bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Investigation of Two-Phase Electrolysis and Multiphysics Modelling
Authors: Mandin Philippe , Derhoumi Zine , Roustan Hervé 
Published: February 2020

During two-phase electrolysis processes, for example for hydrogen production, there are bubbles which are created at electrodes. This implies a great vertical motion source in the normal earth gravity field and then a quite important natural two-phase convection. All other fields are then affected. Heat, mass and electricity transfers are modified due to both bubbles screening (at surface and in volume) and to bubbles transport promotion.
Many numerical modeling for two-phase processes such as kerosene pulverization in engines or coal combustion sciences have shown the difficulties of these multi-physics processes. Both particles and reactor scales must be considered according with a strong coupling modeling. In these processes the particles injection is “in the flow”. In boiling or electrolysis processes, a new difficulty is added: particles birth or injection is strongly coupled to the local flow properties and leads to a complex boundary condition at surfaces. Electrical and electrochemical properties and processes are disturbed. This disturbance can lead to the modification of the local current density and to anode effects for example.
The both experimental and numerical investigation is here presented. Experiments are performed in laboratory and in zero gravity (CNES grant and parabolic flights opportunities).
Electrochemistry in Molten Oxides: From Electrolyte Design to Oxygen Evolution
Authors: Allanore Antoine 
Published: February 2020

The future carbon-free electricity offers substantial promises for electrochemical engineering, in particular its application to materials processing. As a matter of fact, electricity and electrochemical phenomenon have already significantly contributed to modern metal extraction and manufacturing [1]. More developments are however needed to pursue such trends, in particular for the extraction of metals with limited environmental impact. In that respect, molten oxides electrolytes have a particular appeal identified more than a century ago [2], thanks to their remarkable chemical stability at a temperature range that allows the production of liquid metal. This presentation offers first to review the intrinsic performances of molten oxides as electrolytic medium, and their corresponding key physicochemical properties. In a second time, the most recent discoveries related to the oxygen evolution reaction in such electrolyte will be presented, in particular with respect to mass transfer limitations [3] and anode materials design [4].
[1] A. Allanore, Journal of Metals - JOM, vol. 65, issue 2, 131, (2013)
[2] R. H. Aiken, Process of making iron from the ore. US patent 816, 142 (1906)
[3] A. Allanore, Electrochimica Acta, 110, 587-592, (2013)
[4] A. Allanore, L. Yin and D.R. Sadoway, Nature, 497 (7449), 353–356, (2013)
Distributed PEFC Performance during Cationic Contamination
Authors: Uddin Md. Aman , Wang Xiaofeng , Ozdemir M. Ozan , Qi Jing , Bonville Leonard J. , Pasaogullari Ugur , Molter Trent 
Published: February 2020

In our previous studies (1-3), severe performance degradation of PEFCs was observed due to cationic impurities. In this study, we investigate how cations affect the spatial performance distribution in a PEFC using a segmented cell.
The segmented cell hardware consists of an aluminum anode flow field, a segmented aluminum cathode flow field, two aluminum end plates and one cupper current collector. All the aluminum parts were gold plated. Cathode flow field was divided into eight segments. Eight pieces of equal size aluminum current collectors were placed inside a PTFE block and straight flow channels were machined through both the PTFE and the aluminum segments (Figure 1). Total active area of the cell was 5 cm2. 2.85 mM CaSO4solution was introduced in the air stream through a nebulizer (1-3) at a rate of 110 uL/min, corresponding to 21.2 ppm based on dry air flow rate.
Figure 2 shows the voltage and current density distribution profile in each segment. The cell was operated at a constant total current of 1 A. During the baseline test of 24 hours, pure air was injected through cathode. The current in each segment remained constant through this period. Following the baseline test, the contaminant was injected in the air stream. The segments closest to the gas inlet were first affected by the contaminant. The current density in the segments closest to the gas inlet decreased while the segments closest to the outlet increased. Since it was a constant current test, when the current in the segments closest to the gas inlet decrease, other segments picked up that current to maintain total current constant.
During the baseline test, voltage remained constant in all segments. After contaminant injection, the cell voltage started to decrease and after 50 hours, voltages in each segments fluctuated. The voltage fluctuation was found to be mainly due to mass transport loss. The contaminant solution evaporated and deposited on the flow field and the GDL surface (Figure 3), and entered into the GDL which caused the mass transport losses. Moreover, the aluminum flow fields corroded and corrosion byproducts also deposited on the flow field and GDL surface. Throughout the test, there was no significant variation in voltage between segments.

