bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon Iso-Dielectric Separation (CIDS) on Centrifugal Microfluidic Platforms
Authors: Aeinehvand MohammadMahdi , Ramírez Sánchez Edgar , Cárdenas Benítez Braulio , Martínez-Chapa Sergio Omar 
Published: February 2020

Centrifugal microfluidic platforms employ pseudo forces controlled by a spindle motor to automate bioanalytical assays on a single fluidic disc with no need for several syringe pumps [1]. Recently, we employed a portable cutter-plotter to fabricate microfluidic discs with active valves at point of need [2]. To address a healthcare issue of global interest, we developed a microfluidic disc to automate a sTREM-1 immunoassay for the detection of sepsis at late stages of the disease. To enable sepsis detection and monitoring at early stages, recently a gold iso-dielectric separation (GIDS) chip is develop that separates activated and non-activated leukocytes from blood serum [3]. However, the GIDS chip requires several syringe pumps and an off-chip manual step for sample preparation i.e., blood serum separation. As an alternative to GIDS, in this study we have developed 3D carbon IDS (CIDS) chips to reduce the cost of device fabrication. To prevent the need for the syringe pumps and external piping networks, we have integrated the CIDS on a microfluidic disc to automate the whole bioanalytical process from sample preparation to characterization of thousands of particles and cells. The main objective of developing the integrated microfluidic platform is the separation of activated and non-activated leukocytes for automated early sepsis detection at point of care (POC). However, as an early proof of the practicality of CIDS-on-disc, in this study we employed the hybrid centrifugal microfluidic system for separating various sizes of polystyrene microbeads as well as different bacteria.
[1] M.M. Aeinehvand, F. Ibrahim, S.W. Harun, A. Kazemzadeh, H.A. Rothan, R. Yusof, M. Madou, Reversible thermo-pneumatic valves on centrifugal microfluidic platforms, Lab Chip. 15 (2015) 3358–3369. doi:10.1039/C5LC00634A.
[2] M.M. Aeinehvand, P. Magaña, M.S. Aeinehvand, O. Aguilar, M.J. Madou, S.O. Martinez-Chapa, Ultra-rapid and low-cost fabrication of centrifugal microfluidic platforms with active mechanical valves, RSC Adv. 7 (2017) 55400–55407. doi:10.1039/C7RA11532F.
[3] J.L. Prieto, H.-W. Su, H.W. Hou, M.P. Vera, B.D. Levy, R.M. Baron, J. Han, J. Voldman, Monitoring sepsis using electrical cell profiling, Lab Chip. 16 (2016) 4333–4340. doi:10.1039/C6LC00940A.
(Invited) Materials Design of High-Energy Cation/Anion Redox in Li-Rich Cathode Materials: Li5FeO4, Li4Mn2O5, and Li2MO3
Authors: Wolverton Chris 
Published: February 2020

The energy density of many lithium metal oxide battery cathodes is limited by redox reactions associated with the transition metal alone. Anionic redox reactions are affording new opportunities to increase this energy density. Here, we present results from first-principles density functional theory (DFT) calculations aimed at understanding the combined cation/anion redox of Li-rich materials, and designing new materials that will enable high-capacity, reversible cycling with minimal oxygen evolution. We illustrate this approach on three Li-rich compounds: Li5FeO4, Li4Mn2O5, and Li2MnO3.
Li5FeO4: Initial removal of Li is accompanied by Fe migration to form a disordered rocksalt structure. A local Li6-O coordination of oxygen, identified by DFT calculations, raises the O 2p band and enables reversible O-/O2- redox behavior, previously unknown in this material. This insight leads to the prediction and subsequent experimental demonstration of anionic and cationic redox reactions with good reversibility and without any obvious O2 gas release.
Li4Mn2O5: We study the recently-reported, high-capacity, disordered rocksalt-type Li4Mn2O5 compound and also determine the ground state ordered structure of Li4Mn2O5 via a DFT-based enumeration method. DFT calculations show that the delithiation process occurs via a three-step reaction pathway involving the complex interplay of cation and anion redox reactions: i) Mn3+ ➝ Mn4+ (LixMn2O5, 4 > x > 2), ii) O2− ➝ O1− (2 > x > 1), and iii) Mn4+ ➝ Mn5+ (1 > x > 0) concomitant with Mn migration from the original octahedral site to the adjacent tetrahedral site. Finally, we predict that alloying with M = V and Cr in Li4(Mn,M)2O5 would produce new stable compounds with substantially improved electrochemical properties.
Li2
MO3: We catalog the family of Li2
MO3 compounds as active cathodes or inactive stabilizing agents using high-throughput density functional theory (HT-DFT). With an exhaustive search based on design rules that include phase stability, cell potential, resistance to oxygen evolution, and metal migration, we predict a number of new Li2MIO3–Li2MIIO3 active/inactive electrode pairs, in which MI and MII are transition- or post-transition metal ions, that can be tested experimentally for high-energy-density lithium-ion batteries.
Elucidating Singlet Oxygen Production in Li-Ion and Metal-Air Batteries
Authors: Houchins Gregory , Pande Vikram , Khetan Abhishek , Viswanathan Venkatasubramanian 
Published: February 2020

