bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced Niobium Oxide in Carbon Matrix As Anode Materials for Lithium Ion Battery
Authors: Yan Litao , Luo Hongmei
Published: February 2020

Lithium-ion batteries (LIBs) have been extensively investigated as high performance rechargeable batteries for portable electronic devices and electric vehicles (EVs). However, the current LIB technology is handicapped by several critical disadvantages for EV applications including short cycling life and safety hazard resulting from dynamic solid electrolyte interface (SEI) formed at low working potential. Spinel lithium titanate (Li4Ti5O12), anatase titanium dioxide (TiO2) and niobium pentoxide (Nb2O5) have been considered to be as promising anode materials for rechargeable LIBs owing to the considerable safety advantage that their redox potentials match to the lowest unoccupied molecular orbital (LUMO) of the organic liquid-carbonate electrolyte, which prevents the growth of lithium dendrites and the decomposition of electrolyte. Unfortunately, their intrinsic poor electric conductivities, poor lithium ion conductivities, and the capacity decay resulted from pulverization during charge-discharge processes limit their practical use in LIBs, especially for Nb2O5 (σ∼3×10−
6 S·cm−
1).

   Herein, we report a one-step facile hydrothermal synthesis of Nb2O5/carbon matrix using glucose as the carbon source. After post-heat treatment under H2 gas, the glucose is carbonized to form carbon matrix and Nb2O5 nanocrystals are homogeneously immersed in carbon matrix. The stoichiometric Nb2O5 insulator becomes to oxygen-deficient niobium oxide semiconductor, and this carbon matrix can efficiently prevent niobium oxide nanocrystals from pulverization during the charge-discharge processes, resulting in improved recyclability. In addition, the carbon matrix and oxygen-deficient niobium oxide can effectively enhance the electronic conductivity and lithium ion conductivity of our electrode material, which results in enhanced rate performance and cycle durability. We believe that such a kind of niobium oxide/carbon matrix structure provides a new design toward high cycle durability niobium oxide based anode materials.
Enhanced Electrochemical Properties of Carbon Coated TiO2 anode for Sodium-Ion Battery
Authors: Lee Joo-Hyeong , Hwang Jang-Yeon , Oh Seung-Min , Yoon Chong seung , Lu Jun , Amine Khalil , Sun Yang-Kook
Published: February 2020

Many types of commercial batteries use carbonaceous materials materials for the anode, such as meso-carbon microbeads (MCMB) or hard carbon. However, MCMB cannot be used as an anode material for sodium batteries because of the high potential of the Na/Na+(~0.3V higher than Li/Li+) redox reaction and the large ionic radii of the Na+(102 pm).1,2 Therefore, many researchers have been efforts to find a suitable anode material for the sodium – ion battery system. In the case of insertion anodes, various types of non-graphitic carbon materials have been considered and tested.3,4

Here, we confirmed that the carbon coated anatase-type micro-sphere TiO2 anode material has several advantages for the sodium ion battery system, including excellent cycle retention, high efficiency, good rate capability, and high energy density. The carbon coating, introduced by sucrose addition, had an effect of suppressing the growth of the TiO2 primary particles during calcination. The carbon coated TiO2 (sucrose 20 wt.% coated) electrode exhibited excellent cycle retention during 50 cycles (100%) and superior rate capability up to 30 C-rate at room temperature. This cell delivered a high discharge capacity of 155 mAh g-1 at 0.1 C, 149 mAh g-1 at 1 C, and 82.7 mAh g-1 at 10 C-rate, respectively.

(1) Stevens, D. A.; Dahn, J. R. High Capapcity Anode Materials for Rechargeable Sodium-Ion Batteries. J. Electrochem. Soc. 2000, 147, 1271−1273.

(2) Wenzel, S.; Hara, T.; Janek, J.; Adelhelm, P. Room-Temperature Sodium-Ion Batteries: Improving the Rate Capability of Carbon Anode Materials by Templating Strategies. Energy Environ. Sci. 2011, 4, 3342−3345.

(3) Stevens, D. A.; Dahn, J. R. The Mechanisms of Lithium and Sodium Insertion in Carbon Materials. J. Electrochem. Soc. 2001, 148, A803−A811.

(4) Thomas, P.; Ghanbaja, J.; Billaud, D. Electrochemical Insertion of Sodium in Pitch-Based Carbon Fibers in Comparison with Graphite in NaClO4-Ethylene Carbonate Electrolyte. Electrochim. Acta 1999, 45, 423−430.
High Capacity Thick Cathode with a Porous Aluminum Current Collector for Various Rechargeable Lithium Batteries
Authors: Abe Hidetoshi , Kubota Masaaki , Nemoto Miyu , Tanaka Yuichi , Munakata Hirokazu , Kanamura Kiyoshi
Published: February 2020

