bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrocarbon Membrane for Vanadium Redox Flow Batteries
Authors: Kim Haekyoung 
Published: February 2020

With the expanding need for large electrical energy storage systems in connection with renewable energy sources, flow batteries, have been enormously considered due to their high flexibility in upgrade and low cost associated with scale-up. Of all the flow batteries, vanadium redox flow battery (VRFB) use of same element in both half-cell solutions that overcomes the inherent issue of cross contamination by diffusion of different ions across the membrane. Together with the absence of any toxic emissions, the vanadium redox flow battery has demonstrated its uniqueness in terms of safety and long life cycle. Typical charge-discharge reactions of a VRFB involve two vanadium redox couples, V(II)/V(III) and V(IV)/V(V), in the negative and positive half-cells, respectively. In a fashion similar to most batteries, electrons are transferred between the two electrodes through the external circuit during the charge and discharge processes. In a VRFB, the ion exchange membrane is a key component as an ionic conductor and separator: it not only provides an ionic conduction pathway between the two electrolytes but also prevents mixing of the negative and positive electrolytes. The crossover of ions through the membrane, with the diffusion of vanadium ions from one half-cell to the other due to the concentration gradients between the two electrolytes, will result in self-discharge and thus the loss of the chemical energy.
In this study, in order to improve membrane selectivity, hydrocarbon based polymer membranes were synthesized and fabricated for VRFBs. Sulfonated polysulfone membranes (PATS-XX) were characterized in terms of ionic conductivity and permeability with degree of sulfonation. PATS-35 exhibited the ionic conductivity of 0.06 S/cm, which showed 40% lower permeability than Nafion 115 membrane. VRFB cell with PATS-35 exhibited higher coulombic and energy efficiency than that with nafion 115 membrane. The results of VRFBs with blended PATS-xx membrane will be discussed and compared with that with Nafion membrane.
Influence of Convection and Material Properties in Vanadium Redox Flow Batteries
Authors: Houser Jacob , Mench Matthew M. , Pezeshki Alan , Clement Jason T. , Aaron Douglas 
Published: February 2020

Substantial work has been done recently to improve performance of all-vanadium redox flow batteries (VRFB) as a viable large scale energy storage system1. Prototype systems have been installed in small numbers to demonstrate their feasibility. There still exists a lack of understanding of the processes and design tradeoffs which exist in these systems, particularly regarding the relationship between mass transport, performance, realized capacity accessed, and parasitic pressure losses through the system. Despite the literature available regarding this particular chemistry, a thorough analysis of the design tradeoffs and their impact on system optimization is still lacking.
Flow field design is one such area where an opportunity for optimization exists for mass transport and system pressure drop. Such optimization can be experimentally explored, as well as computationally2. This combined experimental and computational study that will be presented will show that optimal flow field design is not simply related to the architecture, but is instead a more complex interplay between architecture, electrode properties, electrolyte properties, and operating conditions. The results of this study should be useful to design engineers seeking to optimize VRB systems through enhanced performance and reduced pressure drop.
1. D.S. Aaron, Q. Liu, Z. Tang, G.M. Grim, A.B. Papandrew, A. Turhan, T.A. Zawodzinski, M.M. Mench, Journal of Power Sources, 206 450-453 (2012).
2. T. Jyothi Latha and S. Jayanti, J. Appl. Electrochem., 44, 995 (2014).

Figure 1
Operando Imaging of Electrochemical Phase Transitions in LiNi0.8Co0.15Al0.
05O2
secondary Particles
Authors: Yu Young-Sang , Kim Chunjoong , Liu Yijin , Cabana Jordi 
Published: February 2020

