bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observation and Analysis of Nafion Solution By Frozen TEM Technology
Authors: Yoshida Toshihiko , Sugimori Hidekazu , Miyazawa Atsuo , Matsumoto Hidetoshi , Konosu Yuichi , Sasabe Takashi , Uemura Suguru , Kameya Yuki , Terao Takeshi , Iriguchi Norio , Shinohara Kazuhiko , Hirai Shuichiro 
Published: February 2020

Nafion has been well known as the standard perfluorosulfonated material in the field of Polymer Electrolyte Membrane Fuel Cell and has been irreplaceable materials as a membrane and an ionomer of catalyst layer. Many researchers have investigated the proton conduction, water-uptake, mechanical property and nano-structure1,2).As for nano-structure researches, small angle X-ray scattering and small angle neutron scattering revealed the morphology characterization of Nafion solution3). X-ray irradiates many molecules in Nafion solution.The characterization was attributed to average information.TEM is very useful apparatus to observe nano-structure of materials. It is applicable to samples which withstand a vacuum condition.Nafion solution is not able to be observed by TEM because of high vapor pressure of solution. Freeze method is an idea to measure Nafion solution. In case of freeze method using liquid nitrogen, vaporized nitrogen severely damaged the sample. In case of another freeze liquid ethane method Figure1, liquid ethane was cooled by liquid nitrogen to avoid vaporization of ethane.Figure 2 shows TEM photograph of Nafion solution. Objects of rod structure were observed, some rods seemed to be linked each other and dark points also observed.
Rod structure with radius 1.2 to 3.6 nm and length 16nm was predicted when entangle molecular weight 54904), EW=1000 and Nafion molecular weight between 0.1million and 1million were applied.Rod structure of TEM photograph is interpreted as the prediction.Dark points of TEM Photograph might be nano-crystals of PTFE part of Nafion.SAXS measurement of Nafion solution also showed nanocrystal with interval of 18nm. This interval value fairly fits to distances between dark points.
This presentation is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
References
1)Kenneth A. Mauritz and Robert B. Moore, “State of Understanding of Nafion”, Chem. Rev. 2004, 104, 4535-4585
2)Adam Z. Weber and John Newman,” Modeling Transport in Polymer-Electrolyte Fuel Cells”, Chem. Rev. 2004, 104, 4679-4726
3)Makoto Yamaguchi, Takuro Matsunaga, Kazuki Amemiya, Akihiro Ohira, Naoki Hasegawa, Kazuhiko Shinohara, Masaki Ando and Toshihiko Yoshida, “Dispersion of Rod-like Particles of Nafion in Salt-Free Water/1-Propanol and Water/Ethanol Solutions”, J. Phys. Chem. B 2014, 118, 14922-14928
4)Souheng Wu; “Characterization of Polymer Molecular Weight Distribution by Transient Viscoelasticity: Polytetrafluoroethylenes”, Polymer Engineering & Science, 1988 - Wiley Online Library

Figure 1
Probing the Active Site Structures of Iron-Based ORR Catalysts
Authors: Hu Yang , Li Qingfeng , Jensen Jens Oluf , Zhong Lijie , Cleemann Lars Nilausen 
Published: February 2020

Highly active and durable electrocatalysts for the oxygen reduction reaction (ORR) are undoubtedly essential for the commercialization of polymer exchange membrane fuel cells. Recently, two types of iron-based catalysts have been extensively studied and reported to be active and stable towards ORR in acidic electrolyte. One is the well-recognized FeNx/C catalyst, and the other is the catalyst with structures of graphitic layer encapsulated metal particles. Generally, catalysts synthesized by pyrolysis of different iron- and nitrogen-containing precursors always contain both structures, making it impossible to distinguish the role of each structure during the ORR. Using a high temperature autoclave approach, we synthesized two model catalysts with almost exclusively one desired structure in each catalyst. Based on detailed characterizations in terms of catalyst structure and composition as well as electrochemical tests, the active site structures of these two catalysts and their correlation with the ORR performance are explored.
Figure 1. Schematic illustration of the two possible active sites.