As one of the methods to improve the energy density of lithium secondary battery, the use of high capacity anode and cathode materials has been focused. Although metals and alloys are mentioned as anode material candidates with high capacity, on the other hand, the candidates for high capacity cathode are insufficient currently. Therefore, a large amount of active material has to be accumulated and compressed to the cathode to achieve high energy density in consideration of the capacity balance with anode (Fig. 1). However, good performance cannot be obtained in the conventional thick coating electrode with a large amount of active material. The thick coating electrode has many problems. The ohmic resistance increases as the distance between a current collector and active material is made longer. In addition, many cracks, dropouts, and exfoliations are caused by volume changes of the coated layer during charge and discharge. In this study, the high capacity thick cathode has been realized by using a porous aluminum as a current collector as a practical method to improve the energy density of lithium secondary battery (Fig. 2). The combination of the thick cathode with a very high capacity per unit area and a high capacity anode can omit the amount of supporting materials such as a separator in batteries, resulting in the high energy density. The various thick cathodes were prepared using lithium iron phosphate, lithium cobalt oxide, and lithium nickel-cobalt-manganese oxide, respectively, and their electrochemical characteristics were evaluated by half-cell test. Though the cathodes had about several times larger capacity than conventional coating cathodes, they exhibited excellent rate performance. For example, the cell comprised of the thick cathode using lithium iron phosphate with a porous aluminum and two pieces of graphite anodes showed approximately 4-5 times capacity of the cell using conventional coating electrode at the same effective electrode area, and  no large difference was observed for a in the polarization of charge-discharge at 1.0CA  (Fig. 3). In a cycle-life test, the cell exhibited an excellent charge-discharge cycle performance, and retained approximately 80% of initial capacity even at 2,000th cycle (Fig.4). Such excellent performance is expected to be due to the easy electrolyte permeation from one side to the other side of the thick cathode, which is achieved by a porous aluminum current collector in addition to three-dimensional current collection. Of course, the lithium-ion diffusion in the cathode is expected to be insufficient for charge and discharge reactions when the cathode and C rate become thicker and larger, respectively. Thus, further optimization is needed for the cathode as well as for the electrolyte solution and separator to improve the ion supply in the cell. Such battery design will be also mentioned in this study.

Figure 1
Co-Synthesis of Hydrogen and Carbon Fuels from Water and Carbon Dioxide
Authors: Li Fang-Fang , Liu Shuzhi , Cui Baochen , Lau Jason , Stuart Jessica , Licht Stuart
Published: February 2020

Non-fossil fuel based, low carbon footprint fuels are needed to ameliorate the effects of anthropogenic climate change. We have previously demonstrated molten hydroxide electrolytes for solar water splitting to hydrogen fuel, and molten carbonate electrolytes for solar carbon dioxide splitting to carbon or carbon monoxide fuels. Solid carbon (as coal) is used as the starting point to generate CO and hydrogen for the Fischer-Tropsch generation of a variety of fuels, such as synthetic diesel. However, that process is carbon dioxide emitting intensive. In this study we present the first molten electrolyte sustaining electrolytic co-production of both hydrogen and carbon products in a single cell (1). Here, hydrogen and carbon products are produced without carbon dioxide emissions and instead produced from water and carbon dioxide. The demonstrated functionality of hydroxide and carbonate electrolytes to co-generate hydrogen and carbon fuels at low electrolysis potentials, and from water and CO2starting points, provides a significant step towards the development of renewable fuels.

Fang-Fang Li, Shuzhi Liu, Baochen Cui, Jason Lau, Jessica Stuart, Baohui Wang, and Stuart Licht, "A one-pot synthesis of hydrogen and carbon fuels from water and carbon dioxide," recommended for publication Nov. 20, 2014, Advanced Energy Materials

Figure 1
A Novel Anion Exchange Membrane Enabling Generation of Syngas from Water and Carbon Dioxide at Industrially Important Rates
Authors: Liu Zengcai , Masel Richard I , Chen Qingmei , Kutz Robert , Yang Hongzhou , Lewinski Krzysztof A. , Matthews Tyler Scott , Kaplun Marina
Published: February 2020

The electrochemical production of syngas would enable production of transportation fuels from carbon dioxide (CO2), water and renewable energy, but a suitable process does not exist.  CO2 reduction to carbon monoxide (CO) has been a particular problem, in that high overpotentials are often needed to drive the CO2 reduction process, so the cost of the process was too high to be economic. Recently, we discovered a helper catalyst, an imidazolium-based ionic liquid (IL), by which CO2 can be reduced to CO at an overpotential as low as 0.17 V on silver (Ag) particle catalysts [1]. The IL suppresses hydrogen evolution on the Ag electrode to a degree tunable by modifying, for instance, the pH and water content of the IL electrolyte.

In previous work, the currents were too low to be practical.  In the present paper, we present results using a newly developed DX4-13 membrane.   We find that the new membranes allow us to obtain 300 mA/cm2 of CO current at room temperature and atmospheric pressure. 

We also find that by changing the membrane composition, or varying the pH, we can produce syngas from a single electrolyzer. We have observed syngas production from a single cell running at room temperature at 100 mA/cm2 total current, however H2production is reduced at higher currents due to CO poisoning of the hydrogen production process.   These and other results will be discussed.     

