bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrocatalytic Reduction of CO2 on Cu and Au/W Electrode Surfaces: Empirical (DEMS) Confirmation of Computational (DFT) Predictions
Authors: Javier Alnald , Baricuatro Jack Hess , Kim Youn-Geun , Soriaga Manuel P
Published: February 2020

This work describes the employment of differential electrochemical mass spectrometry (DEMS) as a supplementary experimental approach to theory in the study of the reaction mechanism of the Cu-catalyzed electrochemical reduction of CO2 by investigating the reduction of reactants and (theoretically postulated) intermediates. The empirical inferences: (i) CO is one of the first products of CO2 reduction, as well as the first intermediate in the formation of more reduced products (hydrocarbons and oxygenates). (ii) Formaldehyde, HCHO, is not a precursor for C=C bond formation but is an intermediate for the production of methane and ethanol. (iii) Both methane and ethanol can be generated from CO2 through the protonation of CO and through the HCHO intermediate. (iv) The generation of CH4 and CH3CH2OH from CO and CO2 has a much higher activation barrier than from HCHO; not unexpected since the formaldehyde intermediate is formed after the (computationally determined) rate-limiting CO-protonation step. In this work, DEMS was also used to test the theoretical prediction suggesting the viability of a bimetallic near-surface alloy (NSA) consisting of Au and W as a CO2-reduction electrocatalyst selective towards the formation of methanol as a product, as opposed to methane, ethylene or ethanol typically produced using Cu as the catalyst. At an overlayer NSA that consisted of n monolayers (ML) of Au on a polycrystalline W electrode, W(pc)-n[(1×1)-Au], no methane, methanol, ethylene or ethanol was detected when the coverage of Au was at submonolayer (n = 0.5) or multilayer (n ≥ 2) coverages. However, when the NSA contained only 1 ML of Au, methanol was generated exclusively. The anticipated CH3OH-product-selectivity of the W(pc)-(1×1)-Au NSA has thus been (qualitatively) confirmed.
(Invited) Enhanced Hydrogen Oxidation Activity at Pt-M Alloy Catalysts in Acid: A DFT Study
Authors: Tryk Donald A. , Shi Guoyu , Yano Hiroshi , Uchida Hiroyuki , Watanabe Masahiro , Iiyama Akihiro
Published: February 2020

Platinum alloys that include first-row transition metals have been examined extensively as CO-tolerant catalysts for the hydrogen oxidation reaction (HOR) in acidic media. The CO tolerance stems from the decreased CO adsorption strength, so that the surface is not easily poisoned. Recently, we have found experimentally that the intrinsic, area-specific HOR activity is also significantly enhanced for stabilized Pt-Co nanoparticle catalysts in aqueous acid solution.1 This is an aspect of the catalysis that has been little studied. We have found that the enhanced HOR activity is consistent with high-quality density functional theory (DFT) calculations, which show that the adsorption of underpotentially deposited (UPD) hydrogen atoms is weakened by the presence of the alloying metal under the (110) surface, which has been recognized to be the most active (Fig. 1). DFT calculations of Ishikawa and coworkers have explained the high activity of the Pt(110) surface as being due to the ease of H2 dissociation, with the rate-determining step being the desorption of HUPD.2

In addition, we have found recently that Pt-Fe and Pt-Ni catalysts also exhibit enhanced area-specific HOR activities, in addition to their enhanced CO tolerance, as will be presented by G. Shi separately. In particular, we found that the DFT calculated adsorption strength of HUPD on the Pt-Fe nanoparticle (110) surface is greatly weakened, consistent with its high HOR activity. Nevertheless, H2 dissociation remains facile.

Acknowledgements

This work has been supported by the Superlative, Stable, and Scalable Performance Fuel Cell (SPer-FC) project funded by the New Energy and Industrial Development Organization (NEDO) of Japan.

References

G. Shi, H. Yano, D. A. Tryk, M. Watanabe, A. Iiyama, and H. Uchida, A novel Pt-Co alloy hydrogen anode catalyst with superlative activity, CO-tolerance and robustness, Nanoscale, 2016, DOI: 10.1039/C6NR00778C.

J. Santana, J. J. Mateo, and Y. Ishikawa, Electrochemical hydrogen oxidation on Pt(110): a combined direct molecular dynamics/density functional theory study, J. Phys. Chem. C, 114, 4995-5002 (2010).

Figure 1
(Invited) A First-Principles Molecular Dynamics Study on Active Sites on Metal Nano Particles: Application of the Compressed Gas Model
Authors: Sugimoto Manabu
Published: February 2020

The first-principles Molecular Dynamics (FPMD) is applied to investigate gas adsorption onto surfaces of metal nano particles. Herein we focus on catalytic reactions for ammonia synthesis and decomposition. Some Ru nano clusters are prepared as a model of the catalyst, and gas adrosptions of the H2, N2, and NH3 molecules are investigated.

In order to do a conceptually unbiased mechanistic study, a natural and reasonable strategy would be to make many models to be investigated by “electronic-structure simulations”. In this study, we apply the compressed gas model in which distribution of gas molecule in high pressure simulations are taken into account. The compressed gas cluster is inserted in the simulation box containing a metal nano particle. Because of the compressed nature of the “ball” of the gas molecules, they automatically diffuse into the vacuum region and hit on the nano particle surface with velocity.

