bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Characterization of Free-Standing Platinum Nanoelectrode Array Using Atomic Layer Deposition for Polymer Electrolyte Fuel Cells
Authors: Sabarirajan Dinesh C , Vlahakis James , White Robert D , Zenyuk Iryna V
Published: September 2016

This paper presents non-conventional thin-film electrodes prepared by atomic layer deposition (ALD) that are a promising alternative to conventional designs and model ionomer-free electrodes for ion conductivity studies. In the ALD process, monolayers of Pt are deposited onto the substrate by dissociative chemisorption in a self-assembling reaction. In this work, we use an ALD thermal exposure mode to deposit Pt nanostructures onto a sacrificial anodized aluminum oxide (AAO) substrates using the trimethylcyclopentadienylmethylplatinum (IV) and oxygen gas as precursors. Thermal exposure mode provides additional time for the reactions in the ALD chamber and allows higher penetration of the precursor into the substrate. We compare various ALD electrode fabrication conditions and provide detailed electrochemical analysis (electrochemical surface area, polarization curves, cyclic voltammetry) of these nanoelectrode arrays.
Air Starvation Accelerated Stress Tests in Polymer Electrolyte Fuel Cells
Authors: Bodner Merit , Schenk Alexander , Marius Bernhard , Rami Mija , Hacker Viktor
Published: September 2016

Polymer electrolyte membrane fuel cells are exposed to various types of degradation in real life operation. While the lifetime of mobile applications is mainly limited by harsh dynamic load changes, stationary applications exhibit longer duration. However, even under very stable load conditions, degradation may occur and failure modes, such as cathode gas supply interruption, can become a lifetime-defining issue. Thus, in this work, the effect of air starvation on the operation of a single cell was investigated. By implementing a segmented current collector plate on the cathode, local phenomena and gradients in current and temperature distribution were identified.
Oxygen Reduction Reaction Activity and Durability for Model Pt Shell Layers on Ir(111) Prepared by Molecular Beam Epitaxy
Authors: Watanabe Hirofumi , Kaneko Soma , Todoroki Naoto , Wadayama Toshimasa
Published: September 2016

We fabricated well-defined Pt–Ir bimetallic surfaces through monolayer-thick Pt epitaxial growth on Ir(111) substrates (Pt
n

ML/Ir(111):n = 1–4) using molecular beam epitaxy in ultrahigh vacuum (UHV). The surface structures of Pt
n

ML/Ir(111) were verified using reflection high-energy electron diffraction in UHV. Electrochemical characterization tests, including evaluations of oxygen reduction reaction (ORR) activity and durability, were performed using cyclic voltammetry and rotating disk electrode techniques in 0.1 M HClO4. Regarding the initial ORR activity for Pt
n

ML/Ir(111) surfaces, Pt2ML/Ir(111) surfaces exhibited the highest ORR activity (24 times that of the clean Pt(111) surfaces). Initial ORR activities declined when square-wave potential cycles (PCs) were applied between 0.6 and 1.0 V vs. reversible hydrogen electrode. The Pt4ML/Ir(111) surface exhibited the highest ORR activity even after 5000 PC loadings (6 times that of the clean Pt(111) surfaces), suggesting that Pt-shell/Ir-core core–shell nanoparticles have potential for use as practical Pt-based bimetallic ORR catalysts.
Oxygen Reduction Reaction Activity and Durability for Pt/TaNx Model Catalysts Fabricated in Ultra-High-Vacuum
Authors: Takahashi Shuntaro , Takahashi Naoki , Todoroki Naoto , Tanabe T , Wadayama Toshimasa
Published: September 2016

The electrochemical structural stability of Pt-shell/Ta nitride-core nanoparticles (Pt/TaNx NPs) on a highly oriented pyrolytic graphite (HOPG) substrate was investigated under the application of square-wave potential cycling in 0.1 M HClO4. The Pt/TaNx/HOPG samples were fabricated through arc-plasma deposition (APD) of TaNx NPs, followed by electron-beam evaporation of Pt in ultra-high vacuum (UHV). X-ray diffraction and X-ray photoelectron spectroscopy results present strong evidence of tantalum nitride generation by the APD of tantalum under the introduction of nitrogen (0.1 Pa) into the UHV chamber. Evaluation of the oxygen reduction reaction (ORR) activity of the catalysts after applying square-wave potential cycling between 0.6 and 1.0 V clearly shows that the nitridation of transition-metal cores is effective for improving the ORR activity and durability of core–shell type NP catalysts.
Development of MEAs by Controlling Carbon Structures in Cathode Layers
Authors: Fu Bo , Minamida Yasuto , Noda Zhiyun , Sasaki Kazunari , Hayashi Akari
Published: September 2016

Pt nanoparticles have been encapsulated into nano-channels of mesoporous carbon (MC), in order to suppress the mobility of Pt particles and then increase the durability. For further enhancing IV performance, especially in the high current density region, addition of carbon nanofiber (CNF) to the cathode catalyst layers was explored, and an optimal condition was evaluated. As a result, MEA with 10 wt.% CNF addition showed the highest IV performance even though porosity itself was better for 20 wt.% CNF addition. Therefore, thickness is another important factor in addition to porosity, especially in terms of Pt active sites per unit thickness.
Porous Graphene Layers on Pt Catalyst for Long-Term Stability of Fuel Cell Electrode
Authors: Kim Heeyeon , Robertson Alex W , Warner Jamie H , Kim Sang Ouk
Published: September 2016