[1] Rosen, B. A.; Salehi-Khojin, A.; Thorson, M. A.; Zhu, W.; Whipple, D. T.; Kenis, P. J. A.; Masel, R. I.  Science, 2011
, 334, 643.
Kinetics and Electrocatalytic Activity of Co(Aminopyrine)-Derived Nitrogen-Doped Porous Nanocomposite for Oxygen Reduction Reaction in Alkaline Electrolyte
Authors: Tang Sheng , Zhu Taishan , Fu Yishu , Qiao Jinli , Zhou Xiao-Dong
Published: February 2020

Non precious metal (NPM) catalysts are considered as promising candidates ofreplacing Pt for the oxygen reduction reaction (ORR) inpolymer electrolyte membrane fuel cells for its low cost and rich resource. It has been reported that the substitution of some carbon atoms withheteroatoms, such as N, S, P, I and B, is an effective way totailor NPM catalysts’ electron-donor properties thus effectively weakening the O−O bonding1 and leading to a high ORR catalytic activity. Up to now, extensive research efforts have been made to explore the N doped non-noble metal oxygen reduction catalysts2 since nitrogen has electronegativity higher than other elements3. In our recent work, we found that sulfur-doping could lead to increased catalyst porosity and therefore promote mass transport4.5. As yet, the S doped ones, in particular the S and N co-doped carbon materials are less reported6-8. On the other hand, the specific surface area and porous structure, which determine the accessible part of active sites and the transport properties of ORR-relevant species (H+, e−, O2, H2O), are believed to play the important role in the performance of NPM catalysts.In this regard, template method has drawn great attention to obtain the specified morphologyand predetermined microstructure9,10. Based on the above conceptions, in this work, we report a novel kind of heteroatom-doped carbon catalyst from N-containing polymer and sulfate by template method and acid leaching.Poly(diallyldimethylammonium chloride)(abbreviate as PDDA) was employed as sources of nitrogen and carbon, ferrous sulfate as precursor of sulfur and metal, while the nanoscale silica as sacrificial supports to create pores.
Sensivity Analysis of a PEM Electrolyser Cathode with Respect to the Platinum and Nafion Loading
Authors: Paciok Paul , Rakousky Christoph , Carmo Marcelo , Maier Wiebke , Stolten Detlef
Published: February 2020

The energy excess of intermittent power sources can be stored as hydrogen. Polymer electrolyte membrane (PEM) electrolysis is an efficient way to produce electrolytic hydrogen.[1] Due to the acidic environment only scarce and expensive noble metals like platinum and iridium are used as cathode and anode catalysts respectively.

To cut down the investment cost of a PEM electrolyzer, one of the main tasks is the reduction of the noble metal amount while retaining or increasing the performance of the electrolyser.[2] Thereby the influence of the decrease of the noble metal loading and possible degradation of the active material on the durability of the HER catalyst are both essential.

In this study we investigated the degradation of catalyst coated membranes (CCM) under constant and intermittent PEM electrolysis conditions. For this purpose we conducted long term test (1000h) with 4 different commercial CCMs each having different cathode loadings. To date, the durability of CCMs is examined under moderate current densities (0.9 to 1.4 A cm-2).[3] However, in this study the long-term test were performed at a current density of 2 A cm-2 to simulate real electrolysis conditions. As a next step we manufactured CCMs with a low platinum loading and different Nafion amounts at the cathode to examine the influence of the ionomer content on the long-term durability. TEM, XRD and EIS were applied to monitor physical and electrochemical changes during the durability test. The cathode and anode potentials were measured with the help of a reference electrode to determine the cause of degradation.[4]

CCMs with a platinum loading of 0.8 mgPt cm-2 showed a small degradation rate at a constant and dynamic operation mode. We observed that the reduction of the cathode loading to 0.05 mgPt cm-2 lead to a 5 fold increase of the degradation rate at the constant and  the dynamic operation mode. The increase of the cathode potential during the durability test indicates a degradation of the cathode catalyst, which was verified by TEM and XRD analyses: Agglomeration of the platinum particles on the carbon support was observed.

Our study clearly identifies the mechanisms responsible for the degradation of the cathode. This information opens up new possibilities to implement counter measures against the deterioration of the Pt/C catalyst, and to produce cost effective CCMs with low loadings and high durability.

1)         M. Carmo, D. L. Fritz, J. Mergel, D. Stolten, Int. J. Hyd. Energ., 2013, 38(12),4901 - 34.

2)         K. Ayers, Annual Merit Review DOE Hydrogen and Fuel Cells and Vehicle Technologies Programs, Washington, DC, 2014. Http://www.hydrogen.energy.gov/pdfs/review14/pd098_ayers_2014_o.pdf

3)         M. Debe, J. Electrochem. Soc., 2012, 159(6), K165-K176.

4)         S.A. Grigoriev, P. Millet, V.N. Fateev, J. Power Sources,
2008, 177(2), 281 - 285.

Figure 1
Alkaline Hydrogen-Iodine Fuel Cell
Authors: Konwar Dhrubajit , Nguyen Trung Van
Published: February 2020

We have considered the acid-based Hydrogen-Iodine (H2-I2) fuel cell along with the acid-based Hydrogen-Bromine (H2-Br2) fuel cell as potential systems for electrical energy storage but decided to drop the H2-I2 system because of its low cell open circuit potential (0.54V), even though the H2-I2 system offers a major advantage of being a much more benign system than the H2-Br2 system because of the high corrosivity and toxicity of bromine.  Recently, we found that by operating the hydrogen reactions in an alkaline medium we could shift the electrode standard reduction potential from 0V to -0.83V which combined with the bromine electrode standard reduction potential of 1.09V increases the cell potential of an alkaline H2-Br2 fuel cell from 1.09V to 1.92V [1]. See Figure 1. 