By repeating this simulation, we could identify some characteristics of the adsorption sites on the metal nano particle and the gas molecule dependence in the adsorption behavior. It was found that the H2 adsorption should be structure insensitive, while the N2 and NH3 adsorptions should be structure sensitive. In the simulation of the NH3 adsorption, we observed formation of the H2 molecule from NH­
3. It was found that the kink plays an important role as a reaction center of the H2 formation. In the simulation, H2 was yielded in a mechanism similar to the Eley-Rideal mechanism.
Engineering Molybdenum Disulfide Protected Silicon Photocathodes for Corrosion Resistance in Acid
Authors: King Laurie Ann , Hellstern Thomas R , Jaramillo Thomas F
Published: February 2020

Photoelectrochemical (PEC) water splitting devices offer a promising path to sustainable production of hydrogen.1 Silicon shows great promise as a small band gap photocathode in tandem photoelectrochemical (PEC) water splitting due to its appropriate band structure, energetic alignment for driving hydrogen evolution, and its band gap of 1.1 eV.2 However, some challenges remain to ensure that silicon photoelectrodes possess the required catalytic activity and stability for use in highly effect PEC water splitting devices.

Molybdenum disulfide (MoS2) is a low permeability material known for its excellent stability and HER activity in acid. We have previously demonstrated MoS2 protected silicon photocathodes which operate for 100 hrs without significant loss of activity.3 Here, we further this study to design strategies, such as the utilization of a molybdenum silicide interface layer, for improved activity and over 600 hour stability with unchanged photoelectrochemical performance (onset potential, fill factor and light limited photocurrent density), which is among the best performance of any precious metal free photocathode.

Critical to developing future electrodes with enhanced stability, we probe the failure mechanism of the MoS2 protected photocathodes. By XPS we observe that the MoS2 is fully absent post stability testing. Detailed failure mechanisms of the photocathodes and electrolyte are uncovered by electrochemical methods, SEM, Raman microscopy and ICP. Furthermore, we implement increased light intensity (10 suns), as well as light and dark cycling to probe accelerated durability testing protocols utilizing MoS2 protected photocathodes. From such analyses we uncover a feedback loop that enables insightful design of future corrosion resistant protection schemes.

(1) Walter, M. G.; Warren, E. L.; McKone, J. R.; Boettcher, S. W.; Mi, Q. X.; Santori, E. A.; Lewis, N. S. Solar Water Splitting Cells. Chem. Rev.
2010, 110, 6446–6473.

(2) Seitz, L. C.; Chen, Z.; Forman, A. J.; Pinaud, B. A.; Benck, J. D.; Jaramillo, T. F. Modeling Practical Performance Limits of Photoelectrochemical Water Splitting Based on the Current State of Materials Research. ChemSusChem
2014, 7 (5), 1372–1385.

(3) Benck, J. D.; Lee, S. C.; Fong, K. D.; Kibsgaard, J.; Sinclair, R.; Jaramillo, T. F. Designing Active and Stable Silicon Photocathodes for Solar Hydrogen Production Using Molybdenum Sulfide Nanomaterials. Adv. Energy Mater.
2014, 4 (18), 1400739.
Permselective Ion Transfer at the Nanoscopic Ities Array
Authors: Su Bin , Huang Xiao
Published: February 2020

Free-standing silica nanochannel membrane (SNM) with perforated channels was utilized to create arrays of nanoscale interfaces between two immiscible electrolyte solutions (nano-ITIES), at which permselective ion transfer and detection were achieved. The SNM consisted of a high density of straight nanochannels with a diameter of 2.3 nm and a length of 70 nm. The silicon wafer coated by 150-nm-thick porous silicon nitride film (p-SiNF) with pores of 5 mm-in-diameter was used to support the SNM in a form of nanochannel-on-micropore. Considering the material surface lipophilicity, the nano-ITIES array was formed at the boundary between SNM and p-SiNF, with a diffusion geometry equivalent to two back-to-back inlaid microdisc interfaces. Thus, the transfer of tetraethylammonium (TEA+) across the nano-ITIES array yielded symmetric sigmoidal current responses in cyclic voltammogram. In addition, due to the ultrasmall size and negatively charged surface of silica nanochannels, the nano-ITIES displayed obvious size and charge permselectivities. Transfer of ions with a size comparable with or larger than the nanochannel, such as meso-tetra(N-methyl-4-pyridyl) porphine and iron(III) meso-tetra(4-sulfonatophenyl)porphine, was sterically blocked. And that of anions with a size smaller than the nanochannels, such as methyl orange, encountered the strong electrostatic repulsion from channel walls, showing obvious dependence on the ionic strength of aqueous solution in accordance with the prediction of classical Gouy-Chapman theory. The present approach is facile and inexpensive for building nano-ITIES array with potential applications in ion detection and separation.

Figure 1
Electrocatalysis for Carbon Dioxide Reduction By Molecular Cobalt Complexes Adsorbed at Liquid/Liquid Interfaces
Authors: Kim Jinheung , Kim Soojin , Jang Ha , Lee Ju
Published: February 2020

