bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of the Transmission Line EIS Model to Fuel Cell Catalyst Layer Durability
Authors: Easton E. Bradley , Saleh Farhana Sultana , Reid O'Rian O. 
Published: February 2020

Typical catalyst layers (CL) employed in PEM fuel cells are composed of a carbon supported Pt catalyst bound together with an ionomer, most often Nafion. Both the carbon support and ionomer play a crucial role in optimizing the catalyst utilization by proving electronic and ionic conductive pathways, respectively, without hindering gas transport. Upon fuel cell operation, the catalyst layer can degrade by one of 3 primary pathways:

Loss of Pt surfaces area through Pt dissolution/Ostwald ripening

Corrosion of the carbon support

Degradation of the ionomer network

The contribution of each of these pathways depends upon CL compositions as well as the cell operating conditions.
The extent of degradation is normally monitored in situby cyclic voltammetry (CV) by measuring changes in the electrochemically active surface area (ECSA) of Pt. However, CV is limited in that it can only conclusively confirm the presence of the first pathway. Contributions from the other 2 pathways are typically confirmed by post mortem analysis of the CL.
We have recently reported that the addition of periodic electrochemical impedance spectroscopy (EIS) measurements to an accelerated degradation testing protocol (ADTP) allows one to clearly diagnose the presence of the other 2 degradation pathways. By performing EIS under conditions where the transmission line model is valid, the presence of carbon corrosion can be clearly detected by a characteristic shift in the EIS response over time [1], as shown in Figure 1. Likewise, the loss of ionic conductivity can also be observed through a unique change in a typical capacitance plot [2].
Our methodology has since been extended and further validated by studying the stability of numerous commercial and in-house prepared catalysts using with different carbon supports. In this presentation, we will describe how EIS can be incorporated into almost any ADTP protocol and how changes in the EIS response can be used for in situdiagnosis of degradation pathways that can be attributed to CL components. In particular we will describe how the presence and absence of both Pt and C impacts the degradation processes and subsequently the EIS response [3]. Furthermore, we will also demonstrate how by carefully selecting the DC bias potential one can quantitatively monitor ECSA degradation (pathway 1) with EIS (instead of CV) by using monitoring the pseudo-capacitance associated with H-adsorption (Figure 2) [4].
References

F. S. Saleh and E. B. Easton, J. Electrochem. Soc., 159, B546 (2012).

J. I. Eastcott and E. B. Easton, J. Power Sources, 245, 487 (2014).

F. S. Saleh and E. B. Easton, J. Power Sources, 246, 392 (2014).

O. Reid, F. S. Saleh, and E. B. Easton, Electrochim. Acta, 114, 278 (2013)
Understanding the Reactivity of Enol Ether Radical Cation: Investigation of Electrochemical [2 + 2] Cycloaddition Reactions
Authors: Yamaguchi Yusuke , Okada Yohei , Chiba Kazuhiro 
Published: February 2020

Electrochemical process has proven to be powerful tool to form carbon-carbon bond and has widely used to construct various carbon skeletons. Especially, the electrochemical carbon-carbon bond forming reactions have demonstrated to afford complicated ring systems effectively, including naturally occurring compounds. For example, enol ether radical cations are readily produced in anodic oxidations of enol ethers and provide versatile reactive intermediates. This reaction is synthetically intriguing due to the umpolung process that polarity of nucleophilic enol ethers is reversed to give enol ether radical cations which function as electrophilic species.
We have developed the electrochemical reactions in lithium perchlorate/nitromethane (LPC/NM) electrolyte solution, which exhibits a remarkable accelerating property as a Lewis acid catalyst and stabilize carbocation intermediates. The feature of LPC/NM allows facile synthesis of biologically relevant compounds, such as dihydrobenzofuran derivatives1 and azanucleoside derivatives.2 In LPC/NM, unactivated olefins can serve as efficient nucleophiles to trap anodically generated cationic species. In this context, we also have developed electrochemical [2 + 2] cycloaddition reactions between enol ethers and unactivated olefins, affording cyclobutane products(Scheme 1).3 The reaction was initiated by anodic oxidation of enol ether (1) and thus generated enol ether radical cation (2) was trapped by unactivated olefin nucleophile to give transient cyclobutyl radical cation (3). In order for successful cyclobutane formation, electron rich aromatic ring was required as an electron donor to form relatively long lived aromatic ring radical cation (4), which was finally reduced by cathode or starting enol ether, affording neutral cycloadduct (5) (Scheme 2).
Although our previous work have focused on the use of enol ether (1) for electrochemical [2 + 2] cycloaddition reactions, the reactivity of enol ether radical cation (2) still remains unclear. To investigate the reactivity of such enol ether radical cations, we designed and synthesized several types of new substrates and then subjected them to the electrochemical [2 + 2] cycloaddition reactions(Scheme 3). Synthetic and mechanistic details would be discussed in the presentation.