Acknowledgements

The authors gratefully acknowledge financial support from NSF (CBET-0748063), DOE-EERE through University of Hawaii-Hawaii Natural Energy Institute (DE-EE0000467).

References

1. X. Wang, J. Qi, M. O. Ozdemir, M. A. Uddin, L. Bonville, U. Pasaogullari, T. Molter, ECS Trans., 58 (1) 529-536 (2013)

2. J. Qi, X. Wang, M. O. Ozdemir, M. A. Uddin, L. Bonville, U. Pasaogullari, T. Molter, ECS Trans., 58 (1) 537-542 (2013).
3. M. A. Uddin, X. Wang, J. Qi, M. O. Ozdemir, L. Bonville, U. Pasaogullari, T. Molter, ECS Trans., 58 (1) 543-553 (2013).
Impact of MPL Thickness on Water Management of PEMFC By Synchrotron X-ray Radiography
Authors: Lee Jongmin , Yip Ronnie , Antonacci Patrick , Ge Nan , Kotaka Toshikazu , Tabuchi Yuichiro , Bazylak Aimy 
Published: February 2020

The polymer electrolyte membrane fuel cell (PEMFC) is an efficient and clean energy conversion device. The performance of PEMFCs at high power operation is governed by product water management. The gas diffusion layer (GDL), a porous carbon fiber sheet, is sandwiched between a catalyst layer and a flow field, providing diffusive pathways for reactant gases and product water. A transient microporous layer (MPL) characterized by sub-micron size pores and hydrophobic contents applied on the GDL or catalyst layer is known to extend limiting current density. Past research [1] has shown that there exists an optimal thickness of MPL. However, the effect of varying MPL thickness has not been studied by visual inspection.
Our research group has successfully investigated liquid water dynamic and distribution in an operating PEMFC using synchrotron radiography [2-3]. For this study, a miniature fuel cell with an active area of 0.48cm2and 0.2mm channel and rib width was designed for improved image quality. MPLs of varying thickness (no MPL, 50μm, 100μm, and 150μm) were coated on TGP-H-60 (Toray Industries Inc.). Each fuel cell was operated according to a pre-determined testing scheme on a Scribner 850e fuel cell testing station (Scribner Inc.). Visualizations were performed at the Biomedical Imaging and Therapy Bending Magnet (05B1-1) beamline at Canadian Light Source Inc. (Saskatoon, Canada). Spatial and temporal resolutions were approximately 10μm and 0.3fps, respectively. Image processing was carried out according to the Beer-Lambert law. The processed image provides information on liquid water profile across components of the fuel cell (Figures 1 and 2). For each types of GDL, liquid water content at the interfaces and within microstructures will be analyzed to isolate effect of MPL thickness on water distribution and performance of the fuel cell.

References:

1. Jin Hyun Nam, Kyi-Jin Lee, Gi-Suk Hwang, Charn-Jung Kim, Massoud Kaviany, Int. J. Heat and Mass Transfer, 52, 2779-2791 (2009).
2. J. Lee, J. Hinebaugh, A. Bazylak, J. Power Source, 227, 123-130 (2013)
3. J. Hinebaugh, J. Lee, A. Bazylak, J. Electrochem. Society, 159 (12) F826-F830 (2012)
Electrodeposition of Cadmium Selenide/Poly-o-Anisidine Composite
Authors: Maranowski Bartosz , Czerwieniec Bartosz , Strawski Marcin , Szklarczyk Marek 
Published: February 2020

Cadmium selenide is under interest due to its optical properties: direct bandgap of the width 1.7 eV and higher abrosption coefficient comparatively to indirect semicoductors. These properties make CdSe a promising candidate for wide range of applications: fotovoltaics, hydrogen photogeneration, and electronics. Photocorrosion is the major problem in the application of CdSe in photogalvanic cells as a photoelectrode. To prevent it, we have been electrosynthesized composite CdSe/poly o-anisidine (POMA).
CdSe/POMA composite was obtained via electrodepostion on HOPG surface. The electrodeposition potentials of CdSe and POMA differs, but it will be shown that there are conditions under which it is possible to deposit one compound over another without decomposition of first one especially CdSe which is easy to oxidize in relatively high anodic potentials where o-anisidine starts to polymerize. The deposits were prepared by a cyclic potentiodynamic technique. Cadmium selenide was deposited from a bath containing 5 mM Cd2+ and 1mM SeO2. POMA was deposited from 0.06 M o-anisidine solution.
The Raman and XPS spectroscopies were applied for the chemical composition of synthesized composite films determination. Photoactivity of the samples was monitored by cyclic voltammetry and potentiostatic techniques in 0.1M HClO4. The formation of composite greatly enhances time stability of the CdSe photoelectrode. Additionally, the formation of p/n junction between CdSe and POMA enhance photoresponse of the studied system. The width of band gap for each compound was determined by reflective UV-Vis spectroscopy and STS techniques. Atomic Force Microscopy was used to show morphology of each sample and to determine thickness of each deposited layer by nanoscrathing technique.
ORR on the Different Surfaces with Different Adsorbents: First Principles Molecular Dynamics Simulations
Authors: Ikeshoji Tamio , Otani Minoru , Qian Yumin 
Published: February 2020