The observation in dynamic conditions of electrochemical transformations relevant to energy storage creates the opportunity of identifying design rules that directly reflect the veiled electrochemical reaction mechanisms which are controlled by kinetics under load. Under the intrinsic limitations of ex-situ methods, opening the circuit to harvest multiple samples of interest at the different stages of reaction can lead to relaxation of the materials to a different, thermodynamically stable state. In addition, these operandoobservations must occur at multiple scales, but are particularly critical at the individual cathode particle level, where incomplete reactions and failure are prone to occur.
In this study, we focused on LiNi0.8Co0.15Al0.05O2 (NCA)-based cathode materials, which are one of the leading candidates for use in high energy density Li-ion batteries for electric vehicle applications. This material offers high storage, but still presents limitations vis-à-vis capacity loss and concurrent increases in impedance. We adopted operando 2D full field transmission X-ray microscopy (FF TXM) coupled with X-ray absorption near edge spectroscopy (XANES) to follow the chemical and microstructural evolution at the secondary particles of NCA with sub-30 nm spatial resolution. Chemical phase maps from quantitative analysis of pixel-by-pixel X-ray absorption near edge structure spectra and morphological information of optical-density images at the post-absorption-edge region were obtained at the different state of charge as shown in Figure 1. As a result, this work successfully revealed the existence of kinetically-induced inhomogeneities during the electrochemical phase transition, and their morphological consequences, within a secondary particle, at nanoscale spatial resolution during an electrochemical reaction. We believe the rich insight provided by high resolution spectro-microscopy could inform the design of optimized architectures and the projection of performance using continuum models.

Figure 1. A. Charge galvanostatic profile of operando Li metal half cell with an NCA composite cathode. The cell charged to capacity of 350 mAh·g-1 with cycling rate of C/15 (C was defined as the current density to achieve the theoretical capacity in 1 hour). Chemical maps were obtained at different state-of-charges (SOCs), labeled as 1 ~ 9, indicated as blue outlined circles. B. A map of white line peak positions for a secondary particle at SOC 5. Higher white line peak position indicates more oxidazed area.

Figure 1
Surface Composition and Oxygen Transport Properties of LSCF: From Bulk Ceramics to Devices
Authors: Druce John , Téllez Helena , Ishihara Tatsumi , Kilner John A. 
Published: February 2020

The exchange of oxygen between the gas phase and a mixed conducting ceramic, and its subsequent solid state diffusion, is key to the operation of electrochemical energy conversion devices such as Solid Oxide Fuel Cells (SOFCs) and Solid Oxide Electrolysers (SOECs), as well as dense membranes for oxygen separation. Indeed, it is often the surface reaction that determines the overall performance in such applications. However, whilst the mechanisms of oxygen diffusion in the bulk of these materials are generally well understood in terms of the defect chemistry and crystal structure, such an atomistic description of the surface exchange reaction still eludes us.
Whilst 18O isotopic tracer diffusion experiments coupled with SIMS analysis have been used for more than 30 years to study the kinetics of oxygen exchange and transport in candidate mixed conductors, relatively little attention has been paid to the characterization of the realistic surface composition of such materials; despite the great attention which is paid to the bulk chemistry, it is often assumed that the surface is a simple termination of the bulk. More recently, it is becoming apparent that the surface and near-surface composition after high temperature treatment is often radically different from the bulk.
Some of this recent work has been facilitated by the availability of new tools to probe the surface composition. Our group in particular has been applying Low Energy Ion Scattering (LEIS) spectroscopy, which is uniquely capable of determining the elemental composition of the single outer atomic layer of a material (i.e. the very same atomic surface that interacts with oxygen in the gas phase).
In this contribution we will use the commonly used perovksite La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF) to illustrate how LEIS and SIMS can contribute to our understanding of the relevant surface composition, complementing the existing understanding of the bulk properties of this commonly used electrode material. Starting from studies of surface segregation and restructuring in dense ceramic pellets after heat treatments similar to sintering conditions, we will then show how compositional changes can also occur at targeted device operating temperatures (around 500 ºC). Finally, we will show how laterally resolved LEIS analysis can be applied to understand compositional changes and interdiffusion occurring in the very outer atomic surfaces of LSCF microelectrode – YSZ electrolyte electrochemical half cells.
Theoretical Study of Inorganic Carbonaceous Species Reaction with the Surfaces of BaTiO3(001)
Authors: Rivera Rocabado David Samuel , Ishimoto Takayoshi , Quang-Tuyen Tran , Shiratori Yusuke , Koyama Michihisa 
Published: February 2020

