bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corrosion of Copper in De-Aerated Water
Authors: Cleveland Christopher , Orazem Mark E. , Moghaddam Saeed 
Published: February 2020

Impedance spectroscopy is being used to study possible mechanisms for the observed corrosion of nanostructured copper wicks intended for use in heat pipes that provide advanced cooling for high-performance electronics. The heat transfer fluid is deionized and deaerated water.
The experimental techniques employed in this study include impedance spectroscopy and linear sweep voltametry. Experiments were performed in 17.6 MOhm cm water de-aerated by N2 until the oxygen concentration of the gas leaving the cell was measured to be < 2ppb by a Hach Orbisphere 3650 analyzer. Copper working electrodes were polished and degreased prior to experimentation. Impedance data were obtained potentiostatically using a Gamry Ref 3000 at perturbation amplitude of 10mV.

EIS Data & Model: The open-circuit impedance responses of 0.025 cm diameter gold, platinum and copper electrodes are presented in Figure 1. The high-frequency loop can be attributed to the dielectric response of water and has been omitted in Figure 1. All impedance data were scaled with respect to the ohmic resistance Re. This result shows that, while gold and platinum show blocking behavior, the slight curvature of the low-frequency data for the copper electrode indicates the presence of electrochemical reactions.
A model for the impedance response should include the parallel contributions of anodic and cathodic reactions. A maximum value for corrosion of 2.5 nm/day was found by extrapolation of the impedance data to low frequency by use of a measurement model.1 The corresponding diagram is presented in Figure 2.

Kinetic Model: In the absence of oxygen, the reactions were assumed to include dissolution of copper, hydrogen evolution, back deposition of copper ions, and oxidation of the hydrogen formed by the reduction of H+. A simulation was performed using kinetic expressions for these reactions coupled with diffusion of reaction products away from the electrode. Spherical diffusion was assumed.
As kinetic data in pure water could not be found, kinetic parameters were taken from experiments in buffered boric acid and sulphate solutions.2,3 The corrosion current was estimated to be 1. nm/day. While this corrosion rate is too small to have a practical consequence in usual applications, it is large enough to influence the structural integrity of nano-scaled structures.

Acknowledgement

This work was supported by DARPA contract number W31P4Q-12-1-0005.

References

P. Agarwal, M. E. Orazem, and L. H. Garcia-Rubio, J.Electrochem. Soc., 139 (1992) 1917-1927.

Z. Stankovic and M. Vukovic, Electrochem. Acta, 41 (1996), 2529-2535.

S. Shari-Asla and D. D. Macdonald, J. Electrochem. Soc.,
160 (2013), H382-H391.
Electrochemical Study on Anodic Dissolution Mechanisms of Copper and Copper-Alloys in Fresh Water
Authors: Itagaki Masayuki , Tabei Kozue , Shitanda Isao , Hoshi Yoshinao 
Published: February 2020

Analyses of dissolution mechanisms of copper and copper-alloys are important to obtain the fundamental knowledge concerning corrosion and etching. Various electrochemical measurements were performed to investigate the electrochemical properties of copper and copper-alloys with a channel double flow electrode (CFDE). CFDE is one of hydrodynamic technique whose principle is similar to a rotating ring disk electrode. The mass transfer in the electrolyte solution can be controlled by the solution flow in the channel. Therefore, the measurement with CFDE allows direct information concerning dissolution rate and the species by monitoring the emitted ions from the working electrode at detecting electrode. For example, the in-situ detections of cuprous and cupric ions were carried out with measuring of polarization curves of copper, brass and bronze. The polarization curve of brass showed two potential regions for different dissolution mechanisms and the dezincing was serious in less noble potential region.
An electrochemical impedance spectroscopy (EIS) was used in order to discuss the detailed dissolution mechanisms because the EIS enables us to discriminate the time constants of elementary steps in the dissolution process. In addition, the formation of porous structure of brass surface due to dezincing was investigated with the equivalent circuit involving transmission line model (TLM).
Chemistry Design for Suppressing Dendritic Growth during Metal Electrodeposition – Applications in Energy Storage Devices
Authors: Akolkar Rohan , Banik Stephen J 
Published: February 2020