At high voltages, Li-ion and Li-air batteries undergo unwanted electrochemical reactions that can permanently decrease the performance of the battery. Recent experiments studying off-gassing from NMC cathodes have yielded different results for the trends of O2, CO2, and CO gas production with varying Ni composition. Studies also disagree on the origin of the elements in the gas. Very recently, it was suggested that not only is Li2CO3 on NMC cathodes responsible for the majority of CO2 production [1] but that singlet oxygen is produced when Li2CO3 is bias above 3.82 V [2]. This and other studies suggest singlet oxygen production as a common degradation pathway in Li-ion, Li-air [3,4], and Na-air [5].
With the use of first principles methods, we attempt to reconcile these experimental works and propose a universal mechanism of singlet oxygen production. We will also discuss a way to experimentally verify our mechanism by varying the electrolyte, which we claim will change the onset potential of singlet oxygen production in a predictable way.
[1] 1. Renfrew, S. E. & McCloskey, B. D. Residual Lithium Carbonate Predominantly Accounts for First Cycle CO2and CO Outgassing of Li-Stoichiometric and Li-Rich Layered Transition-Metal Oxides. J. Am. Chem. Soc. (2017). doi:10.1021/jacs.7b08461
[2] 1. Mahne, N., Renfrew, S. E., McCloskey, B. D. & Freunberger, S. A. Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen. Angew. Chemie Int. Ed. (2018). doi:10.1002/anie.201802277
[3] 1. Mahne, N. et al. Singlet oxygen generation as a major cause for parasitic reactions during cycling of aprotic lithium-oxygen batteries. Nat. Energy (2017). doi:10.1038/nenergy.2017.36
[4] 1. Wandt, J., Jakes, P., Granwehr, J., Gasteiger, H. A. & Eichel, R.-A. Lithium–Air Batteries Singlet Oxygen Formationduring the Charging Process of an Aprotic Lithium–Oxygen Battery.
[5] 1. Schafzahl, L. et al. Singlet Oxygen during Cycling of the Aprotic Na-O2 Battery. Angew. Chemie Int. Ed. (2017). doi:10.1002/anie.201709351
Fabrication and Investigation of Crystalline Non-Porous Conductive Coordination Network Compounds
Authors: Hosseini Pouya , Brand Izabella , Wittstock Gunther , Lenk Thorben , Redel Engelbert 
Published: February 2020

