bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pd-Co/CNF Composite Material as Electro-Catalysts for Lithium-Oxygen Batteries
Authors: Cho Sung Man , Hwang Sunwoo , Koo Bon Seok , Yoon Woo Young 
Published: February 2020

Lithium-Oxygen (Li-O2) batteries have attracted much attention owing to their high energy densities compared to conventional lithium ion batteries, and are one of the promising lithium secondary batteries for electric vehicles (EVs) and hybrid electric vehicles (HEVs). The theoretical specific energy density of the Li-O2 battery with the discharge reaction of 2Li++O2+2e-→Li2O2 is 3505 Wh kg-1. However, the low energy efficiency, poor rate capability, and limited cycle life of these batteries cause problems for their commercialization. The sluggish oxygen redox reaction results in low power and high overpotentials. Also, the pores of oxygen cathode can easily be blocked by insoluble discharge products, which cause incomplete discharge, inhibiting the flow of oxygen to the reaction sites. Therefore, the design of cathodes having oxygen diffusion pathway and uniform distribution of catalysts is the key role which can enhance the performances of Li-O2 batteries. This work focuses on the electrochemical effects of palladium-cobalt (Pd-Co)/carbon nanofiber (CNF) composite catalyst for a cathode. The nanosized Pd-Co catalysts are embedded evenly into CNFs. The high catalytic activity of Pd-Co catalysts reduce the overpotentials, which can improve the energy efficiency. Furthermore, the interconnected pore network structure creates effective gas diffusion channels, thus improving specific capacity and cycle life for Li-O2 cell. PdCo/CNF composite catalysts are synthesized by using polyol method and electrospinning method. Cells were tested at the current densities of 100 mA g-1 and 200 mA g-1with limited voltage of 2.0 to 4.5V. The morphology of the samples was observed on a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The structure of the samples was characterized by X-ray diffraction (XRD) spectroscopy and Inductively coupled plasma atomic emission spectrometry (ICP-AES). The result was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).
[1] Y.C. Lu, B.M. Gallant, D.G. Kwabi, J.R. Harding, R.R. Mitchell, M.S. Whittingham, Y. Shao-Horn, Energy Environ. Sci., 6, 750 (2013).
[2] L.J. Hardwick, P.G. Bruce, Curr. Opin. Solide. St. M., 16, 178 (2012).
[3] M.A. Rahman, X. Wang, C. Wen, J. Appl Electrochem, 44, 5 (2014)
[4] W. Wang, D. Zheng, C. Du, Z. Zou, X. Zhang, B. Xia, H. Yang, D.L. Akins, J. Power Sources, 167, 243 (2007)
[5] B.W. Huang, X.Z. Liao, H. Wang, C.N. Wang, W.S. He, Z.F. Ma, J. Electrochem. Soc. 160, A1112 (2013)
Dynamics of Polysulfide Dissolution for Various Electrolytes in Working Li-S Battery By in-Operando Technology
Authors: Lin Chia-Nan , Chang Chih-Ching , Li Chun-Lung , Wu Nae-Lih , Tsai Li-Duan , Fang Jason 
Published: February 2020

The lithium-sulfur (Li-S) battery is a promising electrochemical system as a high-energy storage device. However, the performance of Li-S battery is strongly limited by the S insulation, dissolution of lithium polysulfide (PS) and high self-discharge rate. These problems can lead to short cycle life and poor efficiency for application. Therefore, the LiNO3 mixed in the electrolyte or used high lithium salt concentration electrolyte was studied, the results showed that coulombic efficiency was enhanced substantially when this additive was used, indicating that the PS/lithium reaction and PS shuttling were decreased.
In this study, we examined the interplay between PS diffusion and cycle processes. Moreover, we was designed to test PS migration in electrolytes featuring distinct salt concentrations, and in-operando TXM (Transmission X-Ray Microscopy) analysis (Fig. 1) was used to study the dynamics of PS dissolution. These findings demonstrated that using the lithium salt at a high concentration in the electrolyte enhanced the electrochemical performance of the battery. The S particle did not dissolve completely until the middle of the 2nd plateau of the lithiation process at high lithium salt concentration, indicating that the dissolution that occurs during lithiation was delayed.
The results presented here demonstrate that using electrolytes containing a lithium salt at a high concentration can not only inhibit the dissolution of lithium PS but also effectively retard the migration of the lithium PS in the electrolyte, which substantially enhances the electrochemical performance of the battery. We believed that the strategy of developing a hybrid electrolyte by incorporating lithium salt and liquid PS is a very promising electrolyte for long cycling Li-S battery.
Solid Electrolytes Based on Fast Fluorine Ion Motions — 19F T1ρ NMR Relaxation vs Conductivity Measurements of Mechanosynthesized Nanocrystalline Ba0.6La0.4F2.4
Authors: Preishuber-Pflügl Florian , Wilkening Martin 
Published: February 2020