Reference

(1) Kim, S.; Hirose, K.; Uematsu, J.; Mikami, Y.; Chiba,K. Chem.
–
Eur.
J.
2012, 18, 6284–6288.
(2) Kim, S.; Shoji, T.; Kitano, Y.; Chiba, K. Chem. Commun.
2013, 49, 6525–6527.
(3) (a) Yamaguchi, Y.; Okada, Y.; Chiba, K. J. Org. Chem., 2013, 78, 2626–2638. (b) Yamaguchi, Y.; Okada, Y.; Chiba, K. Electrochemistry
2013, 81, 331–333 and references therein.
Electrochemical Synthesis of Azanucleoside Derivatives Using a Lithium Perchlorate-Nitromethane System
Authors: Shoji Takao , Kim Shokaku , Kitano Yoshikazu , Chiba Kazuhiro 
Published: February 2020

Nucleoside analogues have played an important role in the viral decease and cancer therapy. To date, various nucleosides analogous have been investigated to improve their therapeutic effects and toxic properties. The modification of the sugar moiety has produced new active analogous. Especially, the design of furanose rings that include various heteroatoms has been one of the most useful approaches in the search for new nucleoside analogues with beneficial biological activity.
Azanucleosides, in which the furanose oxygen atom is replaced by a nitrogen atom, have attracted interest because of possibility of their further modification through the nitrogen atom and structural similarity to the franose ring system. Considerable efforts have been dedicated to develop the efficient method for the synthesis of azanucleoside derivatives. Most of the synthetic strategies have been designed in order that N-glycosyl bond has been formed through an iminium ion intermediate. This process is necessary to incorporate a leaving group into the pyrrolidinyl precursor to generate the key reactive intermediate. However, access to such precursors requires a multi-step synthetic sequence, which includes cumbersome operations and harsh reaction condition. Indeed, this process often removes the opportunity of providing diverse azanucleosides based on further modification of the nitrogen atom.
To address this challenge, we reasoned that direct and selective insertion of a nucleobase to the N-a position of prolinol moiety would avoid the redundant multi-step synthetic operation. We proposed that an electro-organic method might provide such an approach to overcome the challenge of direct introduction of a nucleobase into an unactivated pyrrolidine moiety. Previously, we have demonstrated the direct modification of pyrrolidine derivatives using LiClO4-CH3NO2 electrochemical oxidation system. This reaction system can accumulate desired iminium ion intermediates, anodically derived from N-protected pyrrolidine derivatives by C-H bound activation, enabling coupling with a variety of nucleophiles in one-pot reaction. In this conference, we report the electrochemical azanucleoside synthesis by coupling an unactivated prolinol derivative with a nucleobase through anodic oxidation using LiClO4-CH3NO2 solution system, and demonstrate the utility of this transformation by addition of various nucleophiles to readily available prolinol derivatives in a regioselective manner.
Porous Fe2O3 Doped Cathodes for Lithium-Sulfur Batteries
Authors: Shen Cai , Zhao Chong Chong , Han Weiqiang 
Published: February 2020

Lithium-sulfur (Li/S) battery is a promising electrochemical system that has the possibility to achieve high-energy (theoretical capacity of 1675 mAh/g). However, the system suffers from several drawbacks including dissolution of intermediate polysulphide reaction species into electrolyte. In response to this challenge, novel advances in materials design such as new electrolytes1
,
2 polymer coated sulfur nanosphere core/cell structure3 and conductive mesoporous/nano carbon framework for constraining sulfur have been proposed4
,
5. These techniques significantly improve the cycling performance of Li/S batteries but falls short of completely controlling polysulphide dissolution. Recently, a new concept of embedding small fraction of porous silica particles (SBA-15) within carbon-sulfur nanocomposites and acted as an internal polysulfide reservoir has been proposed by Nazar et al. to stabilize the system6. In line with this concept, here we report the use of porous Fe2O3 doped sulfur cathode to improve the performance of Li/S batteries. A doping of 5% Fe2O3shows improved cycling performance with highly stable reversible discharge capacity of ca. 574 mAh/g after 50 cycles.

