bluuebunny/crossref_metadata_2025 huggingface dataset:
(Research Award of the Electrodeposition Division) Mathematical Modeling in Electrodeposition Studies
Authors: West Alan
Published: February 2020

Mathematical modeling has a long history in electrodeposition. The modeling may range from current distribution simulations for the design of electrochemical cells to molecular modeling for the design of next-generation additives. In other instances, modeling is used for data analysis, for troubleshooting, and for more efficient design of experiment. In some cases, models create value by providing a framework to communicate in interdisciplinary or industrial settings, as a means of protecting intellectual property or as means of explaining to the uninitiated the role of plating-bath constituents.

While models of the impact of transport phenomena on current distribution, may be quite straightforward, models involving reaction mechanisms can be highly controversial. Because of the inherent complexity of electrodeposition processes, modeling efforts are often tightly coupled to experiments, and it is rare that a model can explain all or even most experimental observations. Crafting a model requires a deep understanding of which experimental observations are most relevant to the business or technological goals.

We discuss some of our past experience in modeling electrodeposition systems. We briefly discuss work and practical uses of modeling additives in Cu electrodeposition, a process in which a tremendous understanding is available due to its commercial importance. We then discuss multi-scale modeling of electrochemical nucleation and its impact on current distributions on resistive substrates. As a final example, we discuss the role of relatively primitive modeling in understanding the co-deposition of nanoparticles and microparticles with nickel.
On-Wafer Microwave Devices based on Magnetic Materials
Authors: Celinski Zbigniew , Camley Robert , Harward Ian
Published: February 2020

We present a review of theoretical and experimental results for tunable microwave band-stop filters, band-pass filters, phase shifters, and a signal to noise enhancer, all based on a microstrip geometry and using a variety of magnetic thin films and layered structures. These devices are compatible in size and growth process with on-chip high-frequency electronics. For devices based on metallic ferromagnetic films of Fe and Permalloy, the operational frequency ranges from 5 to 35 GHz for external fields below 5 kOe. For the band-stop filters, we observed power attenuation up to ∼100 dB/cm, and an insertion loss on the order of ∼2–3 dB, for both Permalloy and Fe-based structures. We also will discuss the use of thin films of hexagonal ferrites, and liquid crystals/magnetic nano-rods colloids, and show these materials can be used to make on-wafer microwave devices. The devices based on hexagonal ferrite operate in the frequency range 35-70 GHz while devices based on liquid crystal/magnetic nano-rods colloids operate in the frequency range 5 - 110 GHz. We will also review the properties of hexagonal ferrites doped Al and grown on Si substrates in details.
Photocatalysis of TiO2 – Supported Graphene and Graphene Oxide Towards Phenol Degradation
Authors: Al-Kandari Halema Ali , Abdullah Aboubakr Moustafa , Al-Kandari Shekhah Ali , Mohamed Ahmed meslam
Published: February 2020

Graphene oxide (GO) was prepared using modified Hummer`s method starting from graphite. GO was impregnated on (i) commercial P25 TiO2 (Ti) and (ii) mesoporous TiO2 (mTi). The latter has higher surface area than the former one. After that, GOTi was reduced using (a) hydrogen gas at different temperatures or (b) hydrazine hydrate in microwave using a cyclic technique. Characterization of all used materials was carried out using bulk and surface techniques e.g. XPS, XRD, Raman Spectroscopy, FTIR, SEM, UV-Vis diffuse reflectance, BET, and cyclic voltammetry. The photocatalysis behavior of the synthesized GOTi, GOmTi, RGOTi and RGOTi were tested towards the phenol degradation and compared against the standard commercial P25 TiO2 in presence and absence of H2O2 which was either (i) added to the reaction mixture or (ii) generated locally within the reactor .The study revealed that the TiO2 – supported RGO and GO are showing much higher electrocatalytic performance above the P25 TiO2. Table 1 shows the phenol degradation (60 ppm) after 6 h in presence of different volume of H2O2 over Ti, 0.2-GoTi and 0.1-GGO.
Production of Hydrogen Peroxide By Oxygen Reduction in a FM01-LC Reactor for Electro-Fenton Process. Experimental Characterization and Numerical Simulation
Authors: Pérez Tzayam , Nava José Luis
Published: February 2020

The electro-Fenton process is based on the continuous in situ electrogeneration of H2O2, which with the addition of iron catalysts produce a powerful oxidant ˙OH typically employed to incinerate persistent organic pollutants [1,2]. In this communication we studied the cathodic reduction of oxygen to produce hydrogen peroxide on tridimensional graphite felt and reticulated vitreous carbon used as cathodes under acidic conditions pH=3. The filter-press FM01-LC cell was used as a test reactor. Polarization curves in both carbonaceous electrodes revealed that hydrogen peroxide formation occurs between -0.385 and -0.585 V vs. SHE. The influence of current density and flow rate on the hydrogen peroxide formation in the FM01-LC cell was experimentally characterized. A 3D dispersion model was developed using CFD simulations employing Brinkman equations in porous mediawhich were included in the mass transport and electrode potential balance. The numerical simulation of hydrogen peroxide production in terms of current density and flow rate are in good agreement with the experimentally obtained in both electrodes.

[1] L. Zhou, Z. Hu, Ch. Zhang, Z. Bi, T. Jin, M. Zhou. Sep. Purf. Technol. 111 (2013) 131.

