bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Numerical Simulation Approaches for Understanding Transports Behavior inside Polymer Electrolyte Membrane Fuel Cells
Authors: Shimpalee Sirivatch 
Published: November 2022

Augmentation of polymer electrolyte membrane (PEM) fuel cell (FC) performance at high current densities, particularly under automotive application, is important to improve the overall power density and to reduce the cost of PEMFC systems. Primarily, the fundamental non-linearity of the equations governing PEMFC performance on a three-dimensional model necessitates iterative solutions. As of now, mass transport over-potential is a major barrier to achieving high performance at a high current density. Experimental investigations of oxygen transport in particular are limited by an inability to resolve the water saturation-dependent properties. The alternative approach to understand and overcome transport resistances, predominantly inside the gas diffusion layer, is to use advanced numerical modeling.
Numerical simulation techniques using in PEMFC will be presented including conventional computational fluid dynamics and the meshless Lattice Boltzmann method (LBM) which is an alternative advanced modeling technique [1-14]. This approach can be applied to existing models to visualize the transports inside the structure of microscale geometries, such as: a gas diffusion layer (GDL), micro porous layer (MPL), and catalyst layer (CL). The study where the goal was to use these numerical approaches and directly predict the transports behavior across the length scale (macro-, meso-, micro-, and nano- scales) as shown in Figure 1. The understanding of local kinetic activity inside nanoscale CL implemented into the model will also be discussed. The achievement of this work can enhance the potential capability of a model-based investigation of transport physics inside PEMFC to find solution of designs and operational conditions especially for transport applications.
References:

S. Dutta et al., J of Applied Electrochemistry, 30, 135-146, 2000

S. Shimpalee et al., J. of Power Source, 135, 79 – 87, 2004.

S. Shimpalee et al. Electrochemica Acta, 54, 2899-2911, 2009.

S. Shimpalee, J. of Electrochem. Soc, 161(8), E3138-E3148, 2014.

V. Lilavivat et al., Electrochimica Acta,174,1253–1260, 2015.

S. Shimpalee et al., J. of Electrochem. Soc., 164(11), E3073-E3080, 2017.

P. Satjaritanun et al., J. of Electrochem. Soc., 164(11), E3359-E3371, 2017.

P. Satjaritanun et al., J. of Electrochem. Soc., 165(13), F1115-F1126, 2018.

S. Shimpalee et al., J. of Electrochem. Soc., 166(8), F534-F543, 2019.

P. Satjaritanun et al., J. of Electrochem. Soc., 167(1), 013516, 2020.

M. Sepe et al., J. of Electrochem. Soc., 167, 104516, 2020.

P. Satjaritanun et al., J. of Electrochem. Soc., 168 (4), 044508, 2021.

M. Sepe et al., J. of Electrochem. Soc., 168, 074507, 2021.

P. Satjaritanun et al. In-press Acc. Mater. Res. 2022.

Figure 1
Unique Porous Structures Supported by Anodic Treatments in Liquid Ammonia (-50°C, Patm)
Authors: Bouttemy Muriel , Bechu Solene , Fregnaux Mathieu , Aureau Damien , Etcheberry Arnaud , Goncalves Anne-Marie 
Published: November 2022