During the last years, surface-bound coordination network compounds (CNCs) have found application for sensing purposes (electrical, optical, and magnetic read-out), charge storage, electrochromic and optoelectronic layers, transparent coatings, bipolar switches, thermoelectric materials, catalytic, photocatalytic and light harvesting applications [1]. However, most of these applications require electrically conductive coordination network compounds (CCNCs). This requirement severely limits the choice of CNCs for the above-mentioned applications. Hexacyanometallates are coordinative networks with high electrical and ion conductivity that possess interesting redox properties and tuneable electrochemical redox transitions associated with clear colour changes [2].
We developed and characterized CCNCs such as copper hexacyanoferrate as thin crystalline films and characterized their optical, magnetic, electrical and dielectric properties. Thin films of these compounds were fabricated on gold and silicon oxide coated by self-assembled, cyanide-terminated monolayers using alternating immersion in their precursor solutions. Atomic force microscopy (AFM) confirms the formation of copper hexacyanoferrate with cubic structure on the gold surface (Fig. 1).
Fig. 1: AFM image of copper hexacyanoferrate film on a cyanide-terminated self-assembled monolayer on gold surface via layer-by-layer method.
X-ray diffraction (XRD) analysis confirmed the crystalline nature of the films. The thin films can be switched by exploiting the redox chemistry of the metal centres. The modulation of the electrical transport properties provides great potential benefits for numerous future applications in microelectronic device technologies. Structural and electronic changes of the films were probed by X-ray photoelectron spectroscopy (XPS) and polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) before and after electrochemical oxidation and reduction [3]. Results demonstrate the possibility for electrochemical switching of the material properties for each compound but also indicates the complications in those transitions originating in the existence of different structures and defects in which (mobile) alkali metal cations may or may not reside in the pores and provide charge compensation.

Acknowledgement(s) Financial supports from DFG priority programme (SPP1928, Wi1617/24) is gratefully acknowledged.

References:

[1] J. Liu, W. Zhou, J. Liu, I. Howard, G. Kilibarda, S. Schlabach, D. Coupry, M. Addicoat, S. Yoneda and Y. Tsutsui, Angew. Chem. Int. Ed., 7441, 54 (2015).
[2] J. J. Alexander and H. B. Gray, J. Am. Chem. Soc., 4260, 90 (1968).
[3] P. Hosseini, G. Wittstock and I. Brand, J. Electroanal. Chem.,
199, 812 (2017).

Figure 1
Density Measurement of Small Samples of Metal-Organic Frameworks Using Confocal Microscopy
Authors: Walheim Stefan , Redel Engelbert , Schimmel Th. 
Published: February 2020

A novel approach for precise density measurement of small samples with a weight in the mg-range has been developed recently [1]. Using this approach, a solid object is dropped into a semi-confined cylindrical cavity, which is filled with a nonvolatile liquid. To determine the volume of the sample the rise of the liquid meniscus is measured with confocal microscopy. During the development of new MOFs, the lack of an appropriate amount of material makes it often impossible to determine the bulk density of the new material. Here we demonstrate how the density of small MOF samples can be determined by this novel method. Even with samples in the range of 1.5 mg we can measure the density with an accuracy better than 1%. The effect of previous sorption of other liquids and the distinction of open and closed porosity will be addressed.
1.: Bulk Density Measurements of Small Solid Objects Using Laser Confocal Microscopy. A. Kilmametov, R. Gröger, H. Hahn, Th. Schimmel and S. Walheim: Advanced Materials Technology 2017, 2, 1600115
3D CFD Modelling of Low Temperature Pemfcs
Authors: Klauber Daniel , Heinzmann Marcel , Magagnato Franco , Frohnapfel Bettina 
Published: February 2020

Computational fluid dynamics (CFD) is becoming more and more an essential tool to gain deeper insight into the physics of proton exchange membrane fuel cells (PEMFCs). The goal is to achieve an optimized fuel cell design as a further step towards the commercialization of PEMFCs as an alternative to common automotive fuel engines. Nowadays a validated CFD model provides one means of improving the performance of fuel cells.
The open-source code of Beale et al. [1] is a generic framework for simulating different types of fuel cells. The authors extended it to a full three-dimensional model using additional model equations and modified source terms. According to the integrated cell concept used in the open-source code three additional so-called 'child' meshes are introduced to account for charge transport and water transport in the polymer electrolyte membrane.
The parameters of the Butler-Volmer equation (Figure 1, top), describing the electrochemical kinetics of the fuel cell, are used as fitting parameters in most existing literature. In this work the authors use a set of experimentally determined parameters in order to reduce the number of uncertain/fitting parameters.The method used to determine this set of parameters is electrochemical impedance spectroscopy whereby the data is analysed using the distribution function of relaxation times [2]. This method helps to separate the polarization processes contributing to the overall polarization loss in a clearer way. The numerical results of the model described above are compared to polarization curves measured by experiments. The results show good agreement (Figure 1, bottom) for two different humidifications (40% RH and 70% RH) in the activation and ohmic regions.
References
[1] S. B. Beale, H. Choi, J. G. Pharoah, H. K. Roth, H. Jasak, D. H. Jeon, Open-source computational model of a solid oxide fuel cell, Comput. Phys. Commun. 200 (2016) 15-26.
[2] H. Schichlein, A.C. Müller, M. Voigts, A. Krügel, E. Ivers-Tiffée, Deconvolution of electrochemical impedance spectra for the identification of electrode reaction mechanisms in solid oxide fuel cells, J. Appl. Electrochem. 32 (2002) 875–882.