For the high performance and long-term stability of Pt/C catalyst for polymer electrolyte fuel cell, the deactivation of the catalysts by agglomeration, dissolution or detachment of Pt particles from carbon support have to be improved. For this purpose, we adopted a new shape of nano-carbon material for the surface modification of Pt catalyst. Our Pt nano particles encapsulated with porous graphene shells showed similar initial activity compared with the commercial catalysts showing more than 150% higher long-term stability.
PEFC Alloy Electrocatalysts Supported on SnO2: A Study on the Preparation Method
Authors: Matsumoto Shohei , Iwami Masahiro , Noda Zhiyun , Matsuda Junko , Hayashi Akari , Sasaki Kazunari
Published: September 2016

Pt/C is widely used as a PEFC electrocatalyst. However, Pt detachment and aggregation due to carbon corrosion can occur. Therefore, the conventional Pt/C electrocatalyst has a difficulty in durability. Our research group have developed Pt/SnO2/VGCF-H electrocatalysts and achieved both high catalytic activity and high voltage-cycle durability. In this study, we have focused on PtxCoy alloying and developed PtxCoy/Nb-SnO2/VGCF-H electrocatalysts in order to achieve higher oxygen reduction reaction (ORR) activity. XRD measurements exhibited alloying of PtxCoy but not reduced SnO2. In addition, half-cell measurements revealed that a high ORR activity due to possible PtxCoy alloying has been achieved after performing the proper heat treatment.
Advancement of Group 4 and 5 Metal Oxide Cathode with Oxide Support for PEFCs
Authors: Ota Kenichiro , Tamura Yuko , Nagai Takaaki , Matsuzawa Koichi , Mitsushima Shigenori , Ishihara Akimitsu
Published: September 2016

In order to develop precious-metal-free and carbon-free cathodes, the ORR activities of Group 4 and 5 metal oxide mixtures with Ti4O7 support have been studied. The ORR activity of the TixNbyOz + Ti4O7 is higher than other oxide mixtures, indicating that the TixNbyOz might have high active sites for the ORR. The highest onset potential of the TixNbyOz + Ti4O7 was over 1.1 V with respect to reversible hydrogen electrode. No degradation of the ORR performance of TixNbyOz + Ti4O7 was observed during both start-stop and load cycle tests. TiO2-Nb (0.5 atm%) single crystal was heat-treated at 800 oC in 4%H2/Ar to examine the effect of heat-treatment under reducive atmosphere. The ORR activity of the TiO2-Nb(0.5atm%) electrode was high. Small amount of Nb doping might be enough to get high ORR activity and high temperature treatment was effective to get high activity.
Oxide-Coated Carbon Black for Cathode Catalyst Support
Authors: Nako Yuki , Sonoda Takashi , Itoh Tetsuya , Kinumoto Taro
Published: September 2016

Carbon black is an essential material for PEFC; on the other hand, carbon black is concerned as the critical element which limits the lifetime of PEFC. Especially in the cathode, oxidative degradation depressess the catalyst activity. In order to prevent carbon black support from its oxidative degradation, surface coating with silicon oxide (silica) on acetylene black was carried out using “sol-gel method”. Thin amorphous silica layer was formed at the nanometer thickness on the almost surface on acetylene black. Its effect on the anti-oxidation, Pt supporting function and total behavior of the catalyst are discussed.
Improving Performance in Alkaline Membrane Fuel Cells through Enhanced Water Management
Authors: Omasta Travis J , Peng Xiong , Lewis Connor A , Varcoe John , Mustain William E
Published: September 2016

Water management is one of the most critical parameters in the production of high performance membrane electrode assemblies for anion exchange membrane fuel cells. In this work, we have systematically studied the influence of the feed gas flow rate, hydrophobic vs hydrophilic gas diffusion layers, the presence of a microporous layer, and humidifier temperature on cell performance. Work was performed using both on standardized Tokuyama products as well as quaternary-ammonium radiation-grafted alkaline anion-exchange membranes and ionomers synthesized by our team.
Developing Cobalt Doped Pr0.5Ba0.5MnO3-δ Electrospun Nanofiber Bifunctional Catalyst for Oxygen Reduction Reaction and Oxygen Evolution Reaction
Authors: Zhang Yaqian , Sun Yi-Fei , Luo Jing-Li
Published: September 2016

The porous nanofiber Co doped Pr0.5Ba0.5MnO3-δ (PrBaMnO) was successfully synthesized through electrospinning technology and served as a bifunctional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction(OER). The catalytic activities of the composite catalyst consisting of 50 wt% perovskite catalyst and 50 wt% carbon black (CB) was investigated in alkaline solution. Comparing to the PrBaMnO parent perovskite, remarkable enhancement of ORR and OER performance were achieved on Pr0.5Ba0.5MnCo0.2O3-δ with respect to decreased overpotential and increased current density. A maximum current density of 19.4 mA cm-2 was achieved at 1.95 V (versus. RHE) on Co doped Pr0.5Ba0.5MnO3-δ electrospun nanofiber/CB composite catalyst in OER. In addition, a preferable four electron transfer pathway was demonstrated in the ORR process. All the electrochemical test results suggest the promising application of Co doped Pr0.5Ba0.5MnO3-δ electrospun nanofiber/CB composite as an efficient bi-functional catalyst on fuel cells and metal-air batteries.
Manganese Oxide/Poly(3,4-ethylenedioxythiophene) Hybrid Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Fuel Cells
Authors: Lambert Timothy N. , Vigil Julian A.
Published: September 2016

Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnOx/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnOx/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. The high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT and due to the increase in Mn3+ content at the surface of the oxide.
Origin of Superior Activity of Ru@Pt Core-Shell Nanoparticles towards Hydrogen Oxidation in Alkaline Media
Authors: Schwämmlein Jan Nicolas , El-Sayed Hany A , Stühmeier Björn Marcel , Wagenbauer Klaus F , Dietz Hendrik , Gasteiger Hubert A.
Published: September 2016