Figure 1
Hydrogen Sulfide Tolerance in High Temperature Pemfcs
Authors: Vassiliev Anton , Cleemann Lars Nilausen , Li Qingfeng , Jensen Jens Oluf 
Published: February 2020

The effect of hydrogen sulphide (H2S) poisoning on the anode of H3PO4-polybenzimidazole based fuel cells has been investigated. High temperature PEM fuel cells (HT-PEMFC) offer a number of advantages that allow for a simple electricity generating system. Of the main importance is the ability to operate on reformate hydrogen without extensive purification [1]. Most of the research is concentrated on CO poisoning mitigation, but as the feedstock often contains sulphur contamination or sulphur-containing odorant additives, the poisoning effect of sulphur on Pt electrodes at elevated temperatures should not be overlooked. Little literature is available on the topic [2, 3]. Present work shows the effect of anode H2S poisoning on 25 cm² HT-PEMFCs operated at 160 °C, evaluated by polarisation curves and electrochemical impedance spectroscopy (EIS).
Cells exposed to 0.2 – 50 ppm H2S in the fuel supply show no significant signs of voltage degradation when operated at 160 °C and 200 mA/cm². The main effect is seen at higher current densities with 10 – 50 ppm levels of contamination, where concentration overpotentials cause the voltage to drop off. The effect is partly reversible, as the voltage at high current densities recovers upon switch back to pure hydrogen operation. This is contrary to the low temperature PEM fuel cells, where the voltage degradation with only trace amounts of H2S is rapid even at low currents and irreversible [4, 5].
Prolonged exposure to 1 – 50 ppm H2S in the fuel supply show a time-dependant nature of the sulphur poisoning with the major voltage degradation occurring within the first 24 hours. Again, the effect is only visible at intermediate and high currents and is partly reversible when the fuel is changed to pure hydrogen after several days of operation with H2S contaminated fuel.
EIS measurements at 200 mA/cm² showed no change in the series resistance. Occurrence of a semicircle at low frequencies, growing throughout the prolonged exposure measurements could indicate increased levels of adsorption of sulphur on the Pt sites of the electrode, thus explaining the concentration overpotentials recorded at high current densities.
[1] Q. Li et al., Progress in Polymer Science, 2009, 34 (5), p. 449-477.
[2] T.J. Schmidt and J. Baurmeister, ECS Transactions, 2006, 3 (1), p. 861-869.
[3] G. Qian and B.C. Benicewicz, Ecs Transactions, 2011, 41 (1), p. 1441-1448.
[4] V.A. Sethuraman and J.W. Weidner, Electrochimica Acta, 2010, 55 (20), p. 5683-5694.
[5] I. Urdampilleta et al., ECS Transactions, 2007, 11 (1), p. 831-842.
Degradation of SOFCs By Phosphorus Impuriteis: Impedance Spectroscopy and Microstructural Analysis
Authors: Kikuchi Yuhdai , Sunada Kyouhei , Matsuda Junko , Taniguchi Shunsuke , Shiratori Yusuke , Sasaki Kazunari 
Published: February 2020

Introduction

SOFC is considered as a promising power generation system due to high electric efficiency and fuel flexibility. But, coal gas, for example, contains various impurities. In this study, phosphorus poisoning effect to Ni-ScSZ cermet anodes is analyzed by measuring Electrochemical Impedance Spectroscopy (EIS). Spectroscopy data are analyzed by the distribution of relaxation times (DRT) method1to investigate details of electrode resistance. Furthermore, microstructural analysis was made by electron microscopy.

Experimental

Electrolyte-supported cells with ScSZ (10 mol% Sc2O3
- 1 mol% CeO2-89 mol% ZrO2) plate (20 mmφ×0.2 mmt) were used in this study. Mixture of 56 wt% NiO and 44 wt% ScSZ was used for the anode and was sintered at 1300 oC for 3 h. Mixture of (La0.8Sr0.2)0.98MnO3 (LSM) and ScSZ with a weight ratio of 1:1 was used for the cathode. Electrode area was 8×8 mm2 and Pt mesh was used as the current collector. Figure 1 describes the experimental setup. P2O5 container is locating at the fuel upstream to mix phosphorus impurity which is evaporated as PH3. PH3 concentration was specified as 2ppm by a TG-DTA measurement. The fuel consisted of 67% H2 and 33% H2O. Cell temperature was 800oC. Table 1 shows EIS condition. EIS data analyzed by DRT enable identification of electrode processes. FESEM-EDX was applied to investigate changes in the anode microstructure and composition by the cell performance tests.