This 0.83V shift in the hydrogen electrode potential motivated us to take another look at the alkaline H2-I2 system because of the higher cell potential (1.37V). See Figure 2. This presentation will discuss the alkaline H2-I2 system, its advantages and disadvantages, and recent results obtained by our group at the University of Kansas.

Figure 1
Development of Advanced Hydrogen-Bromine Fuel Cells for Energy Storage
Authors: Lin Guangyu , Chong Pau Ying , Nguyen Trung Van , Yarlagadda Venkata , Wycisk Ryszard , Pintauro Peter N. , Tucker Michael C , Weber Adam Z , Bates Michael , Mukerjee Sanjeev
Published: February 2020

The hydrogen-bromine fuel cell has been shown to be a promising candidate for large-scale energy storage due to its fast kinetics, fully reversible electrodes and low chemical costs. However, today's conventional hydrogen-bromine fuel cells use very expensive membrane materials (such as Nafion®) and platinum catalysts that can be poisoned and corroded when exposed to HBr and Br2.  An advanced H2-Br2 fuel cell is being developed with reduced cost and increased durability for energy storage. We have successfully developed new composite membranes with higher perm-selectivity at a fraction of the cost of Nafion membranes; new catalysts possessing excellent activity and durability in HBr/Br2 environment and novel electrode/cell designs with superior cell performance. The advanced H2-Br2 fuel cell is high-power, high-efficiency with substantially increased durability and reduced cost. The latest progress in development will be discussed.

 Acknowledgements

 This work was funded by Advanced Research Projects Agency-Energy (ARPA-E) of the U. S. Department of Energy under Award No. DE-AR0000262.

 References

M.C. Tucker, K.T. Cho, A.Z. Weber, G. Lin and T.V. Nguyen, Journal of Applied Electrochemistry, October 2014.

H. Kreutzer, V. Yarlagadda and T.V. Nguyen, J. Electrochem. Soc., 159, F331 (2012).
Two-Point State-of-Charge Determination in Lithium-Ion Battery Packs
Authors: Dubarry Matthieu , Devie Arnaud , Liaw Bor Yann
Published: February 2020

The state-of-charge (SOC) estimation is of extreme importance for the reliability and safety of battery operation in large scale energy storage systems. How to estimate SOC for an assembly of cells in a battery pack remains a subject of great interest. Here, a viable method for SOC determination and tracking for multi-cell assemblies is proposed and validated. Using 3S1P strings as an example, an inference of SOC is illustrated in a battery assembly based on an accurate open pack voltage (OPV) versus SOC (i.e. OPV = ¦(SOC)) function. The proposed method only requires the measurement of the rest cell voltages of the single cells on two distinct occasions.

This new method offers great benefits to SOC calibration and tracking, which should improve the accuracy of any SOC tracking method (Figure 1). This method is not calculation intensive and could easily be implemented in any BMS. Additionally, we introduced two parameters which could be used to characterize and follow the imbalance evolution within a pack, and thus, enable remaining useful life determination with improved accuracy.

Coupled with our other diagnostics tools we believe that this approach could lead to a significant improvement of the quality of BMS SOC tracking and SOH diagnostics, for all applications where large battery assemblies are needed. As a matter of fact, and to the best of our knowledge, this is the first time where the pack-level (imbalance) and cell-level (aging) degradation factors of a battery pack could be distinguished and accurately quantified without any disassembly or maintenance downtime required.

Figure 1: Comparison between experimental data and simulation with and without the proposed method.

Figure 1
(Invited) Operando Methods for the Study of Energy Materials
Authors: Abruña Héctor D.
Published: February 2020

This presentation will deal with the development of operando methods for the study and characterization of fuel cell and battery materials. The presentation will begin with a brief overview of the methods employed.  Particular emphasis will be placed on the use of X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM) under active potential control, confocal Raman and differential electrochemical mass spectrometry (DEMS).  The utility of these methods will be illustrated by selected examples including conversion reactions of Mn3O4 as anode material for lithium ion batteries (LIBs), spectroscopic studies of Li/S batteries and the use of DEMS to characterize electrolyte systems for LIBs.  The use of operando TEM will be illustrated by studies of fuel cell catalyst degradation and coalescence and lithiation/de-lithiation dynamics of LiFePO4 via energy-filtered TEM. The presentation will conclude with an assessment of future directions.
(Allen J. Bard Award) The Electrochemical Nucleation and Physical Behavior of Hydrogen Nanobubbles
Authors: White Henry S , Chen Qianjin , German Sean R. , Wiedenroth Hilke , Luo Long , Feldberg Stephen W.
Published: February 2020