The use of mechanosynthesis for the preparation of ion conductors provides access to new compounds whose properties are governed by chemical metastability, defects introduced and size effects present. The benefits of this valuable synthesis method manifest in enhanced ion transport properties of the prepared nanocrystalline ceramics. Such materials are useful candidates to act as solid electrolytes, e.g., in fluorine ion batteries [1]. Here, the introduction of large amounts of La3+ into the cubic structure of BaF2 was carried out by using high-energy ball-milling. The replacement of Ba2+ with a trivalent cation leads to the formation of an increased number fraction of point defects in the metastable crystal structure, which resulted in an increase of the dc-conductivity when compared to pure, nano-sized BaF2 [2]. Until now, only little is known about activation energies and jump rates of the elementary hopping processes of such materials. In the present study, we used broadband impedance spectroscopy and 19F NMR relaxometry to get to the bottom of ion jump diffusion proceeding on short-range and long-range length scales in Ba0.6La0.4F2.4. The dielectric measurements revealed an activation energy of 0.57 eV for macroscopic ion transport, whilst NMR, which is sensitive to both long-range motion and localized jumps, gave much smaller activation energies [3]. This was confirmed by high-frequency impedance measurements carried out at frequencies as high as 3 GHz that enabled us to compare the results from complementary methods applied in the same time window.
[1] C. Rongeat, M. A. Reddy, R. Witter, and M. Fichtner, J. Phys. Chem. C, 117, 4943 (2013).
[2] A. Düvel, J. Bednarcik, V. Šepelák, and P. Heitjans, J. Phys. Chem. C, in press (2014), DOI: 10.1021/jp410018t.
[3] F. Preishuber-Pflügl, and M. Wilkening, Phys. Chem. Chem. Phys., in press (2014), DOI: 10.1039/C4CP00422A.
Invited: the Aprotic Li-O2 Battery: O2 Reduction Mechanisms
Authors: Johnson Lee , Li C , Liu Zheng , Chen Yuhui , Freunberger Stefan A , Bruce Peter G. 
Published: February 2020

While O2 reduction in aqueous environments has been studied extensively for many decades, O2 reduction in aprotic solvents has received much less attention. One spin-off of the recent interest in rechargeable Li-O2 batteries, Fig. 1,1,2 based on aprotic electrolytes is that it has highlighted the importance of understanding the fundamental mechanisms of O2 reduction in such a medium.3-10 Indeed understanding the mechanisms of O2 reduction are essential if progress is to be made towards realizing the potential of the rechargeable aprotic lithium-O2 battery.1,2

A number of authors have made important contributions to understanding O2 reduction in non-aqueous electrolytes.3-5,7
We have combined a range of electrochemical, spectroscopic and microscopy methods to investigate the mechanism of electrochemical O2 reduction in aprotic electrolytes. The results of these studies will be presented, along with the implications of the results for the future of rechargeable Li-O2 batteries.
References
(1) Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J.-M. Nat Materials
2012, 11, 19.
(2) Li, F.; Zhang, T.; Zhou, H. Energy & Environmental Science
2013, 6, 1125.
(3) Adams, B. D.; Radtke, C.; Black, R.; Trudeau, M. L.; Zaghib, K.; Nazar, L. F. Energy & Environmental Science
2013, 6, 1772.
(4) Horstmann, B.; Gallant, B.; Mitchell, R.; Bessler, W. G.; Shao-Horn, Y.; Bazant, M. Z. The Journal of Physical Chemistry Letters
2013, 4, 4217.
(5) McCloskey, B. D.; Scheffler, R.; Speidel, A.; Girishkumar, G.; Luntz, A. C. The Journal of Physical Chemistry C
2012, 116, 23897.
(6) Mitchell, R. R.; Gallant, B. M.; Shao-Horn, Y.; Thompson, C. V. The Journal of Physical Chemistry Letters
2013, 4, 1060.
(7) Trahan, M. J.; Mukerjee, S.; Plichta, E. J.; Hendrickson, M. A.; Abraham, K. M. Journal of The Electrochemical Society
2013, 160, A259.
(8) Peng, Z.; Freunberger, S. A.; Hardwick, L. J.; Chen, Y.; Giordani, V.; Barde, F.; Novak, P.; Graham, D.; Tarascon, J. M.; Bruce, P. G. Angewandte Chemie International Edition
2011, 50, 6351.
(9) Sharon, D.; Etacheri, V.; Garsuch, A.; Afri, M.; Frimer, A. A.; Aurbach, D. The Journal of Physical Chemistry Letters
2012, 4, 127.
(10) Zhai, D.; Wang, H.-H.; Yang, J.; Lau, K. C.; Li, K.; Curtiss, L. A.; Amine, K. Journal of the American Chemical Society
2013.
Towards the Microstructural Optimization of SOFC Electrodes Using Nano Particle Infiltration
Authors: Kishimoto Masashi , Lomberg Marina , Ruiz-Trejo Enrique , Brandon Nigel P. 
Published: February 2020