Conversion of light energy from the sun into chemically stored energy via artificial photosynthesis represents a promising approach to provide renewable energy. In general, catalytic systems are designed to split water photochemically, to O2 and H2. For H2 generation from aqueous protons driven by light, both a photosensitizer (PS) and a catalyst are needed, while an electron source such as a sacrificial donor is required to carry out the reductive half-reaction. In this context, the design and study of new catalysts composed of inexpensive earth-abundant elements are highly desired. Hydrogen production is a kind of a proton-coupled electron transfer reaction. When studying hydrogen production on an electrode, one measures the electron transfer rate by controlling the electrode potential. Electrochemistry at a liquid-liquid interface, called interface between two immiscible electrolyte solutions (ITIES), has appeared recently as a unique approach to study PCET reaction with protons in the aqueous phase and electron donors in the organic phase. In this work, proton-coupled hydrogen production and oxygen reduction by ferrocene involving a molecular cobalt or nickel catalyst at a water/dichloroethane interface is reported. The cobalt and nickel complexes serve as a redox catalyst, generating metal-hydride species and activating O2 reduction via coordination with the cobalt(II) center. Our system provides an example of interfacial molecular electrocatalysis for hydrogen production and oxygen reduction combining the advantages of molecular catalyst and electrocatalysis on the applied Galvani potential difference between the two phases. The reaction is electrocatalytic as the rate which depends on the applied potential difference between the liquid/liquid phases.
Maskless Generation of Highly Periodic 3D Semiconductor Nanostructures in Response to Defined Illumination Inputs
Authors: Carim Azhar I , Batara Nicolas A. , Premkumar Anjali , Atwater Harry A , Lewis Nathan S.
Published: February 2020

Template-free photoelectrodeposition of semiconducting chalcogen alloys resulted in the spontaneous generation of highly periodic nanostructured films over macroscopic length scales. The exact nature of the optical excitation was encoded in the deposit morphology in terms of the feature sizes, periodicities, anisotropies, and orientations of the nanoscale pattern. The use of unpolarized light generated isotropic morphologies consisting of ordered arrays of nanopores whereas linearly polarized light resulted in a highly-anisotropic lamellar morphologies with the long axes of the patterns aligned along the E-field vector. Utilization of two non-orthogonal polarized sources simultaneously generated patterns oriented along the average E-field vector and with degrees of anisotropy related to the difference in orientation between the two input E-field vectors and the phase correlation between the sources. The illumination spectral profile encoded the pattern periodicity and feature width. A single periodicity in single in-plane direction was consistently observed even with the use of broadband and multimodal spectral profiles and the periodicity was found to be sensitive to all investigated tuning of such profiles. The incidence of the illumination set the direction the material grew from the substrate, mimicking natural phototropism: grazing illumination resulted in growth at significant angle to the surface normal. Modeling of the growth using a combination of full-wave electromagnetic simulations of light absorption and scattering coupled with Monte Carlo simulations of mass addition successfully reproduced the experimentally observed morphologies and indicated that the encoding process was a consequence of the fundamental light-matter interactions during growth.

This photoelectrochemical deposition process is unique from other methods of generating ordered mesostructures with electrochemical means as no photomask, no photoactive substrate, no lithographic processing, nor any chemical templating agents (ligands, surfactants) were utilized. Moreover, films were deposited from aqueous solution using oxide precursors at room temperature with low-intensity illumination (~10 mW cm-2). Thus, this process displays significant potential to possibly enable the generation of complex morphologies for functional materials without some of the limitations imposed by traditional fabrication techniques.
Modified Electrodes with Nanocomposite Films Based on Conducting Polymers and Functionalized Carbon Nanotubes
Authors: Branzoi Florina , Branzoi Viorel , Pahom Zoia
Published: February 2020

Nanoporous composite films of functionalized single–walled carbon nanotubes (SWCNTs), 3-methylthiophene and 2-aminophenol were grown electrochemically from aqueous solutions such that constituents were deposited simultaneously onto substrate electrodes. Scanning electron microscopy (SEM) revealed that the composite films consisted of nanoporous networks of SWCNTs (SWANTs- with carboxylic acids functionalized - CNT-COOH and with octadecylamina) coated with polymeric film.

Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that these composite films had similar electrochemical response rates to pure polymeric films but a lower resistance and much improved mechanical integrity. The negatively charged functionalized carbon nanotubes (CNTsF) served as anionic dopant during the electropolymerization to synthesize polymer/CNTsF composite films. The synthetic, morphological and electrical properties of the obtained nanocomposite films were compared. The specific electrochemical capacitance of the composite films is a significantly greater value than that for pure polymer films prepared similarly. Using these composite films, the modified electrodes with improved properties were obtained. These nanoporous composites showed improved mechanical integrity, higher electronic and ionic conductivity and exhibited larger electrode specific capacitance than the polymer alone.

All of the composite films were a very promising electrode material for application in supercapacitor
Mechanism of Ethanol Oxidation on Unsupported Noble Metal Nanoalloys Studied By Differential Electrochemical Mass Spectrometry
Authors: Piwowar Justyna , Lewera Adam
Published: February 2020

Electrooxidation of ethanol on noble metals is of particular interest due to its potential application in low temperature direct ethanol fuel cells (DEFCs). However there is no known ethanol electrooxidation reaction (EOR) catalyst, allowing for complete electrooxidation of ethanol to CO2. Even for the most active systems, incomplete and slow EOR renders the DEFCs not economically viable. As a result significant effort has been devoted to understand the reasons of low activity of known catalysts and to finding better, more active and selective systems. It is widely accepted that systems consisting of platinum, and platinum alloyed with other metals are most active towards ethanol electrooxidation. Pt-Ru and Pt-Sn systems are often reported as those with the highest current density in acidic media. However, despite the higher current, addition of Ru or Sn to Pt further decrease the already small amount of CO2, produced in EOR on pure Pt. Selectivity of a given catalyst towards CO2 in EOR is especially important, due to the facts, that CO2 is the product of complete, 12-electron oxidation of ethanol molecule, where acetaldehyde and acetic acid (other possible products) yields respectively 2- or 4-electrons. Additionally acetic acid cannot be further oxidized in a working fuel cell, thus it is effectively a dead-end of EOR in a working low temperature DEFC. As a result other catalysts, more active and selective toward ethanol electrooxidation to CO2 are needed for a commercially viable DEFC.