Gas nanobubbles formed at solid/liquid interfaces have received significant attention during the past decade due to their remarkable properties.  For instance, interfacial nanobubbles may exist for hours or days, in contrast to their expected short lifetime (< 1 s, based on the theoretical rate of gas dissolution from a nanoscale bubble).  We have developed an electrochemical approach for investigating the formation and properties of a single nanobubble of H2 with a radius between 5 and 50 nm.  To create a H2 nanobubble, a Pt nanodisk electrode, shrouded in a glass sheath, is used to reduce H+ in a concentrated acid solution, creating a supersaturated solution of H2 adjacent to the electrode surface.  As the electrode potential is scanned towards negative potentials, the current arising from H2 generation increases exponentially and then suddenly decreases to near background levels, signaling a liquid-to-gas phase transformation associated with the formation of a single nanobubble at the electrode surface. The critical concentration of dissolved H2 required for nanobubble nucleation, obtained from the electrochemical response, is measured to be ~0.25 M, corresponding to ~310-fold supersaturation of H2.   We estimate the critical size of the smallest stable H2 gas bubble nucleus to be ~4 nm; this nucleus grows and covers the Pt nanodisk surface until it becomes pinned at the Pt/glass interface.  Thermodynamic relations indicate that the internal pressure within these nanobubbles is of the order of 100 atm. 

The nanobubble experiments also provide insight into the structure and chemical dynamics of electrochemical three-phase solid/liquid/gas boundaries.  We demonstrate that a steady-state residual current of ~100 pA, measured after bubble formation, results from continuous electrogeneration of H2 at the Pt/electrolyte/H2 gas interface; steady-state reduction of H+ is required to balanced the rate of H2 dissolution from the nanobubble into the solution.  These experiments allow unique measurements of H+ reduction rates at a three-phase boundary, as well as estimation of the width of the three-phase boundary.  We also report additional experiments that demonstrate that the stability and shape of H2 nanobubbles are sensitive to the applied pressure and to the presence of surfactants.  Finally, we show that individual H2 bubbles can be electrochemically nucleated within nanopores.
Localized Investigations of the Electrochemical Properties of Lithium Battery Materials Using Micro-Pipets
Authors: Snowden Michael Edward , Mauzeroll Janine , Schougaard Steen Brian
Published: February 2020

Lithium ion batteries are a commercially successful method for portable electrical energy, demonstrated by their use in portable electronics and the recent application as an alternative automotive power source to the internal combustion engine.1 However, for lithium ion batteries to be a competitive alternative to fossil fuels in the automotive industry, electrode materials with improved capacity and charge/discharge rates are required. As new anode and cathode materials are developed2 they are typically screened for advantageous properties by assembly into a working battery. This involves the fabrication of a film from a mixture of conductive material (e.g. carbon), a binder (e.g. polyvinylidene fluoride), and the active material of interest. A film is cast onto a conductive material to form the active electrode, before assembly within a coin cell. How the film is cast, the ratio of the individual components of the film, the drying procedure for the film and the final assembly of the coin cell can significantly alter the performance of the battery.3,4 In order to avoid misleading information about the effectiveness of a novel active material many coin cells are required to validate findings.

Here we present micro-pipet measurements5 which demonstrate the suitability of the technique for probing lithium ion battery materials. Specifically, we probed dispersions of active materials to determine the oxidation and reduction potentials, and the charge capacity of the material. Data obtained on candidate materials by the micro-pipet method was compared to coin cell measurements, to critically assess this technique for characterisation of active battery materials.

1) Wagner, F. T.; Lakshmanan, B.; Mathias, M. F.; J. Phys. Chem. Lett., 2010, 1 (14), 2204–2219

2) Whittingham, M.S.; Chem. Rev., 2004, 104 (10), 4271–4302

3) Bruce, P. G.; Scrosati, B.; Tarascon, J.-M.; Angew. Chem.-Int. Ed.
2008, 47 (16), 2930-2946

4) Ban, C.; Wu, Z.; Gillaspie, D. T.; Chen, L.; Yan, Y.; Blackburn, J. L.; Dillon A. C.; Adv. Mater. 2010, 22, E145–E149

5) Williams, C. G.; Edwards, M. A; Colley, A. L.; Macpherson, J. V; Unwin, P. R.
Volammetric and Chronopotentiometric Study of Nonstationary Process on Oxygen-Evolving Anodes in KF-Naf-AlF3-Al2O3
Authors: Suzdaltsev Andrey , Khramov Andrey , Limanovskaya Oksana , Zaikov Yuriy , Nekrasov Valentin
Published: February 2020

Some specific aspects of mechanism and kinetics of the anode processes at Pt and Cu-Fe-Ni alloy in the KF-NaF-AlF3-Al2O3 melts in the temperature range of 725-800 °С were studied using cyclic voltammetry and chronopotentiometry.

