bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Synthesis of Bilayer Coatings of New Polymer Composite for Carbon Steel Corrosion Protection
Authors: Branzoi Florina , Pacuretu Catalina , Branzoi Roxana
Published: February 2020

Bi-layered composites of polydimethylaniline (PDMA) and polypyrrole (PPY) were investigated for corrosion protection of carbon steel. In this work, PNDMA, PPY and PNDMA-AOT/ PPY coatings have been electropolymerization on carbon steel by potentiodynamic and galvanostatic synthesis techniques from aqueous solutions 0.1 M dimethylaniline, 0.1M pyrrole, 0.05 M sodium dioctyl sulfosuccinate (AOT) and 0.3 M oxalic acid. In order to include dioctyl sulfosuccinate ions as dopant in the dimethylaniline, AOT was also added to the polymerization solution of dimethylaniline. Characterization of monolayer and bilayer polymer coatings was carried out by cyclic voltammetry, Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) techniques. Corrosion behaviour of PDMA-AOT/PPY coated carbon steel was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in 0.5M H2SO4solutions. The results of the corrosion tests showed that PDMA-AOT/PPYI coatings ensure good corrosion protection of carbon steel in aggressive media. Bilayer coatings revealed better corrosion inhibition efficiencies than monolayer coatings

A.M.Fenelon, C.B.Breslin, Corros.Sci., 2003,45, 2837

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A. Yagan, N.O. Pekmez, A. Yildiz, Electrochim. Acta, 2008, 53, 2474

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G. de T. Andrade, M.J. Aguirre, S.R. Biaggio, Electrochim. Acta, 1998, 44, 633.

R.Hasanov, S.Bilgic, Progress in organic coatings, 2009, 64, 435-445.

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, 49-55.

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F. Branzoi,V. Branzoi, A. Musina, Surface and Interface Analysis, 2012, 44, 1076-1081
An Indirect Impedance Technique to Determine Reinforcing Steel Properties
Authors: Alexander Christopher , Chen Yu-Min , Orazem Mark E.
Published: February 2020

Studies have shown that the application of an electric field to the surface of an electrolytic medium can indirectly polarize a metal within the solution.1,2,3,4 This technique can be applied to the study of reinforcing steel in concrete, and in this particular paper, to the study of post-tensioning steel in grouted cylinder tendons used in bridge construction. With the use of Electrochemical Impedance Spectroscopy, a ﬁnite-element model has been developed to solve for the frequency-dependent potential distribution through a cylindrical grout specimen containing one axially-located steel strand. Impedance simulations were performed at diﬀerent steel corrosion states while incorporating the kinetics at the current-injecting electrodes.

Following the procedure of Huang et al.5, the electrode kinetics are expressed as an oscillating current density as the summation of a charging and faradaic current. The grout is modeled as a uniform conductivity media and Laplace’s equation is used to solve for the potential distribution. The impedance is simulated over a range of frequencies as the potential difference between two reference electrodes divided by the current of the working electrode. The results are compared to experimental measurements throughout the hydration process.

The effectiveness of this method relies on the use of accurate representations of the steel surface impedance. Passive film models developed from rotating disk experiments in simulated pore solution are used to describe the steel boundary condition in the finite element model. The simulated results incorporating these models show a similar impedance response as the measured impedance of an aged cylinder put through a wetting and drying cycle.

Barring an accurate model, this technique has the potential to effectively determine the interface properties of the embedded steel from the overall response of the system.

References

J. Zhang, P. J. Monteiro, F.H. Morrison, “Noninvasive surface measurement of corrosion of reinforcing bar in concrete: Part I Experimental results”, ACI Materials Journal,
98 (2001) pg. 116-125.

M Keddam, X. R. Novoa, V. Vivier, “The concept of floating electrode for contact-less electrochemical measurements: Application to reinforcing steel-bar corrosion in concrete,” Corrosion Science,
51 (2009) pg. 1795-1801.

C. Andrade, I. Martnez, “Metal corrosion rate determination of diﬀerent solutions and reinforced concrete specimens by means of a noncontacting corrosion method,” Corrosion
66 (2010) pg. 056001-056001.