Due to the variety of component elements and their high chemical stability at elevated temperatures, various perovskite oxide materials have been used to replace catalyst containing precious metals as oxidation catalysts or oxygen-activated catalysts (1). Additionally, because of their oxygen mobility through the material the C accumulation is not promoted. Such is the case of the resistance towards C deposition of Ni/BaTiO3-Al2O3 when employed as catalyst for low temperature dry reforming of CH4 (2). During the CH4 reforming, the C deposition is caused mainly due the CH4 decomposition or the CO disproportionation reaction that will lead to the formation of CO2 and C. On the other hand, one of the drawbacks of some perovskite materials such as BaTiO3 is that in the presence of CO2 the formation of a localized stable carbonate phase on the surface is possible (3). This carbonate phase will affect not only the catalytic activity of the material, but also may influence in its electronic properties. In this study the density functional theory (DFT) will be employed to analyze from a theoretical point of view the interaction of CO2 and the CO disproportionation reaction on the surfaces of BaTiO3(001). Our first approach with the BaO-terminated surface revealed that the CO molecule chemisorbs on the surface O atom. Additionally, if another CO molecule from the gas phase will interact with the already adsorbed CO molecule (Eley-Rideal reaction mechanism), the formation of trioxydehydroethene showed high spontaneity and the least stable but still probable to occur is the formation of CO2 and C that chemisorbs on top of an O atom (disproportionation reaction). Moreover, for the CO2 reaction with the BaO-terminated surface, the formation of CO3 anion showed to be quite stable. Furthermore, the CO2 reaction and CO disproportionation reaction will be also analyzed for the TiO2-terminated surface.

References

J. T. S. Irvine, in Perovskite Oxide for Solid Oxide Fuel Cells, T. Ishihara, Ed., p. 167, Springer, Fukuoka (2008).

X. Li, Q. Hu, Y. Yang, Y. Wang, and F. He, Appl. Catal. A, 413– 414, 163, (2012).

M. Wegman, L. Watson, A. Hendry, J. Am. Ceram. Soc., 87, 371 (2004).
Simulation and Prediction of 3-D Microstructural Evolution and Long Term Performance of Ni-YSZ Anode
Authors: Wang Xin , Atkinson Alan 
Published: February 2020

The electrochemical performance of SOFCs degrades over the operation time due to a number of factors. The electrochemical activity of the anode is one of these changing parameters due to microstructure coarsening. The change in microstructure of a Ni cermet anode is mainly due to the mobile Ni phase at high temperatures and can be accelerated by the presence of water vapour. The reduced triple phase boundary (TPB) density caused by coarsening leads to degradation of electrochemical performance of the anode. In order to manufacture SOFCs with long- lasting high performance and predict their useful lifetime, it is necessary to understand and predict the microstructural evolution of the anode under different operation conditions. In this contribution, we will demonstrate that the evolution of a 3D real microstructure of a Ni-YSZ anode can be simulated and predicted using our newly developed cellular automaton approach. For this simulation, the YSZ is assumed to be immobile while the mobility of Ni is by the route of evaporation-condensation. In the model the surface energy of Ni and the YSZ/Ni interface energy are simulated based on a new concept of material structural imbalance. The 3D microstructures of anodes subjected to different aging conditions are reconstructed experimentally using focus ion beam (FIB) slice and view. It is shown that the simulation results fit the experimental results very well. Using these short time experimental observations as a calibration of the model, we demonstrate that it is feasible to predict the long time microstructure evolution of the Ni-YSZ anode and hence its long term performance and lifetime.
Density Functional Theory Study of Dopant Effect on Sintering in the Anode of Solid Oxide Fuel Cell
Authors: Xu Jingxiang , Higuchi Yuji , Ozawa Nobuki , Kubo Momoji 
Published: February 2020