There is an ongoing discussion about the nature of the high hydrogen oxidation reaction (HOR) activity of bimetallic Pt-Ru catalysts in alkaline media. We provide an insight on the HOR mechanism for this type of catalyst, excluding bifunctionality as the main driving force for the oxidation of hydrogen. In order to do so, we prepared and evaluated Ru@Pt core-shell nanoparticles with sub-, mono- and multilayered Pt-shells. Rotating disk electrode (RDE) studies in 0.1 M NaOH solution of all prepared catalysts, including Pt/C as a reference show that Ru particles fully encapsulated with a Pt-shell show significantly higher activity than Ru particles that are solely covered with Pt-submonolayers. Furthermore, we found a 4-fold enhancement of Ru@Pt vs. pure Pt with respect to the surface normalized HOR activity. The Ru@Pt catalysts were characterized by COads-stripping voltammetry, as well as cyclic voltammetry (CV) in order to identify the Pt-coverage and shell thickness.
Methanol Oxidation on Ru- or Ni-Modified Pd-Electrocatalysts in Alkaline Media: A Comparative Differential Electrochemical Mass Spectrometry Study
Authors: Jurzinsky Tilman , Kintzel Birgit , Bär Robin , Cremers Carsten , Pinkwart Karsten , Tübke Jens
Published: September 2016

In this work, the methanol oxidation mechanism was investigated in detail on Ru- or Ni-modified, Pd-based electrocatalysts. The electrochemical activity towards methanol oxidation reaction, the surface inhibition behavior and the CO2 current efficiency was evaluated for the catalysts by cyclic voltammetry, chronoamperometry, CO adsorbate stripping and CH3OH adsorbate stripping experiments in a differential electrochemical mass spectrometry flow cell setup. Pd5Ni/C and Pd3Ru/C catalysts showed higher current densities, lower oxidation onset potentials and lower sensitivity to surface inhibition than Pd/C. Due to detailed studies on the CO2 current efficiencies, side products and adsorbate reactions via differential electrochemical mass spectrometry, novel insights into the electrooxidation of methanol on Pd5Ni/C and Pd3Ru/C were provided. While modification with Ru resulted in CO2 current efficiencies well over 80%, Ni-modified catalyst was not able to enhance the CO2 current efficiency.
Realizing the Potential of Micro-Phase Separated Block Copolymer Electrolytes: Ion Domain Connectivity Plays a Prominent Role in Ion Conduction
Authors: Arges Christopher George , Kambe Yu , Dolejsi Moshe , Wu Guangpeng , Segal-Peretz Tamar , Ren Jiaxing , Nealey Paul F.
Published: September 2016

Block copolymer electrolytes (BCEs) offer the prospect of membranes with high ionic conductivity at lower ion-exchange capacities leading to membranes with robust mechanical properties. However, the microphase separated structure of such BCE membranes and its impact on membrane conductivity is poorly understood. Most studies assume that aggregated ionic domains in microphase separated BCEs, or random copolymers, is sufficient to foster facile ion conductivity. However, microphase separation alone cannot spur rapid ion conduction. In this paper, we demonstrate that ion domain connectivity greatly influences ion conductivity in BCEs. The results emphasize the importance of maximizing ion domain connectivity while minimizing terminal defects to realize BCEs with optimal ion transport properties.
Nitrogen-Incorporated Amorphous Carbon Catalysts with Higher Reactivity toward Oxygen Reduction Reaction
Authors: Honda Kensuke , Shimai Yohosuke , Waki Yuta , Okafuji Keigo , Ohtomo Shinpei , Kobayashi Ryutaro , Naragino Hiroshi
Published: September 2016

Amorphous carbon (a-C) based catalysts having higher oxygen reduction reaction (ORR) activity and higher stability for ORR were realized by inserting nitrogen atoms in the valleys of zigzag edges of sp
2 cluster surface in a-C. ORR activity could be controlled by varying sizes and volume density of sp
2 cluster. The maximum number of electrons of 2.82 for ORR was achieved. The N-doped a-C catalysts have the activity of 4-electron O2 reduction reaction. The catalytic activity was stable in long term (150 times) measurements. Consequently, the N-doped a-C catalysts possesss ly, imes) measurements higher stability for ORR.
On-Line Mass Spectrometry for Ethanol Oxidation on Well-Defined Sn/Pt(hkl) Electrode Surfaces
Authors: Nakamura Hiroki , Inoue Tatsuhiko , Matsuda Tetsuhiko , Todoroki Naoto , Wadayama Toshimasa
Published: September 2016

Onset potentials of ethanol oxidation reaction (EOR) and potential-dependent evolution of gaseous products from well-defined Sn/Pt(hkl) electrode surfaces were investigated. The electrode surfaces were prepared by vacuum deposition of Sn on a Pt(hkl) single-crystal substrate in ultra-high vacuum. The EOR onset potentials of anodic currents for Sn/Pt(hkl) shifted to lower potentials in comparison to unmodified Pt(hkl). Online electrochemical mass spectrometry (OLEMS) analysis of the gaseous products formed on the Sn/Pt(hkl) surfaces showed that acetaldehyde, rather than CO2, was generated at lower applied voltages and that the product evolution was sensitive to the atomic arrangement of the surface Pt (Pt(hkl)). EOR anodic current measurements and OLEMS analysis showed that EOR onset potential is the lowest for Sn/Pt(110). The findings can be attributed to the effectiveness of Pt(110) steps in ethanol C-C bond cleavage and an ensemble effect of the Pt and Sn atoms against CO poisoning.
(Invited) Conventional and Innovative Electrocatalysts for PEM Water Electrolysis
Authors: Millet Pierre
Published: September 2016