Oxygen Reduction Reaction (ORR) is the hard task in the fuel cell operations and has been studied extensively not only from practical point of view but also from fundamental one. Although various calculations by both MO and DFT calculations were reported, many of them are under the static conditions (i.e. at 0 K) or they are on simple surfaces. We are currently working for it with more realistic models at a certain temperature under the electric bias. First Principles Molecular Dynamics (FPMD) combined with Effective Screening Medium (ESM) [1,2] to apply the potential on the electrode in the similar manner as the real double layer region. We first used it for the simple electrode reaction of the first step of the hydrogen evolution reaction (Volmer reaction) on Pt(111) [3] and then we are extending it to ORR [4,5,6] on various surfaces with various adsorbents.
Electronic structure calculations in the FPMD are based on DFT with ultrasoft-pseudopotentials and PBE functional for the exchange correlation. Program code "STATE" is used. MD is performed at constant temperature 353 K by a velocity scaling thermostat. Electrode potential is controlled by the charges added by the ESM method shown in the figure.
The last step of ORR (=the first step of oxygen evolution) is
H3O+ + OH(ad) + e– --> 2 H2O
The reversibility of this reaction was confirmed on Pt(111) surface with surface charge density σ = 7 µC/cm2(corresponding to ca. 0.6–0.7 V vs. SHE) [4,5] with a pre-adsorbed OH. With higher or lower σ, reaction was remained in only one side. If we introduce a defect (a pit) on the surface, the reaction did not take place [6].
In order to see an effect of the different surface, we simulated a full ORR from O2adsorption to H2O formation on (111), (110) and (100) surfaces. The main reaction scheme observed in the several time simulations for each surface is (dissociation scheme):
O2 --> 2O(ad)
O(ad) + H3O+ + e– --> OH(ad) + H2O
H3O+ + OH(ad) + e– --> 2 H2O
In some cases, following H2O2 formation takes place as an intermediate species (association scheme).
2O(ad) + e– + H3O+ --> H2O2

We are also testing another kind of coadsorption species as a reaction promoter.
In summary, we could confirm that water liquid layer (not only single or bilayer) on the Pt surface plays an important role to proceed to a complete ORR.
[1] M. Otani and O. Sugino, Phys. Rev. B 73, 115407 (2006). [2] O. Sugino, I. Hamada, M. Otani, Y. Morikawa, T. Ikeshoji Y. Okamoto, Surf. Sci., 601 (2007) 5237. [3] M. Otani, I. Hamada, O. Sugino, Y. Morikawa, Y. Okamoto, T. Ikeshoji, J. Phys. Soc. Jpn.. 77 (2008) 024802, Phys. Chem. Chem. Phys., 10 (2008) 3609. [4] T. Ikeshoji, M. Otani, I. Hamada and Y. Okamoto, Phys. Chem. Chem. Phys., 13 (2011) 20223. [5] T. Ikeshoji, M. Otani, I. Hamada, O. Sugino, Y. Morikawa, Y. Okamoto, Y. Qian, and I. Yagi, AIP Advances, 2, 032182 (2012). [6] Y. Qian, I. Hamada, M. Otani, and T. Ikeshoji, Catal. Today, 202, 163-167 (2013).
Dopant Based Stabilization of LiCoO2: Insight from First-Principles Calculations
Authors: Santana Juan A. , Kim Jeongnim , Kent Paul R. , Fernando Reboredo A. 
Published: February 2020