Sintering of Ni nanoparticles in a Ni/YSZ porous anode of a solid oxide fuel cell (SOFC) during the long-term operation take places easily due to the high operation temperature, which leads to the degradation of the Ni/YSZ porous electrode. In previous studies, we developed a multi-nanoparticle modeling methodology that can consider the effects of the properties of the porous structure such as porosity and YSZ nanoparticle framework, etc., for investigating the sintering process in the porous structure and revealed that the porous structure plays a critical role in suppression of the sintering [1,2]. Moreover, the porous structure is determined by the framework consisting of many nanoparticles. Thus, the design of the framework structure that can effectively prevent the sintering during the operation is demanded. For this purpose, the investigation of the YSZ nanoparticle size effect on the framework structure and its effect on the sintering is needed, because the framework structure is determined by the nanoparticle size, nanoparticle ratio and so on. However, the mechanism of different sintering behavior by changing the size of YSZ nanoparticle has not been revealed. In this study, we investigated the effect of YSZ nanoparticle size on the sintering of Ni nanoparticles in the Ni/YSZ porous structure by using our multi-nanoparticle sintering simulation based on the large-scale molecular dynamics simulation method. Our results show that Ni nanoparticles make contact with each other and the sintering proceeds by the growth of the contact area between the Ni nanoparticles. Then, we quantified the degree of sintering and found that the degree of sintering in the Ni/YSZ model with the large YSZ nanoparticles compared to Ni nanoparticles is larger than that with the small YSZ nanoparticles compared to Ni nanoparticles. In the Ni/YSZ model with the large YSZ nanoparticles compared to Ni nanoparticles, the framework of large YSZ nanoparticles generates the large pore. The Ni nanoparticles are easy to move in the framework structure, and the sintering of Ni nanoparticles takes place easily. On the other hand, the framework of small YSZ nanoparticles generates the small pore in the Ni/YSZ model with the small YSZ nanoparticles compared to Ni nanoparticles. The framework of small YSZ nanoparticles restrains the movement of the Ni nanoparticles. Thus, the sintering of Ni nanoparticles is inhibited in the Ni/YSZ model with the small YSZ nanoparticles compared to Ni nanoparticles.
[1] J. Xu et al., J. Phys. Chem. C 117 (2013) 9663.
[2] J. Xu et al., ECS Trans. 57, (2013) 2459.
Permeability of Gases in the Anode of an Anode Supported SOFC
Authors: Geagea Maya , Genov Ivaylo , Stoynov Zdravko , Vladikova Daria , Chesnaud Anthony , Thorel Alain 
Published: February 2020

In the high current density regime, the performance of SOFCs is limited by concentration overpotentials, which are particularly significant at the anode side where a competition occurs between incoming hydrogen and outgoing water. In standard SOFCs where the anode is made of YSZ and Ni, this becomes crucial when the demand for reactants exceeds the capacity of the porous cermet anode to supply them by gas diffusion mechanisms. A delicate compromise should be found between maintaining a high level of activation in the anode, i.e. high density of triple phase boundaries (TPB), favored by a distribution of small interconnected pores with high tortuosity and small grains size, and high gas permeability, favored by a distribution of large interconnected pores with low tortuosity, while the percolation of both electronic and anionic conductivity phases is maintained.
The present work aims at determining experimentally anodes gas permeability as a function of the experimentally determined percolation, tortuosity and volume fraction of the pores, assuming that the diffusion of gases is described by the Darcy Law. Anodes with varying porosity ensured by different quantities of the pore former were obtained by cold pressing and sintering. SEM image analysis, mercury intrusion porosimetry and permeability measurements for different gases were performed. The obtained results show that permeability increases with the volume fraction of the pore former. However, non-linearity as a function of the gases molecular weight is observed and discussed as a function of the mean free path and thus of possible mixed Darcy and Knudsen diffusion.
3D Printing of Functional Layers for Solid Oxide Fuel Cells and Electrolysers
Authors: Farandos Nick , Kleiminger Lisa , Hankin Anna , Ong Chin Kin , Kelsall Geoff H. 
Published: February 2020