[2] B. R. Garza-Camposa, J. L. Guzmán-Mara, L. H. Reyesa, E. Brillas, A. Hernández-Ramíreza, E. J. Ruiz-Ruiz. Chemosphere 97 (2014) 26.
Degradation of Indigo Carmine and Reactive Black 5 Dyes with Sb2O5-Doped Ti/RuO2-ZrO2 DSA in a Parallel-Plate Flow Reactor Via Active Chlorine
Authors: Rodríguez Francisca Alicia , Rivero Eligio Pastor , González I.
Published: February 2020

Wastewater from the textile industry is highly colored and of a complex and variable nature. The substantial amount of dyestuffs used in the dyeing stage of textile manufacturing processes represents an increasing environmental danger due to their refractory nature [1]. The treatment of textile wastewater by conventional methods such as biological and chemical processes or their combination are in common practice but have several drawbacks, e. g. inefficient color removal and/or the formation of toxic by-products [2]. On the other hand, electrochemical oxidation is a very promissory process for refractory pollutants degradation since no chemical reagents are needed and no secondary wastes are formed.

In the present study, electrochemical degradation experiments were conducted to degrade a textile dyes namely indigo carmine (IC) and reactive black 5 (RB). A FM01-LC reactor was used to investigate the effect of various operating parameters using a dimensionally stable anode (DSA, Sb2O5-doped Ti/RuO2-ZrO2). The oxidation of IC and RB takes place in the bulk solution with electrolytically generated active chlorine (chlorine, hypochlorite ion and hypochlorous acid). Figure 1 shows the normalized color decay. For the indigo carmine decolorization occurs in 80 min, whereas for the reactive black it takes 2 h. The difference in the time of decolorization is due to the structure of each dye the structure of reactive black 5 is larger than that of indigo carmine.

[1] Balcioglu I.A., Arslan I. and Sacan T. Homogenous and heterogenous advances oxidation of two commercial reactive dyes, Environment technology, 22 (2001), pp. 813-822.

[2] Rajkumar D., Joo Song B. and Guk Kim J., Electrochemical degradation of Reactive Blue 19 in chloride medium for the treatment of textile dyeing wastewater with identification of intermediate compounds, Dyes and Pigments, 72 (2007), pp. 1-7.
Electrochemical Oxidation of 4-Chlorophenol over a Lamellar Double Znal Hydroxides-Modified Carbon Paste Electrode
Authors: Hernandez-Fuerte Luis Daniel , Palomar-Pardavé Manuel , Licona-Sánchez Teresa de Jesús , Romero-Romo Mario A. , Sánchez-Valente Jaime
Published: February 2020

A study is presented on the electrochemical oxidation of 4 chlorophenol (4cp), dissolved in water, using a bare carbon paste electrode, EPC, and another that was modified with lamellar double ZnAl hydroxides (EPC/ZnAl-LDH). The electro-oxidation was effected within the 3-11 pH interval. It was found through cyclic voltammetry that this process was irreversible, namely, there were no reduction peaks, and that depending on the nature of the electrode, the rate limiting steps were: adsorption (EPC) and diffusion (EPC/ZnAl-LDH). The energy required and the oxidation reaction rate depended on the pH and on the nature of the electrode, such that the greater rates were obtained when the EPC/ZnAl-LDH electrode and acid pHs were used.
Performance of Two Reactors Used to Remove Silica from Water with Electrogenerated Al(OH)3
Authors: Gelover Silvia , Pérez-Castrejón Sara , Montes Agustín , Villegas Iván , Martín Alejandra
Published: February 2020

Two reactors were tested to generate Al3+, that quickly form Al(OH)3 used to remove dissolved silica. Reactor (A) has parallel plates with a vertical zig-zag hydraulic path; this configuration has the disadvantage of important load lost due to the opposition between a going down water flux and the electrochemically generated gas bubbles naturally moving up in some regions. Reactor (B) consisted on an alternating arrangement of a reaction camera with only ascendant flow of water, followed by a chamber designed for water drop. The reaction zone, where bubbles generate is the same where the water moves up. Reactor (B) saves energy and had a better performance for equivalent conditions when compared with reactor (A) to remove silica.
Simulation of Current Distribution Under Turbulent Flow Conditions in a Laboratory Filter-Press Flow Cell
Authors: Nava José Luis , Pérez Tzayam , Ponce de León Carlos , Walsh Frank C
Published: February 2020

A theoretical analysis of primary, secondary and tertiary current distributions along a planar nickel electrode in a laboratory filter-press flow cell has been carried out using the reduction of Fe(CN)6
3
− ions in a sodium carbonate electrolyte as a model reaction system. The primary current distribution decreased at the inlet and outlet of the cell and became uniform away from the entrance and exit. The secondary current distribution predominated throughout the electrode; edge effects appearing only at the corners of the cell. The tertiary current distribution presented higher edge effects compared to those experienced under secondary current distribution due to jet flow at the inlet of the cell. The limiting current density incorporated numerically calculated local flow velocities under turbulent flow which were simulated by solving the Reynolds averaged Navier-Stokes (RANS) equation, expressed in terms of turbulent viscosity and a standard turbulence model.
Physics-Based CFD Simulation of Lithium-Ion Battery Under a Real Driving Cycle
Authors: Li Genong , Li Shaoping
Published: February 2020

Lithium-ion battery has been widely used in electric appliances due to its high energy density. It also has been used in hybrid electric vehicles (HEVs) and electric vehicles (EVs). Battery's performance, life and safety are of great engineering importance. Using the simulation tool, battery's electric performance and thermal behavior can be computed to provide useful information in battery's design and optimization.