References:

(1) Ryu, H. S.; Ahn, H. J.; Kim, K. W.; Ahn, J. H.; Cho, K. K.; Nam, T. H.; Kim, J. U.; Cho, G. B. J Power Sources
2006, 163, 201.
(2) Wang, J.; Chew, S. Y.; Zhao, Z. W.; Ashraf, S.; Wexler, D.; Chen, J.; Ng, S. H.; Chou, S. L.; Liu, H. K. Carbon
2008, 46, 229.
(3) Li, W. Y.; Zheng, G. Y.; Yang, Y.; Seh, Z. W.; Liu, N.; Cui, Y. P Natl Acad Sci USA
2013, 110, 7148.
(4) Ji, X. L.; Lee, K. T.; Nazar, L. F. Nat Mater
2009, 8, 500.
(5) Xin, S.; Gu, L.; Zhao, N. H.; Yin, Y. X.; Zhou, L. J.; Guo, Y. G.; Wan, L. J. J Am Chem Soc
2012, 134, 18510.
(6) Ji, X. L.; Evers, S.; Black, R.; Nazar, L. F. Nat Commun
2011, 2.
Electrolyte Additive Performance in Lithium Ion Batteries: From Coin Cells to 400-Mah Pouch Cells
Authors: Polzin Bryant J , Trask Steve E , Zhu Ye , Li Yan , Bettge Martin , Abraham Daniel P , Jansen Andrew N. 
Published: February 2020

Electrolyte additives have been widely reported to improve Lithium-Ion battery performance. Even small quantities of various additives have been shown to create stable SEIs on both the anode and cathode, improve safety, and stabilize electrolytes. Our work has focused on SEI forming additives that work on both the anode and cathode electrodes. Promising bi-functional additives that we have chosen to study in coin cells and larger format pouch cells are lithium bis(oxalate)borate (LiBOB) and lithium difloro(oxalate)borate (LiDFOB).
As part of DOE’s Applied Battery Research for Transportation (ABR) Program, a high voltage and high capacity cathode was paired with a high capacity graphite anode for this study. This electrode couple has the potential for applications in plug-in hybrid (PHEV) and battery electric vehicles (EV). The cathode selected was from the LMR-NMC class of materials; Toda HE5050 ( Li1.2Ni0.15Mn0.55Co0.1O2) and the anode was A12 graphite from Phillips 66. Coin cells were assembled with these materials and tested with a number of different electrolyte and additive combinations. Several compositions have shown an improvement in the coin cell performance, shown in Figure 1.
Based upon promising coin cell results from electrolyte and additive combinations, they were tested in 400-mAh pouch cells. The improved performance that was present in the coin cells was not observed in the pouch cells. Figure 2 shows the 400-mAh pouch cell performance of these additive combinations.
This presentation examines the differences in coin cells and pouch cells relative to additive performance. Examples of these differences are: formation conditions, electrolyte quantity, additive concentrations, etc. By studying these conditions, we will be able to simulate and vary pouch cell conditions via coin cell analysis. The coin cell conditions and performance will be verified against 400-mAh pouch cell performance data to ensure that the conditions and performances are scalable. By following this process less battery materials will be required and will speed up the optimization process in pouch cells.
Lastly, knowing the challenges that electrolyte additives present in scaling up cell size, we will provide some recommendations for coin cell testing that should be considered in the evaluation of research materials.
Study of Diffusion Kinetics and Microstructure for FeF3-CF (Carbon-Fiber) 3D Composite Electrodes
Authors: Zhou Hui , Martha Surendra K , Li Juchuan , Pannala Sreekanth , Dudney Nancy J , Nanda Jagjit , Wang Junjie , Braun Paul V 
Published: February 2020