In this report we used unsupported ultra-pure platinum-containing nanoalloys as a catalyst for EOR, to determine the possible changes in mechanism of EOR (based on product distribution determined by DEMS) as a function of nanoalloy composition. We focused on possible changes in surface morphology and changes in electronic properties due to alloying and how those factor impact electrode reaction mechanisms.

Using DEMS experiments we determined how the amounts of products like carbon dioxide, acetaldehyde and acetic acid per active surface area changed as a function of nanoparticle composition and how it impacted the onset potential for particular products. As a result we were able to comment on the selectivity and activity of unsupported Pt-containing nanoalloys in EOR as well as on the activity of this material in C-C bond scission.
Electrochemical Photocurrent X-Ray Spectroscopy: A Novel Analytical Surface Technique
Authors: Strom Matthew James , Roeper Donald F. , Natishan Paul M. , O'Grady William E.
Published: February 2020

X-ray absorption spectroscopy (XAS) is a powerful tool for characterizing the chemical nature and environment of atoms in molecules. However, in situ techniques are limited to transmission and fluorescence techniques and are not surface sensitive. A novel in situ technique that uses synchrotron radiation to produce photoelectrons was developed to provide information on the surface and near surface regions. The results obtained from this technique, Electrochemical Photocurrent X-ray Spectroscopy (EPXS) were compared transmission and fluorescence X-ray absorption spectroscopy (XAS). Surface sensitive information was obtained by collecting X-ray induced photocurrent from a polarized electrode. An Au working electrode in 0.1 N H2SO4 was polarized to 300 mVSCE and exposed to high energy X-rays. The photocurrent response was recorded during Au L3 edge scans while X-ray fluorescence yield data was collected concurrently. The photocurrent data showed good agreement with fluorescence data and transmission data collected on Au foils (Figure 1). Investigations using electrochemical impedance spectroscopy and cyclic voltammetry we conducted to insure the photocurrent response was not due to double layer charging or solution radiolysis. Minor differences in peak characteristics were observed between photocurrent and fluorescence data. We believe this to be due to the surface sensitivity of the photocurrent technique. A comparison of the surface sensitivity of fluorescence and photocurrent techniques was accomplished by evaluating signal response to X-ray beam intensity changes. The results show that the photocurrent technique, as expected, was more surface sensitive than fluorescence. Current work is focusing on EXAFS analysis of photocurrent spectra to quantify the techniques surface sensitivity.

This novel technique has the potential to provide information on electron distribution on conductive surface atoms and changes in charge of surface atoms as a function of electrochemical potential. It could significantly impact fields where measurements of surface electron distribution during electrochemical charge transfer are of primary importance, such as corrosion, catalysts and semiconductor research.

Figure 1- XAS spectrum of Au foil using transmission (left) and a spectrum of Au in 0.1N H2SO4 polarized to 300 mVSCE using the photocurrent technique.

Figure 1
Methods for Determining the Working Electrode Interfacial Area for Electroanalytical Measurements of Metal Ions in Molten LiCl-KCl
Authors: Rappleye Devin , Horvath David , Wang Zhonghang , Zhang Chao , Simpson Michael Forrest
Published: February 2020

Voltammetry is a promising approach to determining the concentration of actinides and rare earths in molten chloride salts for real time or near real time monitoring of nuclear fuel electrorefining. In this process, actinides and rare earths accumulate in eutectic LiCl-KCl from reaction of UCl3 with spent nuclear fuel. Monitoring the salt composition is key in order to maintain optimal process conditions, to determine when to treat or discard salt, and to safeguard the process against nuclear material diversion. Voltammetry methods such as cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA), normal pulse voltammetry (NPV), and square wave voltammetry (SWV) have been extensively reported in the literature for application to molten LiCl-KCl typically containing one rare earth or actinide chloride. Our studies have expanded the salt matrices to include quaternary salts with two electrochemically active metal chlorides. We believe this to be the first step in determining if these basic electrochemical analysis methods can be applied to salts containing many components with similar standard reduction potentials. In the simpler ternary salt systems, classic diffusion limited rate equations such as those derived by Randles-Sevcik and Berzins-Delahay have been applied to correlate CV peak height to concentration. Application of these equations requires knowledge of both the diffusion coefficient of the salt compound in the LiCl-KCl and the interfacial area between the working electrode and salt. In our experimental investigations, we have determined that both of these quantities can be difficult to establish a priori. Diffusion coefficients for metal chlorides in molten LiCl-KCl appear to vary with concentration. And the high temperature electrochemical cells located in insulated furnaces make it challenging to precisely determine the electrode-salt interfacial area. In this paper, we focus on empirical evaluation of methods for determining this area—ranging from the simplest approach of dipping a cold electrode into the molten salt to measure the film height to more elaborate approaches such as using a vertical electrode actuator, coating the electrodes with glass, and integrating a pre-peak which may represent formation of a monolayer of metal on the electrode. Salt mixtures investigated include LiCl-KCl-UCl3, LiCl-KCl-UCl3-MgCl2, LiCl-KCl-ThCl4-LaCl3, LiCl-KCl-LaCl3-GdCl3, and LiCl-KCl-LaCl3-MgCl2. It will be shown that with accurate determination of the electrode-salt interfacial area that concentration correlations can be developed with error as low as 2-3%. Both using differential insertion depth with the vertical electrode translator and using glass-coated working electrodes are promising approaches—the latter of which is believed to be more easily implemented in a production operation scenario.
Influence of Ion Diffusivity and Gas Solubility in Ionic Liquids on Li-Air Battery Performance
Authors: Seo Samuel , Song Tangqiumei Maggie , Mizuno Fuminori , Takechi Kensuke , Brennecke Joan F
Published: February 2020

Owing to its extreme high theoretical energy density1, the non-aqueous Li-air battery has received remarkable attention in recent years as a promising candidate for electric vehicle applications. Ionic Liquids (ILs), molten salts that are liquid at room temperature, have been investigated as potential electrolytes in Li-air batteries due to their negligible vapor pressure, good thermal stability, and wide electrochemical windows.