The physics-based electrochemical model, Newman's Pseudo-2D (P2D) porous electrode model, has been widely accepted in the study of lithium-ion batteries. However, the model is built on the electrode scale. There are two challenges to apply such models in the electrochemical-thermal coupled battery simulation. The first one is how to use such electrode-scale models in the large scale simulation (battery dimension scale). The other one is how to make the physics-based model cost-efficient in a computational fluid dynamics (CFD) simulation. In this work, the multi-scale multi-dimensional approach (MSMD) [1] is used to address the first technical issue, and a linear approximation method for source terms [2] is used to address the second issue. As a result, Newman's P2D model can be used to simulate a lithium-ion battery's behavior under a real driving cycle in a three dimensional CFD simulation. In this work, a single battery cell under the FUDS driving cycle is simulated, and spatial distributions and time histories of many key variables related to the thermal and electrical behavior are presented.

References

1. G-H Kim et al, ``Multi-Domain Modeling of Lithium-Ion Batteries Encompassing Multi-Physics in Varied Length Scales," J. of Electrochem. Soc. 158 (8) A955-A969, 2011.

2. M. Guo and R.E. White, ``A Distributed Thermal Model for a Li-ion Electrode Plate Pair," J. of Power Resources, 221, pp. 334-344, 2013.
High Energy Non-Aqueous Al-S Battery
Authors: Cohn Gil , Archer Lynden A.
Published: February 2020

Advanced high energy storage systems, beyond Li-ion technology, are highly desired to meet the demands of high performance electronic devices and future electric vehicles. Aluminum is the third most abundant element and the most abundant metal in the earth’s crust. A rechargeable battery that utilizes an aluminum-based redox couple, which involves three electron transfers during electrochemical charge/discharge reactions, is desired and attractive for research. The low cost, suitable redox potential (E0 (Al3+/Al) =-1.676 Vs. NHE), and high charge density are all factors that have fueled this interest over the years. Sulfur has likewise received great attention as a cathode for Li-S and Na-S batteries because of its high charge-storage capacity, high natural abundance, low cost and environmental friendliness.

In our study we present a new class of high energy system, a non-aqueous aluminum – sulfur battery. This battery is based on the coupling of Al metal anode and sulfur-carbon blend as the cathodic material. The system is employing electrolyte blend of AlCl3 and EMI∙Cl ionic liquid, where its composition controls its Lewis acidity. Our preliminary results show that the Al-S cell exhibits discharge voltage of around 1.2V, and a specific energy greater than 1700 Wh/kg, which exceeds most of today’s state-of-the-art batteries. Battery operation mechanism, product characteristics and limiting factors are studied using spectroscopic and electrochemical tool. This type of battery would be cheaper compare to current Li-ion and Li-S batteries, would be less prone to safety problems, and may lead to a major advance in the search for better batteries.
Oxygen Reduction and Evolution Examined Using Quartz Crystal Microbalance and Electrochemical Methods in Non-Aqueous Li-Ion Electrolytes
Authors: Lindberg Jonas , Lindbergh Göran , Behm Mårten
Published: February 2020

The Lithium-Oxygen battery is one of the most promising battery technologies being researched, it is also one of the more challenging ones due to the various problems associated with the battery. One of these problems is the poor understanding of the reaction occurring during oxygen reduction and evolution. It is known that the intermediates of the reaction are highly reactive and take part in unwanted side reactions. It is also known that the oxygen reduction products are poorly soluble in the electrolyte.

This study sets out to further examine these effects. Qualitatively these aspects are somewhat known but quantitatively the answer is less straight forward. By combining a Quartz Crystal Microbalance with electrochemical techniques the mass, current and voltage can be measured simultaneously to help shed further light on the species solubility and occurrence of side reactions. Obtaining this information about the chemical nature of the species formed will serve as a well needed compliment to the more frequently used surface characterization methods used when trying to determine the reactions occurring at the oxygen electrode.
Charging-Discharging Phenomena on P2-Na2/3Co2/3Mn1/3O2 Observed by X-ray Absorption Spectroscopy
Authors: Hwang Bing-Joe , Cheng Ju-Hsiang , Pan Chun-Jern , Lee Jyh-Fu , Chen Jing-Ming , Guignard Marie , Delmas Claude , Carlier Dany
Published: February 2020

Charging-discharging phenomena of P2-Na2/3Co2/3Mn1/3O2 prepared by a co-precipitation method were investigated by ex situ and in situ X-ray absorption spectroscopy [1, 2]. The electronic transitions at the O K-edge and the charge compensation mechanism, during the sodium intercalation process, were elucidated by combining Density Function Theory (DFT) calculations and X-ray absorption spectroscopy (XAS) data. The pre-edge of the oxygen K-edge moves to higher energy while the integrated intensity dramatically decreases, indicating that the population of holes in O 2p states is reduced with increasing numbers of sodium ions. From the K-edge and L-edge observations, the oxidation states of pristine Co and Mn were determined to be +III and +IV, respectively. The absorption energy shifts to lower positions during the discharging process for both the Co and Mn edges, suggesting that the redox pairs, i.e. Co3+/Co2+ and Mn4+/Mn3+, are both involved in the reaction.

[1] J.-H. Cheng, C.-J. Pan, J.-F. Lee, J.-M. Chen, M. Guignard, C. Delmas, D. Carlier, and B.-J. Hwang, Chem. Mater., 26 (2014
) 1219–1225.