C. Andrade, J. Sanchez, I. Martinez, N. Rebolledo, Analogue circuit of the inductive polarization resistance,” Electrochimica Acta
56 (2011) pg. 1874-1880.

V. M. W. Huang, V. Vivier, M. E. Orazem, N. Pbre, B. Tribollet, “The apparent constant-phase-element behavior of a disk electrode with faradaic reactions a global and local impedance analysis,” Journal of the Electrochemical Society
154(2007) C99-C107.
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).
A Study on the Effect of Heat Treatment and Magneto-Electropolishing on in-Vitro Corrosion and Surface Properties of Ternary Nitinol
Authors: Pulletikurthi Chandan , Munroe Norman , Rokicki Ryszard
Published: February 2020

The development of new materials with tailored properties has found wide application in the medical, automobile and electronic industries. Ternary Nitinol alloys are a class of such emerging materials that require further research and development for application in such industries. Heat treatment is known to affect their transformation temperature, oxide layer composition, wettability and flexibility that directly impact their biocompatibility, performance and ease of installation. Magneto-electropolishing affords a thin and compact oxide layer that renders corrosion resistance, nano-textured morphology with reduced thrombogenicity. This investigation assessed the effect of heat treatment and magneto-electropolishing on the surface chemistry and corrosion resistance of NiTi10Ta. Martensitic phase transformation, a crucial parameter that determines the alloy’s application was determined using a differential scanning calorimeter (DSC). Electrochemical impedance spectroscopy (EIS) and potentiodynamic tests were performed as per ASTM standards to assess corrosion resistance. Surface topography, morphology, surface chemistry and crystallinity were determined using atomic force microscopy (AFM), scanning electron microscopy (SEM)/ Energy-dispersive X-ray spectroscopy (EDS) and x-ray diffraction (XRD) respectively.
Three-Dimensionally Structured Conversion Compound Electrodes for High Energy Density Lithium Batteries
Authors: Wang Junjie , Braun Paul V , Zhou Hui , Nanda Jagjit
Published: February 2020

Transition metal based conversion compounds have attracted extensive attention due to the possibility of multiple redox states enabling storage of more than one lithium per transition metal atom, resulting in much higher specific capacity than conventional intercalation compounds. However, conversion compound electrodes often suffer from poor power density and poor cyclability at least in part because of the intrinsically poor ionic and electronic conductivity of the materials. Addition of a conductive agent, usually carbon, improves cyclability significantly, but with a reduction of the overall capacity. Here, using a colloidal templating strategy, we three-dimensionally architecture and nanostructure conversion compound electrodes to overcome the sluggish kinetics. We focus on Fe2O3 nanoparticles as active materials. Bicontinuous Ni inverse opals formed via colloidal templating with pore size of about 500nm were used as the current collectors, and Fe2O3 nanoparticles (30-50nm) were electroplated onto this scaffold. By using a pulsed voltage deposition method, a uniform coating of nanoparticles on the Ni scaffold was realized. After optimizing the phase of the materials, cycling tests showed a good specific capacity (~1000mAh/g at 0.5C). The high-rate performance of the three-dimensional electrodes was impressive. At a rate of 20C, more than 400mAh/g capacity could still be delivered. The good capacity and cyclability of the three-dimensional electrodes was due to the combination of the porous electrode support structure and the nanostructured active phase which provided short pathways for both ions and electrons.
Metal Oxide Coated Porous Silicon electrode fabricated By Anodized Liquid Phase Deposition
Authors: Mizuhata Minoru , Katayama Akihito , Maki Hideshi
Published: February 2020