In conventional polymer electrolyte membrane (PEM) water electrolysis cells, platinum particles are used at the cathode for the hydrogen evolution reaction (HER) and iridium oxide particles at the anode for the oxygen evolution reaction (OER). Although noble metal contents are small, the large scale deployment of PEM technology for power-to-gas applications is calling for cheaper materials. Molecular organo-metallic complexes containing transition metals as active centers offer some promising alternative. Examples with cobalt and iron clathrochelates used for the HER are reported in this communication.
Impact of Pressure and Temperature on Hydrogen Permeation in PEM Water Electrolyzers Operated at Asymmetric Pressure Conditions
Authors: Trinke Patrick , Bensmann Boris , Reichstein Sven , Hanke-Rauschenbach Richard , Sundmacher Kai
Published: September 2016

The present work investigates the hydrogen permeation through a polymer electrolyte membrane (PEM) of a fumea EF-40 catalyst coated membrane (CCM) during water electrolysis. The permeation rate is measured at different cell temperatures and different pressure gradients across the membrane. The determined permeation fluxes show a quadratic dependence on pressure difference. This can be described qualitatively very well with a permeation model that considers a diffusive and convective hydrogen transport through the membrane. The determined diffusive permeability coefficient Keff
P,diff = 2.95E-14 mol/(m s Pa) at 60 °C and its temperature dependence agrees very well with comparable literature values. The proposed convective permeability coefficient Keff
P,conv = 9.02E-21 mol/(m s Pa²) at 60 °C indicates a high hydraulic permeability for the investigated EF-40 in comparison with recently reported values for Nafion membranes.
Optimization of Annealing Catalyst Powder for High Temperature PEMWE
Authors: Li Hua , Nakajima Hironori , Ito Kohei
Published: September 2016

To investigate the impact of annealing conditions on electrolysis performance, annealed IrO2 powders are examined as anode catalysts in a high temperature polymer electrolyte membrane water electrolyzer (PEMWE). The IrO2 powders were annealed for from 1 to 8hours under 350oC and 490oC. The effect of annealing time and temperature on the IrO2 phase, specific surface area of IrO2 and high frequency resistance (HFR) is investigated through analyzing the current-voltage (I-V) characteristics. The experiment result shows that annealing impacts on electrolysis performance majorly through changing IrO2 phase. Both lengthening annealing time and elevating annealing temperature change IrO2 phase from amorphous phase to crystal phase. The optimum annealing conditions is annealing IrO2 powder at 350oC for 1hour.
Simplified Microwave Assisted Solvothermal One Pot Synthesis of Highly Active Nickel-Iron Layered Double Hydroxide as Oxygen Evolution Reaction Catalyst
Authors: Dresp Sören , Strasser Peter
Published: September 2016

Nickel-Iron layered double hydroxides (NiFe-LDH), known as highly active material for the oxygen evolution reaction (OER) in alkaline media, needs better and simpler synthesis routes. Due to high energy efficiency of microwave heating, microwave assisted solvothermal synthesis could play a major role in environmental friendly synthesis routes. This approach could further be a key step for sustainable production of highly active materials like electro-catalysts. Therefore, we developed a simplified and shortened solvothermal microwave assisted one pot synthesis to produce highly active NiFe-LDH supported on Vulcan XC-72r material. The synthesis was studied for reproducibility in loading, composition and activity using inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction and rotating ring disk electrodes (RDE) in a three electrode set-up.
Anion Exchange Membrane Electrolyzers Showing 1 A/cm2 at Less Than 2 V
Authors: Masel Richard I , Liu Zengcai , Sajjad Syed
Published: September 2016

This paper reports initial data on anion exchange membrane water electrolyzers using Sustainion™ membranes. These are styrene based membranes, that are functionalized with imidazoliums or pyridiniums as described in US patent 9,370,773. Initial work was done with platinum anode catalysts and iridium cathode catalysts. By optimizing the membrane composition and the choice of ionomer initial currents of 1 amp/cm² at 1.69V and 6 amp/cm² and 6 amp/cm² at 2.05 V are observed in a cell at 60 C with 1 M KOH. So far we have been able to maintain 1 A/cm² at about 1.7 V for hours. The run is continuing. These results show the advantage of Sustainion™ membranes for water electrolyzers.
Selective Reversible Absorption of the Industrial Off-Gas Components CO2 and NOx by Ionic Liquids
Authors: Kaas-Larsen Peter Kjartan , Thomassen Peter , Schill Leonard , Mossin Susanne , Riisager Anders , Fehrmann Rasmus
Published: September 2016

Ionic liquids are promising new materials for climate and pollution control by selective absorption of CO2 and NOx in industrial off-gases. In addition practical cleaning of industrial off gases seems to be attractive by use of ionic liquids distributed on the surface of porous, high surface area carriers in the form of so-called Supported Ionic Liquid Phase (SILP) materials. The potential of selected ionic liquids for absorption of CO2 and NOx are demonstrated and the possible interference of other gases influencing the stability and absorption capacity of the ionic liquids are investigated as well.
A New Electrolytic Production Process of Silicon Using Liquid Zn Alloy Cathode in Molten Salt
Authors: Nohira Toshiyuki , Ido Akifumi , Shimao Takeyuki , Yang Xiao , Yasuda Kouji , Hagiwara Rika , Homma Takayuki
Published: September 2016