Solid oxide fuel cells (SOFCs) are receiving increasing attention because of their ability to convert the chemical energy of fuels into electrical energy in an efficient and clean manner. It is generally accepted that electrode microstructure plays an important role in determining the performance and durability of SOFC electrodes because it has a significant influence on various transport phenomena and electrochemical reactions within the electrodes. In order to satisfy the growing demand for their performance and reliability, it is strongly required to understand the microstructure-performance relationships, and to optimize the microstructure.
Here we focus on electrodes fabricated with nano-particle infiltration technique, where ceramics structure constructs a framework structure called scaffold, to which nickel particles are introduced in the form of nano particles. 3D microstructural analysis using the focused ion beam scanning electron microscopy (FIB-SEM) (e.g. Figure) revealed that the infiltration technique has a greater potential, compared with the conventional powder mixing and sintering approach, to control the electrode microstructure, which is significantly useful to satisfy the requirements for the electrode microstructure, such as transport properties and electrochemical activities. Numerical simulations for the electrochemical and mechanical analyses are also conducted using the acquired 3D microstructures, delivering a guideline to optimize the electrode microstructure.
Figure. 3D reconstructed microstructure of an SOFC anode prepared using infiltration technique. A ceria scaffold (grey), infiltrated nickel particles (green) and extracted triple-phase boundary lines (red).
Benchmarking ORR Activity of Pt-Alloy/C Electrocatalysts Utilizing Improved TF-Rde Methods
Authors: Shinozaki Kazuma , Zack Jason , Pylypenko Svitlana , Pivovar Bryan S , Kocha Shyam S 
Published: February 2020

Thin-film rotating disk electrode (TF-RDE) measurements have been performed to screen the Oxygen Reduction Reaction (ORR) activity of electrocatalysts for PEMFC applications. Through progressive refinement of the technique by several researchers, a number of factors that play a critical role -on measured ORR activity -have been recently reported. Some of the factors include catalyst loading (electrode thickness), film uniformity (spin coating), Nafion cap thickness, ink dispersion/formulation, corrections for iR and background currents, etc. However, for most of these studies, Nafion was typically employed either to improve the catalyst ink dispersion or to glue catalysts on a glassy carbon substrate.
In our previous study, we verified the effect of Nafion on the ORR activity as a function of I/C ratio. The measured activity enhancement was reported ~1.8 times for a Pt/HSC catalyst when Nafion was completely eliminated. Further studies demonstrated that the activity could be further enhanced (~2.7 times compared to a Nafion-based catalyst layer) for extremely thin, uniform films that were Nafion-free. The thin films of low Pt loading were prepared either by incorporation of a surfactant in the dispersion or by drying of the electrodes under controlled conditions.
While relative standard deviation (RSD; based on ~30 samples for each method) for Nafion based catalyst films ranged ~9–15%, RSD for Nafion-free thin, uniform films was ~6%. This clearly demonstrates high reproducibility of measured ORR activity with the Nafion-free thin, uniform films. Although the reason of the increase has not been elucidated yet, O2 transport and proton transport resistances within the catalyst layer are the most probable causes. Comparison of Tafel plots for Nafion-free and Nafion-based films to a polycrystalline Pt electrode provides some insight into the mechanism. Definitive anion adsorption features of Nafion ionomer were not observable for the Pt/C catalysts in our studies. Although further study is necessary to identify the cause of the large increase, the use of thin films without Nafion seems justified to reduce O2 transport and proton transport resistance within the catalyst layer.
In this work, we have studied the ORR activity for various commercially available Pt based alloy catalysts to provide improved baselines using our new techniques. Figure 1 is a plot comparing the ORR activity of baseline Pt/C to PtCo/C catalysts films deposited by conventional Nafion incorporation method (thick coffee ring structured film) and the Nafion-free method (thin-uniform film).
The measured specific activity (Figure 1) for Nafion-free, thin-uniform Pt/C films compared to that for a similar Nafion-based film increased by a factor of ~2.7 and is very similar to the enhancements observed for PtCo/C films. Additionally, the specific activity enhancements due to alloying with Co are similar for Nafion-based and Nafion-free films.
Invited: Development of Highly Phosphonated Polymers for Fuel Cell Membranes
Authors: Jannasch Patric 
Published: February 2020