Figure 1
Numerical Study of Liquid Water Saturation inside Gas Diffusion Layer and Micro Porous Layer during PEMFC Operations Using Multiscale and Multiphase Modeling Approach
Authors: Shimpalee Sirivatch , Satjaritanun Pongsarun , Weidner John W. , Hirano Shinichi 
Published: February 2020

The objective of this study is to use multidimensional/multiscale/multiphase polymer electrolyte membrane fuel cell (PEMFC) model [1-10] to enhance understanding of water transport inside gas diffusion layer (GDL) and microporous layer (MPL) during fuel cell operations. The outcomes of this work will improve the development of a fuel cell stack and electrochemical cells with increasing in performance at high current densities. Experimental investigation of oxygen transport has been limited by an inability to resolve water saturation-dependent properties. This work also shows the successful in development of a multiscale calculation technique that incorporates detailed structure of each scale dimension in every component of a fuel cell and simultaneously performed a prediction. The effect of operating conditions and GDL/MPL properties on the transports including liquid water inside PEMFC will be the primary focus of this work.
Figure 1 shows an example of simulation works to predict the effect of MPL thermal properties on liquid water transport and performance of PEMFC. In this figure, three specific thermal conductivities were simulated. Figure 1 shows liquid distributions at cathode side of PEMFC using SGL 25BC GDLs. The amount of water condensation increases from low thermal conductivity to high thermal conductivity and the condensed water starts from the areas under the rib instead of the areas under the channels. This is because the areas under the rib has lower temperature than the areas under the channel. This figure also presents the local liquid saturation profiles inside GDL/MPL. The higher liquid saturation profiles are presented in MPL (Locations 5 and 6) than in GDL (Locations 1 to 4). In the particular operating condition, the performance increases when the thermal conductivity is higher. This simulation shows a possibility of model based engineering to optimize MPL thermal property and operating conditions.
References:

Shimpalee, D. Spuckler, and J. W. Van Zee J. Power Sources, 167 (2007) 130-138.

Shimpalee, M. Ohashi, C. Ziegler, C. Stoeckmann, C. Sadeler, C. Hebling, J. W. Van Zee, Electrochemica Acta, 54 (2009) 2899-2911.

Shimpalee, J. of Electrochem. Soc., 161 (2014) E3138-E3148.

Frisch, B. Hasslacher, Y. Pomeau, Physical review letters 56 (14) (1986) 1505-1508.

R. McNamara, G. Zanetti, Physical Review Letters 61 (1988) 2332-2335.

Satjaritanun et al., J. Electrochem. Soc. 164 (2017) E3359-E3371

Satjaritanun et al., ECS Transactions, 80 (2017) (8) 187-195

Hirano et al., Abstract# 1419, 232nd Electrochemical Society Meeting, October 1-5, 2017, National Harbor, Maryland.

Shimpalee et al., Abstract# 1418, 232nd Electrochemical Society Meeting, October 1-5, 2017, National Harbor, Maryland.

Satjaritanun et al., Abstract# 1373, 232nd Electrochemical Society Meeting, October 1-5, 2017, National Harbor, Maryland.