Electrolytic production process for solar-grade Si utilizing liquid Si–Zn alloy cathode in molten CaCl2 has been proposed. Toward the establishment of the process, the behavior of liquid Zn metal was investigated in molten CaCl2 at 1123 K. The evaporation of Zn metal was largely suppressed by an immersion into molten salt, which enables the use of Zn electrode in spite of the high vapor pressure of Zn. The cyclic voltammetry suggested the reduction of SiO2 at 1.45 V vs. Ca2+/Ca on a Zn cathode. After the potentiostatic electrolysis at 0.9 V, Si particles with diameters of 2–30 µm were precipitated in the solidified Zn matrix by the slow cooling process of the produced liquid Si–Zn alloy. The alloying rate between solid Si and liquid Zn was measured as 4.56 μm s−1, and it linearly decreased with the Si content in liquid Zn phase.
Ionic Liquids and Organic Ionic Plastic Crystals Based on Tris(fluorosulfonyl)methide
Authors: Matsumoto Hajime , Mizukado Junji , Wan Peng-cheng
Published: September 2016

New ionic liquids and organic ionic plastic crystals based on tris(fluoromethylsulfonyl)methide were prepared and the physico-chemical, thermal and electrochemical properties were investigated and compared to that of the corresponding tris(trifluoromethyl-sulfonyl)methide salts.
(Invited) Quantifying the Impact of Ionic Liquid Cations on the Properties of Cellulose Nanocrystals
Authors: Gilman Jeffrey W. , Woodcock Jeremiah , Fox Douglas M
Published: September 2016

Ionic liquids, and the novel cations and anions which they are comprised of, have been used to modify the properties of many classes of materials. This includes their use as co-solvents and co-catalysts in simple chemical reactions. However, ionic liquid cations and anions have also been used to improve the properties and processing of nanomaterials as well. This paper will present recent efforts utilizing ionic liquid cations to dramatically improve the properties of cellulose nanocrystals (CNCs) such as water sensitivity, thermal stability, dispersibility, and polymer-miscibility. This is accomplished via a classic continuous, industrial process using ion-exchange resin. Novel measurement methods, used to characterize the impact of these cations on the CNC properties such as dynamic vapor desorption (DVS), optical imaging and inverse gas chromatography (iGC), will also be presented.
Fluoride Addition Effects on Voltammograms and UV-Vis Spectra of Neodymium Cation in Molten Chlorides
Authors: Matsuura Haruaki , Nezu Atsushi , Akatsuka Hiroshi , Uehara Akihiro , Fujii Toshiyuki
Published: September 2016

The modification of electrochemistry and electronic absorption spectra of neodymium in various molten chlorides depending on additional fluoride in the melt bath has been investigated. Disproportionation reaction is restricted by fluoride addtion and absorption spectra is highly modified in molten NaCl-2CsCl as compared with that in molten LiCl-KCl. These facts would be explained by modification of local structure around neodymium cation depending on fluoride addition.
Development and Optimization of Voltammetry for Real Time Analysis of Multi-Component Electrorefiner Salt
Authors: Zhang Chao , Rappleye Devin , Simpson Michael Forrest
Published: September 2016

Normal pulse voltammetry was performed on LiCl-KCl-UCl3-MgCl2 molten salt mixtures while varying parameters such as pulse time, relaxation potential, and interval time. Concentrations of UCl3 up to 7 wt% were tested with a fixed 1.5 wt% MgCl2 concentration. The correlation between diffusion limited partial current density to UCl3 concentration exhibited an excellent fit to a 2nd order polynomial. A similar fit was obtained for the correlation between MgCl2 concentration and the diffusion limited partial current density at a fixed UCl3 concentration of 1.0 wt%.
(Invited) Challenge of Industrializing Novel Molten Salt Electrochemical Processes
Authors: Ito Yasuhiko , Nishikiori Tokujiro , Tsujimura Hiroyuki
Published: September 2016

Various novel molten salt electrochemical processes can be used to create new industries in the fields of energy, the environment, resources, and materials. Of these, the following four topics are selected, and their principles, experimental data, and current developmental stages towards industrialization are explained. (1) Electrolytic synthesis of ammonia from water and nitrogen under atmospheric pressure; (2) Electrochemical formation of carbon film; (3) Plasma-induced discharge electrolysis to produce nano-particles; and (4) Recycling of crucial metals using a ‘bifunctional’ electrode.
Intermediate-Temperature Operation of Sodium Secondary Batteries with High Rate Capability and Cyclability Using Ionic Liquid Electrolyte
Authors: Matsumoto Kazuhiko , Chen Chih-Yao , Kiko Tomohiro , Hwang Jinkwang , Hosokawa Takafumi , Nohira Toshiyuki , Hagiwara Rika
Published: September 2016

Electrochemical behavior of Na metal is one of the key factors to construct high performance Na secondary batteries. The present study reports temperature dependence of Na metal deposition/dissolution efficiency and morphology of the deposited Na metal in the Na[FSA]-[C2C1im][FSA] ionic liquids (C2C1im+ = 1-ethyl-3-methylimidazolium and FSA− = bis(fluorosulfonyl)amide). The deposition/dissolution efficiency shows the minimum at 298 K and increases by both increasing and decreasing temperature. Optical microscopic analysis reveals that Na metal is grown in a whisker-like form during cathodic polarization at 298 K, whereas smooth deposits are observed at 363 K. Although the deposition form at 273 K is also whisker-like, the thickness and length of each whisker is smaller and shorter, respectively, than those at 298 K. Such differences in morphology affect the Na metal deposition/dissolution efficiencies.
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: September 2016