Results and discussion

Figure 2 shows EIS spectra measured after 1h, 50h, and 100h. Figure 3 shows the DRT result of the Fig. 1 data. DRT peak becomes gradually visible due to the increase in impedance. DRT peak around 10-1~10-2 sec may originate from the diffusion of H2 gas2. Figure 3 shows SEM-WDX mapping of nickel and phosphorus. Ni particle is condensed and Ni-P compounds are formed on the anode surface. Therefore, cell performance degradation by inhibiting gas diffusion and forming Ni-P compound in the phosphorus poisoning of Ni-based anodes.

References

(1) A. Leonide et al., Journal of The Electrochemical Society, 155(1), B36-B41 (2008).
(2) T.H. Wan et al., Electrochimica Acta, 184, 483-499 (2015).

Figure 1
Effect of PEALD YSZ on Bi-Layered Electrolyte with Nanoscale Structure
Authors: Yu Wonjong , Cha Suk Won , Cho Gu Young , Hong Soonwook , Lee Yeageun , An Jihwan 
Published: February 2020

Low temperature solid oxide fuel cell (LT-SOFC) has been considered as a one of the solution for alleviating a few drawbacks of conventional solid oxide fuel cells such as limited material selection, high performance degradation, and sealing problem. To lower the operating temperature of SOFC, reducing thickness of the electrolyte down to nanometer scale has been suggested as an effective way for lowering ohmic resistance mainly caused by ionic transport.
Atomic layer deposition (ALD) is a superior method for providing conformal and high aspect ratio thin film due to its sequential process. Recently, plasma enhanced ALD (PEALD) shows advanced properties for lowering C contamination and improving the crystallinity of the thin film. We believe that PEALD with these characteristics could be used to fabricate ultrathin and high quality ionic conducting electrolyte. In this study, PEALD is utilized for fabricating yttria-stabilized zirconia (YSZ) on nanoporous substrate and, furthermore, electrochemical performance of PEALD YSZ is comparatively characterized with sputtered YSZ.
The effect of PEALD YSZ electrolyte on bi-layered YSZ/YDC electrolyte was electrochemically characterized. Nanoporous anodic aluminum oxides (AAOs) were used as substrates for the fabrication of YSZ/YDC bi-layered electrolyte SOFCs. A cell with PEALD YSZ electrolyte showed higher open circuit voltage (OCV) of ~1002 mV and peak power density of ~182 mW/cm2 at 450 oC comparing with a cell with sputtered YSZ electrolyte. This OCV value of PEALD YSZ signifies high quality of electrolyte for gas tightness and electron blockage. The surface grain structures of YDC electrolyte sputtered on different underlying layers were comparatively analyzed by employing field emission scanning electron microscope (FESEM). The analysis indicated larger grain boundary of YDC electrolyte on PEALD YSZ resulting in higher performance of thin film SOFCs.
Figure1. Electrochemical impedance spectroscopy (EIS) analysis for PEALD and sputter YSZ cells measured at 0.6V

Figure 1
Current Constriction at Electrode/Electrolyte Interfaces in Solid Oxide Cell Electrochemical Devices Calculated Via 3D Reconstructions
Authors: Nielsen Jimmi , Jørgensen Peter Stanley , Graves Christopher 
Published: February 2020