Phosphonated polymers may show high intrinsic proton conductivities at low water contents provided that the local concentration of phosphonic acid groups is very high [1,2]. Moreover, the lower acidity of aryl- and alkylphosphonic acids in relation to sulfonic acids requires higher acid contents to reach high conductivities also at higher water contents. In this context, poly(vinylphosphonic acid) (PVPA) has emerged as an interesting component for fuel cell membranes because of its extremely high concentration of phosphonic acid, corresponding to 9.25 mmol –PO3H2 per g dry material. However, the high ionic content leads to complete water solubility as well as poor mechanical properties in the solid state. Consequently, it is necessary to develop synthetic strategies to efficiently immobilize the PVPA in the membranes before practical use.
We have previously immobilized PVPA by preparing various block and graft copolymers with PVPA segments [3]. These copolymers where found to self-assemble and form robust membranes with nanostructured morphologies and high proton conductivities. Very recently we have pursued a number of novel synthetic strategies towards different highly phosphonated membranes. These approaches include phosphonated norbornene copolymers prepared via ring opening metathesis polymerization (ROMP) [4], multiblock copolymers selectively grafted with PVPA via anionic polymerization [5], as well as block and graft copolymers containing the more acidic poly(tetrafluorostyrenephosphonic acid) via atom transfer radical polymerization (ATRP) [6]. Challenges and selected results on the synthesis and properties of these copolymers and membranes will be presented and discussed along with future prospects.

Acknowledgement

We gratefully acknowledge the financial support from the Danish Council for Strategic Research through contract no.09-065198, as well as the funding from the European Community’s Seventh Framework Programme (FP7/2010–2013) under the call ENERGY-2010-10.2-1: Future Emerging Technologies for Energy Applications (FET) under contract 256821 QuasiDry.

References

[1] Steininger, H. Schuster, M., Kreuer, K. D., Kaltbeitzel, A., Bingol, B., Meyer, W. H., Schauff, S.,Brunklaus, G., Maier, J.,Spiess, H. W., Phys.
Chem. Phys., 2007, 9, 1764.
[2] Bingöl, B., Jannasch, P., Proton Conducting Phosphonated Polymers and Membranes for Fuel Cells, in Phosphorus-Based Polymers - From Synthesis to Applications, ed. S. Monge and G. David, 2014, Royal Society of Chemistry, in press.

[3] a) Perrin, R., Elomaa, M., Jannasch, P., Macromolecules, 2009, 42, 5146, b) Parvole, J., Jannasch, P. Macromolecules
2008, 41, 3893, c) Ingratta, M., Elomaa, M., Jannasch, P. Polym. Chem.,
2010, 1, 739.
[4] Bingol, B., Kroeger, A., Jannasch, P., Polymer, 2013, 54, 6676.
[5] Sannigrahi, A., Takamuku, S., Jannasch, P., Polym. Chem.,
2013, 4, 4207.
[6] Dimitrov, I., Takamuku, S., Jankova, K., Jannasch, P., Hvilsted, S., J. Membr. Sci.,
2014, 450, 362.
Effect of Oxygen Concentration on Current Density Distribution in the Land-Channel Direction
Authors: Shrivastava Udit N , Tajiri Kazuya 
Published: February 2020

Fundamental study of reactants and products distribution in a proton exchange membrane fuel cell (PEMFC) has always been focus of research. Baker at. el. applied limiting current density as a tool to predict the overall oxygen diffusion resistance from the channel to the catalyst layer. Their results showed that at high current densities operation (relatively wet condition) the oxygen diffusion resistance is much higher than the low current densities operation (relatively dry condition) [1]. However, this method is unable to determine the effect of land-channel geometry on the oxygen diffusion resistance.
In our previous studies, we have measured the current density distribution in the land-channel geometry at 340 µm resolution and found that in a wet condition, current densities are higher in channel areas than in land areas [2-3].
In this work, we are going to present current density distribution as a function of oxygen concentration in the land-channel direction. This method can be used to obtain local polarization curves at 35 degree C and 100% RH (see attached Figure) under the land and channel. Subsequently, it will be used to measure local limiting currents and can be used to resolve oxygen diffusion resistance distribution in the land-channel direction. Similarly, using hydrogen pumping, in low hydrogen concentration effect of land-channel geometry on the current density distribution can be analyzed.
References

D.R. Baker, D. Caulk, K.C. Neyerlin, M.W. Murphy. J. Electrochem. Soc., 156, B991 (2009).

