: February 2020

Electrostatic interaction between a charged species and the ions composing ionic liquids is considered much stronger than that in conventional electrolyte solutions. Strong electrostatic interaction is expected to influence electrochemical reactions of the charged species. We have already reported the diffusion and charge transfer of tris(2,2'-bipyridine) and tris(1,10-phenanthroline) complexes of some transition metals are affected by the charge densities of redox species and the ions composing ionic liquids[1-6]. In the present study, the electrochemical behavior of tris(2,2'-bipyridine)cobalt complex ( [Co(bpy)3]3+ and [Co(bpy)3]2+) was investigated in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) and 1-ethyl-3-methylimidazolioum tetrafluoroborate (EMIBF4).
BMPBr was prepared by the reaction of methylpyrrolidine and butyl bromide, purified by recrystallization and dried under vacuum. BMPTFSA was prepared by the metathesis of BMPBr and LiTFSA. EMIBF4 was purchased from Kanto Chemical. [Co(bpy)3](TFSA)2 was prepared by addition of LiTFSA into CoCl2 and bpy aqueous solution. [Co(bpy)3](TFSA)3 was prepared by oxidation of [Co(bpy)3]2+ with H2O2 under acidic condition and addition of LiTFSA. [Co(bpy)3](BF4)2 and [Co(bpy)3](BF4)2 were prepared in the same way using NaBF4 instead of LiTFSA. Electrochemical measurements were performed with an air-tight three electrode cell assembled in a glovebox of dry Ar atmosphere. Platinum was used as a working and counter electrode. Silver immersed in BMPTFSA containing 0.1 M AgCF3SO3was used as a reference electrode.
The diffusion coefficients of [Co(bpy)3]3+ and [Co(bpy)3]2+ were determined by chronoamperometry at various temperatures. The diffusion coefficients of [Co(bpy)3]3+ and [Co(bpy)3]2+ were close to those of [M(bpy)3]3+ and [M(bpy)3]2+ (M = Fe and Ru) in each ionic liquid, verifying the diffusion of the charged species is related to the size and charge density of the diffusing species. The charge transfer rate of [Co(bpy)3]3+/2+ was slower than those of [M(bpy)3]3+/2+ (M = Fe and Ru), probably due to the difference in the electron configurations. Furthermore, the apparent reaction entropy change of [Co(bpy)3]3+/2+ was larger than those of [M(bpy)3]3+/2+ (M = Fe and Ru), suggesting the large contribution of the difference in the electron configurations of [Co(bpy)3]3+ and [Co(bpy)3]2+to the apparent reaction entropy change.

References

[1] Y. Katayama, M. Yoshihara, and T. Miura, J. Electrochem. Soc., 162, H501 (2015).
[2] Y Katayama, Y. Toshimitsu, and T. Miura, Electrochim. Acta, 131, 36 (2014).
[3] Y. Yamato, Y. Katayama, and T. Miura, J. Electrochem. Soc., 160, H309 (2013).
[4] Y. Katayama, Y. Toshimitsu, and T. Miura, J. Electrochem. Soc., 160, H219 (2013).
[5] Y. Toshimitsu, Y. Katayama, and T. Miura, Electrochim. Acta, 82, 43 (2012).
[6] N. Tachikawa, Y. Katayama, and T. Miura, J. Electrochem. Soc., 154, F211 (2007).
The Choice of Substrate Material and Electrodeposition of High Purity Niobium Coatings
Authors: Dubrovskiy Anton R. , Okunev Maxim A. , Makarova Olga V. , Kuznetsov Sergey A. 
Published: February 2020