We fabricated titanium oxide/PSi nanocomposite by anodic liquid phase deposition (LPD) method. This method is soft-solution process for preparation of metal oxide thin film via hydrolysis of metal fluoro-complex with assist of F- scavenger (e.g. H3BO3, SiO2 and Al). Titanium oxide is superhydrophilic material and changes little volume during Li insertion and extraction, therefore this composite is expected to be high efficiency anode material. PSi was formed by etching of silicon wafer(p-type, 3-4 mΩ•cm) with 60 mA/cm2 in HF(47 %):EtOH (1:1, in vol) for 10 min[3] and immersed in (NH4)2TiF6-H3BO3 solution (LPD-H3BO3), thermaloxidized and immersed in (NH4)2TiF6 solution (LPD-SiO2) or anodized in H2TiF6-EtOH solution (LPD-anodized Si). Each sample was characterized by SEM-EDX, XPS, N2-isotherm and electrochemical measurement. The deposition amount of titanium was quantified by ICP-AES.The diameter of PSi was ca.7.4 nm and titanium oxide was deposited on all samples. However, the fine structure of LPD-H3BO3 was removed by covering of titanium oxide. After depositon of Ti oxide, the Ti2P binding energy decreased during the LPD reaction measured by XPS. This result suggests titanium oxide deposition derived from removal of fluorine from metal fluoro-complex via hydrolysis with H3BO3, SiO2 or anodized Si. Anodic electrodepostion of titanium oxide on PSi was performed at 0.3 V vs Ag/AgCl, and the deposition amount; ca. 3x10-6 mol m-2 as shown in Fig.1.
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).
Investigation of Lithium Dendrite Necking and Formation of Dead Lithium Crystals
Authors: Aryanfar Asghar , Hoffmann Michael , Colussi Agustin
Published: February 2020

We have investigated the mechanism of formation of dead lithium in manually-fabricated symmetric lithium metal cells. Furthermore, we have characterized the amount of dead lithium based on current intensity and number of cycles and it’s effect on cell impedance.
Electroless Atomic Layer Deposition
Authors: Stickney John Lewellen , Benson David M. , Jagannathan Kaushik , Robinson David B.
Published: February 2020

Atomic layer deposition (ALD) is a group of methods for the formation of nanofilms of materials, an atomic layer at a time using surface limited reactions. The majority of those methods are based on use of the vacuum environment. However there are methods such as sequential ionic layer adsorption reaction (SILAR) which used the condensed phase, that is, aqueous solutions of precursor ions. In addition, this group has been working on an electrochemical form of ALD for 25 years. That work is referred to as electrochemical atomic layer deposition (E-ALD) or electrochemical atomic layer epitaxy (EC-ALE), and is based on using underpotential deposition (UPD) for surface limited reactions. The problem with using an electrochemical methodology for the formation of nanofilms is that many substrates are not conductive. This has stimulated investigations into the growth of materials using an electroless form of ALD (EL-ALD). An example of an EL-ALD process would be the use of a solution containing H2 to poise the potential of a Pd surface. This will result in the adsorption of a layer of hydrogen atoms which can then be exposed to precursors for Pt or Pd, forming an atomic layer of the metal. That process can then be repeated to grow a nanofilm. That example takes place on a conducting surface, however. Work is continuing on development of an EL-ALD method which can start on an insulating surface, and results will be discussed.
Mxenes As High Capacity Electrodes Materials for Metal (Li, Na, K, Ca)-Ion Batteries
Authors: Er Dequan , Li Junwen , Naguib Michael , Gogotsi Yury , Shenoy Vivek B.
Published: February 2020

Two-dimensional (2-D) materials are capable of handling high rates of charge in ion batteries since metal ions do not need to diffuse in a 3-D lattice structure. However graphene, which is the most well-studied 2-D material, is known to have no Li capacity. Here, adsorption of Li, as well as Na, K, and Ca on Ti3C2, one representative MXene, is predicted by first-principles density functional calculations. In our study, we observed that these alkali atoms exhibit different adsorption energies depending on the coverage. The adsorption energies of Na, K, and Ca decrease as coverage increases, while Li shows little sensitivity to variance in coverage. This observed relationship between adsorption energies and coverage of alkali ions on Ti3C2 can be explained by their effective ionic radii. A larger effective ionic radius increases interaction between alkali atoms, thus lower coverage is obtained. Our calculated capacities for Li, Na, K, and Ca on Ti3C2 are 447.8, 351.8, 191.9, and 320.0 mAh/g, respectively. Compared to materials currently used in high-rate Li and Na ion battery anodes, MXene shows promise in increasing overall battery performance.
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.
Defective Graphene As a High-Capacity Anode Material for Na- and Ca-Ion Batteries
Authors: Datta Dibakar , Li Junwen , Shenoy Vivek B.
Published: February 2020