LiCoO2 is widely used as cathode material for Li-ion batteries (1). However, the usable specific capacity of LiCoO2 is limited to approximately half of its theoretical capacity. This limitation comes from the mechanical failure of the cathode when more than 50% of Li is deintercalated. The stability of LiCoO2 and its electrochemical performance can be improved by coating its surface with inner metal oxides (2). Such approach has been used for different cathode materials, but the origin of the stabilization effect is poorly understood. The enhanced stability of the cathodes has been rationalized invoking many effects, e.g., i) the inner metal oxides act as a physical barrier to prevent cathode-electrolyte reactions (3), and ii) the layered structure of the cathode material is stabilized by the migration of metal ions from the coating oxides (1). To have a better understanding of the stabilization mechanism, we have performed Density Functional Theory calculations of LiCoO2doped with inner metal ions (Figure 1). Such calculations allow us to study how the migration of metal ions from the coating oxides modify the structure of the cathode materials.

Acknowledgments.Research supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

Reference:

1. H. Li, Z. Wang, L. Chen, and X. Huang, Adv. Mater., 21, 4593–4607 (2009).
2. Z. Chen, Y. Qin, K. Amine, and Y.-K. Sun, J. Mater. Chem., 20, 7606–7612 (2010).
3. J.-S. Kim et al., J. Electrochem. Soc., 151, A1755–A1761 (2004).

Figure 1. Schematic of some possible sites for metal dopants in LiCoO2: the left and central panels show the dopant on Li and Co sites, respectively, and the right panel shows substitution on both Li and Co sites.
Computational Thermodynamic Modeling of Mixed Polyanion Glasses for Lithium Ion Battery Cathode Materials
Authors: Shin Dongwon , Kercher Andrew Keith , Kiggans Jim , Dudney Nancy J 
Published: February 2020

We have used computational thermodynamic approach to model Lithium-bearing mixed polyanion (LBMP) as an effort to predict electrochemical properties of glass cathode materials. Individual LBMP have been modeled within the framework of the compound energy formalism (CEF) as implemented in the CALPHAD (CALculation of PHAse Diagram) approach [1, 2].
To model the baseline material Li/FePO4 thermodynamic descriptions for the crystalline solid and liquid phases of constituent Fe2O3 and P2O5 have been taken from the Scientific Group Thermodata Europe (SGTE) Substance Database and used as reference states. Thermodynamic model parameters for FePO4 and Fe4(P2O7)3 have been self-consistently evaluated to reproduce Fe2O3-P2O5 pseudo-binary phase diagram reported in the literatures. Afterward thermodynamic model parameters for the FePO4-LiFePO4 pseudo-binary system has been evaluated to represent experimentally determined phase equilibrium data [3, 4]. The model successfully reproduces the miscibility gap at low temperatures by introducing positive interaction between FePO4 and LiFePO4.
FIG. 1. Calculated cell circuit voltage of Li
x
FePO4 of crystalline and glass phases. Different ratios between the liquid and solid phases of LiFePO4 and FePO4(L:S) have been used to model glass phase.
From the developed thermodynamic database the open circuit voltage (OCV) of crystalline and glass Li/FePO4 have been predicted by calculating chemical potential of Li (see FIG. 1). In order to model the Li
x
FePO4 glass phase, different ratios between the liquid and solid phases of LiFePO4 and FePO4(L:S) have been used and ideal mixing between two end-members have been assumed. The glassy form is more sloping, and has a significantly lower potential.
Thermodynamic modeling of Li-Fe2O3-V2O5 has been carried out to incorporate additional polyanion species in the model for the glass cathode materials. From the completed thermodynamic modeling of Li/FeVO4
which combined with the baseline system, the cell voltage of Li/Fe4(0.5P2O7×0.5V2O7)4 has been benchmarked against experimental measurements. The ratio between the solid and liquid thermodynamic descriptions to describe the electrochemical behavior of the LBMP glass materials has been established and will be used for other polyanion species to be added in the baseline system.

