bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of 2R-Cell Degradation under Thermal Cycling and RedOx Cycling Conditions by Electrochemical Impedance Spectroscopy
Authors: Diethelm Stefan , Singh Vaibhav , Van herle Jan 
Published: February 2020

The prevalent anode supported thin electrolyte solid oxide fuel cells (ASC) used today are highly susceptible to failure under redox conditions. The expansion caused during the oxidation of Ni to NiO can destroy the support, leading to irreversible cell damage. To counter this problem, Fiaxell SOFC Technologies (Switzerland) has engineered the microstructure of their cells, to confer added redox stability to their anode supported cell (2R-cell™). This commercial cell was investigated within the Eurostars-Roxsolidcell project against thermal and redox cycling.
A 2R-cell with a 10cm2 active area LSCF cathode on a CGO buffer layer, was placed between alumina felts, mounted inside a seal-less open flange setup kept in an oven, and operated at a temperature of 780°C. A nickel foam and a gold grid were used for the current collection at the anode and cathode respectively. Dry hydrogen (180 Nml/min) was fed to the anode and air (500 Nml/min) to the cathode. 20 thermal cycles were performed between 780 and 100°C, using 200°C/h heating ramps and natural cooling, followed by 20 redox cycles, during which air was fed to the anode for 1 hour at 780°C, causing the cell potential to drop to zero.
V-i polarisation curves and electrochemical impedance spectroscopy (EIS) measurements were performed before and after each consecutive cycle in order to monitor the performance losses. The OCV remained stable during the whole test whereas the area specific resistance (ASR) measured at 0.5 A/cm2 increased by +1.3 mΩcm2 per thermal cycle and by +1.8 mΩcm2per redox cycle. The EIS measurements showed that the degradation during the thermal cycling was mainly due to an increase of the ohmic losses. In the case of the redox-cycling, the cell degradation after stabilisation principally came from high frequency polarisation losses (cf. Figure), which were attributed to changes in the anode functional layer microstructure.
The cell was examined after the test by scanning electron microscopy (SEM). No delamination of the cathode was observed, however, fragmentation of the anode active layer was apparent.

Figure 1
Elaboration and Electrochemical Characterizations of up-Scaled Protonic Ceramic Cells
Authors: Dailly Julian , Ancelin Marie , Marrony Mathieu 
Published: February 2020

Protonic Ceramic Cell in fuel cell mode (PCFC) is benefit to produce water at the air electrode side, avoiding the dilution of the fuel. Moreover, co-generation of heat and electricity is possible in this temperature range and ageing and reactivity of materials should be less critical than these observed at higher temperature. Proton Conducting Ceramic Cell is now widely investigated for a variety of applications, in particular fuel cell, steam electrolysis and hydrogen separation but such technology has to face to a low industrial scale maturity.
In the frame of METPROCELL project supported by European Community’s 7thFramework Programme (FP7/2011-2014) for the Fuel Cells and Hydrogen Joint Technology Initiative and coordinated by TECNALIA (SP), up-scaled anode-supported cells (ASC) have been elaborated by wet chemical routes. ASC requires the use of tape-casting method in order to manufacture the support. Then, both electrolyte and cathode are screen-printed on the NiO-electrolyte substrate (cf. Figure 1).
Based on previous works [1-3], promising performances (170 mW/cm² at 0.7V, 600°C, cf. Figure 2) and long term testing (thousand hours) have been measured on middle-scaled protonic cells (20 cm²). Microstructure evidenced by SEM analysis and electrochemical performances (IV-curves, Impedance Spectroscopy measurement) as well as durability measurement will be presented and discussed.
[1] Taillades G., Dailly J., Taillades-Jacquin M., Mauvy F., Essouhmi A., Marrony M., Lalanne C., Fourcade S., Jones D.J., Grenier J.-C., Rozière J., “Intermediate temprerature anode-supported fuel cell based on BaCe0,9Y0,1O3-
d electrolyte with novel Pr2NiO4 cathode”, Fuel Cells (10), 2010, 166
[2] Dailly J., Marrony M., Taillades G., Taillades-Jacquin M., Grimaud A., Mauvy F., Louradour E., Salmi J., “Evaluation of proton conducting BCY10-based anode supported cells by co-pressing method: Up-scaling, performances and durability”, Journal of Power Sources (255), 2014, 302-307
[3] Dailly J., Marrony M., “BCY-based proton conducting ceramic cell: 1000 h of long term testing in fuel cell application”, Journal of Power Sources (240), 2013, 323-327