Because of their abundance, sodium and calcium can be attractive in ion batteries for large-scale grid storage. However, many of the anode materials being pursued have limitations including volume expansion, lack of passivating films, and slow kinetics. Here, we investigate the adsorption of Na and Ca on graphene with divacancy and Stone−Wales defects in graphene. Our results show that although adsorption of Na and Ca is not possible on pristine graphene, enhanced adsorption is observed on defective graphene because of increased charge transfer between the adatoms and defects. We find that the capacity of graphene increases with the density of the defects. For the maximum possible divacancy defect densities, capacities of 1450 and 2900 mAh/g for Na- and Ca-ion batteries, respectively, can be achieved. For Stone−Wales defects, we find maximum capacities of 1071 and 2142 mAh/g for Na and Ca, respectively. Our results provide guidelines to create better high-capacity anode materials for Na- and Ca-ion batteries.
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.
Performance of 3D-Printed Fuel Cells and Stacks
Authors: Gould Benjamin D. , Rodgers Joseph A. , Schuette MIchael , Bethune Keith , Louis Shaquille , Rocheleau Richard , Swider-Lyons Karen
Published: February 2020

3D-printing, a.k.a. additive manufacturing (AM), has become a popular topic in the general public and in industry [1]. There is recent interest in using AM to fabricate fuel cell components because of AMs ability to build metal parts with complex geometries with relatively short lead times [2]. Fuel cell bipolar plates (BPPs) require complex internal passageways for coolant flow fields making them a good candidate for AM. By building one piece BPPs the number of parts, the number of seals and the complexity of assembly can be decreased.

We present the performance characteristics of a 400W fuel cell system made with BPPs made of Ti-alloy (Ti-6Al-4V) and built by 3D-printing. The BPPs are made by direct metal laser sintering (DMLS) and are coated by Treadstone Inc. with Au-microdots and a TiO2layer to decrease contact resistance and protect against corrosion. Titanium alloy is examined because of its high strength-to-weight ratio which makes it an ideal material for aerospace applications. This work extends our previous work regarding the contact resistance of 3D-printed metal BPPs to include functional fuel cell stacks [3]. The performance characteristics of single cells and stacks will be discussed in the context of surface finish, flatness, feature tolerance, weight, cell-to-cell variability, scaling and contact resistance.

Overall DMLS is an exciting new technique with great promise for future rapid prototyping of BPP designs and many other fuel cell components. However, greater advances in surface finish, feature thinness and flatness are needed before BPPs built by 3D-printing will compete with the traditional machined or formed BPPs.

References

[1] http://techland.time.com/tag/3d-printing/ (2014)

[2] http://energy.gov/eere/articles/doe-announces-webinars-natural-gas-biomass-technologies-additive-manufacturing-fuel. (2014)

[3] C. J. Netwall, B. D. Gould, J. A. Rodger, N. J. Nasello, K. E. Swider-Lyons, J. Power Sources, 227, 137 (2013).
Gold-Metal (Ni, Cu) Deposited on the Titania Nanotubes as Electrocatalysts for Borohydride Oxidation
Authors: Balciunaite Aldona , Stankevičienė Ina , Zabielaite Ausrine , Vaiciuniene Jurate , Selskis Algirdas , Juskenas Remigijus , Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus
Published: February 2020