Since the first anodic porosification of semiconductors in the 1950s, numerous studies have reported a wide range of porous structures. The conditions used during the growth of pores can explained the shapes obtained but the formation mechanism and especially the influence of surface chemistry during porosification still raise many questions.
It is in such context that the contribution of liquid ammonia (-55°C) is crucial. Indeed, this remarkable non-aqueous solvent allows, on the one hand, to obtain novel porous structures on n-InP and, on the other hand, it allows for the first time a specific and original interfacial chemistry, governed by the chemistry of nitrogen.
In fact, in liquid ammonia, the dissolution of III-V semiconductors (GaAs, InP) is systematically done after a surface passivation step. This passivation step is particularly stable on InP and revealed the formation of a phosphazene type film (monolayer) resulting from the concomitant oxidation of the solvent and the semiconductor. The "multi-material" approach is a key factor, as it underlines the determinant role of the surface chemistry. In fact, at higher current densities, the porous structures of n-InP and n-GaAs show contrasting structures, which give an original behaviour compared to the aqueous medium. In order to determine the efficiency of the dissolution mechanism (at lower and higher current density), the quantity of indium (or gallium) salt will be quantified by Inductively coupled plasma optical emission spectroscopy analysis after ammonia evaporation.
Moreover, the remarkable reproducibility of the anodic behaviour allowed physico-chemical characterisations of the porous surface, supported by scanning electron microscopy and the variation of the interfacial potential, photoluminescence and X-ray photoelectron spectroscopy.
More specifically on n-InP, where an original structure was revealed, these analyses, during the early stages of porosification, led to the identification of a porosification mechanism in this solvent. Furthermore, at higher current densities, an amorphous film becomes thicker on the surface of the porous structure. Further porosification requires the permeability of this amorphous structure which would most probably result from the polymerisation of phosphazene since the presence of nitrogen could be clearly identified on the pore walls by Auger spectroscopy.
Assessing and Modifying Selective Transport for Nonaqueous Flow Battery Membranes
Authors: Koenig Gary , Mccormack Patrick , Geise Geoffrey 
Published: November 2022

Membranes are a critical component for redox flow battery (RFB) systems. An ideal membrane must be stable in the RFB solvent and process environment, and to obtain desirable electrochemical performance must facilitate transport of the charge compensating ion while minimizing crossover of the dissolved electroactive species (e.g., redox shuttles). For more established aqueous RFB systems commercial membranes, such as sulfonated fluoropolymers, have been used to successfully facilitate development of RFB power stacks at industrial scales.
Recently, there has been interest in developing nonaqueous, or organic, RFB systems. A potential advantage of a nonaqueous RFB is the accessibility of higher voltages per cell, which would result in higher energy density for the RFB system. Membrane materials for nonaqueous RFBs are not well established, and thus the composition and processing for these membranes is an open area for further research.
In this talk, efforts towards the understanding and development of a nonaqueous RFB membrane material will be described. Assessment of the conductivity and crossover of the membrane material system will be discussed, as well as efforts to improve electrochemical properties and membrane stability. Initial results suggest that the interactions between the redox shuttles and the membrane are in many cases fundamentally very different for nonaqueous RFB membranes compared to aqueous RFB membranes, providing possibilities for different routes to design nonaqueous RFB membrane materials.
(Invited) Glassy Carbon Electrodes Modified with Micromagnets: Magnetoelectrocatalysis of HER
Authors: Knoche Gupta Krysti , Lee Heung Chan , Coduto Joshua Richard , Leddy Johna 
Published: November 2022

Electrode kinetics for the hydrogen evolution reaction (HER) on glassy carbon electrodes are inherently slow. Voltammetric responses are marked by large overpotentials η and small exchange current densities j0.
HER rates are markedly increased on glassy carbon electrodes modified with composites of Nafion® and siloxane coated micromagnets. Comparison of linear sweep voltammograms of glassy carbon electrodes modified with either Nafion films or composites of magnetized iron oxide microparticles identifies enhanced HER rates where magnetic gradients are established.

For magnetized 1 𝜇m γ-Fe2O3 microparticles in Nafion, η is decreased by 0.191 ± 0.019 V at 0.4 mA cm-2 compared to Nafion films. This corresponds to an energetic advantage of -18.4 kJ/mol and a 40-fold increase in j0.

For magnetized 5 𝜇m Fe3O4 microparticles in Nafion, η is decreased by 0.28 V at 0.4 mA cm-2, which corresponds to an energetic advantage of -27 kJ/mol and 230-fold increase in exchange current.