Recently, we investigated the role of electrode architecture on the capacity retention and hysteresis of iron (II and III) fluoride conversion compound.1 The unique electrode architecture consists of nanometer sized iron fluoride particles (~ 25-50nm) coated with multilayer graphitic platelets and bound to an electronic backbone comprising of an interconnected network of carbon fibers (5-9 µm diameter). The carbon coated fluoride particles are bound to the carbon fiber through a carbonaceous binder derived from petroleum pitch.2 This unique combination of reduced particle size and electrode architecture significantly improves the local electronic conductivity enhancing the electrochemical performance such as better capacity retention and C-rate performance. Further, we observe a significant reduction of voltage hysteresis to ~ 0.9V compared to 1.5 V for normal FeF3 slurry electrodes3. Electrochemical cycling at elevated temperature (60oC), improves the reaction transport kinetics yielding almost theoretical specific capacity (700 mAhg-1) with reasonably good cycle life with a small concomitant reduction in the hysteresis (Figure 1). The estimated overall energy density based on the active mass of FeF3 in the electrode is about 1650 Wh kg-1covering both the intercalation and conversion window (1.5–4.5 V). The overall performance of this 3D-structured cathode is impressive, and may provide a new cathode/electrode concept for next generation high energy density batteries.

Figure 1. (a). Voltage vs. capacity profiles of a Li/FeF3 cell (on carbon fiber) cycled between 1.5 V and 4.5 V (C/50 rate) at 60oC. (b) Capacity plotted as a function of cycle number for the Li/FeF3 cell. Capacity is evaluated based only on FeF3 active material.
Although initial cycle life looks promising, we notice capacity fade after 50 cycles clearly suggesting that further investigation are needed to understand the diffusion kinetics and/or structural stability of various intermediate conversion phases. We will present detailed investigation of various reaction phases and the kinetics of FeF3 and FeF2 electrodes at room temperature, 45 and 60 °C based on potentiostatic intermittent titration (PITT), electrochemical impedance spectroscopy (EIS), electron microscopy (S/TEM) and X-ray diffraction (XRD).
Acknowledgement
This research is sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.
References:

S. K. Martha, J. Nanda, H. Zhou, J. C. Idrobo, N. J. Dudney, S. Pannala, S. Dai, J. Wang, and P. V. Braun, RSC Advances. (Accepted 2013).

S. K. Martha, N. J. Dudney, J. O. Kiggans and J. Nanda, J. Electrochem. Soc., 159, A1652-A1658 (2012).

P. G. Bruce, B. Scrosati, and J-M. Tarascon, Angew. Chem. Int. Ed., 47, 2930-2946 (2008).
Glass-Ceramic Solid Electrolytes for Lithium and Sodium Ion Batteries
Authors: Rost Axel , Schilm Jochen , Langklotz Ulrike , Schneider Michael , Kramer Dörte , Michaelis Alexander 
Published: February 2020

Common Lithium and Sodium Batteries have crucial drawbacks in operation caused by the type of separators and electrolytes. Polymeric separators used in Li-batteries show an insufficient stability against rising temperatures and the growth of dendrites. So hot spots, internal shortcuts, and even fire can result. The used solid electrolytes for Na Batteries made of β/β’’-Al2O3 work at temperatures around 300 °C what leads to low efficacies by energy consumption for heating of the battery system. Cracks in Al2O3 separators can cause severe failure by leakage of molten sodium. For both types of batteries solid glass-ceramic electrolytes can contribute to a higher level in security and safe operation of battery systems by several superior material properties. By high mechanical strength, a precise distance between the electrodes is defined. Due to high thermal stability, thermal runaways are impeded. Glass-ceramic and ion conducting materials can be used as particles or porous solids in combination with liquid electrolytes for common batteries but gastight solid electrolytes even enable new battery concepts like lithium-air batteries. Thin and mechanical stable Na-Ion conducting electrolytes show high conductivities even at ambient temperatures and enable room temperature sodium batteries. Dense galss-ceramic solid electrolytes also enable the use of two different types of liquid electrolytes for anode and cathode compartment.
In the study glasses are molten, quenched and crystallized to obtain ion conductive solid state glass-ceramic electrolytes. The material systems therefore are Li1+xAlxTi2-x(PO4)3 for Li-Ion Batteries and Na3+3x-yRE1-xPySi3-yO9 (RE: rare earth) for Na-Ion Batteries respective both are analogues of the NaSiCON-Structure. Glasses with varying ratios of Al/Ti and RE/P/Si are molten and after crystallization by different thermal treatments widely characterized (HTM; DTA; XRD; REM). Impedance spectroscopy measurements are carried out to determine the conductivity with respect to the chemical composition, thermal treatment and microstructure. Room temperature conductivities up to 10-4 S/cm will be presented and discussed. Promising compositions are processed as slurry for tape casting to gain thin and dense glass-ceramic solid electrolyte tapes for the application in room temperature Batteries.
Atomic Friction at Electrodes: Anisotropy Effects at Regularly Stepped Gold Electrodes
Authors: Baltruschat Helmut , Podgaynyy Nikolay , Iqbal Shahid 
Published: February 2020