Electrochemical devices such as batteries, fuel cells, electrolysers, electrochemical reactors and electrochemical sensors are important technologies for the present and the future society. For further improvement or maturing of the various technologies it is important to understand, characterize and minimize the different losses within the devices.
Historically the first generation of solid oxide fuel cell (SOFC) was electrolyte supported. In order to be able to reduce the electrolyte thickness and thus improve performance, the second generation anode supported solid oxide fuel cell (AS-SOFC) was developed. Today’s state-of-the-Art AS-SOFC has an electrolyte thickness of approximately 10 μm. Efforts are currently being made to reduce the electrolyte thickness further to achieve even higher performance [1-2]. However, as will be evident from the present study this may have its limitations, as a further reduction in the electrolyte thickness may lead to an increase in resistance due to the onset of lateral currents within the electrolyte layer.
The magnitude of the current constriction resistance of the individual electrode/electrolyte assemblies and the optimum electrolyte thickness depend on the structural characteristics of the electrodes. Attempts at quantifying the current constriction resistance have previously been made and models have been developed which assumes a uniformly distributed array of either squares or circles [3-4]. However, this is often not a good assumption as the electrode/electrolyte interfaces are much more complex. First of all, the electrode and electrolyte interface is not planar nor is the electrode and electrolyte transition infinitely sharp. Secondly, the contact points are neither squares nor circles, which are distributed as an array. The aim of the present study is therefore to use 3D tomography electrode/electrolyte interfacial reconstructions in numerical Finite-Element-Method (FEM) calculations to get more accurate estimations of the current constriction resistance and the effect of varying the electrolyte thickness.
[1] F. Han et al., Journal of Power Sources, 218, 157–162 (2012).
[2] C. Ding and T. Hashida, Energy Environ. Sci., 3, 1729–1731 (2010).
[3] T. Kenjo and T. Nakagawa, J. Electrochem. Soc., 143, L92–L94 (1996).
[4] J. Fleig, J. Maier, in: Proc. 5th Int. Symp. Solid Oxide Fuel Cells, U. Stimming, S. C. Singhal, H. Tagawa, W. Lehnert, Editors, p. 1374, The electrochemical Society, Pennengton NJ (1997).
Oxygen-Excess-Type Ionic Conducting Thin Film for Fuel Cell Application
Authors: Mineshige Atsushi , Kobayashi Mio , Saito Atsushi , Yoshioka Hideki , Mori Ryohei , Yazawa Tetsuo 
Published: February 2020

Oxygen-excess-type lanthanum silicate (LSO) is a promising electrolyte material for intermediate-temperature SOFCs because of its high ion conductivity and low activation energy for conduction. In this study, the anode-supported solid electrolyte cell based on Mg-doped LSO, La9.8(Si5.7Mg0.3)O26.4(MDLS), was developed, and its electrical properties and fuel cell performances were evaluated.
The MDLS film was applied on top of the Ni-MDLS substrate by spin coating using nano-sized MDLS printable paste. The half cell obtained was then coated with (La0.6Sr0.4)(Co1-y
Fe
y
)O3-δ
cathode material.
The open circuit voltage of the cell was about 1.1 V, indicating that MDLS is a pure ionic conductor, and good gas-tight electrolyte was obtained. The ohmic and polarization resistances of the cell at 873 K were 3.2 and 3.1 Ω cm2, respectively. Both were able to be reduced with optimizing preparation conditions of MDLS, and inserting an interlayer between cathode and MDLS. As a result, the cell performance was largely improved, and the cell showed the power density of 855 and 97 mW cm-2 at 1073 and 873 K, respectively. It is expected that high performance intermediate-temperature SOFCs will be constructed using LSO-based electrolyte.
3D Printing Microstructured Li-Garnet Electrolytes for Solid-State Lithium Batteries
Authors: McOwen Dennis W. , Hitz Gregory , Wen Yang , Gong Yunhui , Hamann Tanner , Hu Liangbing , Wachsman Eric D 
Published: February 2020

Recent advancements in solid electrolytes have brought all solid-state lithium batteries much closer to a commercial reality. Lithium garnet materials such as Li7La3Zr2O12, or LLZ, are ceramic lithium conductors that have several uniquely advantageous properties: they are completely non-flammable, low cost to produce, and stable to lithium metal, which has an energy density more than 10x higher than standard graphite electrodes (3860 mAh/g). The main areas challenging the development of all-solid-state Li-ion batteries, however, have been relatively low ionic conductivity compared organic liquid electrolytes (~1 mS/cm compared to 10 mS/cm) and high interfacial impedance due, in part, to poor solid-solid contact at the electrolyte/electrode interface. However, by controlling the thickness of the electrolyte separating the two electrodes down to the order of tens of microns, the contribution of the conductivity to the overall resistance of the bulk electrolyte can become negligible. To address the interfacial impedance requires tailoring the architecture of the electrolyte surface to maximize accessible interfacial area and reduce the resistance for Li+ cation transfer at that interface.
Using an advanced 3D printer, different approaches were taken to optimize fabrication of both thin, low resistance solid electrolyte films and films with sophisticated surface microstructures. The creation of various geometries (e.g., grid patterns, multilayer structures, etc.) and their impact on pore structure and interfacial area was investigated in depth and will be discussed. Furthermore, electrodes were infiltrated into each of the pore structures and analyzed using SEM to determine which geometry facilitated the most extensive and intimate electrode-electrolyte contact. As a demonstration of the potential impact of microstructured solid electrolytes, electrochemical testing results of the 3D printed ordered structures was compared with the random-porosity structures of the same material created by tapecasting. The ordered microstructures consistently delivered better performance due to improved electrode-electrolyte contact. This work sheds light on the importance of the solid electrolyte surface, and how tuning its structure can help to overcome the challenges of solid-state batteries.
The Effect of Heating Rate on Li Losses from Al Stabilized Li7La3Zr2O12
Authors: Dermenci Kamil Burak , Turan Servet 
Published: February 2020