Figure 1
Characteristics of Water Droplet Release from Gas Diffusion Layers
Authors: Büchi Felix N , Mularczyk Adrian , Lamibrac Adrien , Marone Federica , Schmidt Thomas J. , Eller Jens 
Published: February 2020

Droplet formation and detachment in the gas flow channel are important steps in the water management in polymer electrolyte fuel cells. Formation and detachment of the droplet are expected to cause changes in the local saturation in the GDL, which are important to understand the relevant forces determining formation and detachment.In order to control the two important boundary conditions of water feed rate and gas dynamics in the channel accurately, a non-operating set-up was developed. Water is injected through a 0.5 mm hole from the bottom into a SGL 25 BA gas diffusion layer (GDL) facing a gas flow channel on its top. The liquid water distribution in the GDL and the behaviour of droplet detachment at the GDL-gas channel interface are monitored using sub-second X-ray tomographic microscopy (XTM) with 0.75 s scan time and 2.55 s repeating frequency and fast X-ray 2D radiography (3 ms exposure time).
With the constant water injection rates, the droplet formation was found to be very periodic with droplet growth showing a repeating pattern. The droplet diameter evolution for two different injection rates is shown in Figure 1 (a). The final droplet volumes were found to be 17.6 nL at an injection rate of 350 nL/min and 10.3 nL at 1000 nL/min.Figure 1 (b) shows the water volume in the GDL. The liquid volume in near the inlet was found to be high and decreasing towards the gas channel, corresponding to a high saturation near the inlet and a low saturation near the gas channel. In the bulk of the GDL, no changes occurred at droplet detachment. But in the upper layers of the GDL, for the injection rate of 350 nL/min, a fluctuation of water volume caused by droplet detachment can be observed.

Figure 1
Experimental Study on Ionic Conductivity of Carbon Support within Polymer Electrolyte Fuel Cell Catalyst Layers
Authors: Hu Leiming , Guo Yuqi , Litster Shawn 
Published: February 2020

Conventional polymer electrolyte fuel cells (PEFCs) use carbon supported Platinum (Pt/C) as the catalyst. With decades of efforts, researchers have brought down the loading of Pt below 0.1 mg/cm2 on the anode and 0.4 mg/cm2 on the cathode. However, the high cost of Pt based catalyst still serves as a big barrier for PEFCs’ fully commercialization. Within the catalyst layer, polymer electrolyte ionomer (e.g. Nafion) is usually used as the proton conducting media. During the catalyst layer fabrication process, Pt/C particles are present as aggregates. Due to size exclusion, the polymer electrolyte mainly coats the large mesopores of the Pt/C aggregates, i.e. ionomer covers the secondary pores. In high surface area carbon supports, a significant amount of Pt exists within the smaller mesopores and micropores of the support, which is inaccessible to the ionomer. Although it is known that protons are able to reach Pt within the aggregates when those pores are filled with liquid water, the magnitude and mechanism of proton transport is largely unknown.
In past studies, the proton conductivity of continuous Pt surfaces have been studied (1), with hypothesis proposing that proton can transport through Pt surface by surface diffusion or through electric double layer (EDL) at the metal/water interface. It has also been reported that proton conductivity is severely hindered over extended glassy carbon surfaces (2). However, the widely used Pt/C catalyst doesn’t have continuous metal surface, and unlike glassy carbon, the carbon support used in the catalyst layer usually has a mixture of functional groups on the surface (e.g., carboxyl and sulfur species), which will alter the surface ionic conductivity through deprotonation. In this work, we measure the conductivity in ionomer free carbon (Vulcan XC72R) and ionomer free Pt/C (10 wt.% HiSPEC 2000) electrodes to better understand the conduction properties of ionomer-free carbon support surfaces. Our experiments evaluate the effects of both electrode potential and the relative humidity (RH) on the conductivity. Electrochemical impedance spectroscopy (EIS) and transmission line modeling show the proton conductivity of the ionomer-free electrode decreases as electrodes’ potential increase (see Figure 1). The potential dependence of the ionic conductivity is supported by a cyclic voltammetry (CV) analysis. Herein, we present several aspects related with the proton conductivity within the ionomer-free carbon domains of the catalyst layer and their effects on fuel cell performances.
Acknowledgement
This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271.
References

E. L. Thompson and D. Baker, ECS Trans., 41, 709 (2011).

U. Paulus, Z. Veziridis, B. Schnyder, M. Kuhnke, G. Scherer and A. Wokaun, J. Electroanalytical Chemistry, 541, 77 (2003).

Figure 1