HER rate on platinum electrodes is unchanged for Pt electrodes modified with Nafion films and with composites of magnetized micromagnets in Nafion.

Enhancements are not due to either magnetohydrodynamics or mediation as there is no bulk solvent volume in Nafion to convect and siloxane coating renders the iron oxide microparticles chemically and electrochemically inert. Voltammetry for glassy carbon electrodes modified with Nafion films and with composites of Nafion and demagnetized microparticles are comparable.
The chemistry of magnetized and demagnetized composites are the same; the rate enhancements arises from the physical impact of the magnetic gradients in the magnetized composites.
The enhanced rate for HER on glassy carbon arises through magnetoelectrocatalysis.
Work is undertaken at the University of Iowa. The National Science Foundation (NSF CHE-1309366 and NSF CHE-0809745) and the Army Research Office (W911NF-19-1-0208 (74912-CH-II)) supported these projects.
(Invited) ALE Based Manufacturing of Nanostructures below 20 Nm
Authors: Suyatin Dmitry B. , Jafari Jam Reza , Karimi Mohammad , Khan Sabbir A. , Sundqvist Jonas 
Published: November 2022

Continued downscaling of electronic components, such as transistors and capacitors for advanced processors and memory chips, is ever harder and at the same time very important for our society. Atomic layer etching (ALE) is the most advanced etching process used in industry today. ALE enables material removal with atomic precision and is potentially damage-free for remaining material, which motivated its introduction to the industry. Together with atomic layer deposition (ALD) and atomic layer cleaning (ALC) ALE enables the new era of atomic-scale processing which is critical for the most advanced semiconductor technology nodes. In new technology nodes, the ALE is expected to be used together with advanced lithographical tools [1] and may enable new patterning schemes [2]. In this talk, we will present an overview of recent progress in ALE for manufacturing nanostructures with critical dimensions (CD) below 20 nm with the main focus on our work.
We discovered that by combining ALE and other already existing production technologies in a unique way, we cut the number of process steps increasing the throughput, saving on production costs, and lowering the CO2 footprint [3, 4]. And we push the resolution limits also. This is enabled by the recently discovered ALE selectivity to inclined surfaces which turns walls of tapered structures into etch masks. The inclined surfaces can be readily fabricated by e.g. dry etching or epitaxial growth. This process provides access to the fabrication of extremely small structures in a very delicate, precise, and efficient way. All this by relying on changes in already existing equipment and processes, saving investments for the industry. We compete with already established semiconductor technologies and complement them at the same time.
References:

S. Khan, D.B. Suyatin, J. Sundqvist, et al. ACS Applied Nano Materials, 1, 6, 2476, DOI: 10.1021/acsanm.8b00509 (2018).

N. Marchack, K. Hernandez, B. Walusiak, J.-I. Innocent
‐
Dolor, S. Engelmann, Plasma Process Polym., DOI: 10.1002/ppap.201900008 (2019).

D. B. Suyatin, S. A. Khan, J. Sundqvist, et al. presented at 16th Int. Conf. on ALD, Dublin, Ireland, July (2016).

Sabbir Khan, Dmitry B. Suyatin, Jonas Sundqvist, A Method for Selective Etching of Nanostructures. WO2017157902A1 (2017).
(Invited) Investigating Surface Reaction Thermodynamics: In Situ Calorimetry for Atomic Layer Deposition
Authors: Bielinski Ashley R. , Martinson Alex B. F. 
Published: November 2022