The interaction of different materials with the NaCl-KCl-NaF(10 wt.%)-K2NbF7(8 wt.%)-Nb melt was investigated. As substrate materials the ceramic, beryllium and carbopyroceram of different shape (spheres, cylinders, parallelepipeds) were chosen. The time of the experiments was varied from 10 minutes to 12 hours. The spherical ceramic samples were coated with protective molybdenum film by magnetron sputtering. Porous area of these films was at an average 200 μm2. After the experiment (exposition time 10 min) the exfoliation of molybdenum film was observed due to interaction of the substrate with the melt and the porous area was increased in to 27 times. The XRD data showed niobium oxides formation such as NbO, Nb4O5, NbO2 on the ceramic surface. The same XRD data were obtained for the samples without protective films. The beryllium samples regardless of the shape and the presence of the protective films were dissolved in the niobium containing melt due to more negative electrode potential comparing with niobium one. The carbopyroceram samples were exposed in the melt during 3 and 12 hours. After 3 hours of exposition, no changes of XRD data and weight of samples were found, but after 12 hours, XRD data indicated the formation of niobium carbide (NbC) of insignificant thickness. On the base obtained results, the carbopyroceram was chosen as a perspective material for electrodeposition of high purity niobium coatings because it not corrodes in the niobium containing melt.
The electrolyte mentioned above was used for niobium coatings electrodeposition on carbopyroceram spheres. Due a spherical shape of substrates, a special form of the cathode should be used for plating of samples by niobium in molten salts. In the present study construction of the cathode was developed. It consists of two parts: top part is fixed, bottom part is rotating by digital controlled stirrer. Construction of the cathode provides the electrical contact in random point of the sample. Due to such contact a uniform coatings were obtained. The optimal regimes (temperature, current density, time of electrolysis and rotation speed of the cathode) for electrodeposition of smooth uniform niobium coatings with the thickness up to 50 µm on carbopyroceram spheres were found. Purity of the coatings was determined by spectral quantitative analysis. The impurity content is given below (ppm): Mn < 2.0; Mg < 3.0; Si < 10; Fe = 2.3; Ni < 5.0; Pb < 5.0; Sn < 5.0; Ti < 10; Al < 5.0; Co < 10; Mo < 10; Ca < 10; Zr < 20; V< 3.0; Cu ≤ 10; Cr < 5.0.
Red-Ox Reactions in Ionic Liquids and Their Impact on Electrodeposition of Metals and Alloys
Authors: Freydina Evgeniya , Abbott Joshua G. 
Published: February 2020

Electrodeposition from ionic liquids has some significant benefits over aqueous electrolytes in that there are no side reactions associated with the presence of water and oxygen. Metal deposits can be plated without deleterious oxides or hydrogen inclusions, which may cause a loss of mechanical and corrosion resistance properties. However, these benefits come with practical limitations and implications.
In the absence of water, there are fewer restrictions on the nature of ionic metal species that can exist in the electrolyte. In some ionic liquids, multivalent metals like niobium or vanadium may have several stable oxidation states under the same conditions. Ions with high valencies can react with low valent species to form ions of intermediate oxidation states. They can also comproportionate with freshly electrodeposited metal, dissolving it back into the bath in a low valent state.
In the case of alloy deposition, two or more metallic ions with different reduction potentials are dissolved in the electrolyte. The initial oxidation states of the metals in the system may change spontaneously if a red-ox reaction between different ions is possible. The resulting species may be insoluble or otherwise not suitable for the electrodeposition. The more positive ion can be reduced to the metallic state and precipitate out of solution. This makes some metals incompatible with each other in the electrolyte and limits the combinations of alloying elements.
Options for anodic reaction during electrodeposition from ionic liquids are usually limited to the dissolution of sacrificial anodes. Without oxygen or water, the surface of the anode remains free of a passivating oxide layer and therefore remains very chemically active. Ions with more positive reduction potentials will attack the anode and this reaction may continue until all of the more positive ions in the bath have been reduced.
Water-sensitive ionic liquids, in particular chloroaluminates, may also have H+ ions present as a result of reactions with traces of moisture. The protons can participate in the oxidation of some ions, forming hydrogen gas that eventually leaves the system.
Examples of red-ox reactions in selected ionic liquid electrolytes are discussed, as well as some proposed methods of taking these processes into account.
(Invited) Electrochemical Soft Devices
Authors: Takada Kazutake 
Published: February 2020