Li-ion batteries are considered as the most promising candidate for energy storage systems of EV’s. However, if the range of vehicle is increased, widely used flammable and explosive electrolytes will decompose. To enhance safety for EV applications, nowadays, solid electrolytes come forward. Among them, Al stabilized cubic Li7La3Zr2O12 (LLZO) shows superior electrochemical properties in terms of conductivity and stability window. During synthesis excess amount of Li must be supplied because of the volatile behavior of Li at high temperatures. The amount of excess Li is strongly dependent on heating rate during heat treatment. So, the optimization of heating rate is necessary to prevent excess Li losses.
In this study, Al stabilized LLZO will be synthesized by solid state reaction method with a heating rate of 1, 2, 5 and 10 °C/min. Their thermal behavior will be evaluated with Thermal Analysis with a heating rate of up to 10 °C/min. Their crystal structures and impurity phases will be determined by X-Ray Diffraction Techniques. Scanning Electron Microscopy will be used in order to present microstructure of synthesized pellets. Their electronic conductivities will be assessed with Potentiostatic polarization method by applying 10 V.
In-Situ AFM Observation of Highly Oriented Pyrolytic Graphite in PC-Based Electrolyte Solution Containing Magnesium Ion
Authors: Kokumai Ryohei , Song Hee-Youb , Fukutsuka Tomokazu , Miyazaki Kohei , Abe Takeshi 
Published: February 2020

Introduction

Graphite is used as a negative active material in lithium-ion batteries. The surface film, called solid electrolyte interphase (SEI) formed in ethylene carbonate (EC)-based electrolyte solution, plays an important role in reversible lithium-ion intercalation and de-intercalation reaction. When propylene carbonate (PC) is used as organic solvent, electrolyte decomposition and exfoliation of graphite layers occurred. We reported that lithium-ion intercalation and de-intercalation in PC-based electrolytes was succeeded using high concentrated lithium salt electrolytes or containing multivalent cations[1-3]. However, the SEI formation mechanism in PC-based electrolyte solution containing multivalent cation was not clarified. In this study, we investigate the surface morphology changes of highly oriented pyrolytic graphite (HOPG) electrode in PC-based electrolytes containing Mg2+ by in-situ Atomic Force Microscopy (AFM) to clarify the SEI formation mechanism.

Experimental

A three-electrode cell was used for electrochemical measurements. A HOPG was used as a working electrode and lithium foils were used as a counter electrode and a reference electrode. Electrolytes were prepared from lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2, LiTFSA), magnesium bis(trifluoromethanesulfonyl)imide (Mg(N(SO2CF3)2)2, Mg(TFSA)2), and PC. The molar ratio of two cation was fixed to be Mg2+/Li = 1.2. AFM observation was conducted during the CV measurements. All potentials were referred to Li/Li+.

Results

Figure 1 shows the cyclic voltammograms and in-situ AFM image at 1st cycle of HOPG. Large reduction peak at around 0.7 V appeared in the first cycle but disappeared in the second cycle. This result indicated that irreversible electrolyte decomposition, which was related to SEI formation, occurred at the initial cycle. In the AFM image obtained between 0.508 V and 1.204 V, precipitates appeared on the HOPG surface at 0.66 V. In EC-based electrolyte solution, hill-like structures and blister structures by the co-intercalation and decompostion of solvated-lithium ion were observed around 0.9 V. However, these structures were not observed in this system. Therefore, it is proposed that the addition of Mg2+ suppressed the co-intercalation of solvated lithium ion and SEI was formed by the surface reaction.

Reference

[1] S.-K. Jeong et al., J. Power Sources, 175 (2008) 540.
[2] S. Takeuchi et al., Electrochim. Acta, 56 (2011) 10450.
[3] S. Takeuchi et al., submitted.

Acknowledgment

This work was partially supported by CREST, JST and JSPS KAKENHI Grant Number 16H04216.

Figure 1