Figure 1
Ageing of Materials at Inlet and Outlet Fuel Manifolds in a SOFC Stack
Authors: Piccardo Paolo , Pecunia Andrea , Bongiorno Valeria , Spotorno Roberto , Wuillemin Zacharie , Ouweltjes Jan Pieter 
Published: February 2020

The ageing behaviour of glass-ceramic seal materials and of alloys is a key element for a durable performance of SOFC stacks. Post-experiment analyses performed on a stack operated for more than 4000h at 750°C and at high fuel utilization (80%) reveal significant differences in ageing behaviour of such materials when comparing fuel inlet and fuel outlet areas.
Two samples were cut from the fuel inlet and outlet manifolds of an operated SOFC stack. The glass-ceramic sealing material and the alloy were exposed to a dual atmosphere (external air and internal fuel stream). The fuel composition was of dry H2/N2 (60:40 vol. %) at the inlet and of H2O/H2/N2 (48:12:40 vol. %) at the outlet. The stack was operated in co-flow configuration, with a large excess of air. The paper is focused on the sealant, on the structural steel and on the interfaces between both materials. The following figure schematically describes the samples and the zones of interest.
Both samples were mounted in epoxy-resin, polished and observed by optical microscopy and SEM-EDX.
It was found that the interfaces between the seal and the alloy were significantly affected by the difference in fuel composition, with more severe degradation at the fuel outlet side. Further, an increased porosity of the sealant was observed on the same location, while the inlet sample remained less affected. Finally, the sealant exposed to the outgoing air was significantly polluted by chromium generated in the stack and transported by the air stream.
These investigations therefore reveal that the long-term evolution of the sealing and of the metallic support depends on the local conditions in the stack, as well as on additional interactions with other degradation phenomena.

Acknowledgement: The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) Fuel Cells and Hydrogen Joint Undertaking (FCH-JU-2013-1) under grant agreement No 621207.

Figure 1
Ab-Initio and Experimental Studies of Silicon Dioxide Anode Material for Lithium Ion Battery
Authors: Moon Janghyuk , Cho Kyeongjae , Cho Maenghyo 
Published: February 2020

Silicon sub oxide SiOx (x ≤ 2) has been considered as a potential LIB anode. Although SiOx is thermodynamically unstable at all temperature, it consists of amorphous Si and SiO2 clusters leading to active/ inactive structures that help buffer the strain during cycling and hence much improved reversible capacities. It was thought that the role of SiO2 was buffer matrix of Si, however, some researchers reported that amorphous SiO2 reacts with Li and can be used for anode material for LIBs. And recently, communities both academy and industry have considered the idea of tailoring oxidation of proportionated SiOx to increase the initial capacity and cycle ability compared to Si. Despite these encouraging developments of Si oxide anode, the fundamental understanding is still limited and no atomistic study has been reported.
In this presentation, we study the structural stability of SiOx (0 ≤ x ≤ 2) , reaction mechanisms of Li in c-SiO2, and possibility reaction in amorphous Si sub oxide using both theoretical and experimental method. Based on the analysis of SiO2, we also discuss structural evolution and voltage profile of LiySiOx (0 ≤ y ≤ 4) during lithiation with respect to oxygen contents (0 ≤ x≤ 2).
Gallium Arsenide As a New Alloying Anode for Lithium Ion Batteries
Authors: Hays Kevin Alan , Wagner Michael J , Banek Nathan A 
Published: February 2020