[2] D. Carlier, J. H. Cheng, R. Berthelot, M. Guignard, M. Yoncheva, R. Stoyanova, B. J. Hwang and C. Delmas, Dalton Trans.,40 (
2011), 9306.
Insights into the Solvation Structure of Multi-Valent Ions for Multivalent Battery Applications
Authors: Persson Kristin Aslaug , Rajput Nav Nidhi , Qu Xiaohui
Published: February 2020

Multivalent batteries, such as those based on divalent Mg2+ ions, have the potential to provide significant gains in energy storage density, at lower cost and with enhanced safety compared to Li-ion devices. However, the development of Mg-ion battery technologies require innovation not only in the design of novel electrode materials but also in electrolytes that facilitates transport and charge transfer of the doubly-charged Mg ion.Thus, a fundamental understanding of the intrinsic interactions in these novel electrolytes is imperative for design of liquids systems with improved electrochemical stability as well as charge transfer properties. Using the high-throughput capability of the Materials Project (www.materialsproject.org), we are able to rapidly screen electrolyte systems for suitable properties. In this work, we present molecular dynamics simulations coupled with first-principles calculations for a range of Mg salts in common solvents, benchmarked against available experimental information on radial distribution function and diffusion coefficient. The results are also compared to similar studies available for Li-ion systems. In the comparison, it is obvious that the inter-molecular solvation structure for multivalent ions is very different from the one we are used to in well-performing monovalent ion (e.g. Li and Na) electrolytes and hence points to a design metric for future electrolyte work.
Ionic Conductivity of Eusz Thin Films
Authors: Paredes Israel , Ramírez Efrén Bernardo , Alonso Juan Carlos
Published: February 2020

In this work, we deposited Eu doped ZrO2 thin films by ultrasonic spray pyrolysis method, using zirconium acetilacetonate and europium acetilacetonate as precursors and atmospheric air as carrier gas in function of dopant molarities. The structure, morphology, chemical composition and dielectric properties were characterized by X-ray diffraction (XRD), Atomic force microscopy (AFM), X-ray Photoelectron spectroscopy (XPS), and Impedance spectroscopy (IS). The XRD technique showed that all the peaks correspond to a cubic structure.
Low-Polarization Composite Cathodes Based on Nanocatalysts and Oxygen Ion Conductor for Solid Oxide Fuel Cell (SOFC) Applications
Authors: Fung Kuan-Zong , Tsai Shu-Yi , Lai Min-Hon , Ni Chung-Ta
Published: February 2020

SOFCs have shown apparent advantages over other types of fuel cells, including relatively less expensive materials, tolerance to impurities containing in the fuel, long life and high efficiency. However, low-temperature operation also slows down the electrode kinetics and induces large interfacial polarization resistances. Moreover, the cathode polarization is the main obstacle to achieving high power densities at temperatures lower than 700°C.

An ideal cathode may be made of highly conducting ionic and electronic conductor with desired nanostructure. Thus, the objective of this work is to develop high performance composite cathode consisting of an oxygen ion conductor and metallic and/or nonmetallic catalysts with nanostrcutrures. A one-step synthesis method is developed to form colloidal Ag nanocatalysts by reducing silver ions with sodium borohydride (NaBH4) using adequate capping and stabilizing agents. As a result, a composite cathode made of Bi2O3-based ionic conductor and well-dispersed Ag nanocatalysts is obtained at the temperature as high as 600 °C. The commonly used composite cathode, LSM-YSZ, is also investigated for comparison. The crystal structure, microstructure, and electrical/electrochemical properties of the developed composite cathode are investigated using XRD, FESEM, TEM, and impedance spectroscopy.
A New Family of Proton-Conducting Conducting Materials in Layered Oxides
Authors: Tao Shanwen , Lan Rong
Published: February 2020

To identify a good ionic conducting material for use as electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs) remains a big challenge. In this report, we demonstrate that good proton conductor can be obtained in transition element rich intercalation materials such as LixAl0.5Co0.5O2. OCV of 1.0 ~ 1.1V was observed for a H2/air fuel cell at temperature 475 – 575 °C indicating it is nearly a pure ionic conductor under fuel cell operating conditions. A power density of 173 mW cm-2 has been achieved at 525 °C with a thick electrolyte (0.79 mm thick) when silver was used as both cathode and anode. The ionic conductivity of LiAl0.5Co0.5O2 was 0.1 S/cm at 500 °C, deduced from the series resistance of the H2/air fuel cell. This is the highest among known poly-crystalline proton-conducting materials. This study will provide a new approach to discover new proton conducting materials for use in IT-SOFCs. It is expected that an ideal proton-conducting oxide may be identified in layered oxides.

References:

[1] H. Iwahara, T. Esaka, H. Uchida, N. Maeda, Solid State Ionics 1981, 3-4, 359.

[2] T. Norby, Solid State Ionics 1999, 125, 1.

[3] K. D. Kreuer, Annual Review of Materials Research 2003, 33, 333.

[4] D. Pergolesi, E. Fabbri, A. D'Epifanio, E. Di Bartolomeo, A. Tebano, S. Sanna, S. Licoccia, G. Balestrino, E. Traversa, Nature Materials 2010, 9, 846.

[5] R. Lan and S.W. Tao, Advanced Energy Materials, 2014, DOI: 10.1002/aenm.201301683.
Electrode/Electrolyte Interphase Studies of Ceria Based Electrolytes for IT-SOFCs
Authors: Baqué Laura Cecilia , Padmasree Karinjilottu , Fuentes Antonio F. , Serquis Adriana , Soldati Analía
Published: February 2020

Solid oxide fuel cells (SOFCs) have emerged as an efficient and environmental friendly tecnology to convert directly hydrogen and fosil fuels into electric energy. Usually these devices use ytria based electrolytes, requiring operation temperatures around 1000ºC. These high temperatures challenge the long term stability and induce rapid degradation of the cell. Ceria based oxides are interesting alternatives because they present higher conductivities at lower operation temperatures. However, these materials require sinterization temperatures in the 1300-1600ºC range to achieve complete densification, which produces very large grain sizes and poor mechanical properties. The addition of transition metals oxides is effective in improving the densification and thus, lowering the sinterization temperatures. In this work we studied Ce0.8(Gd,Nd)0.2O2 with and without Co doping synthesized by a molten salt route [1], which allows obtaining smaller grain sizes at lower temperatures, improving microstructural properties. The synthesis methodology is fast, simple and cheap and combines a metathesis or displacement reaction and a low-temperature molten salt flux.