Electrodeposition of metals such as lithium (Li) and zinc (Zn) is central to charging of advanced energy storage devices including lithium-metal batteries and zinc-halogen flow batteries. However, a key technological hurdle facing the development of high energy density rechargeable metal anodes is the formation of dendritic morphology during battery charging and cycling [1,2].
In the present talk, key mechanisms underlying the development of dendritic morphology during Li and Zn electrodeposition will be discussed. Mechanistic effects associated with electrolyte components (additives and solvents) will be elucidated through in situ ‘live’ monitoring of the dendrite evolution process [3]. Performance of a variety of additives (polymers, sulfides, carbonates) and solvents (aqueous and organic) in the Li and Zn system will be discussed. In situ dendrite propagation studies will be complemented with electroanalytical studies such as polarization measurements on a rotating disc electrode. As shown in attached Figs. 1 and 2, polarization measurements provide valuable insights into the modulation of surface electrochemical kinetics by additives and solvents. Knowledge of surface polarization then enables quantitative modeling of the dendrite growth propensity and the additives-assisted dendrite suppression efficacy [4,5]. A combination of theory and experiment allows development of a comprehensive framework for characterizing the surface chemistry responsible for the dendritic morphology. Based on this framework, quantitative guidelines for designing chemistries to suppress dendrite formation will be presented.

References:

M. Skyllas-Kazacos et al., J. Electrochem. Soc., 158, R55 (2011).

K. Xu, Chem. Rev., 104, 4303 (2004).

S. Banik and R. Akolkar, J. Electrochem. Soc., 160 (11) D519 (2013).

R. Akolkar, J. Power Sources, 232, 23 (2013).

R. Akolkar, J. Power Sources, 246, 84 (2014).
Towards Understanding Li-O2 Electrochemistry on Precious Metal Electrocatalyst Surfaces in Non-Aqueous Electrolytes
Authors: Omichi Kaoru , Kreidler Eric , Xu Qingmin , Brooks Christopher 
Published: February 2020

With expanding expectations for vehicle electrification, energy storage systems with high specific energy densities are attracting increased interest. In particular, Lithium-Oxygen (Li-O2) batteries are considered one of the best candidates for post lithium ion batteries due to their high specific energy density (2600Wh/kg-electrode mass). However, Li-O2batteries have several major issues including electrolyte decomposition[1] and carbon support corrosion[2] which inhibits cell reversibility. The reaction products and mechanism of product formation were investigated on various precious metal electrocatalyst surfaces using cyclic voltammetry (CV), rotating ring-disk electrodes (RRDE), in-situ electrochemical scanning probe microscopy (EC-SPM), and in-situ Raman spectroscopy.
Gold, palladium, and platinum were investigated as Li-O2 oxygen reduction electrocatalysts under various operating conditions. Oxygenated 0.1M LiTFSI/DMSO and 0.1M LiClO4/DMSO were employed to investigate the influence of electrolyte salt on product formation. In order to obtain electrochemical characteristics of the various electrocatalyst surfaces, CV and RRDE were conducted using Li metal as the counter electrode and a Ag/Ag+reference electrode. For EC-SPM and in-situ Raman spectroscopy experiments, a two electrode configuration was utilized where Li metal served as both the counter and reference electrode. Additionally, constant current and voltage control modes were used case by case.
Through our experiments, we have confirmed that the discharge product morphology and reversibility of the Li-O2 electrochemical reaction were influenced by the solvent, the electrolyte salt species, electrocatalyst metal, and electrochemical operating condition (current density and discharge cut-off voltage). The fact that discharge conditions can induce different Li2O2 product morphologies has been reported [3]. Once large Li2O2 particles form, decomposition becomes more difficult and larger charging overpotentials are observed. Additionally, under certain experimental conditions, a transition from Li2O2 formation via disproportionation to a 2nd electron transfer mechanism is observed, which also influences decomposition overpotentials. Finally, Li salts containing the perchlorate anion produce a uniform film-like morphology as opposed to a particle morphology produced by the TFSI anion containing electrolyte. Thus, a complex interaction between the solvent, electrolyte salt anion, LiO2 intermediate species, and operating condition appears to influence Li2O2formation mechanism and morphology and thus apparent reversibility. Further details of this investigation will be presented.
[1] S.A. Freunberger, J.Am.Chem.Soc., 2011, 133, 8040–8047.
[2] B.D. McCloskey, J. Phys. Chem. Lett. 2012, 3, 997-1001.
[3] B.D. Adams, Energy Environ. Sci., 2013,6, 1772-1778.
Understanding the Structural Evolution of the New Iron-Based Mixed-Phosphate Na4
-XFe3(PO4)2(P2O7) in a Na Rechargeable Battery
Authors: Kim Hyungsub , Park Inchul , Lee Seongsu , Kim Hyunchul , Park Kyu-Young , Park Young-Uk , Kim Haegyeom , Kim Jongsoon , Lim Hee-Dae , Yoon Won-Sub , Kang Kisuk 
Published: February 2020