There has been a great deal of researches to add functionalities to soft materials with intent to develop intelligent device, as they are potential candidates for bio-mimic materials. Our group has been developing functional devices by introducing redox active species and groups to polymer gels. We have employed gels because they are known to show abrupt volume change, which can be used as a driving force of the devices. A variety of stimuli has been used as trigger of changes in volume of the gel, including light, temperature, pH, ionic strength, voltage/potential, and magnetic field. Electric potential has been one of the most widely used stimulus since it can easily be controlled. The devices we have developed can be operated at low potential of a few volts, which depend on the redox species used. Further, since they are mainly composed of polymer gels, they can easily be downsized. I will present some of our representative devices, electrochemical actuators and an electrochemical micro pump.
The electrochemical actuator consists of two poly(acrylic acid) gel films which sandwich a polyimide film (5 mm x 25 mm x 12.5 μm thick or 1.5 mm x 3 mm x 12.5 μm thick) coated with Au layers on both sides. It is driven by changes in the volume of the gel induced by redox reaction of p-hydroquinone (QH2)/p-benzoquinone (BQ). The oxidation of QH2 results in decrease in pH, which gives rise to collapse of the gel, whereas the reduction of BQ causes expansion. The Au film electrodes on both sides of the actuator are used as two electrodes setup. Thus, when the oxidation takes place at one electrode, the reduction does on the other electrode at the opposite side at the same time. In a solution of 5 mM QH2 and 5 mM BQ containing 1 x 10-4 M NaClO4the actuator bent to left (anode) side at 1.3 V, and bent to right side after the reversal of the polarity (Fig. 1). The actuator showed repeated stretching/bending at least 400 cycles (Fig. 2). Further, it was able to actuate after 6 times of repeated drying/wetting of the gel.
The electrochemical micropump consists of poly(acrylic acid) gel containing Cu2+ serving as a piston and a Au pipe (1 mm i.d. x 14 mm length) serving as cylinder. It discharges and charges liquid at a level of a few hundred of picoliter per second upon expansion and contraction of the gel induced by reduction and oxidation of the copper, respectively. The pump discharged and charged equal volumes of 3.5 ml water under potentiostatic control at –1.1 V vs. Ag/AgCl and at +0.8 V for 3 h each, showing excellent reversibility. Under galvanostatic control the volumes expelled and taken were nearly controlled with the charge at steady states with flow rates of 3 x 10 pl s–1 for the discharging and 1.6 x 102 pl s–1 for the charging.

Figure 1
Electrochemical Characterization of Au(111)| EMMImNTf2 and Au(111)|2,2Bipyridine+EMMImNTf2 Interfaces
Authors: Siinor Liis , Siimenson Carolin , Doneux Thomas , Buess-Herman Claudine 
Published: February 2020

Room temperature ionic liquids (RTILs) are non-conventional electrolytes that have been under intensive investigation in recent years. Due to their unique physical properties they are interesting media to study at fundamental level and in novel electrochemical devices. [1-4]
Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods were used to characterize the electrochemical behavior of 1-ethyl-2,3-dimethyl imidazolium bis(trifluoromethanesulfonyl)imide (EMMImNTf2) in the presence of 2,2′-bipyridine (2,2’-BP) at a Au(111) electrode. All the experiments were carried out in a nitrogen controlled atmosphere in a glove-box.
CV method was used to determine the region of ideal polarizability (ΔE) and to evaluate the electrochemical characteristics of both systems under investigation. The capacitance (C) vs. potential (E) curves were measured using electrochemical impedance at a fixed ac frequency (113 Hz). Capacitance values depend on the composition of the electrolyte (i.e. addition of 2,2’-BP) as well as on the applied potential. At more positive E values C depends noticeably on the chemical composition of the electrolyte i.e. C values are lower in the mixture than those measured in pure EMMImNTf2 at E > – 0.1 V. This effect is caused by the adsorption of 2,2′-BP molecules at the electrode surface. This is also confirmed by phase angle values, which are lower than − 80° for Au(111)|2,2’-BP + BMMImNTf2 in a wide range of frequencies. Only at low frequency values (f < 1 Hz) mixed kinetic processes (adsorption, diffusion and partial charge transfer) were observed.
The shape and values of C
s- E curves, which were calculated from Nyquist plots at several ac frequencies (C
s
= (Z''i2πf)−1), depend strongly on the ac frequency and potential applied on the system. C
s values are higher at lower frequencies and more negative electrode potentials. We attribute this to a pseudocapacitive behavior linked to the adsorption/desorption of 2,2’-BP at these potentials. Investigating the adsorption of organic additives is a strategy to contribute to a better understanding of metal|RTILs interfaces.
Acknowledgments:
This project is supported by a FNRS (BE) grant (PDR n°T.0090.13).
References:
[1] S. Vanderaspoilden et al., Electrochim. Acta, 2015, 162, 156-162.
[2] P. Pikma et al., Electrochem. Commun., 2015, 61, 61-65.
[3] A. Lahiri et al., J. Phys. Chem. C, 2015, 119 (29), 16734–16742.
[4] T. Tooming et al., J. Power Sources, 2015, 280, 667-677.
Understanding Inclusion Mechanisms and Effects in Hardened Gold Electrodeposits
Authors: Perez Carlos R. , Pillars Jamin Ryan , Hollowell Andrew E , Arrington Christian L. , Yelton W. Graham 
Published: February 2020