Based on the obtained nonstationary volt-ampere dependencies a conclusion regarding similarity of the anode processes occurred at Pt and Cu-Fe-Ni, i.e. a stage of electrochemical oxidation is proved to precede a two-stage electrochemical evolution of the molecular oxygen. It was found that the rate of this stage depends significantly on the melt temperature.
Multi-Scale Theory in the Molecular Simulation of Electrolyte Solutions
Authors: Pratt Lawrence R , Zhang W. , You X.
Published: February 2020

To define a role for AIMD simulation on the limited time and space scales accessible to those demanding methods, this paper organizes McMillan−Mayer theory, the potential distribution approach, and quasi-chemical theory to provide theory for the thermodynamic effects associated with long-length scales. The theory treats composition fluctuations that would be accessed by larger-scale calculations, and also longer-ranged interactions that are of special interest for electrolyte solutions. The quasi-chemical organization breaks-up governing free energies into physically distinct contributions: packing, outer- shell, and chemical contributions. Here we study specifically the outer-shell contributions that express electrolyte screening. For that purpose we adopt a primitive model suggested by observation of ion-pairing in tetraethylammonium tetrafluoroborate dissolved in propylene carbonate. Gaussian statistical models are shown to be effective physical models for outer-shell contributions, and they are conclusive for the free energies within the quasi-chemical formulation. With the present data set the Gaussian physical approximation obtains more accurate mean activity coefficients than does the Bennett direct evaluation of that free energy. 

Figure 1
Multiscale Modeling of a Proton Exchange Membrane Fuel Cell: Effect of Electric Double Layer Structure
Authors: Castañeda Ramírez Sergio , Carmona Juan , Pérez Mendoza Alejandro Esteban , Ribadeneira Paz Rafael Esteban
Published: February 2020

Proton Exchange Membrane Fuel Cells (PEMFCs) are very promising to generate electric energy for transport and electronic devices because they produce minimal pollutant emissions and can operate at low temperature [1]⁠. Despite of enormous progresses made to date, this technology has to reach all technical requirements in order to be competitive.

The presence of solvated cations as charge-transporting species has a direct influence on the potential profile at interfaces involved in PEMFCs. This leads to a shift in the electric potential acting on the reactants and modifies their activation energies. In this way, the rate of mass and charge transfer processes are determined by the electric double layer (EDL) morphology and structure. For instance, a simple modification in the medium permittivity close to the surface results in appreciable increase of the apparent reaction rate constant [2].

The importance of EDL structure on transfer mechanisms has led to several researches based on mean field theories and molecular simulations [3-4]. However, an integration of EDL structure simulations with PEMFC reaction model is still lacking. This will contribute to understand and cuantify the effect of electrolyte and solvent compositions on the reaction kinetics.

In order to simulate the EDL structure and its modifications with respect to applied potential and solution composition, it is required a proper molecular model that resembles the size, polar and chemical characteristics of reactants, electrolyte and solvent species involved in PEMFCs, which is proposed to carry out in this work by means of molecular dynamics (MD) simulations.

The results achieved by molecular simulations would enable to evaluate the modification of reaction rates by the EDL structure, under an applied potential in PEMFC. In order to accomplish this, it is employed the Stillinger-Weber interaction potential of water and platinum [7], coupled with electrostatic interactions for the molecular simulations of EDL.

References:

[1] Y. Wang, K.S. Chen, J. Mishler, S.C. Cho, X.C. Adroher, Appl. Energy 88 (2011) 981.

[2] Zhdanov, V. P. and Kasemo, B., Role of the field fluctuations in electrochemical reactions, Surf. Sci. 521 (2002) L655.

[3] Guidelli, R. and Schmickler, W., Recent developments in models for the interface between a metal and an aqueous solution, Electrochim. Acta.45 (2000) 2317.

[4] Fawcet, W. R. and Smagala, T. G., New developments in the theory of the diffuse double layer, Langmuir 22 (2006) 10635.

[5] Siepmann, J. I. and Sprik, M., Influence of surface topology and electrostatic potential on water/electrode systems, J. Chem. Phys. 102 (1995) 511.
Predictive Particle-Based Simulation of the Fabrication of Li-Ion Battery Electrodes
Authors: Forouzan M. Mehdi , Chien Chao-Wei , Bustamante Danilo , Lange William , Mazzeo Brian A , Wheeler Dean
Published: February 2020

The microstructure of commercially made lithium-ion battery electrodes is not necessarily optimal for cell performance. In an attempt to optimize the performance, detailed understanding of the microstructure is necessary. Factors that influence electrode microstructure include high-level variables such as composition and porosity; as well as detailed fabrication conditions that are part of the film-making, drying, and calendering steps.

Here we report on initial efforts to model the particle-level microstructure of lithium-ion cathodes and how this relates to fabrication conditions. LAMMPS, a molecular simulation code, was adapted for these mesoscale particle simulations. In particular we simulate a cathode composed of irregular-shape active material particles using a superposition of spheres to imitate complex particle shapes and aggregates of carbon and binder. Equations of motion coupled to inter-particle forces are solved to simulate particle motion and subsequent immobilization during fabrication steps.

Both the slurry and dried film are simulated and validated by comparing to experimental results for microstructure, tortuosity, and mechanical properties like viscosity and elasticity. Initial work includes simulations of NCM cathodes. Such simulations are a first step in allowing us to predict electrode microstructure and therefore battery performance from fundamental fabrication conditions.

This work is supported by the U.S. Department of Energy through the BATT program.