Li alloying metals have much greater specific and volumetric energy densities than current state of the art graphite used in commercial Li ion batteries. However, the extremely large volumetric changes that the metals undergo when alloying with Li lead to the structural degradation of the electrode with consequent poor cycle life. We are attempting to make stable Li alloying metal electrodes, specifically with gallium arsenide, by akalide reduction on carbon matrices.
Arsenic has been largely ignored as a candidate for Li alloying anode materials despite having the third best gravimetric capacity of the alloying metals and being abundant and inexpensive, on par with the cost of bulk silicon1. Gallium, a lithium alloying metal that melts at 29.8°C, has shown promise because of its self-healing ability at increased temperatures2, although it suffers from a lower gravimetric capacity than some of its more popular lithium alloying counterparts.
Here we show the synthesis of Gallium Arsenide by akalide reduction. It is characterized by powder x-ray diffraction, transmission electron microscopy, thermo-gravimetric analysis, and x-ray fluorescence spectroscopy. Electrochemical testing of lithium half-cells, cycled from 0.02 to 1.5V versus lithium at a rate of C/10, showed a reversible capacity of 630 mAh/g with good capacity retention.
(1) Nitta, N.; Yushin, G. Particle & Particle Systems Characterization, 31, 317-336.
(2) Deshpande, R. D.; Li, J. C.; Cheng, Y. T.; Verbrugge, M. W. Journal of the Electrochemical Society, 158, A845-A849.

Figure 1
Monodispersed Poly(ethylene oxides) and Their Role in Conductivity Mechanism in Crystalline Polymer Electrolytes
Authors: Hekselman Aleksandra K. , Bruce Peter G 
Published: February 2020

Previous research in the area of polymer electrolytes has been mainly focused on complexes prepared with alkali metal salts and polydispersed poly(ethylene oxides) (abbreviated to PEO).1 Previous studies have shown that polymer chain length may play a significant part in the ion transport in the crystalline phase but high distribution of molecular weight of the commercially available polymers complicates the understanding of the conductivity mechanism.2

By employing monodispersed polymers (with a discrete chain length) we attempt to reduce a number of variables that are likely to influence the ion transport process. However, monodispersed poly(ethylene oxides) are not readily available and therefore, a synthetic method has been developed to obtain a series of monodispersed homologues in a variety of chain lengths.
These monodispersed polymers were used to prepare a series of crystalline complexes with a lithium salt (PEO6:LiPF6). Correlation between chain length of the polymer and unit cell parameters of the crystalline complexes in combination with molecular dynamics simulations3 revealed different structural arrangements at polymer chain-end regions. These arrangements and their role in coordination of lithium ions, ion mobility and transport, and the resulting conductivities will be presented.
[1] P. G. Bruce, B. Scrosati and J. M. Tarascon, Angewandte Chemie-International Edition 2008, 47, 2930-2946. [2] E. Staunton, Y. G. Andreev and P. G. Bruce, Faraday Discussions 2007, 134, 143-156. [3]A. Liivat, D. Brandell, A. Aabloo and J. O. Thomas, Polymer 2007, 48, 6448-6456.
Proton Transport in Hydrocarbon Membranes for Fuel Cell Applications
Authors: Choe Yoong-Kee 
Published: February 2020

The nature of proton transport in various hydrocarbon membranes are investigated using the first-principles molecular dynamics simulations. Three hydrocarbon membranes, sulfonated poly ether sulfones (SPES), sulfonated poly(4-phenoxybenzoyl-1,4-phenylene) (SPPBP) and sulfonated poly (arylene ether ether nitile)s (SPAEENs) were studied in detail. Especially, we focus on the effects of various native chemical structure of the membranes on the transport of protons. We found that a hydrophillic functional group in those membranes can be protonated by accepting a proton when a hydronium ion (H3O+) comes close to its vicinity. Such a result indicates that hydrophillic functional groups, such as a carbonyl group, affect the proton transport in a negative manner. The negative effects were found to be dominant under low hydration conditions.
Furthermore, it was observed that hydrophillic functional groups tend to attract water molecules, which, in turn, depletes hydration around the sulfonate group where such an effect hinders proton dissociation under low hydration conditions.

Figure 1
Pressureless Sintered Dense, Free Standing, Li+ Conducting Garnet Thin Films (< 50 µm) from Flame Made Nanoparticles
Authors: Yi Eongyu , Wang Weimin , Laine Richard 
Published: February 2020