Storing the energy from renewable energy sources has become a critical issue in recent years. In order to develop a large-scale energy storage system (ESS) connected to green and sustainable energy beyond the conventional size of batteries, cost effectiveness must be the foremost requirement. For a large-scale ESS, battery electrode materials that are based on earth-abundant, readily available, and low-cost elements are highly desired. In this regard, using electrochemistry that utilizes an iron-based redox reaction combined with Na guest ions would be an optimal choice for such batteries because of the unlimited availability of Na from seawater and the ready availability of iron. However, only a limited number of such materials have been reported to date (NaFePO4, Na2FePO4F, NaFeSO4F, and Na2FeP2O7). 1–6

Recently, we reported a new iron-based mixed-phosphate cathode, Na4Fe3(PO4)2(P2O7), which shows promising electrochemical properties in both Na- and Li-ion cells (H. Kim et al., J. Am. Chem. Soc.
2012, 134, 10369−103722). 7 However, a fundamental understanding of the electrochemical reaction mechanism and structural stability under various conditions, which is essential for further development of this promising cathode, had not yet been achieved. In this report, we clarify the electrochemical reaction of Na4Fe3(PO4)2(P2O7) in Na-ion cells. We discovered that the electrode reaction is governed mainly by a one-phase reaction with a small volumetric change of less than 4%, despite significant distortion of pyrophosphate (P2O7) occurring upon electrochemical cycling. Furthermore, the partially desodiated phases are thermally stable at temperatures up to 530 °C at all states of charge. With its open framework, high voltage (~3.2 V vs. Na), low volumetric change (~4%) and safety characteristics, Na4Fe3(PO4)2(P2O7) should be an outstanding candidate for a Na rechargeable battery electrode.

References

1. Moreau, P.; Guyomard, D.; Gaubicher, J.; Boucher. F. Chem. Mater.
2010, 22, 4126–4128.
2. Lee, K. T; Ramesh, T. N.; Nan, F.; Botton, G.; Nazar, L. F. Chem. Mater.
2011, 23, 3593–3600.
3. Ellis, B. L.; Makahnouk, W. R. M.; Makimura, Y.; Toghill, K.; Nazar, L. F. Nat. Mater.
2007, 6, 749–753.
4. Barpanda, P.; Chotard, J.; Recham, N.; Delacourt, C.; Ati, M.; Dupont, L.; Armand, M.; Tarascon, J. –M. Inorg. Chem.
2010, 49, 7401–7413.
5. Barpanda, P.; Ye, T.; Nishimura, S.; Chung, S–C.; Yamada, Y.; Okubo, M.; Zhou, H.; Yamada, A. Electrochem. Commun.
2012, 24, 116–119.
6. Kim, H.; Shakoor, R. A.; Park, C.; Lim, S–Y.; Kim, J–S.; Jo, Y–N.; Cho, W.; Miyasaka, K.; Kahraman, R.; Jung, Y.; Choi, J. –W. Adv. Funct. Mater.
2012, 23, 1147–1155.
7. Kim, H.; Park, I.; Seo, D. –H.; Lee, S.; Kim, S. –W.; Kwon, W. J.; Park, Y. –U.; Kim, C. S.; Jeon, S.; Kang, K. J. Am. Chem. Soc.
2012, 134, 10369−103722.
Kröhnkite Na2M(SO4)2.2H2O (M = 3d metals) Family of Sulphate Cathodes for Sodium-Ion Batteries
Authors: Barpanda Prabeer , Oyama Gosuke , Ling Chris D , Yamada Atsuo 
Published: February 2020