Figure 1
Effects of Alkali Metal and Organic Cations on the Hydrogen Oxidation Reaction in Alkaline Electrolytes
Authors: McCrum Ian T. , Meduri Praveen , Hickner Michael A , Janik Michael J.
Published: February 2020

Spectator ionic species in electrolyte solutions affect the rate and mechanism of electro-catalytic reactions. For example, it is well known that many anions, including (bi)sulfate and organic sulfonate can specifically adsorb to a platinum electrode at high potentials and affect the rate of the oxygen reduction reaction, important to fuel cell performance. If organic anions can specifically adsorb at high potentials and effect reaction rates, it should be determined if the organic cations proposed for use in new anion exchange membrane (AEM) fuel cells could specifically adsorb to platinum at low potentials and affect the rate of the hydrogen oxidation reaction. Recent evidence has shown that alkali metal cations can affect a variety of electro-catalytic reactions on platinum, including methanol oxidation, hydrogen oxidation, and oxygen reduction, but direct experimental evidence for their specific adsorption is lacking. Previously, we have used density functional theory (DFT), an ab initio quantum mechanics based technique to show that alkali metal cations can specifically adsorb to platinum and palladium electrodes at low potentials and compete with hydrogen adsorption in high pH electrolytes. We have found experimentally that the rate of the hydrogen oxidation reaction is dependent on the cation present in an alkaline electrolyte solution. We proposed and evaluated a mechanism for this effect using DFT to show alkali metal cations can specifically adsorb to the most active low index platinum facet for hydrogen oxidation, Pt(110), and can promote the adsorption of hydroxide, an important reaction intermediate. We have extended both our computational and experimental work to find that quaternary ammonium cations can also specifically adsorb to low index platinum electrode surfaces. The development of the mechanism for the effect of alkali metal cations on the rate of the hydrogen oxidation reaction and the DFT methods for simulating alkali metal cation and organic cation specific adsorption will be discussed.
Highly Active LiNi1-X

Mx
O2 (M = Mn, Co, Fe) Electrocatalysts for Oxygen Evolution Reaction in Alkaline Conditions
Authors: Augustyn Veronica , Turner Travis , Manthiram Arumugam
Published: February 2020

The efficient electrocatalysis of the oxygen evolution and reduction reactions (respectively, OER and ORR) remains a serious challenge for the development of electrochemical energy conversion and storage devices such as fuel cells, electrolyzers, and metal-air batteries.  In addition to the need for new non-noble metal catalysts is the need for improved understanding of their electrocatalytic mechanisms.  This presentation will describe a new class of alkaline OER electrocatalysts based on layered LiNi1-x

Mx
O2 (M = Mn, Co, Fe) where the Ni content is ≥ 0.85.  In this class of materials, the catalytic activity can be tuned over two orders of magnitude by engineering the bulk properties of the layered oxide.  Due to the rich compositional space afforded by the O3 layered structure of LiNiO2, the M content and composition and the Li content can be varied while maintaining relatively similar surface areas.  First, Fe-doped materials exhibit the highest activities, with the maximum activity for 0 ≤ Fe ≤ 0.1.  The Li content can be varied during the solid-state synthesis as well as after the synthesis by chemical lithium extraction with an appropriate oxidizing agent.  During the solid-state synthesis, Li deficiency introduces Ni2+ into the structure which is correlated with poor electrocatalytic activity.  This indicates that Ni3+, with a single eg
orbital electron, may be important for high catalytic activity.  Indeed, NiO and Li-doped NiO synthesized under similar conditions exhibit low activities.  On the other hand, chemical delithiation leads to increased Ni4+ content as well as increased surface areas, resulting in an improvement in catalytic activity.  Lastly, appropriate heat treatment conditions result in materials with electrocatalytic activities on par with the best bulk electrocatalysts, on the order of 178 mA/mg for a 0.4 V overpotential.  In addition to the correlation of bulk properties with electrocatalytic activity, the surfaces of the materials were also characterized with XPS.  Further improvements in the activity of LiNi1-x

Mx
O2 should be possible with higher surface, nanostructured materials.
(Invited) Perspectives for Design of Active and Stable Oxygen Evolution Electrocatalysts
Authors: Zeradjanin Aleksandar R. , Topalov Angel A. , Cherevko Serhiy , Mayrhofer Karl J.J.
Published: February 2020

One of the key challenges for the large-scale application of electrochemical energy conversion, employing reactors for water electrolysis and CO2 reduction, is still relatively low energy-efficiency of the anodic oxygen evolution reaction (OER). Although, oxides are perceived to be representative class of compounds used as catalytic materials, after more than 40 years of intensive research on OER, it is still not clear what really determines activity and stability trends. At technically relevant current densities, the critical point for obtaining a conclusive picture about the electrode performance is to understand the dynamic behavior of the triple-phase boundary. Fluctuations in the magnitude of the active surface area, due to blockage of a fraction of the overall number of active sites by the gas, induces great uncertainty in kinetic analysis which is usually based on stationary electrochemical methods. Consequently, the task of the highest merit is to employ advanced analytical tools and create methodologies which allow realistic insight into dynamic behavior of the polarized electrode/electrolyte interface during the gas release. In this work, recently developed approaches for comprehensive activity/stability studies will be discussed. Namely, activity is estimated using scanning electrochemical microscopy (SECM) in a mode adjusted for local electrochemical noise measurements. A positioned microelectrode was used as a sensor in order to estimate/monitor the frequency of gas-bubble detachment from the electrode surface. Recorded potential-dependent frequency spectra are the fingerprints of temporal fluctuations at the electrode/electrolyte interface. At the same time stability analysis was conducted using a miniaturized  electrochemical scanning flow cell coupled to the inductively coupled mass spectrometer (SFC-ICPMS). Obtained time-resolved potential dependent dissolution profiles were used as indication of the character of the dissolution process. In the final section of the work, based on the information gathered from SECM and SFC-ICPMS, was proposes a design of the electrode surface which could help to achieve the elusive goal of having simultaneously highly active and highly stable catalysts for the oxygen evolution reaction.