Li7La3Zr2O12 (LLZO) garnet electrolytes show the highest potential utility in future solid state Li batteries due to a wide electrochemical stability window, stability in contact with lithium metal, and high ionic conductivity. The literature is replete with methods of optimizing compositions targeting optimal conducting properties, however, no examples of thin films (< 50 µm) with ionic conductivities rivaling bulk counterparts (0.1-0.3 mS cm-1) have been reported.
To date, LLZO has been pressed into pellets (1-2 mm) and either pressureless sintered at 1100-1200 ºC for 10-40 h covered in mother powder or at 40-60 MPa at 1000-1100 ºC for 1-4 h. Both approaches are energy intensive and the scalability is questionable.
Although LiTi2(PO4)3 solid electrolytes have been studied extensively and processed by tape-casting, a low cost approach, no similar LLZO examples have been reported. Some challenges in processing LLZO thin films include high lithium loss rates, reaction of LLZO with common ceramic crucibles, and energy and equipment intensive sintering processes.
In this work, LLZO nano-powders produced by LF-FSP (liquid-feed flame spray pyrolysis) are used to formulate ball-milled suspensions that are then cast. Dried green films can be made in a process that offers potential for continuous casting. Films are cut and sintered at selected sintering schedules providing dense thin films. 30-50 wt. % excess lithium is used to compensate for lithium loss during sintering.
Green films were sintered above 900 ºC for selected dwell times to show that even a difference of 0.2 h at peak temperature undergo phase composition changes due to lithium loss. Sintered films show trans-granular fracture mode with ionic conductivities of 0.1-0.2 mS cm-1 and >95 wt. % LLZO.
The very first example of LLZO thin films with similar properties to bulk counterpart is reported. Furthermore, shorter processing steps and lower energy input for sintering compared to other reported methods make usage of LF-FSP synthesized nano-powders more desirable.
(Invited) Efficient Electrocatalytic CO2 Reduction with Dinuclear Iron Complexes
Authors: Naruta Yoshinori 
Published: February 2020

Recently, reductive conversion of CO2 to useful carbon resources draws broad attentions from environmental and catalytic to biological sciences. Though many metal complexes as well as pure metals including mainly mononuclear rare metals such as Ru or Re have been proposed to date, they show rather high overpotentials and/or poor product selectivities. Thus, new catalyst design for efficient and robust CO2reduction is strongly demanded.
In biological systems, anaerobic bacteria and archaea use oxygen-sensitive Ni-/Fe-containing carbon monoxide dehydrogenases (CODHases), which realize efficient mutual conversion between CO2 and CO at extremely low overpotentials (< 100 mV) (Fig. 1A).[1] The dinuclear active site motif with base metal ions is attractive as chemical models. According to this strategy, we designed iron porphyrin dimers linked by 1,2-phenylene group (Fig. 1B) as the catalysts and applied them for electrochemical CO2 reduction. The catalysts show extremely high catalytic TOF and high CO selectivity at relatively low overpotentials (η). When electron-withdrawing meso-aryl groups are used, η
becomes as low as 0.4 V.[2] From the detailed CV analysis, Fe porphyrin monomer, e.g., FeTPP, shows the dischage current at its Fe0 state in CO2 atmosphere and FeII/III and FeI/II couples appear at the same potential as observed in Ar. The FeTPP dimer, however, shows a considerable positive shift of its FeI/II couple in CO2. This suggests that the FeII state of the dimer will make strong association with CO2 molecule and the resultant complex shows its reduction peak at more positve potential than its original FeI/II couple. Since FeII porphyrin monomesr are generally intact with CO2, this is the first example of the formation of the CO2-binding to FeII porphyrin by its dimerization. This is the reason of the considerable decrease of the CO2 reduction overpotential. This result also supports the two nucleus motif as observed in CODHase active site promote the CO2 reduction at low η.
When two Fe ions are separated in a larger distance as observed in 1,3-phenylene linked Fe dimer, this cooperative effect of the two FeII ions is not work any longer and the m-dimer just work as two monomers.
The present Fe porphyrin dimmr catalysts are quite robust and any current drop was not observed after 12 h at a constant potential electrolysis. High CO selectivity of these Fe catalysts is also advantage for their practical use on the aspect of easy product separation.
Regerences
[1] J.-H. Jeoung and H. Dobbek, Science, 318, 1461 (2007); J. Fesseler, J.-H. Jeoung, and H. Dobbek, Angew. Chem. Int. Ed., 54, 8560 (2015).
[2] E. Mohamed, Z. Zaharan, and Y. Naruta, Chem.
Commun, 51, 16900 (2015). (Cover article)