Banking upon Sodium, the fifth most-abundant element, materials chemists have recently given renewed effort to develop large-scale and economic Na-ion batteries. Similar to Li-ion batteries, the battery community has explored many possible oxides and oxyanionic insertion systems with great success. In the quest to unravel new positive insertion system, our group has discovered Na2
MP2O7 pyrophosphate cathodes with redox potentials ranging from 2.5 to 3.8 V (Adv. Energy Mater., 2, 841, 2012). In an effort to further increase the redox potential, one possible way is to replace the PO4 units by more electronegative SO4 units, where the role of inductive effect triggers potential up shift.
Using the sulphate chemistry, we have discovered a new Fe-based cathode material, namely Na2FeII(SO4)2.2H2O (Chem. Mater., 26, 1297, 2014). It can be easily synthesized by simple dissolution and precipitation mechanism involving heat treatment below 80 °C. Unknown till date, this new compound assumes the kröhnkite mineral structure containing Fe Octahedra linked with two structural H2O units. It offers nice one dimensional tortuous channel for Na-ion migration (see the Figure). Upon electrochemical cycling at C/20 rate (at 25 °C), the as-synthesized compound delivers capacity approaching 80 mAh/g with the average Fe3+/Fe2+ redox potential located at 3.25 V. It is a relatively high voltage operation for Fe-based cathodes in sodium batteries. We will describe various aspects of synthetic, structural and electrochemical properties of novel Na2FeII(SO4)2.2H2O cathode. Further, exploring this system, we have discovered yet another Fe-based sulphate polyanionic system, which offers high rate performance with high operating potential above 3.5 V. We will update the current state-of-the-art on SO4-based polyanionic cathode systems for sodium-ion batteries.
Pore-Scale Transport Resolved Model Incorporating Cathode Microstructure and Peroxide Growth in Lithium-Air Batteries
Authors: Zhang Long , Andersen Charles , Qiu Gang , Kalra Vibha , Sun Ying 
Published: February 2020

The lithium-air (Li-air) battery, shown schematically in Fig. 1, with its usable energy density close to 1,700Wh/kg has captured worldwide attention as a promising battery solution for electric vehicles. However, a major hurdle facing the development of Li-air systems is their poor round-trip efficiency owing to the formation of electrically insulating lithium peroxide (Li2O2) at the cathode surface. Although it is well known that Li2O2 inhibits the reduction process during cell charging, how the deposition morphology of Li2O2 affects the cell performance is poorly understood. Ex-situ imaging has shown that the Li-air cathodes have highly intricate structures and the deposition of Li2O2 is equally complex. However, all existing simulations thus far treat the electrode/Li2O2 matrix as a homogenous continuum and utilize simply-shaped electrode morphologies, such as spheres and rods, to construct volume-averaged expressions (see Fig. 2a) for porosity and surface area. The formation of Li2O2 is then modeled as growing uniformly above these simplified electrodes, and manifests merely as a change in bulk porosity. Such assumptions are insufficient in characterizing the precise effect of the complex electrode/Li2O2microstructure on cell performance.
In this paper, we present a pore-scale transport resolved model (see Fig. 2b) of the Li-air battery that fully accounts for the electrode microstructure and peroxide growth. This approach requires no empirical correlations regarding the electrode morphology. Additionally, the growth of Li2O2 is modeled locally and no longer requires the assumption of uniform deposition. Utilizing this pore-scale transport resolved model, the complex electrode and Li2O2 morphologies can be directly incorporated into the numerical model and their effects on system-level performance can be evaluated. Incorporating the thickness-dependent electron resistivity and rate-dependent growth morphology of Li2O2, results obtained from our pore-scale model agree well with experiments. The validated model is then used to predict the galvanostatic discharge behavior of a Li-air cell for a variety of electrode/Li2O2 morphologies. The effects of pore-size (e.g., macro-, meso-, and micro-pores), electrode structure, discharge/charge rate, and oxygen solubility on Li2O2 growth and cell performance are presented. Figure 3 shows the cell voltage versus specific capacity curves for electrodes with different microstructures. The model presented here will be a valuable tool for rational design of electrode microstructures for improved cell performance.
Mechanical and Electrical Properties of Ceramic Electrodes for Solid Oxide Fuel Cells
Authors: Gore Colin M. , Hussain A. Mohammed , Yoon Hee Sung , Blackburn Bryan M. , Wachsman Eric D. 
Published: February 2020