Friction under ambient conditions often involves wet surfaces, and thus electrochemical interfaces. Yet measurements of friction at an atomic scale under electrochemical conditions are scarce though accessible by combination of AFM with an electrochemical cell. For HOPG, a change of friction forces at steps edges was observed with a change of potential.[1] Our interest has been in the influence of potential, Cu UPD on Au(111) and organic adsorption on atomic-scale friction.[2]
We will present friction measurements performed on Au(111) single crystal electrodes and the effect of adsorbates on atomic stick-slip resolution. The range of normal force necessary to observe stick-slip resolution depends on the type of ionic adsorbates. At the small normal load of 15 nN transition to atomic stick-slip resolution is observed, when sulfate is adsorbed on the surface. The reason for that transition could be a penetration of the tip in to the double layer. At the pzc on clean gold stick-slip behaviour not shows any transition or penetration effects. The adhesion on the force-distance curve disappear with a copper adsorption.
However, with a monolayer of Cu on Au(111) a transition to stick-slip behavior is present, but without atomic resolution. We found 3 different types of stick-slip pattern on copper monolayer in diapason of normal loads between 0 and 100 nN; slip length is equal 4,6; 9,2; and 13,8 Å. The slope of stick combines the stiffness of tip and sample. That stiffness is independent from adsorbat or normal load and always have the same value at about 12 nN/nm, which is much smaller than torsion spring constant of cantilever 190 nN/nm.
Friction is increased at step edges due to the the Schwoebel barrier. This effect is reduced when steps are decorated by Pd on Au. Due to this effect of steps on friction, vicinally stepped surfaces show a large anisotropy for friction, although atomic resolution is obtained even when scanning perpendicular to the steps.

[1] E. Weilandt, A. Menck, O. Marti, Surface and Interface Analysis
1995, 23, 428; B. Schnyder, D. Alliata, R. Kötz, H. Siegenthaler, Applied Surface Science
2001, 173, 221.
[2] M. Nielinger, H. Baltruschat, Physical Chemistry Chemical Physics
2007, 9, 3965.; F. Hausen, M. Nielinger, S. Ernst, H. Baltruschat, Electrochimica Acta
2008, 53, 6058.
Advances in the Use of Carbon Anodes for Pyrochemical Electroreduction of Used Nuclear Fuel
Authors: Motsegood Perry , Willit James L. , Williamson Mark A. 
Published: February 2020

Pyrochemical processing of used nuclear fuel is a molten salt process performed at elevated temperatures and is part of a series of processes resulting in the separation of actinides from fission products. Used metal oxide fuel (MOX) is reduced electrochemically to generate metals prior to electrorefining, typically performed at 650oC in LiCl-Li2O. The reduction of kilogram lab scale quantities of UO2 have been successfully performed as surrogates to actual fuel using platinum anodes1-2, but progression toward engineering or pilot scale-up presents different requirements for anode materials.
Carbon (graphite) is commonly used in commercial molten salt processes within the ore refining industry. It is cost effective, readily available, and a logical choice for scale-up needs. However, different chemistries result from this change in anode materials in both the salt and off gas streams. Instead of forming oxygen at a platinum anode, CO/CO2 becomes the byproduct gas. Although initially insoluble, CO/CO2 residence time within the LiCl-Li2O salt is thought to be problematic because of the formation of reactive carbon species, with respect to the metal, that are soluble and could lead to undesirable side reactions in the system.
This report will discuss an advanced test cell for evaluating the use of carbon as an anode material for the electroreduction of UO2 to uranium metal in molten LiCl-Li2O. We will present design challenges and report on the implementation of advances for the accommodation of process changes with respect the new anode material. Finally, preliminary results on the efficiency and chemical effects of carbon anodes will be discussed.

References

Laszlo Redey and Karthick Gourishankar, “Direct Electrochemical Reduction of Metal-Oxides” US Patent US6540902 B1, Granted April 1, 2003

S. D. Herrmann, S. X. Li, M. F. Simpson and S. Phongikaroon, Separation Science and Technology
2006, 41, 1965-1983.