A (La,Sr)(Co,Fe)O3 nanostructured electrode with high electrochemical performance [2,3] was deposited by spin coating techniques on electrolyte pellets. The assemblies were studied by Electrochemical Impedance Spectroscopy, X-Ray Diffraction and Transmission and Scanning Electron Microscopy. The correlation between the electrochemical behavior within the 300-600ºC range, and the bulk and interfacial characteristics will be discussed.

[1] Mendoza-Mendoza E., Padmasree K., Montemayor S. and Fuentes A., J Mater Sci 47 (2012) 6076-6085.

[2] Baqué L, Caneiro A, Moreno MS, Serquis A., Electrochem Commun 10 (2008) 1905-1908.

[3] Soldati A., Baqué L., Troiani H., Cotaro C., Schreiber A., Caneiro A, Serquis A. Int J Hyd Energy 36 ( 2011) 9180-9188.
Ceria Based Composite Membranes for Oxygen Separation
Authors: Gurauskis Jonas , Ovtar Simona , Kaiser Andreas , Søgaard Martin , Hendriksen Peter Vang
Published: February 2020

Mixed ionic-electronic conducting membranes for oxygen gas separation are attracting a lot of interest due to their promising potential for the pure oxygen and the syngas production. Apart from the need for a sufficiently high oxygen permeation fluxes, the prolonged stability of these membranes under the large oxygen potential gradients at elevated temperatures is decisive for the future applications.

The gadolinium doped cerium oxide (CGO) based composite membranes are considered as promising candidates due to inherent stability of CGO phase. The CGO matrix is a main oxygen ion transporter; meanwhile the primary role of a secondary phase in this membrane is to compensate the low electronic conductivity of matrix at intended functioning conditions.

In this work thin film (15-20 μm) composite membranes based on CGO matrix and LSF electronic conducting phase were fabricated and evaluated. Composite thin film was deposited on tubular structural support made of porous MgO phase. Porous CGO layers (20 μm) were implemented as backbones for catalytic phase on both sides of a composite membrane (Fig. 1).

During initial trials, the catalytic phase free CGO/LSF composite membranes demonstrated oxygen fluxes close to 1 ml×min×cm-2 at 900 °C and the oxygen driving force of log pO2=-2.

Issues related to processing parameters and new results on performance of these asymmetric geometry CGO/LSF composite membranes will be presented.

Figure 1. Cross-section of asymmetric CGO-LSF composite membrane.
Improving Thermo-Electrochemical Cells Using Carbon Nanotubes
Authors: Cola Baratunde
Published: February 2020

Thermo-electrochemical cells (TECs) allow us to recover the heat wasted from many sources directly, although the efficiency of the process is currently low. TECs are electrochemical devices that produce a steady electric voltage and current under an applied temperature difference between the electrodes. In order to improve the efficiency of TECs, it’s important to search for electrolytes with high electrical conductivities and low thermal conductivities. To this goal, we used impedance spectroscopy to study the effect of carbon nanotubes in ionic liquids used in TECs. Our research indicates that the addition of carbon nanotubes can result in a 3- to 5-fold increase of the mixture’s electrical conductivity. We further tested the power of coin sized-TECs using these novel mixtures. The results show that the addition of 0.06 wt% of carbon nanotubes to imidazolium-based ionic liquids with a modified cobalt redox couple improves the electrical power up to 80%, while there is no detectable change in the thermal conductivity of the mixture at this concentration of carbon nanotubes.
Performance Comparison between Ni–SDC and Ni–YSZ Cermet Electrodes for Carbon Dioxide Electrolysis on Solid Oxide Electrolysis Cell
Authors: Singh Vandana , Muroyama Hiroki , Matsui Toshiaki , Eguchi Koichi
Published: February 2020

Solid oxide electrolysis cells (SOECs) have already proven their ability to electrolyze steam (H2O). Recently, the attention has been drawn towards the electrolysis of carbon dioxide (CO2). In this paper, the electrochemical reduction of CO2 over Ni–Ce0.8Sm0.2O1.9 (SDC) and Ni–8 mol% Y2O3–ZrO2(YSZ) electrodes was studied on SOEC device.

Cells used in this work consist of Ni–SDC or Ni–YSZ cermet electrodes, YSZ electrolyte, and (La0.8Sr0.2)0.97MnO3 (LSM) electrode. Electrochemical properties of SOEC were evaluated by impedance spectroscopy and current–voltage (I–V) curves with a supply of CO2/H2 and pure O2 gases to the cathode and anode sides, respectively, at 1000 oC.