Owing to their extremely high theoretical energy density, non-aqueous Li-air batteries have received remarkable attention in recent years. 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, compared to conventional organic electrolytes, ILs generally have higher viscosity and, consequently, lower ionic conductivity and ion diffusivity. Therefore, we have selected eight low-viscosity ILs containing the bis(trifluoromethanesulfonyl)imide ([TFSI]-) anion, and their physical properties were characterized. The diffusivities of the cation and anion of the ILs were measured with pulsed-field-gradient spin-echo (PFG-SE) NMR Spectroscopy. In addition, the I-V performances of three characteristic ILs were tested in a Li-O2 battery. The solubility of O2 in the ILs and IL-Li[TFSI] mixtures, an additional property that can affect Li-air battery performance, was also measured using a gravimetric microbalance.
Hydrogen Diffusion and Trapping in Fluoride Salt Melts and Graphite Electrodes
Authors: Scarlat Raluca , Carotti Francesco , Wu Huali , Macdonald Digby D.
Published: September 2016

This paper presents an approach currently under development at University of Wisconsin Madison to study tritium transport in high temperature fluoride salt systems and absorption in graphite. This work has applicability to tritium management in Fluoride Salt Cooled High Temperature Nuclear Reactors (FHRs). The applicability of the Double Potential Step Method (DSPM) and Electrochemical Impendence Spectroscopy (EIS) originally developed for the study of hydrogen transport in metals from water solutions is discussed for the salt-graphite system. Mechanistic models for hydrogen transport and trapping in graphite are reviewed. The experimental setup and electrochemical cell used with 2LiF-BeF2 (flibe) salt at 500-700°C is described. The design and preliminary characterization data for a Ni/Ni(II) flibe thermodynamic reference electrode are presented.
"Click Synthesis" of Mercaptosilyl-Functionalized Ionic Liquids via Thiol-Ene Chemistry for Use as Hydrophobic Surface Coating Agents
Authors: Sanchez Zayas Manuel , Nestor Stephen , Gaitor Jamie , Reardon Melissa , Mirjafari Arsalan
Published: September 2016

The thiol-ene “click” transformation described here is a high-yielding and simple fusion process, leading to a series of hydrophobic, multifunctionalized ionic liquids containing long thioether spacers (C7, C11 and C15) with low melting points and high thermal stability. The process exhibits broad scope and provides a series of imidazolium-based mercaptosilyl-functionalized ionic liquids in excellent yields and exclusive anti-Markovnikov regioselectivity. The synthesized ionic liquids were found to be active surface coating agents and were successfully immobilized on magnetite supermagnetic Fe3O4 nanoparticles. The representative ionic liquids with different side chains were immobilized on the surface of Fe3O4 magnetic nanoparticles and showed high organic loading and low size of nanoparticles.
Availability Evaluation of SiC Anode in Chloride Molten Salt Electrolysis
Authors: Takahashi Yoshihiro , Takenaka Toshihide
Published: September 2016

Carbon or graphite is commonly used to anode material in molten salt electrolysis, but they are consumed by a electrochemical reaction with a residual O2- in the bath. In this study, the dependence of anodic behavior in molten chloride containing O2- on some carbon materials with different structure has been investigated in LiCl-KCl-ClO melts at 723K. The anodic behavior of SiC was also investigated in the bath. In all materials, reactions of CO2 and CO3
2- occurred, and electrodes were consumed; a graphitization degree slightly influenced the consumption at graphite material, and the consumption of GC seemed the lowest. Although SiO2 was formed on SiC material, the consumption of SiC was not prevented completely. The unevenness of SiO2 layer on SiC might cause the consumption of SiC.
The Effect of the Second Coordination Sphere on Vanadium Speciation in Molten Chlorides
Authors: Polovov Ilya B. , Chernyshov Mikhail V. , Volkovich Vladimir A. , Vasin Boris D. , Griffiths Trevor R.
Published: September 2016

Vanadium speciation in a variety of alkali chloride based melts was studied in situ using high temperature electronic absorption spectroscopy. The experimental spectra were resolved into constituent Gaussian bands. Octahedral VCl6
3– complex ions is the only soluble species of V(III). Oxidation of VCl6
3– complexes or chlorination of V2O5, V2O4 or V2O3 by hydrogen chloride produces soluble vanadyl-based complexes. The results obtained indicate that the coordination environment of vanadyl-species in NaCl–2CsCl melts is different from the melts containing smaller cations. Anodic dissolution of metallic vanadium in chloride melts produces vanadium(II) ions. Increasing temperature and the mean radius of the salt-solvent cation resulted in changes of the electronic spectra as a result of shifting VCl6
4–↔VCl4
2– equilibrium towards the tetrahedral complexes.
Currentless Deposition of Niobium-Based Protective Coatings for Application in Molten Salts
Authors: Abramov Aleksandr V. , Polovov Ilya B. , Volkovich Vladimir A. , Rebrin Oleg I.
Published: September 2016

A novel method of forming niobium-based coatings by currentless deposition in molten salts was developed. The protective coatings were produced on nickel and various nickel-based alloy substrates. The corrosion resistance of the obtained coatings was tested and characterized in fused niobium- and uranium-containing chloride electrolytes at different temperatures. The method of protecting nickel-based alloys by currentless niobium deposition can be used in industrial technologies of rare earth and refractory metal electrowinning from molten salt baths.
Ionic Conduction Mechanism Analysis for Neodymium Complex in Phosphonium Ionic Liquids and Potassium Bis(trifluoromethylsulfonyl)amide Melts
Authors: Nishimura Atsuki , Matsumiya Masahiko , Tsunashima Katsuhiko
Published: September 2016