However, comparing to conventional organic electrolytes, for example, ethylene carbonate (EC), ILs generally have higher viscosity and consequently lower ionic conductivity and ion diffusivity. Therefore, two low viscosity ILs, [Pyrr12O1][TFSI], N-methoxyethyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide, and [PP12O1][TFSI], N-methoxyethyl-N-methyl piperidinium bis(trifluoromethanesulfonyl)imide, and their mixture with Li[TFSI], were investigated.

In this work, the diffusivity of the cation and anion of the IL, as well as the diffusivity of the Li+ cation, were measured with pulsed-field-gradient spin-echo (PFG-SE) NMR Spectroscopy. In addition, the I-V performances of the two ILs were characterized in a Li-O2 battery and compared with a non-ether-functionalized IL, [PP13][TFSI]2. Physical properties of the ILs and IL-Li[TFSI] mixtures, including densities, viscosities, ionic conductivities, and electrochemical windows are reported. An additional property that can affect Li-O2 battery performance, the solubility of O2 in the ILs and IL-Li[TFSI] mixtures, was also measured, using a gravimetric microbalance.

References

[1] Cho, J. (2015). Metal–Air and Redox Flow Batteries. ChemPlusChem, 80(2), 257-258.

[2] Nakamoto, H., Suzuki, Y., Shiotsuki, T., Mizuno, F., Higashi, S., Takechi, K., Asaokab, T., Nishikooria, H.,& Iba, H. (2013). Ether-functionalized ionic liquid electrolytes for lithium-air batteries. Journal of Power Sources, 243, 19-23.

Figure 1
An Ionic Liquid Consisting of Crown Ether – Coordinated Hydronium Cation and Amide Anion
Authors: Takeoka Shun , Kitada Atsushi , Fukami Kazuhiro , Murase Kuniaki
Published: February 2020

There are reports on ionic liquids (ILs) with strongly Lewis-acidic metal cations such as Li+ and K+ coordinated by ether-ligands to decrease charge density [1-2]. Crown ether 18-crown-6 (18C6) has a suitable cavity for encapsulation of K+ and hydronium ion (H3O+) [3-4]. Various compounds with H3O+ encapsulated by 18C6 ligand ([H3O+·18C6] cation) have been reported, the counteranions of which are such as hexafluorophosphate (PF6
–), tetrafluoroborate (BF4
–) and trifluoromethanesulfonate (TfO–; Tf = CF3SO2) ions [3-4]. However, their melting point are higher than 100 °C. Furthermore, as far as we know, nothing has been reported on [H3O+·18C6] complexes using bis(trifluoromethylsulfonyl)amide (Tf2N–) anion. Here, we report ILs that consist of [H3O+·18C6] cation or [H3O+· dicyclohexyl-18C6 (Dh18C6)] cation and an amide anion.

 The IL comprised of [H3O+·18C6] cation or [H3O+·Dh18C6] cation and Tf2N– anion was synthesized by adding equimolar amount of 18C6 or Dh18C6 and HTf2N in water, followed by vacuum-drying. In the obtained samples, a characteristic infrared band appeared at 2200 cm–1 that was not observed in pure 18C6, was attributable to the first harmonic of symmetric bending mode (Figure 1) [5]. The H2O content of the 18C6 complex and the Dh18C6 complex was estimated to be 3.29 wt% and 2.61 wt% from Karl-Fischer titration, in good agreement with the ideal value (3.20 wt% and 2.68 wt%). From elemental analysis, infrared spectra and Karl-Fischer titration, the composition of the obtained complexes were concluded as [H3O+·18C6][Tf2N–] and [H3O+·Dh18C6][Tf2N–] (Figure 2).

 1H NMR spectrum of [H3O+·18C6][Tf2N–] contained a sharp singlet near 11 ppm, characteristic of H3O+ encapsulated by 18C6. The melting point of [H3O+·18C6][Tf2N–] was 66–68 °C and [H3O+·Dh18C6][Tf2N–] was a yellowish transparent liquid at room temperature (RT) (Figure 3). At 70 °C, the viscosity and conductivity of [H3O+·18C6][Tf2N–] were 39.5 mPa s and 1.9 mS cm–1, while those of [H3O+·Dh18C6][Tf2N–] were 33.8 mPa s and 1.4 mS cm–1. In linear sweep voltammetry, potential for hydrogen production by [H3O+·18C6][Tf2N–] was similar to those of general protic liquids. The crown ether-coordinated hydronium amide IL may have potential application as electrolyte materials toward a new class of fuel cells.

[1] T. Tamura et al., Chem. Lett., 39, 753 (2010).

[2] Y. Song, H. Jing, B. Li, and D. Bai, Chem. Eur. J., 17, 8731 (2011).

[3] R. Chénevert et al., Can. J. Chem., 60, 853 (1982).