The results of preliminary experiments indicated that in CO2/H2 mixture, CO2 reduction proceeds indirectly via kinetically fast reverse water-gas shift reaction (RWGSR, CO2 + H2 ⇌ CO + H2O). The impact of cathode material on CO2 reduction was studied as depicted in Fig. 1 (a) and (b), which shows I–V curves of single button cells employing Ni–SDC and Ni–YSZ electrodes, respectively. The cell with Ni–SDC electrode exhibited relatively high current density compared with Ni–YSZ electrode. The better performance of Ni–SDC electrode depends on the conductivity of doped ceria; it exhibits higher ionic conductivity than YSZ and shows electronic conductivity under a reducing atmosphere. These two factors are most likely extended the effective triple phase boundary (TPB) region and improved the electrochemical reactions at electrode/electrolyte interface.
Testing of Large Format Lower Temperature SOFCs and Stacks with Hydrocarbon Fuels
Authors: Blackburn Bryan M. , Yoon Hee Sung , Gore Colin M. , Wachsman Eric D.
Published: February 2020

Redox Power Systems and the University of Maryland Energy Research Center have been developing lower temperature solid oxide fuel cell (SOFC) stacks and systems for a variety of applications.

In this work, results will be presented from single cell and short stack testing using reformate mixtures consisting of CH4, H2, CO, CO2, and steam. Tests utilized large format (approximately 10 cm by 10 cm) cells based on GDC electrolytes with an active area of ~80 cm2. Current-voltage characteristics and impedance spectroscopy data were collected at various currents using electronic load and potentiostat/FRA equipment. Additionally, gas compositions in the fuel exhaust stream were determined using gas chromatography.

Initial results at 650 °C showed a single cell power of ~53 W running on hydrogen and ~51 W running on 100% reformate slip (~21% CH4). Long term test results using a constant applied load of 18 A for a 2 cell short stack showed no evidence of coking even when run on 50% CH4/50% H2O for ~50 hours and 97% CH4/3% H2O for ~150 hours. Additional long term test results will be presented along with a study on degradation.
Impact of Leakage Current on Performance of Solid Oxide Fuel Cell Stacks with Gadolinia-Doped Ceria Electrolytes
Authors: Wang Lei , Jackson Gregory S. , Blackburn Bryan M.
Published: February 2020

Gadolinia-doped ceria (GDC) has been studied as an electrolyte material for solid oxide fuel cells (SOFCs) at intermediate temperatures (500–650°C) due to its high oxide-ion conductivity and better compatibility with high-activity lanthanum strontium cobalt ferrite (LSCF) cathodes. Recent studies have shown high surface activity for fuel oxidation and suppression of carbon deposition in GDC-based SOFC anodes due to mixed ionic and electronic conductivity (MIEC) at the reducing environments1, 2. On the other hand, the MIEC behavior results in deleterious leakage (electronic) current, which reduces the open circuit voltage (OCV) and SOFC stack efficiency during operation3. The electronic current depends strongly on electrolyte thickness and external current load. In this study, a 3-D model has been developed in COMSOL which calculates the leakage current through GDC-based electrolytes and evaluates its impact on the cell OCV and overall performance of an GDC-based SOFC stack operating from 550 to 650°C.

The model incorporates both ionic and electronic current in the GDC electrolyte driving by the electrochemical gradient. The model employs irreversible electrodes and allows for a nonlinear potential distribution across the electrolyte to capture the distribution of oxygen defect concentrations following the work of Duncan et al3. In the current study, the model is used to analyze the relationship between leakage current and electrolyte thickness for a full stack cell wherein the conditions and effective oxygen partial pressure P
O2 can vary significantly particularly in the anode channels. Figure 1 plots average ionic, electronic, and total current density as a function of cell voltage for a cell with a 20 µm GDC electrolyte operating at 600°C. OCV deviation from theoretical value due to electrode/electrolyte interfaces overpotentials and Ohmic losses contributed by the ionic and electronic current. The effect of the leakage current on stack performance and efficiency provides a basis for understanding how fuel oxidation due to the leakage current impacts the relationship between stack current and fuel utilization. Results provide guidance for designing high-performance intermediate-temperature SOFCs with GDC electrolytes.

References

1. S. Baron, N. Brandon, A. Atkinson, B. Steele, and R. Rudkin, Journal of Power Sources, 126(1-2), pp. 58-66 (2004).

2. T. Nakamura, T. Kobayashi, K. Yashiro, A. Kaimai, T. Otake, K. Sato, J. Mizusaki, and T. Kawada, Journal of the Electrochemical Society, 155(6), pp. B563-B569 (2008).

3. K.L. Duncan, and E.D. Wachsman, Journal of the Electrochemical Society, 156(9), pp. B1030-B1038 (2009).
Electronic Structure Measurements of Heteroepitaxial Solid Oxide Fuel Cell Cathode Thin Films
Authors: Yu Yang , Ludwig Karl F , Pal Uday Bhanu , Gopalan Srikanth , Basu Soumendra Nath
Published: February 2020

Synchrotron based hard x-ray photoelectron spectroscopy (HAXPES) technique has been utilized to measure the oxidation states of the associated ions on the surface of strontium doped lanthanum cobalt iron oxide (LSCF), as a function of strontium dopant concentration and gas composition. LSCF is a widely used cathode material for solid oxide fuel cells (SOFCs), which are ideally suitable for environmentally benign electricity generation. However, LSCF suffers from long term stability issues by surface segregation phenomena under typical SOFC working conditions. Leveraging the capability of HAXPES to overcome surface contamination issues and obtaining information from tunable penetration depth, depth dependence information about changes in the electronic structure were obtained, which helps better understand the segregation phenomena. Surface chemistry of both as-deposited and post-annealed LSCF thin films with different Sr concentrations are discussed.
Development of Anode Materials for SOFCs Having Enhanced Durability by Employing Sintering Inhibitors
Authors: Lee Seung-Bok , Khan Muhammad Shirjeel , Wahyudi Wandi , Song Rak-Hyun , Lee Jong-Won , Lim Tak-Hyoung , Park Seok-Joo
Published: February 2020