It is important to investigate the ionic conduction mechanism for neodymium complex; Nd(III) in ionic liquids and low-temperature molten salts. The temperature dependence of ionic conductivities in [P2225][TFSA] dissolving 0.05-0.50 M Nd(III) was evaluated from Vogel-Fulcher-Tammann (VFT) equation in this study. The concentration dependence of ionic conductivities for Nd(III) in [P2225][TFSA] was evaluated from Kohlrausch law. Considering from Walden plot, this result indicated that the ionic conduction was attributed to the transfer of [P2225]+ and Nd3+ cations, and [TFSA]- anions even in the presence of Nd(III). Moreover, The VFT parameters of the ionic conductivities in [Nd1/3,K][TFSA] melts with molar fraction of Nd; x
Nd=0.010-0.075 were also estimated in this study. Furthermore, the self-diffusion coefficients of cation and anion in [P2225][TFSA] were calculated from molecular dynamics simulation. This tendency of diffusivity for each ion was consistent with the ionic conductivity.
Influence of Fluid Dynamics on the Electrochemical Deposition of Tantalum
Authors: Martens Sladjana , Ispas Adriana , Asen Ludwig , Seidl Lukas , Stimming Ulrich , Schneider Oliver , Bund Andreas
Published: September 2016

In the electrochemical deposition of Tantalum from ionic liquids at moderate temperatures, the preparation of purely metallic coatings with thicknesses in the micrometer range and the accurate control of the crystallographic parameters remain challenging. In this work, preliminary experiments on the influence of fluid dynamics during the electrodeposition of tantalum in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide using ultrasound as an additional source of energy were carried out. This included a study on the influence of the ultrasound amplitude on the deposition rate of tantalum by using cyclic voltammetry and the in-situ electrochemical quartz crystal microbalance technique.
Measurement of Adhesion Strength of Al Electroplating Film on AZ31, AZ61, and AZ91 Substrates
Authors: Onishi Masato , Ueda Mikito , Matsushima Hisayoshi , Habazaki Hiroki , Washio Kota , Kato Akira
Published: September 2016

To investigate the relationship between adhesion strength of Al electroplated film and Al concentration in Mg alloy substrates and the grain size of the Mg alloy, Al electroplating was carried out with AZ31, AZ61, AZ91, and of AZ31 with different grain sizes in an ionic liquid of a mixture of aluminum chloride and 1-ethyle-3-methyl-imidazolium chloride at 283 K. Dense Al electrodeposits were formed on all the substrates. The adhesion strength increased with increases in the Al content of the Mg alloys. Increasing the average grain size also resulted in increases in the adhesive strength.
Precipitation of Rare Earth Phosphates from Molten Salts: Particle Size Distribution Analysis
Authors: Ivanov Alexander B. , Volkovich Vladimir A. , Maltsev Dmitry S. , Sukhikh Vladislav V. , Griffiths Trevor R.
Published: September 2016

Particle size distribution of phosphates of 13 rare earth elements formed in NaCl–2CsCl eutectic based melts at 650 oC was determined. Sodium orthophosphate was used as a precipitant. Initial phosphate-to-rare earth molar ratio in the reaction mixture corresponded to 50 and 100 % degree of precipitation. Particles in the powders obtained after aqueous treatment of quenched melts tend to agglomerate and ultrasonic treatment was employed in the particle size measurements. Normally particles of the phosphates have a size of 0.1–100 μm. The position of the maxima in PSD curves depends on the nature of RE element. In addition, precipitation of mixtures of RE elements mimicking their content in spent nuclear fuels was investigated in NaCl–2CsCl (at 650 oC) and NaCl–KCl (at 750 oC) melts.
Electrodeposition of Pt - Rare Earth Alloys as ORR Catalysts for Fuel Cells
Authors: Asen Ludwig , Ju Wenbo , Mostafa Ehab , Martens Sladjana , Heiz Ueli , Stimming Ulrich , Schneider Oliver
Published: September 2016

Electrochemical deposition was studied as a potentially scalable method for the preparation of Pt-rare earth alloys for application as cathode catalyst in proton exchange membrane fuel cells. For this purpose, experiments both on electrodeposition of platinum and of the rare earth elements yttrium and lanthanum were carried out in two different types of ionic liquid. While the electrodeposition of platinum was successful in both liquids, the deposition of the rare earth metals was more challenging. The deposition of Y in a TFSI based liquid was prevented by electrode passivation, while in a BF4
- liquid no passivation was seen, but also no clear indication of a deposition process was seen. For La, there was deposition using different precursors, but only at very low deposition rates. The nature of the deposit could not yet be unequivocally determined. Initial attempts in alloy deposition were not successful.
Electrochemical Study of Zn/Zn2+ Redox Behavior in Functionalized Ionic Liquids: Water Effect
Authors: Zhou Wei , Qi Chengzi , Yu Aoqiu , Wu Xinhu
Published: September 2016

Zn/Zn2+ redox has been studied in functionalized ionic liquids based on imidazolium cations, which are structurally tuned by different length of alkyl chain or –CN and –OH group. The effect of the imidazolium cations size has been investigated, indicating that large size of the cations leads to high over-potential of the Zn reduction process. Introduction of –CN and –OH group into the cations respectively largely improves the reversibility of Zn/Zn2+ redox. Trace water introduced into the ILs significantly enhances the Zn/Zn2+ redox current density, and improves the reversibility largely. Design and understanding of the solvation of Zn2+ in water-mixed functionalized ILs is of important value in the development of rechargeable Zn-air battery.
Influence of the Alkaline Earth Metal Cations on the Standard Rate Constants of Charge Transfer for the Redox Couple Ti(IV)/Ti(III) in Chloride-Fluoride Melts
Authors: Vetrova Daria A. , Kuznetsov Sergey A.
Published: September 2016