Energy conversion efficiencies of solid oxide fuel cells (SOFCs) and electrolysers (SOEs) can be increased, principally by increasing the density of triple phase boundaries (electrode | electrolyte | reactant gas in pores) where reactions occur. SOFCs and SOEs with infiltrated-scaffold composite electrode structures have been shown to have greater densities of triple phase boundaries (TPBs), and enhanced control of particle size and porosity compared with structures derived from powder mixing [
1
]. However, methods that fabricate reproducible and explicitly tailored scaffolds with micrometre length scales have yet to be reported. Hence, we are developing 3D inkjet printing, using a Ceradrop X-Series inkjet printer with three multi-nozzle print heads, to fabricate reproducible, structured ceramic frameworks with ca. 5 µm resolution, prior to sintering. Ultimately, this should enable fabrication of percolated (porous) cathode | (non-porous) electrolyte | (porous) anode structures much more reproducibly and with greater definition than hitherto, to achieve increased energy conversion performances. The reproducible geometries will also enable more facile comparison of experimental performance and model predictions [2].
One prerequisite is the development of stable dispersions (‘inks’) of sub-micrometre sized metal oxide particles (i.e. (ZrO2)0.92(Y2O3)0.08, NiO, La1-xSrxMnO3-δ) in liquid phases with suitable solids fractions and physical properties, for which results will be presented (Fig.1a). These inks have been used to print the functional layers of SOFCs/SOEs (Fig.1b). However, geometries of electrode | electrolyte structures are subject to limitations imposed by the requirement to minimise the spatial distributions of potential and current densities. Hence, results will also be presented for predictions (Fig.2) of those parameters, modelled using finite element software, and preliminary current density-potential difference data for a printed SOE.
Firstly, yttria-stabilized zirconia (YSZ) particles were deposited onto a planar YSZ | NiO substrate, as pre-cursors to a thin (ca. 10 µm), gas-tight electrolyte, formed by heating the green structure to ca. 500°C to burn out organics used to stabilise ink particles against aggregation, followed by sintering YSZ at ca. 1400°C. Subsequently, YSZ and NiO nanoparticles were co-printed with an organic polymer to fabricate porous electrode structures on non-porous YSZ electrolyte layers.

Reference

M. Kishimoto, M. Lomberg, E. Ruiz-Trejo, N.P. Brandon, Enhanced triple-phase boundary density in infiltrated electrodes for solid oxide fuel cells demonstrated by high-resolution tomography, J. Power Sources, 266 (2014) 291-5.

U. Doraswami, P. Shearing, N. Droushiotis, K. Li, N.P. Brandon and G.H. Kelsall, Modelling the Effects of Measured Anode Triple-Phase Boundary Densities on the Performance of Hollow Fiber SOFCs, Solid State Ionics, 192 (2011) 494–500.

Figure 1
Development of Electrochemical Methanation Reactor with Co-Electrolysis of Humidified CO2
Authors: Yamaguchi Toshiaki , Shimada Hiroyuki , Honda U , Kishimoto Haruo , Ishiyama Tomohiro , Fujishiro Yoshinobu 
Published: February 2020

Solid oxide fuel cells (SOFCs) have received a great deal of attention recently, due to in part to their high energy conversion efficiency and environmental compatibility. Recently, an electrochemical cell with the same components as SOFCs has also been used as a solid oxide electrolysis cell (SOEC) for Power-to-Gas process. The use of alternative high performance electrolytes and electrodes materials means that the input power for electrolysis can be reduced. Co-electrolysis of CO2 and H2O with SOEC is considered to be one of the effective technologies to convert CO2 and H2O into CO and H2 gases [1]. Typical operation temperature of SOEC above 600ºC prevents further methanation reaction of CO and H2, while CO and H2 gases (syngas) are useful raw material for CH4 at lower reaction temperatures around 400ºC. Very recently, various researchers reported the excellent electrochemical performances and durability of heat-cycles for SOEC designs. Most of the cells are supported by a porous fuel-electrode tube. Therefore the tubular fuel-electrode support works as a current collector and gas diffusion layer as well as support medium of SOEC. Thus, the aim of this study is to realize the electrochemical reactor development with a reliable electrolyte layer on the excellent gas permeation, conductivity and mechanical strength for direct methanation process using co-electrolysis of CO2 and H2O at lower cell operation temperatures. In this presentation, we will report SOEC reactor fabrication technologies and the methanation properties.
This research is partially supported by CREST program of the Japan Science and Technology Agency (JST).
Ref 1. Energy and Environmental Science, 7 (2014) 4018-4022