In the present work the optimization of the preparation of titania nanotube supported Au-Ni and Au-Cu catalysts (denoted as Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs) via the galvanic displacement technique is presented. The catalysts were prepared according the following procedures: i) preparation of TiO2 nanotube arrays by anodization of titanium sheets in an aqueous sulfuric acid solution containing some NH4F; ii) deposition of an electroless Ni or Cu sublayers on the synthesized TiO2 nanotube arrays [1-3] and iii) subsequent immersion of the Ni/TiO2-NTs or Cu/NiTiO2-NTs electrodes into the gold-containing solution for various time periods. The morphology and composition of the catalysts were examined by means of Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray diffraction and Inductively Coupled Plasma Optical Emission Spectroscopy. The electrochemical behavior and electrocatalytic activity of the fabricated catalysts towards borohydride oxidation were measured by means of cyclic voltammetry. The electroactive area of gold surface created on fabricated catalysts was determined from cyclic voltammograms of Au/TiO2-NTs electrodes recorded in a deaerated 0.5 M H2SO4 solution at a scan rate of 10 mV s-1.

The prepared Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs electrodes exhibited a high catalytic efficiency towards the oxidation of borohydride when compared to that of bulk Au electrode. A higher catalytic activity of the prepared Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs catalysts under various conditions may be related to production of smaller gold nanoparticles and their fine and uniform dispersion on the surface.

The Au-Ni and Au-Cu catalysts deposited on the titania nanotube surface seem to be a promising anodic material for direct borohydride fuel cells.

Acknowledgement

This research was funded by a grant (No. ATE-08/2012) from the Research Council of Lithuania.

References

[1] L. Tamasauskaite-Tamasiunaite, A. Balciunaite, D. Šimkunaite, A. Selskis. J. Power Sources 202 (2012) 85-91.

[2] L. Tamasauskaite-Tamasiunaite, A. Balciunaite, R. Cekaviciute, A. Selskis. J. Electrochem. Soc. 159 (2012) B611-B618.

[3] L. Tamasauskaite-Tamasiunaite, A. Balciunaite, A. Zabielaite, I. Stankeviciene, V. Kepeniene, A. Selskis, R. Juškenas, E. Norkus. J. Electroanal. Chem. 700 (2013) 1-7.
Statistical and Block Copolymers for Anion-Exchange Membranes with High Local Concentrations of Quaternary Ammonium Groups
Authors: Weiber E. Annika , Jannasch Patric
Published: February 2020

Cationic polymers in the form of anion-exchange membranes (AEMs) may enable a route towards low platinum or even platinum-free alkaline membrane fuel cells with the potential to oxidize more complex fuels than hydrogen and methanol [1-4]. The main challenges for the AEMs are currently to enhance the alkaline stability of the cationic group and to improve the ion conductivity. In this context, there have been many attempts to enhance the properties by varying the backbone polymer structure and the nature and content of the cations [1-4]. However, clearly promising strategies to prepare high-performance AEMs have not yet been described. While several lessons can be learnt from the development of proton-exchange membranes (PEMs), the cationic polymers in AEMs have different characteristics. For example, the organic cations of AEMs, such as quaternary ammonium (QA) groups, are larger and have a lower propensity to cluster and form a distinct ionic phase in the polymer matrix in comparison with the sulfonic groups of PEMs. This characteristic may seriously limit the transport properties of AEMs.

We have recently developed synthetic strategies where single phenylene rings in aromatic polymers can be directly functionalized with precisely two, three, or four QA groups, allowing an excellent and systematic control over the local density and distribution of ionic groups along the polymer backbone. We have used this approach to prepare several series of statistical and multiblock copolysulfones with very high local QA concentrations to promote membrane properties. Small angle X-ray scattering of AEMs based statistical copolymers containing phenylene rings functionalized with two, three and four QA groups, respectively, showed clear ionomer peaks to indicate efficient ionic clustering. The clustering was promoted by an increasing density of QA on the single phenylene rings. Corresponding randomly functionalized copolymer membranes showed no ionomer peaks. At moderate ion-exchange capacities, the Br- conductivity of the densely functionalized copolymers was higher than that of randomly functionalized copolymers, despite a significantly higher water uptake of the latter. In the current presentation, we will discuss selected results on the synthesis and structure-property relationships of the copolymers and AEMs.