U.N. Shrivastava, K. Tajiri. ECS Trans., 58, 1643 (2013)..

U.N. Shrivastava, K. Tajiri. Electrochemistry letters. Submitted.
Optimization of Component Material Properties and Flow Channel Geometric Parameters in a PEM Fuel Cell Cathode
Authors: Lange Kyle , Lueth Christopher , Godfrey Aaron , Hartridge Steve 
Published: February 2020

PEM fuel cells are generally composed of components which have spatially uniform material properties. In other words, the material properties in one location in a fuel cell component are the same as those in a different location in the same component. Such components are cost-effective and easy to manufacture and model. However, recent advances in additive manufacturing at the micro- and nano-scale level have enabled the creation of parts and components whose material properties are spatially non-uniform. Components with spatially non-uniform material properties could potentially improve the performance of a PEM fuel cell.
To further illustrate the potential benefit of fuel cell components with spatially non-uniform material properties, consider the cathode side of a fuel cell with a serpentine flow channel. At the inlet, the oxygen concentration is highest, while at the outlet, the oxygen is depleted due to electrochemical reactions. However, the material properties of the typical gas diffusion layer are the same near the inlet as they are near the outlet. Due to the non-uniformity of the reactant concentration profile, it stands to reason that the performance of the fuel cell could be impacted by a gas diffusion layer which has a spatially variable effective diffusivity.
In this work, we use STAR-CCM+ to simulate heat transfer/production, flow, species transport, electrodynamics, and electrochemical reactions in the cathode side of a fuel cell with a serpentine flow channel. We use Optimate+, a STAR-CCM+ embedded optimization package, which uses a proprietary hybrid-adaptive algorithm named SHERPA, to maximize the total current generated in the cathode side of the fuel cell by changing the porosity profiles in the gas diffusion layer and catalyst layer, the platinum loading profile in the catalyst layer and the geometric parameters of the flow channel design. We will present results from our simulations and optimization study in addition to discussing the limitations of our physical model and future topics for research.
2D Platinum Network ORR Catalyst on Carbon and Niobium Oxide Hybrid Support
Authors: Xu Chunchuan , Yang Jun , Pence Benjamin , Gath Kerrie , Pietrasz Patrick , Sulek Mark , Sun Kai , Sohm Evan , Meng Guangnan 
Published: February 2020

2D platinum network catalyst on graphitic carbon and amorphous NbOx hybrid support has been synthesized by Arc Plasma Deposition (APD) method. The 2D platinum structure on the conductive, corrosion resistant amorphous metal oxide significantly increases the catalyst stability under RDE accelerated stress tests. RDE and 5cm2MEA single cell test results showed that the catalyst has higher specific and mass activities than those of conventionally prepared platinum on graphitic carbon (Pt/C) catalyst. The microstructures of the catalyst were characterized by transmission electron microscopy (TEM).
Amorphous NbOx conductive metal oxide was deposited from either Nb2O5 in Ar or Nb in a gas mixture of 30 vol.% of O2 in Ar onto carbon particles by using Arc Plasma Deposition (APD) system (Ulvac-Riko, Inc). The obtained NbOx on carbon particle are isolated amorphous islands, with the value of x between 1 and 2.5. When Pt was deposited onto the formed NbOx islands, a platinum 2D nano-network was obtained, as schematically shown in Figure 1. The platinum particles with about 5 nm size can be uniformly deposited on the support NbOx and carbon. Figure 2 shows the percentage change of ECSA and mass activity under AST using square wave 1.0V~1.5V for carbon corrosion (a) and 0.1V~1.0V for Pt (b). The specific (SA) and mass activities (MA) are about 400 m A/cm2
Pt and 350A/gPt, respectively. The accelerated stress tests show that the durability of the catalyst is about 3~5 times higher than those of synthesized Pt on carbon catalyst through wet chemical methods under the same carbon corrosion and platinum stress conditions. The polarization curve and EIS data of Pt/C and Pt/NbOx/C on a 5 cm2 single cell are shown in Figure 3. Pt/NbOx/C cell with 0.07mg/cm2 Pt loading and Pt/C cells with 0.19mg/cm2 Pt loading have a similar polarization curve.