The standard rate constants of charge transfer (ks
) for the redox couple Ti(IV)/Ti(III) in the (NaCl-KCl)equimol.-NaF(10 wt.%)-K2TiF6 melt were determined. It was shown, that k
s increase with temperature increasing. Influence of strongly polarizing cations on the charge transfer kinetics was studied. It was determined the linear dependence of ks
on ionic potential of alkaline earth metal cations and the activation energies of charge transfer were calculated.
Intervalence Charge Transfer of the Nb(V)/Nb(IV) Redox Couple in Alkali Chloride Melts: Experiment and Quantum-Chemical Calculations
Authors: Popova Anna V. , Kremenetsky Vyacheslav G. , Kuznetsov Sergey A.
Published: September 2016

The standard rate constants of charge transfer (k
s) for the Nb(V)/Nb(IV) redox couple in KCl-NbCl5 and CsCl-NbCl5 chloride melts are determined. The Nb(V) electrochemical reduction process in the NaCl-KCl-NbCl5 melt was shown being reversible; hence, the determination of k
s appeared impossible. Values of k
s in the KCl-NbCl5 melt are higher than those in the CsCl-NbCl5 one. Previously, in a quantum-chemical calculations of nM+·[NbCl6] model systems (M = Na, K, Cs), containing a complex anion with cations outer-sphere (OS) shell (nM+) have been done. It was found that compositions with an intermediate number of OS cations n < n
lim, where n
lim is the limiting number of OS cations bound to a given complex, are thermodynamically most stable. The aim of this quantum-chemical study is an estimation of the temperature effect on the composition of the stable particles in the extended systems M+∙[NbCl6]+18MCl (M = Na, K, Cs).
Electrochemical Reduction of Zirconia in Melts Based on Mixture of Calcium Chloride and Calcium Oxide
Authors: Gritsai Larisa V. , Omel'chuk Anatolii A
Published: September 2016

It has been found that the reduction of zirconium dioxide from the CaCl2-NaCl-CaO and CaCl2-LiCl-CaO melts involves calcium and gallium intermetallics, which are formed during the cathodic polarization of the gallium cathode, calcium being not consumed for reduction, and evolved oxygen being discharged at the anode. Zirconium deposits on the gallium cathode as a fine powder, whose specific surface area decreases with increasing current density. Calcium is discharged at the gallium cathode irreversibly with considerable depolarization. The degree of zirconium reduction is the higher, the lower the acid strength of the oxide-chloride melt.
Separation of Lanthanides and Actinides in a Chloride Melt - Liquid Metal System: The Effect of Phase Composition
Authors: Volkovich Vladimir A. , Maltsev Dmitry S. , Melchakov Stanislav Yu. , Yamshchikov Leonid F. , Novoselova Alena V. , Smolensky Valery V.
Published: September 2016

Separation of lanthanides and actinides can be achieved in a “molten chloride – liquid metal” system. Here, the effect of temperature, cationic composition of the alkali chloride based melts, and composition of the liquid metal on the separation factor are considered, and separation of neodymium and uranium is studied as an example. Gallium, indium, aluminum, tin and their mixtures of various compositions were chosen as low melting metals. Possible separation coefficients were calculated on the basis of thermodynamic and electrochemical properties of uranium and neodymium. To confirm the results of calculations, experiments on separating Nd and U were conducted. The experiments were performed under various conditions and the experimentally achieved separation factors compared with the theoretical expectations.
Protective Ceramic Coatings on the Base of the Refractory Metals Carbides
Authors: Stulov Yuriy V. , Dolmatov Vladimir S. , Kuznetsov Sergey A.
Published: September 2016

The refractory metal carbides were deposited on carbon steel and fibers by currentless transfer in molten salts at temperatures 1073-1123 K. The microhardness of refractory metal carbides on carbon steels at the cross section had the values 21 GPa, 29 GPa, 31 GPa for Cr7C3, NbC and TaC, respectively. The corrosion resistance of these carbides was studied in concentrated HCl, H2SO4 and H3PO4 acids. The wear resistance was evaluated by the mass loss of samples. Deposition of NbC coatings on parts of oil pumps increased their lifetime in several times. Coatings of Cr7C3 or TaC on the knifes for cutting rubber, made of St. 3, improve their wear resistance and increase a tool life in 2.0 and 2.5 times respectively.
Rest Potentials of Binary Mixtures of Ionic Liquids and Threshold Voltages of Electric-Double-Layer Transistors
Authors: Nanjo Chihiro , M. Matsushita Michio , Awaga Kunio
Published: September 2016

We examined the rest potentials of ionic liquids, and the performance of the electric-double-layer (EDL) transistors in which the gate dielectrics consisted of binary mixtures of the ionic liquids with vastly different rest potentials. It was found that the rest potentials changed non-linearly with respect to the mixing ratio of the ionic liquids. This strongly suggested that the rest potentials of ionic liquids were governed by their chemical potentials. For the EDL transistors, there was a linear relation between the rest potentials of the binary ionic liquids and the transistor threshold voltages. This means that the threshold voltages can be controlled continuously by changing the mixing ratio of the ionic liquids.
Electrochemical Methods for Determination of Activity Coefficients of Lanthanides in Molten Salts
Authors: Bagri Prashant , Bastos Tarcisio , Simpson Michael Forrest
Published: September 2016

In this paper, we have calculated Raoultian standard reduction potentials (E0) for 14 elements of interest for the pyroprocessing of spent nuclear fuel. Also discussed here is the sound experimental methodology and challenges associated with the employment of an electrochemical cell to determine the activity of species in molten salt systems. Finally, experimental activity data is presented for LaCl3 and NdCl3.