Acknowledgment. BMBF for the financial support in the framework of the project ECCO2 (Kz: 033RC1101A).

References:

1. A.R. Zeradjanin et al. ChemSusChem 5 (2012) 1905.

2. A.A. Topalov et al. Angew. Chem. Int. Ed. 51 (2012) 12613

3. A.R. Zeradjanin et al. RSC Adv. 4 (2014) 9579

4. K.J.J. Mayrhofer et al. Angew. Chem. Int. Ed. 53 (2014) 102

5. A.R. Zeradjanin et al. Int. J. Hydrogen Energ. 39 (2014) 16275
Simultaneous Detection of Dopamine and Oxygen Species Using Coated Electrodes
Authors: ALshandoudi Laila Mohammed
Published: February 2020

The various coatings were used for simultaneous determination of dopamine and oxygen species for biological application. The conditioning waveform at bare electrode was found to give more reproducible Oxygen Reduction Reaction (ORR) amperometric response than those coatings (without condition waveform).

This work provides some examples of how the variation of surface composition can alter the electrocatalytic properties of Pt and Carbon Fiber (CF) electrodes towards the ORR and dopamine oxidation. Various types of modifications show advantages and limitation in measuring the redox species under study.

Based on these preliminary investigations, coated Pt electrode in most cases is better as a catalyst for detecting dopamine and oxygen. However, this noble metal is well known for instability for practical use in vivo. Employing Differential Pulse Voltammetry (DPV) technique, the detection of dopamine was not superior in enhancing dopamine signal, although its capability in the discrimination of the background effect and the presence of coating.

The data obtained also showed the better reproducibility of the response for the electroreduction of oxygen when applying the conditioning waveform at the bare electrode rather than use of coatings (without any conditioning waveform) at the Pt electrode. Polypyrrole and poly(phyenlene) coatings are the best two coatings for the oxidation of  dopamine species and to obtain a reproducible surface for the amperometric response of oxygen.

Electrodes covalently modified with substituted diazonium salts can be used for further chemical modification. This in turn suggests the ability to tune the property of the modified electrode to be used for many applications like dopamine and other neurotransmitter determinations.

Voltammetric investigations in biological media encounter the problem of interferences. Adsorption of protein molecules is another difficulty in the measurement. For the tried coatings the electrochemically modified electrodes can be used then to test the ability to prevent protein adsorption at the electrode.  The stability of the electrode is another issue which needs to be taken into account and the trials for prolonging the use of the coated electrodes are some targets that need to be achieved in further work.
(Invited) Fundamentals for Effective Research in Materials Science at a Primarily Undergraduate Institution
Authors: Lofland Samuel E
Published: February 2020

Over the past 15 years, Rowan University has strived to include hands-on experiences into the curriculum for science and engineering majors.  While it may seem that such efforts lead to increased faculty load and a concomitant reduction in scholarly work, proper integration of education and research is synergistic.    Consider that since 2001, more than 40 undergraduates have co-authored over 50 peer-reviewed papers with the speaker, and many more have worked on a variety of other projects.  The list of majors involved includes chemistry, engineering, physics, and even science education.   Not only can these opportunities boost the productivity of cutting-edge research, but they prepare students for success in graduate school or careers in industry and greatly enhance their chances for admission or hiring.  There are several important factors that are key to effective implementation.  These include flexibility in the curriculum, institutional support, interdisciplinary collaborations, summer programs, and institutional partnerships.  We will discuss each of these areas in detail and how each component is necessary for sustaining advanced research programs with students at undergraduate institutions.
(Invited) Making Electrochemical Research Accessible to an Undergraduate Audience
Authors: LeSuer Robert J
Published: February 2020

In principle, undergraduate students are introduced to electrochemical reactions within the first year of the chemistry program.  In practice, the amount of content covered in the second semester of general chemistry is oftentimes limited to oxidation numbers and possibly balancing redox reactions.  Coverage of electrochemical concepts in higher level classes seems to be largely dependent on how comfortable the instructor is with the material.  While increased exposure to the topic within the formal curriculum is certainly encouraged, training in electrochemistry is perhaps better served by a more informal undergraduate research learning environment.  Presented here is one approach towards establishing a rigorous research program designed to train and teach undergraduate students utilizing principles derived from Bloom's taxonomy of learning.  Development of a successful electrochemical research program has involved several factors, including: identifying projects that are accessible to undergraduate students given their limited exposure to the topic; developing tools and resources to facilitate training and learning; establishing forums for formal and informal scientific communication opportunities; and creating partnerships and collaborations that not only appreciate the challenges of undergraduate research, but leverage them in order to add meaningful value to the research program.  Strategies for implementing direct and indirect methods to assess scholarly and instructional outcomes will also be presented.