Sintering of Ni in solid oxide fuel cell (SOFC) anodes (Ni-YSZ) is a major cause of anode degradation. To reduce this growth rate, several sintering inhibitors (SiC, SiN, Al2O3, AlN, CeO2 and GDC) were added into Ni-YSZ anode using powder methods. The modified anodes were screen printed on YSZ electrolyte to prepare symmetric half-cells and their performance was investigated by long term stability test at high temperature. X-ray diffraction (XRD) analysis showed that the most sintering inhibitors were chemically compatible with anode materials except Al2O3 and AlN. During the long term test, area specific resistance (ASR) was measured at 1000 ºC in 25vol% H2 and 75vol% N2 environment. Triple phase boundary (TPB) density was calculated by image analysis techniques before and after operation. A clear relation was found between ASR change rate determined from electrochemical measurements and TPB density change rate calculated from image analysis. Moreover, among the various sintering inhibitors, CeO2 and GDC exhibited the best performance by showing the lowest ASR and TPB density change rates after long term testing. ASR change rate is discussed in view of loss in TPB density during operation.
Incorporation of the Stefan-Maxwell Multicomponent Diffusion Model into a Pore Network Model of the PEMFC Electrode
Authors: Aghighi Mahmoudreza , Gostick Jeff T.
Published: February 2020

Polymer electrolyte membrane fuel cells are one of the best candidates to replace internal combustion engines. The key requirement for commercial success of PEMFCs is to demonstrate optimal performance at high current density. However, because of liquid water generation, the power density is reduced by mass transport limitations at the cathode. Accordingly, precise modeling of mass transfer inside the porous structure of fuel cell electrodes is crucial.

Ordinary diffusion is the most commonly considered diffusion model for PEMFC in the literature. In most of these studies, the gas transport is considered as a binary system of oxygen diffusing through nitrogen (and sometimes water vapor). However, realistic simulation of fuel cell operation requires simultaneous modeling of both oxygen and water vapor transport in a stagnant film of nitrogen. In multicomponent diffusion, the fluxes of all of the species are important to consider since they might affect the diffusive transport of the other species.

A pore network modeling has been developed using the Stefan-Maxwell approach, to simulate the diffusion of gases mixtures inside fuel cell electrodes. Pore network models (PNM) provide an alternative approach for the continuum modeling in porous media. Rather than using finite element models of transport in the pore space, PNMs use pore-to-pore nodal balances to model species transport. They also enable the structural properties of the porous material to be incorporated directly into the model, rather than through constitutive relationships.

The SM model is notoriously difficult to solve numerically for pore networks, but some simplifications and solution schemes have been proposed in the literature [1,2] based on decomposing Jacobian matrix of the equations, which are less computationally expensive. In this work, these methods have been evaluated to determine an appropriate solution algorithm for the pore network. These advantages come at the expense of rigorous transport phenomena calculations since some simplification to the SM model are made.

References

1. Wood, J., L. Gladden, and F. Keil, Chemical Engineering Science, 2002. 57(15): p. 3047-3059.

2. Rieckmann, C. and F.J. Keil, 1997. 36(8): p. 3275-3281.

Acknowledgements

This work was funded by AFCC and the NSERC CRD program.
Characteristics of Pd-Pt Nanoparticles with Core-Shell Structure on Polybenzimidazole-Wrapped Graphene for Fuel Cell Electrocatalyst
Authors: Kim Chaerin , Fujigaya Tsuyohiko , Nakashima Naotoshi
Published: February 2020

Introduction

Pt has received unremitting interest in the proton-exchange polymer electrolyte fuel cell (PEFC) technology as electrocatalysts for both the hydrogen oxidation and oxygen reduction reactions [1]. However high cost limits its application and the reduction of the amount of Pt in the catalyst is required (it was ca. 48.83 $ per gram at the beginning of 2014) [2].To reduce the usage of Pt, arranging Pt as shell on proper metal core is promising “core-shell approach”. This strategy is attractive and practical because only the outmost few layers of Pt atoms in a catalyst are actually needed in facilitating a reaction while most atoms in the bulk are more or less wasted [3, 4]. Among various metal, we chose Pd as a core metal due to the stability under strong acidic condition in PEFC [5]. Here, we attached Pd-Pt core-shell nanoparticles on Graphene which are ideal materials as conductive supporting due to the large surface area, remarkable electric conductivity and excellent electrochemical durability. This study, we utilize polybenzimidazole (PBI) as a polymeric anchor to load Pd-Pt core-shell nanoparticles on to the surface of Graphene.

Experiments

Graphene wrapped with PBI (Graphene/PBI) (5.0 mg) was added to a 60-vol% aqueous ethylene glycol (EG) solution (20 mL) and dispersed by sonication. Pd (OAc)2 (3.3 mg) dissolved in the methanol (5.0 mL) was added to the Graphene/PBI dispersion, and then the mixture was heated at room temperature for 3 h. H2PtCl6 •6 H2O (0.45 mg) dissolved in a 60 vol% aqueous EG solution (20 mL) was added to the Graphene/PBI/Pd dispersion and the mixture was stirring for room temperature for 24 h. The solid material was collected by filtration and washed with water and then dried under vacuum to obtain Graphene/PBI/Pd-Pt (Figure 1).

Results and Discussion

To inspect the structure of Pd-Pt core-shell nanoparticles, we observed scanning transmission electron microscopy (STEM). STEM operated at 200 kV are presented in Figure 2.

Figures 2a and 2b show the STEM image of a Graphene/PBI/Pd-Pt. Figures 2c and 2d show the EDS mapping of Pd (red) and Pt (blue). It is obvious that Pd is surrounded by Pt as indicated in overlay (Figure 2e). The results strongly indicate the successful formation of Pd-Pt core-shell structure on Graphene/PBI.