References

[1] M. A. Hickner, A. M. Herring, E. B. Coughlin, J. Polym. Sci., Part B: Polym. Phys.,
2013, 51, 1727.

[2] J. R. Varcoe, R. C. T. Slade, Fuel Cells, 2005, 5, 187.

[3] N. Li, M. D. Guiver, Macromolecules, 2014, online DOI: 10.1021/ma402254h.

[4] K. D. Kreuer, Chem. Mater.,
2014, 26, 361.
Cu-Pd/C Electrocatalyst with Low Pd Content toward Methanol Electro-Oxidation
Authors: Maya-Cornejo Jose Antonio , Arjona Noé , Guerra-Balcázar Minerva , Álvarez-Contreras Lorena , Ledesma García Janet , Arriaga Luis Gerardo
Published: February 2020

Cu-Pd/C electrocatalyst was synthesized by chemical reduction method from CuSO4 and K2PdCl4 as metallic precursors in the presence of polyvinylpyrrolidone as surfactant and ascorbic acid as reducing agent. The morphology, composition and electrocatalytic properties were investigated by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Transmission Electron Microscopy (TEM), cyclic voltammetry, and chronoamperometry techniques. The electrocatalyst were obtained with homogeneous distribution, average particle size around 5 nm and low percent of Pd (Pd 35%, Cu 65% according to XRF and EDS results) for a catalyst with 70-30 composition. XRD patterns show the typical faced-centered cubic structure, where the (111) plane exhibited a slightly shift. The electrocatalytic activity of Cu-Pd/C was evaluated in terms of methanol electro-oxidation at three concentrations (0.1, 0.3 and 0.5M) in KOH aqueous solution. The results obtained from voltamperometric studies showed that the current density achieved with Cu-Pd/C electrocatalyst is 3 times higher than that reached with commercial Pd (30% from ETEK) and a shift to negative values for electro-oxidation potential.
Effect of the Inlet Gas Humidification on PEMFC Behavior and Current Density Distribution
Authors: Sanchez Daniel G , Ruiu Tiziana , Biswas Indro , Friedrich K. Andreas , Sanchez-Monreal Juan , Vera Marcos
Published: February 2020

Water management represents one of the main challenges in the design and operation of PEMFCs. The influence of inlet gas humidification on cell performances is analyzed in general and especially the effect of low humidity conditions in both cathode and anode is studied. Hereby in situ diagnostic tools like EIS and current density measurements are used.

Dry cathode air supply and a fully humidified anode gas stream lead to a periodic transition between low- and high-current cell operations. A review of the main variables involved in this phenomenology is given. Furthermore, this oscillatory behavior is used as a tool to study degradation processes.

Figure1 Overall cell current density oscillations (symbols) and current density distributions at the low current (lower inset) and high current (upper inset) states of a single PEM cell operated with dry cathode air supply (RHc=5%) and a fully humidified anode gas stream (RHa=100%); Cell voltage= 600mV, Flow H2= 209 ml·min-1, Flow Air= 664 ml·min-1, Pressure= 1.5 bar,Tc=80°C
Synthesis and Corrosion Studies of Sb-Doped SnO2 (ATO) Support for Electrolysis Systems
Authors: Gurrola Mayra Polett , Guitiérrez Ramírez Jaime , Rivas Gandara Sandra , Guerra-Balcázar Minerva , Ledesma-García Janet , Arriaga Luis Gerardo
Published: February 2020

This work deals with the corrosion resistance evaluation in acidic medium and electrochemical stability in a wide range (0 - 1.8 V vs ENH) for two different supports based on Sb doped SnO2 (ATO), one with low surface area (85 m2g-1) and the second one with a high surface area (216 m2g-1). Both materials were synthesized by sol - gel method and characterized by XRD, BET and HR-TEM. Both supports were compared with commercial Carbon Vulcan XC-72. The results show good chemical stability when the ATO and the modified-ATO are subjected to these conditions, whereas Vulcan carbon corrodes easily. This indicates that Sb-doped SnO2 is a good candidate for electrocatalyst supports for energy-conversion systems such as electrolysers and unified regenerative fuel cells.