Gold electroplating, now over two centuries old(1), remains a mainstay of the electronic industry, where the good electrical and mechanical properties of hard gold in particular make for excellent contacts. Electrodeposited gold is hardened by the incorporation of minute amounts of inclusions, both metallic and non-metallic, which affect the microstructure of the growing film as well as its final surface(2). As previously demonstrated(3), the main contributor to hardening is the inclusions’ effect on decreasing grain size. In addition to the metal inclusions, carbon-containing by-products of the electroplating bath, particularly AuCN and CN-complexed cobalt have been found, affecting both hardness and wear resistance(4).
In our work, we aim to better understand the inclusion mechanism in cobalt-hardened gold in particular, and by extension that of other additions such as nickel, and the resulting microstructure and properties. We will electrodeposit gold with systematically varying bath compositions under several deposition conditions, while measuring the nucleation rate using Tafel plots, and characterize the resulting films in terms of microstructure, hardness and wear resistance. The effect of thermal aging on the inclusion profile will be studied by Auger electron spectroscopy.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
1. Kohl PA. Electrodeposition of gold. In: Schlesinger M, Paunovic M, editors. Modern Electroplating, Fifth Edition. New York, NY, USA: Wiley; 2000. p. 201-25.
2. Okinaka Y. Significance of inclusions in electroplated gold films for electronics applications. Gold bulletin. 2000;33(4):117-27.
3. Lo CC, Augis JA, Pinnel MR. Hardening mechanisms of hard gold. Journal of Applied Physics. 1979;50(11):6887-91.
4. DeDonker R, Vanhumbeeck J. Cobalt in gold electrodeposits. Transactions of the Institute of Metal Finishing. 1985;63:59.
Modelling the Electrochemical Interface: Applications to CO2 Reduction
Authors: Chan Karen 
Published: February 2020

The electroreduction of CO2 has the potential to store energy from intermittent renewable sources and to produce carbon-neutral fuels and chemicals [1, 2]. In recent years, theoretical studies of CO2 reduction have usually applied the computational hydrogen electrode model, which allows for the determination of the energies of reaction intermediates without explicitly treating the potential and the ions in solution [3]. In this talk, I will briefly review the application of this approach to CO2 reduction: the determination of lowest free energy pathways and correlation of theoretical activity volcanoes with experimental onset potentials [4, 5], and the computational screening of new catalysts [6]. I will then focus on recent developments in the explicit treatment of the electrochemical interface [7], required for an understanding of charge transfer barriers, kinetics, and selectivity. I will discuss the scaling of CO2 reduction barriers, field effects, C-C coupling [8], and the integration of these effects into microkinetic models.

Whipple, D. T. & Kenis, P. J. a. Prospects of CO 2 Utilization via Direct Heteroge- neous Electrochemical Reduction. J. Phys. Chem. Lett. 1, 3451–3458 (Dec. 2010).

Graves, C., Ebbesen, S. D., Mogensen, M. & Lackner, K. S. Sustainable hydrocarbon fuels by recycling CO 2 and H 2 O with renewable or nuclear energy. Renewable and Sustainable Energy Reviews 15, 1–23 (2011).

Nørskov, J. K., Rossmeisl, J., Logadottir, A., Lindqvist, L., Kitchin, J. R., Bligaard, T. & Jónsson, H. Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. J. Phys. Chem. B 108, 17886–17892 (Nov. 2004).

Shi, C., Hansen, H. a., Lausche, A. C. & Nørskov, J. K. Trends in electrochemical CO2 reduction activity for open and close-packed metal surfaces. Phys. Chem. Chem. Phys. 16, 4720–7 (Mar. 2014).

Kuhl, K. P., Hatsukade, T., Cave, E. R., Abram, D. N., Kibsgaard, J. & Thomas, F. Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces (2014).

Chan, K., Tsai, C., Hansen, H. A. & Nørskov, J. K. Molybdenum sulfides and selenides as possible electrocatalysts for CO2 reduction. ChemCatChem 6, 1899–1905 (2014).

Chan, K. & Nørskov, J. K. Electrochemical Barriers Made Simple. J. Phys. Chem. Lett. 2663–2668 (2015).