Acknowledgement

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy

References

[1] L. Kaufman, H. Bernstein, Computer Calculation of Phase Diagram, New York, Academic Press Inc., 1970.
[2] N. Saunders, A. P. Miodownik, CALPHAD (Calculation of Phase Diagrams): A Comprehensive Guide, Oxford, New York, Pergamon, 1998.
[3] J. L. Dodd, R. Yazami, B. Fultz, Electrochem. Solid State Lett., 9(3): A151-A5, 2006.
[4] C. Delacourt, P. Poizot, J. M. Tarascon, C. Masquelier, Nature Mater., 4(3): 254-60, 2005.
Synchotron Enabled Ex-Situ and in-Situ Mechanistic Interrogation of Energy Storage Systems
Authors: Takeuchi Esther S , Takeuchi Kenneth J , Marschilok Amy C 
Published: February 2020

Introduction

Full understanding of the electrochemical processes taking place in batteries continues to be elusive due to the complex nature of the reactions associated with discharge and charge processes, and the difficulties of analytical interrogation of these reactions. Ex-situ measurements at various states of electrochemical reduction and oxidation can provide mechanistic insight. A direct approach to the interrogation of the reactions taking place inside batteries is to employ in-situ strategies. Unfortunately, in-situ measurements are often hindered by diminution of signal due to the housing of an electrochemical cell or by the need to create special housings that enable the measurement.

Results and Discussion

Strengths and limitations of diffraction and spectroscopy based approaches characterization of energy storage systems will be discussed, with an emphasis on the unique characterization opportunities provided by synchrotron radiation. X-ray absorption spectroscopy (XAS) is sensitive to local structure within a few coordination shells around the absorbing atom, and can therefore characterize local structure even if long-range order is absent.1,2 Energy dispersive x-ray diffraction (EDXRD) approaches allow in-situ measurement of an battery electrode in its native environment.3 Specifically, electrode interrogation as a function of depth by EDXRD will be presented, enabling identification of the chemical reaction front within the battery electrode.

References

1) Patridge, C. J.; Jaye, C.; Tesfaye, A. A.; Ravel, B.; Fischer, D. A.; Marschilok, A. C.; Zhang, P.; Takeuchi, K. J.; Takeuchi, E. S.; Banerjee, S. J. Phys. Chem. C, 2011
,
115
(29),14437–14447.
2) Menard, M. C.; Takeuchi, K. J.; Marschilok, A. C.; Takeuchi, E. S., Physical Chemistry Chemical Physics. 2013,
15,18539-18548.
3) Takeuchi, E. S.; Marschilok, A. C.; Takeuchi, K. J.; Ignatov, Alexander; Zhong, Zhong; Croft, Mark. Energy and Environmental Science. 2013,
6, 1465-1470.
Nanoimprinted Carbon Structures As High Performance Lithium Ion Battery Anodes
Authors: Wang Peiqi , Li Jiangyu 
Published: February 2020

We demonstrated the synthesis of carbon thin film with ordered nanostructure via nanoimprint lithography starting from thermal plastic polymer polyvinylpyrrolidone (PVP). After the pattern is completely transferred onto PVP thin film during the nanoimprinting process, a three-step thermal treatment is performed to convert the polymer into patterned carbon thin film. Feature size of the pattern ranges between 250 nm up to 2 um with various shapes including 1D line, 2D hole and pillar. Characterized with Raman spectroscopy, the carbon thin film shows a high degree of disorder with a small in-plane graphitic crystallite size of about 1.346 nm calculated using the peak intensity of D band and G band of sp2carbon. Those patterned carbon thin film exhibits good electrical conductivity. When used as anode of lithium ion battery, it shows an enhanced cyclic performance compared to those unpatterned carbon thin films and also graphite. Further study with Electrochemical Strain Microscope (ESM) helps to understand the enhanced Li ion storage capacity locally on the nanoscale.
Figure 1. (A) Atomic force microscopy topography scan of imprinted carbon thin film, (B) cyclic charge/discharge performance of imprinted and unpatterned carbon.
Pre-Lithiated Si Micro Wire Array Anodes Vs. Binder Free S8 Cathodes for Next Generation High Energy Storage
Authors: Hagen Markus , González Enrique Quiroga , Dörfler Susanne , Schumm Benjamin , Tübke Jens , Althues Holger , Kaskel Stefan , Föll Helmut 
Published: February 2020

Li-S is a popular chemistry to obtain possible future high energy cells. Nevertheless, the unstable ether based electrolyte and safety + reliability concerns due to the Li metal anode are still major hurdles that are difficult to overcome. By replacing the Li anode with Si at least some of these problems can be addressed at the cost of losing some potential energy density.
To compare the Li-S and the LixSiy-S system, optimized and pre-lithiated Si microwire anodes and binder free CNT-S cathodes were used. The capacity retention is greatly dependent on charging conditions and electrolyte additives and will be discussed next to possible degradation effects.
The works is part of the joint project AlkaSuSi – Alkalimetal, sulfur and silicon and was financed by German ministry BMBF.