[4] G. S. Heo and R. A. Bartsch, J. Org. Chem., 47, 3557 (1982).

[5] R. Chénevert et al., Can. J. Chem., 62, 2293 (1984).

Figure 1
Solubility of Calcium and Zirconium Oxides in Melts CaO-(CaCl2-MCl)eut and CaO-CaCl2-MCl (M - Li, Na, K)
Authors: Savchuk Ruslan N , Gritsai Larisa V. , Omel'chuk Anatolii A
Published: February 2020

This paper presents results of a study of the solubility of calcium and zirconium oxides in melts corresponding to polythermal sections CaO – (CaCl2 – MCl)eut of ternary systems CaO – CaCl2 – MCl (where M is Li, Na or K). The liquidus temperatures of the studied areas of the polythermal sections are given in Table 1.

Table 1. Composition and crystallization temperature of the investigated areas of polyttermal sections.

CaCl2(42.0) –LiCl(58.0)
CaCl2(25.7) –KCl(74.3)

Temperature, K
CaO Content
Temperature, K
CaO Content

wt. %
mol. %
wt. %
mol. %

768
1.0
2.6
903
0.5
1.64

773
5.0
11.9
933
1.0
3.17

783
11.0
23.1
963
1.5
4.72

923
13.0
26.1
1023
2.0
6.18

1023
15.0
29.1

The interaction of calcium oxide with molten CaCl2–LiCl is accompanied by the formation of calcium oxychloride compounds [CaOCln](n-2)–. But such compounds are not detected in the products of fusion of CaO with the eutectic melt CaCl2–KCl. Compared with calcium oxide, zirconia is much less soluble in the investigated melts. This difference in behavior can be explained by the different nature of the bond of the metal ions to oxygen anions and the acid-base properties of the melt-solvent. At sufficiently high temperatures, the solubility of CaO, ZrO2 is the higher, the higher the acid strength of the melt-solvent. Chlorides or oxychlorides of zirconium in the melt samples were not found after saturation with zirconia. This suggests that zirconia dissolves by a physical mechanism by the incorporation of ZrO2 molecules in the free volume of the solvent melt. The dependence of the solubility of zirconium dioxide on temperature in melts-solvents of different composition is satisfactorily approximated by the linear equation lnS = A – B/T (Table 2.).

Table 2: Values of the coefficients A and B of the temperature dependence of the solubility of zirconia in oxide–chloride melts of different cationic composition

Melt, mol .%
Coefficients of equation lnS = A – B/T

A

B

CaO(5.0) – {CaCl2 – LiCl}eut
.(95.0)
29.90
–31463.16

CaO(5.0) – {CaCl2 – NaCl}eut
.(95.0)
11.30
–11189.44

CaO(5.0) – {CaCl2 – KCl}eut
.(95.0)
11.50
–13134.50

The obtained results can be used to select the conditions for the electrolytic reduction of zirconium dioxide by the Fray – Farthing – Chen (FFC) Cambridge Process.
Electrochemical Reaction of Bis(acetylacetonato)Palladium in an Amide-Type Ionic Liquid
Authors: Yoshii Kazuki , Oshino Yosuke , Tachikawa Naoki , Toshima Kazunobu , Katayama Yasushi
Published: February 2020

Palladium is well known as a useful metal for such as catalytic reaction, hydrogen absorption and improvement of corrosion resistance. Although the electrochemical reaction and deposition of palladium has been researched in some ionic liquids so far, the palladium sources have been limited to halogeno complexes such as [PdBr4]2− or [PdCl4]2−.1,2 We have already reported electrodeposition of Pd from 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing bis(acetylacetonato)palladium (Pd(acac)2).3 In the present study, the electrochemical reaction of Pd(acac)2in BMPTFSA was investigated using a rotating ring-disk electrode.

BMPTFSA was prepared by metathesis reaction of LiTFSA and BMPBr, which was synthesized by quaternization reaction of 1-methylpyrrolidinium with n-butyl bromide in acetonitrile, followed by recrystallization with ethyl acetate. Pd(acac)2 was used as received. Electrochemical measurements were conducted in a glovebox of dry Ar atmosphere. A ring-disk electrode (Pt ring: 1.2 cm2; Pt disk: 0.79 cm2) was used as a working electrode. A Pt wire was used for a counter electrode. A silver wire immersed in BMPTFSA containing 0.1 M AgCF3SO3was used as a reference electrode. The counter electrode was separately set from the working and reference electrode by a glass filter.

The UV-vis spectrum of BMPTFSA containing 0.25 mM Pd(acac)2 was well accorded with that of ethanol solution, suggesting that Pd(acac)2 exists as a tetra-coordinated Pd complex coordinated by the oxygen atoms of acetylacetonate in BMPTFSA. The deposition of metallic palladium was confirmed on the electrode after the potentiostatic cathodic redction at −1.9 V. An anodic current was observed at the ring electrode kept at −1.25 V when the cathodic current corresponding to reduction of Pd(acac)2 was observed on the disk electrode at the potentials more positive than –1.9 V. It has been reported that some intermediate species were detected by polarogram in N, N-dimethylformamide solution containing Pd(acac)2.4 The obtained result indicated that the intermediate species, [Pd(acac)2]−, also formed by the reduction of Pd(acac)2 in this study. Thus, it is considered that the metallic palladium may be formed by the disproportionation reaction of [Pd(acac)2]−.

Acknowledgments

Part of this study was financially supported by MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2012–2016.