Solid oxide fuel cells (SOFCs) operate efficiently on both hydrogen and hydrocarbon fuels. Their fuel flexibility makes them lucrative energy conversion devices; they can integrate immediately into the current hydrocarbon infrastructure and can utilize renewable fuels in the future once that infrastructure exists. Carbon deposition, or coking, due to the CO disproportionation reaction (Eq. 1) or CH4cracking (Eq. 2) can occur when using hydrocarbon fuels, which blocks the anode gas channels.
2CO -> CO2+ C(s) (1)
CH4 -> 2H2+ C(s) (2)
Typical nickel-based cermets used for anode-supported cells exacerbate coking problems because Ni surfaces catalyze solid carbon deposition. Furthermore the ~60% expansion of Ni upon reoxidation complicates its use as supporting material. Many researchers have suggested and demonstrated conductive ceramic anodes as supports for SOFCs to avoid the coking and mechanical problems of conventional cermet anode supports. The anodes must be >30% porous to allow for effective gas transfer to the electrochemically active triple phase boundary (TPB). Unfortunately, the properties of porous materials for this purpose are not as well characterized as the dense materials used for electrolytes or cermets for supporting anodes. To employ these materials in anode-supported cells, it is imperative to better understand the relationship between porosity and the electronic and mechanical properties of anode materials. General relationships between the elastic modulus and flexural strength of ceramics are described by Eq. 3 and 4, respectively, where n is an empirical fitting parameter and P is porosity.
E=Eo(1-1.9P+0.9P2) (3)
σfs = σoe-nP(4)
Original work in preparing and characterizing porous ceramics of gadolinia doped ceria (GDC), yttria-stabilized zirconia (YSZ), and niobium-doped strontium titanate (SNT) for electrodes is presented. The empirical parameters that relate flexural strength of the materials to their porosity are determined as shown in Fig. 1 for GDC10 and YSZ3. The effect of pore former on pore geometry and strength is discussed. Finally, the electrical properties of the anodes are measured, both in their native state and with the addition of conductive and catalytic materials to the scaffolds.
Invited: Recent Advances on Energy Conversion Using Microfluidic Fuel Cells Technology, Case: Glucose Membraneless Micro Fuel Cell Stack
Authors: Cuevas-Muñiz Francisco Mherande , Chavez Abraham Ulises , Guerra-Balcázar Minerva , Godínez Mora-Tovar Luis Arturo , Ledesma-García Janet , Arriaga Luis Gerardo 
Published: February 2020

In recent years the microfluidic fuel cells (μFFC) have emerged as a promising solution for small-scale power demands (e.g., cell phones, sensors, biomedical devices and medical implants). µFFCs are fed by liquid fuels and oxidants under laminar flow regimen; their principal goal is a longer operational time without frequent recharging. µFFCs operate without a physical barrier to separate the anode and the cathode, which implies the use of fewer components than conventional micro-direct PEM fuel cells and consequently their simplest operation and low maintenance events. The design of µFFCs must consider the optimization of size, weight and lifetime to improve the power supply for portable applications.
Different µFFCs generations have been already developed by our group in the last years with a tendency to reduce the cell size and channel dimensions. The first µFFC generation uses a “Y” shape channel and was constructed using a hot-pressing technique onto a PMMA [poly(methyl methacrylate)] plate to form the channel base. In the second µFFC generation the use of micro-fabrication technology became an important tool in order to reduce the dimensions; the assembly consisted in a silicone polymer microchannel sandwiched between two SU-8 current collectors with a “T” configuration. The third µFFC generation simplifies the fabrication process and reduces significantly the costs by substitution of SU-8 material with a cellulose acetate film. The main modification of this generation resides on the integration of an air-exposed electrode as cathode enabling oxygen delivery directly from air (air-breathing). Furthermore, the substitution of 3-metal sputtering deposition by a single thin carbon film in direct contact with the catalytic material. This device that uses formic acid as fuel, is capable to achieve up to 29 mW cm-2 of power density, which is the highest value reported to date.