Montoya, J. H., Shi, C., Chan, K. & Nørskov, J. K. Theoretical Insights into a CO Dimerization Mechanism in CO2 Electroreduction. The journal of physical chemistry letters 6, 2032–2037 (2015).
Design of Photonic and Plasmonic Materials for Photocatalytic CO2 Reduction
Authors: Gaulding E. Ashley , Sharp Ian D. , Toma Francesca M. 
Published: February 2020

This work explores the effects of photonic structuring and localized surface plasmon resonance (LSPR) and on CO2 reduction reactions (CO2RR). We design photonic crystals where the photonic bandgap is tuned by changing the periodicity of the inverse opal cavities. The photonic bandgap of an inverse opal structure can be tuned by the material and pore size/periodicity. These photonic properties control how the incoming light is reflected and refracted within the material. We investigate a variety of photonic crystal materials, such as metal oxides, by infilling the voids of an opal template of polystyrene (PS) spheres to obtain an inverse opal photonic crystal by subsequently removing the PS spheres.
Similarly, the LSPR can be tuned in metal or degeneratively doped semiconductor nanoparticles by tuning the size, shape, and material composition. This increases absorption near the resonance peak. Additionally, hot carriers can be generated as the LSPR decays, providing the potential to access kinetic pathways normally difficult for desired products in CO2RR chemistry. Since we can tune the photonic bandgap simply by changing the size of the PS spheres in the template, we can investigate how matching the photonic bandgap with the plasmonic resonance of a metal particle affects CO2 reduction. We then study the effects of combining both of these physics phenomena on chemical transformation and selectivity in CO2 reduction. From this basis, one could potentially tune CO2RR processes to a desired hydrocarbon fuel product.
We use a combination of SEM, TEM, and XRD to analyze the morphological structure and crystallinity of our materials as well as material composition via EDX. Surface analysis of our structures is done using XPS. We characterize the films’ optical properties, monitoring shifts in the photonic bandgap and LSPR, via UV-Vis-NIR spectroscopy. We monitor CO2 reduction products using in line GC for gas products and NMR for liquid products.
(Invited) Photo-Electro-Chemical Water Splitting and the Making of Renewable Chemicals
Authors: Chorkendorff Ib 
Published: February 2020

Hydrogen is the simplest solar fuel to produce and in this presentation we shall give a short overview of the pros and cons of various tandem devices [1,2]. The large band gap semiconductor needs to be in front, but apart from that we can chose to have either the anode in front or back using either acid or alkaline conditions. Since most relevant semiconductors are very prone to corrosion the advantage of using buried junctions and using protection layers offering shall be discussed [3-5]. In particular we shall show how doped TiO2 is a very generic protection layer for both the anode and the cathode [6]. Next we shall discuss the availability of various catalysts for being coupled to these protections layers and how their stability and amount needed may be evaluated [7, 8, 9]. Examples of half-cell reaction using protection layers for both cathode and anode will be discussed though some of recent examples both under both alkaline and acidic conditions. Notably NiOx promoted by iron is a material that is transparent, providing protection, and is a good catalyst for O2 evolution [10]. Si is a very good low band gap semiconductor and the optimal thickness of this in a tandem device will be discussed [11]. Finally if time allows we shall also discuss the possibility of making high energy density fuels by hydrogenation of CO2 instead of hydrogen evolution [12]. We shall here show how we can investigate the recent ethanol synthesis on oxygen derived Cu found by Kanan et al. and show how acetaldehyde seems to be an important intermediate [13].

References

[1] A. B. Laursen et al., Energy & Environ. Science 5 5577 (2012)
[2] B. Seger et al. Energy & Environ. Science 7 2397 (2014)
[3] B. Seger, et al. Angew. Chem. Int. Ed., 51 9128 (2012)
[4] B. Seger, et al., JACS 135 1057 (2013)
[5] B. Seger, et al., J. Mater. Chem. A, 1 (47) 15089 (2013)
[6] B. Mai et al. J. Phys. Chem. C 119 15019 (2015)
[7] R. Frydendal, et al. Chem.Elec.Chem 1 2075 (2014).
[8] E. A. Paoli, et al. Chemical Science, Chemical Science, 6 190 (2015)
[9] E. Kemppainen et al. Energy & Environmental Science, 8 2991 (2015)
[10] B. Mei, et al. J. Phys. Chem. Lett. 5 1948 (2014)
[11] B. Dowon et al. Energy & Environ. Sci. 8 650 (2015)
[12] A. Verdaguer-Casadevall et al. J. Am. Chem. Soc. 137 9808 (2015)
[13] E. Bertheussen et al. Angew. Chem. Int. Ed. 55 1450 (2016)