References

1. Y. Bando, Y. Katayama, and T. Miura, Electrochim. Acta, 53, 87 (2007).

2. I.-W. Sun and C. L. Hussey, J. Electroanal. Chem., 274, 325 (1989).

3. K. Yoshii, Y. Oshino, N. Tachikawa, K. Toshima, and Y. Katayama, Electrochem. Commun., 52, 21 (2015).

4. M. Hirota and S. Fujiwara, Bull. Chem. Soc. Jpn., 48, 2825 (1975).
Electrochemical Behavior of Samarium in Molten LiCl-KCl
Authors: Singh Vickram , Chidambaram Dev
Published: February 2020

The mass transport behavior of samarium was investigated in molten eutectic LiCl-KCl in order to develop real-time concentration monitoring capabilities for the pyrochemical reprocessing of used nuclear fuel. Pyrochemical reprocessing relies on electrolysis in molten LiCl-KCl to recycle fissile material from used nuclear fuel. Without the capabilities to monitor concentrations of various actinides and fission products, pyrochemical reprocessing cannot be commercialized due to strict material accountability requirements set by the International Atomic Energy Agency (IAEA) [1]. Therefore, physical electrochemical properties of these species in molten salts is extremely important. Cyclic voltammetry was utilized to investigate electrochemical behavior of samarium in LiCl-KCl. By establishing valid relationships between these parameters and the peak current, the diffusion coefficient of samarium in our system can be reported with confidence [2]. Experiments were conducted in a high-purity argon atmosphere glove box using a three-electrode cell contained in an alumina crucible inside a resistive furnace. A high-resolution translation stage equipped with ceramic electrode mounts was used to accurately control electrode positions inside the melt. Tungsten was used as the counter and working electrodes, and a silver wire was used as a quasi-reference (Ag|AgCl2). The variation in peak current that resulted from changing the concentration, scan rate and electrode surface area will be reported, along with calculated diffusion coefficient values for samarium in molten LiCl-KCl at 500°C. The effects of using molybdenum as a working electrode will also be reported and compared to results obtained using tungsten. A comparison between reported diffusion coefficient values obtained by separate research organizations and results obtained in these studies will also be discussed.

Acknowledgements: This work was performed under the auspices of the Department of Energy (DOE) under contracts DE-NE0008262 and DE-NE0008236 as well as the US Nuclear Regulatory Commission (USNRC) under contracts NRCHQ-11-G-38-0039. Dr. Kenny Osborne serves as the program manager for the DOE award and Ms. Nancy Hebron-Isreal serves as the grants program officer for the NRC awards.

References

1. Iizuka, M., et al., Application of normal pulse voltammetry to on-line monitoring of actinide concentrations in molten salt electrolyte. Journal of Nuclear Materials, 2001. 297(1): p. 43-51.

2. Tylka, M.M., et al., Method Development for Quantitative Analysis of Actinides in Molten Salts. Journal of The Electrochemical Society, 2015. 162(9): p. H625-H633.
(Invited) Ion Diffusion in Ionic Liquids: Effects of Electric Fields
Authors: Welton Tom , Edel Joshua B , Ivanov Aleksandar , Kuimova Marina K , McIntosh Alastair J.S. , Nawawi Mohd A. B.
Published: February 2020

An ionic liquid is an ionic substance in which its constituent ions are in motion. Consequently, it is not possible to understand the nature of an ionic liquid without understanding how its constituent ions move. However, gaining a thorough understanding the nature of ion motion in ionic liquids remains a fundamental challenge.

Single molecule fluorescence (SMF) confocal spectroscopy offers a powerful, but as yet largely underutilized tool to measure the diffusion of probe ions in an ionic liquid under a variety of conditions.

To enable SMF measurements, it was necessary to develop the synthesis of ionic liquids with very low background fluorescence. The SMF derived diffusivity of the cationic probe dyes in dilute (ca. 100 pM) solutions in [C4C1im][NTf2] and [C4C1pyrr][NTf2] solutions was compared to diffusivity of the ionic liquid cations derived from Pulse Gradient Stimulated Echo NMR measurements. The SMF derived diffusivities of the cationic probes were measured under various applied potentials and throughout the system’s relaxation back to its unperturbed state. This relaxation was found to be markedly slower than in salt solutions in molecular solvents. These results were compared to measurements of microscopic viscosity using the fluorescence spectra of molecular rotors.
Electrodeposition of ZnNi Alloys from Ethylene Glycol/Choline Chloride Based Ionic Liquid
Authors: Panzeri Gabriele , Tresoldi Matteo , Nobili Luca , Magagnin Luca
Published: February 2020

Zinc alloys containing transition metals (Ni, Co and Fe) have attracted the attention because of their high corrosion resistance [1,2]; particularly high is the interest of ZnNi system for practical application. In addition, electrodeposition of ZnNi alloys is generally described as anomalous codeposition (Brenner [3]). In this work ZnNi electrodeposition from ionic liquid system is studied; particular attention is paid to the formation Zn rich alloys (15-25 % Ni). The plating bath consists of 1 choline chloride: 2 ethylene glycol containing metal salts in different concentration. All the electrodepositions have been carried out at constant temperature T=70°C on steel. Codeposition of ZnNi is studied by means of potentiostatic electrodeposition. Compositional and morphological analysis are performed to evaluate the effect of the plating conditions and bath formulation. Electrochemical characterization of the solution is performed for those baths compositions allowing the formation of 𝛾-phase ZnNi. Metastable 𝛾-ZnNi with short-range order has been observed with XRD analysis; thermal treatment are carried out to evaluate phase reorganization.