Conclusions

We fabricated Graphene/PBI/Pd-Pt core-shell composite. STEM results indicate that the Graphene /PBI/Pd-Pt core-shell catalyst exhibited the core-shell nanostructure.

References

N. Nakashima et. al,
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Invited: Alkaline Anion Exchange Membrane Fuel Cell
Authors: Yu Hongmei
Published: February 2020

Alkaline anion exchange membrane fuel cell (AEMFC) is expected as a promising candidate for getting rid of the dependence of nobel metals, it will shows advantage on polymer electrolyte and cheap electrocatalyst options. However, the AEMFC needs high anion conductive membrane material which should be stable under fuel cell operating condiction. Comparing with proton exchange membrane, anion conductive material is facing more chanllenges, i.e., low anion conductive rate, less stable in fuel cell conditions. The possiblity of composite anion exchange membranes were investigated in this work. Based on the in-house composite anion exchange membrane, membrane electrode assemblies were prepared. Measurements in a single cell, as well as in a stack, were impemented to evaluate the performance and the application possiblity in AEMFC.
Performance Variation of Flexible Polymer Electrolyte Fuel Cell with Ag Nanowire Current Collector under Torsion
Authors: Park Taehyun , Chang Ikwhang , Lee Jinhwan , Ko Seung Hwan , Cha Suk Won
Published: February 2020

The purpose of flexible and bendable fuel cell is to support future electronics, wearable electronics for example, which require more electrical energy than current portable electronics. As widely used lithium-ion battery technology is converging to its maximum ideal energy density, it is inevitable to find other solutions to cope with the increase of energy consumption of developing electronics. In addition, one of the most highlighted electronics in future is wearable electronic device. It has different characteristic that it requires flexibility and bendability. For this reason, flexible polymer electrolyte fuel cell (PEFC) was researched in our previous report [1]. Here, electrochemical performances of the cell were evaluated under bent position and decreasing tendency of the maximum power density was observed with increase of bending. However, the performances of flexible PEFC under various positions, torsion for example, should also be evaluated in order to investigate if it is possible to operate in fully bendable electronics such as wearable electronics.

This study shows the performance variation of flexible PEFC under torsion. Ag nanowires percolation network which can be stretched upto strain of 370% with less than 30 % increase of electrical resistance was adopted as material for current collector [2]. Polydimethylsiloxane (PDMS) was used to fabricate bendable fuel cell stack. Cross-sectional sizes of flow channels on flow-field plates for anode and cathode were 1 x 1 mm2 and 2 x 1 mm2, respectively. Degrees of torsion were 0, 5, 10, 15 and 20°. The results showed that maximum power density of flexible PEFC decreases as torsion increases. From the previous results [1], it is speculated that compressive stress perpendicular to membrane-electrode assembly (MEA) decreased with increase of torsion degree. In order to investigate causes of performance loss, electrochemical impedance spectra were measured. It showed that ohmic and faradaic resistances of the cell increased with increase of torsion. It corresponds with the previous results that ohmic and faradaic resistances increase when normal compressive stress to MEA decrease. However, it was found that decreased percentage of maximum performance of the cell was less than 35 %, meaning that flexible PEFC can be used for flexible electronic devices if overdesigned.

Acknowledgement

This work was supported by the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Education, Science and Technology, Korea (2011-0031569).

Reference

[1] I. Chang et al., Bendable polymer electrolyte fuel cell using highly flexible Ag nanowire percolation network current collectors, J. Mater. Chem. A, 2013, 1, 8541-8546.

[2] P. Lee et al., Highly Stretchable and Highly Conductive Metal Electrode by Very Long Metal Nanowire Percolation Network, Adv. Mater., 2012, 24, 3326-3332.
Potentiality of Hydrocarbon Membrane for Durability Improvement of Pt and PtCo Alloy Catalyst and Pt Loading Reduction
Authors: Izuhara Daisuke , Umeda Hiroaki , Ito Yumiko , Shintaku Yuta , Adachi Shinya
Published: February 2020

One of the major cost drivers in polymer electrolyte fuel cells (PEFCs), particularly for automotive application, is the use of platinum-based electrodes to facilitate electrochemical reactions such as hydrogen oxidation and oxygen reduction. Improving the durability of Pt and PtCo alloy catalyst shall reduce total active area and/or Pt loading per unit active area without any sacrifice in performance of fuel cell stacks, and it can also significantly be beneficial to the reduction of total Pt usage on fuel cell vehicles (FCVs). Catalyst durability during fuel cell operation remains a key challenge to developing the fuel cell system with acceptable overall cost in automotive applications.

Toray has been developing advanced hydrocarbon (HC) membranes to give a better total solution in terms of overall cost reduction of fuel cell systems, which includes i) the potentiality for durability improvement of Pt and PtCo alloy catalyst and Pt loading reduction due to less Pt particle dissolution, ii) no emission of super acids such as HF and perfluorosulfonic acids, iii) low gas crossover, and iv) environmental friendliness, in comparison with conventional PFSA membranes.

We will describe in the meeting that Toray HC membrane would potentially improve the durability of PtCo alloy catalyst owing to less Pt particle dissolution, and thereby reduce total active area and/or Pt loading per unit active area by 45% ((1-0.24V/0.43V)x100) vs Nafion HP as a reference in case judging at 1000 hours in the accelerated chemical and mechanical durability test. We hope Toray HC membranes could help to form a pathway toward FCV wide commercialization.

ACKNOWLEDGEMENT

This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.