Figure 1
(Invited) Tetrapyrrole-Based Metal Complexes Designed for Bio-Inspired Catalysis and Solar Fuel Production
Authors: Knör Günther 
Published: February 2020

Light-induced substrate transformations in artificial photosynthetic devices and functional enzyme model systems strongly depend on the feasibility of multielectron transfer catalysis [1,2]. The crucial advantage of coupling multiple redox equivalents and proton transfer steps in photocatalysis is to avoid free radical reaction pathways and energetic constraints due to charge accumulation, as these processes can decrease both the long-term stability and the efficiency of the corresponding systems. In this context, certain coordination compounds including tetrapyrrole-based derivatives such as porphyrin, corrole and phthalocyanine complexes have been shown to achieve an efficient fusion of the complementary functions of a light-harvester, a photoredox interface, a substrate recognition site and a mediator for chemical reactions [3-6]. To further improve the performance of such systems, the design of long-term stable processes for artificial photosynthetic energy storage and green synthetic chemistry using artificial (photo)enzymes has to be achieved with sustainable, environmentally benign and earth-abundant bulding blocks. Another crucial aspect in the context of solar chemistry and catalysis is not only the requirement for using visible light, but also to shift the threshold wavelength of the photosensitizers as far as possible to the red and NIR-spectral regions. Some of our recent developments in this direction will be presented in this contribution.
[1] G. Knör, Chem. Eur. J.
2009, 15, 568
[2] G. Knör, Coord. Chem. Rev.
2015, 304-305, 102
[3] M. Hajimohammadi, C. Schwarzinger, G. Knör, RSC Advances
2012, 2, 3257
[4] C. Uslan, K. T. Oppelt, L. M. Reith, B. Ş. Sesalan, G. Knör, Chem. Commun.
2013, 49, 8108
[5] K. T. Oppelt, E. Wöß, M. Stiftinger, W. Schöfberger, W. Buchberger, G. Knör, Inorg. Chem.
2013, 52, 11910
[6] M. Ertl, E. Wöß, G. Knör, Photochem. Photobiol. Sci.
2015, 14, 1826
(Invited) Metal Assembly of a Dendrimer with a Porphyrin Core
Authors: Yamamoto Kimihisa 
Published: February 2020

Dendrimers are highly branched organic macromolecules with successive layers or “generations” of branch units surrounding a central core. Organic inorganic hybrid versions have also been produced, by trapping metal ions or metal clusters within the voids of the dendrimers. Their unusual, tree-like topology endows these nanometre-sized macromolecules with a gradient in branch density from the interior to the exterior. Here we show that tin ions, SnCl2 and FeCl3complexes to the imines groups of a spherical polyphenyl-azomethine dendrimer in a stepwise fashion according to an electron gradient, with complexation in a more peripheral generation proceeding only after complexation in generations closer to the core has been completed.
Many metal halides can be assembled inside the phenylazomethine dendrimer with a Zn-porphyrin core(DPA-ZnP) by the strong coordination ability of the imines in DPAs. The 60 equivalents of SnCl2 should be included in the fourth generation DPA-ZnP (DPAG4-ZnP), which has 60 imine sites, because SnCl2 is complexed with an imine at the ratio of 1:1. Complexation of DPA G4-ZnP with SnCl2 was confirmed as a shift in the absorption based on p-p* transition of imines in the UV-vis spectra. During the complexation of DPA G4-ZnP with SnCl2, four shifts in the isosbestic point were observed in the spectra. If SnCl2 molecules are complexed with the imines in DPAs at random, the isosbestic point is not shifted during the titration of SnCl2. However, the isosbestic point was observed at 370, 368, 366, and 362 nm during the addition of 0-4, 5-12, 13-28, and 29-60 equivalents of SnCl2 to the dichloromethane/ acetonitrile solution of DPA G4-ZnP, respectively. These shifts show that the complexation proceeds in four steps. The amounts of the added SnCl2 in each step, i.e., 4, 8, 16, and 32 equivalents, agree with the number of imines in the 1st to 4th shells. This result shows that SnCl2 molecules are assembled from the core to the terminals of DPA G4-ZnP in a stepwise fashion. This radial stepwise complexation was also observed for the other dendrimers with phenylazomethine dendron skeletons. This complexation behavior means that the number and the position of the metal ions in the dendrimers are controllable.