[1] R Fratesi, G Roventi. Corrosion resistance of Zn-Ni alloy coatings in industrial production, Surface and Coatings Technology. 82 (1996) 158.

[2] R Ramanauskas, P Quintana, L Maldonado, R Pomés, MA Pech-Canul. Corrosion resistance and microstructure of electrodeposited Zn and Zn alloy coatings, Surface and Coatings Technology. 92 (1997) 16.

[3] A Brenner. A. Electrodeposition of Alloys. Vol. 1, General Survey, Principals, and Alloys of Copper and of Silver, (1963).
Natural Fiber Welding of Chitin and Chitosan on a Cotton Cloth Substrate: Novel Materials Displaying Antimicrobial Properties
Authors: Russell Robert Allen , Fox Eric T , Nolan Robert , Chandler Molly , Head Audrey C. , Brusoski Michael , De Long Hugh C , Trulove Paul C
Published: February 2020

Ionic liquids (ILs) can be used as solvents for biopolymers due to unique chemical and physical properties that enable mobilization and disruption of the hydrogen bonding present in the biopolymer structure. Chitin and chitosan are biopolymer known to have natural antimicrobial properties. The goal of this work is to functionalize a composite cotton yarn or cloth with a chitin or chitosan biopolymer, in order to exploit the bio-active properties of chitin or chitosan, while maintaining the intrinsic physical and chemical properties of cotton yarn. We will be using a method called Natural Fiber Welding (NFW) to incorporate chitin or chitosan biopolymers into cotton materials.

Natural Fiber Welding is the process of full or partial dissolution of a substrate and the regeneration using ILs, such as 1-ethyl-3-methylimidazolium acetate. Using this process, chitin or chitosan is able to be permanently adhered and chemically bonded to the outer and inner surface of the native yarn. Changing factors, such as ionic liquid solution composition (introducing DMSO), temperature, time, and concentration of biopolymers alters the degree of biopolymer mobilization which influences what properties the composite yarn displays. In this study we will show results for chitin or chitosan welded into cotton composite materials. We will present data characterizing the physical, chemical, and biochemical properties of these composites. Data from confocal fluorescence microscopy (CFM), SEM imaging, and Bactericidal Killing Assays will be shown using E.Coli transfected with Green Fluorescent Protein. In conclusion, it appears that we can effectively coat and integrate chitin or chitosan onto the cotton material and the material exhibits antimicrobial properties.
the Enhanced Electrocatalytic Activity over Carbon-Supported Pd-Based Ordered Intermetallic Compounds
Authors: Gunji Takao , Tanabe Toyokazu , Kaneko Shingo , Ohsaka Takeo , Matsumoto Futoshi
Published: February 2020

In recent years, the direct fuel cells (DFCs) have attracted increasing interest as next energy device in the area of polymer electrolyte membrane fuel cells due to its high efficiency and high power density. Formic acid (FA) has been receiving paramount attention as fuel for DFCs because of its high energy density (1740 Wh kg-1, 2086 Wh L-1) and fuel crossover of FA is smaller than that MeOH [1]. In addition, the electrooxidation current density (and mass activity) of FA over Palladium (Pd) nanoparticles (NPs) is higher than that Platinum (Pt) electrocatalyst [2]. Therefore, the DFCs, which FA is used as fuel, can be operated without Pt electrocatalyst. However, electrocatalytic activity towards electrooxidation of FA is still in need of improvements.

In order to enhance electrocatalytic activity towards electrooxidation of FA, Pb was used as secondary material for alloying with Pt because of CO-poisoning tolerance of electrocatalysts. Recently, we have previously reported that ordered intermetallic PtPb efficiently electrochemically catalzed for electrooxidation of FA, MeOH and EtOH [3]. In particular, core shell structure of bimetallic Pt3Pb exhibited efficient electrocatalytic activity for the electrochemical oxidation of FA, MeOH and EtOH. These indicate that Pb atom in ordered intermetallic PtPb (and/or bimetallic Pt3Pb) facilitates more efficiency of FA electrooxidation not only enhancement of electrocatalytic activity but also CO-poisoning tolerance.

This study demonstrates the new approach in preparation of carbon supported ordered intermetallic Pd3Pb NPs (Pd3Pb NPs/CB), which has a Cu3Au type structure, via polyol method under air atmospheric air without anneal treatment. In addition, Pb atom in ordered intermetallic Pd3Pb NPs were dissolved under acidic environment by cyclic voltammetry up to 1.1 V, resulting in formed surface-dealloyed Pd-shell ordered intermetallic Pd3Pb core structure (Pd@Pd3Pb NPs/CB). The surface of prepared Pd@Pd3Pb NPs/CB was characterized by using XPS and HR-TEM. The electrochemical activity of prepared Pd@Pd3Pb NPs/CB is compared to commercially available Pt NPs/CB, PtRu NPs/CB and Pd NPs/CB. In addition, electrochemically surface-dealloyed Pd@Pd3Pb NPs/CB has better catalytic activity towards the electrooxidation of FA than other electrocatalysts.

[1] Rice, C.; Ha, S.; Masel, R. I.; Wieckowski, A. J. Power Sources
2003, 115, 229.

[2] Capon, A.; Parsons, R. J. Electroanal. Chem.
1973, 44, 239.

[3] Gunji, T.; Tanabe, T.; Jeevagan, A. J.; Usui, S.; Tsuda, T.; Kaneko, S.; Saravanan, G.; Abe, H.; Matsumoto, F. J. Power Sources
2015, 273, 990.