Atomic layer deposition (ALD) is comprised of sequential self-limiting surface reactions that are inherently sensitive to the surface chemistry of the substrate and the reactivity of the chosen precursors. In order to better understand ALD processes and direct their future development we must investigate the fundamental mechanisms of ALD reactions. This is commonly done using a combination of computational modeling and experimental investigations using techniques like spectroscopic ellipsometry and IR spectroscopy. We present pyroelectric calorimetry for ALD as an in situ technique to measure the time resolved heat generation from ALD reactions. This provides a new dimension of thermodynamic and kinetic reaction data.
As an experimental technique, pyroelectric calorimetry measures ALD reactions on realistic surfaces as opposed to idealized models. We have designed and constructed custom calorimeters that are compatible with typical ALD process parameters. These calorimeters have been calibrated with a thermal resolution down to 0.1 μJ/cm2 and a temporal resolution of 50ns. To put this in perspective for an ALD reaction, this corresponds to about 0.1% of the heat evolved in the trimethylaluminum (TMA) and water ALD process and about 104 faster than our measurement of the TMA half reaction. The temporal resolution of our calorimeters is orders of magnitude faster than most complementary in situ analysis techniques including ellipsometry, IR spectroscopy, quartz crystal microgravimetry, and mass spectrometry. This time resolution provides information on precursor flow dynamics and reaction kinetics.
Pyroelectric calorimetry was used to investigate the TMA and water half reactions for ALD Al2O3 along with in situ spectroscopic ellipsometry thickness measurements and Rutherford backscattering spectrometry (RBS) composition analysis. This enabled comparisons of the change in thickness with the amount of heat generated as each half reaction saturates. Atomic growth rates calculated form RBS were used to calculate the heat generated on a per-atom basis. These results were then compared with proposed reaction mechanisms and energy changes from density functional theory (DFT) computational modeling.
Measurements of reaction and adsorption heats can also be used to compare and evaluate different precursors and inhibitor molecules for ALD growth inhibition in area-selective ALD. We investigated how the thermodynamics of adsorption can guide our choice of precursor-inhibitor pairs when using small molecule inhibitors that rely on competitive adsorption and chemical passivation to prevent ALD growth. Pyroelectric calorimetry offers new insight into what drives and limits ALD reactions and provides many opportunities for future investigations.
Kinetics of TiCl4 Vapor Phase Infiltration (VPI) into PMMA and the Resulting Thermophysical and Optical Properties of the TiOx -PMMA Hybrids
Authors: Balogun Shuaib Adesina , Steiner Adam , Losego Mark D 
Published: November 2022

Vapor phase infiltration (VPI) is a post-polymerization modification technique that imbues inorganic materials into polymers to create organic-inorganic hybrid materials with new properties distinct from the parent polymer. While several VPI precursor-polymer chemistries have been explored, a lack of chemical intuition remains for fully understanding the thermodynamics and kinetics that govern the VPI process. This study seeks to continue to build this knowledge by examining the VPI process kinetics for TiO2 infiltration into PMMA via the use of TiCl4 and H2O precursors. In this research, polymethylmethacrylate / TiO2 hybrid materials are prepared using VPI. The depth of infiltration of the TiO2species into ~200 nm PMMA thin films is studied using x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR) spectroscopy and spectroscopic ellipsometry. The kinetics for TiCl4 infiltration increases with both VPI process temperature and TiCl4 exposure time. However, the rates of infiltration are considerably slower than those observed in the more commonly studied trimethylaluminum (TMA) / PMMA system. Even at 150 °C, process times of at least 12 hours are required to fully infiltrate a 200 nm PMMA film whereas using TMA similar films are fully infiltrated within 1 hour at the same process temperature. Films that we believe to be fully infiltrated at 150 °C and 24 hours of TiCl4 exposure have a 6 at% Ti in the innermost bulk, as determined by XPS. Interestingly, unlike AlOx-PMMA hybrids, these TiOx – PMMA hybrids exhibit significant changes in their optical properties. Increased titanium loading leads to a 4% increase in refractive index and increased UV absorbance in the UV range of 270-350nm. Furthermore, films infiltrated at 150 °C and 24 hours of TiCl4 exposure had a 50 % and 70 % reduction in coefficients of thermal expansion (CTE) below and above Tg respectively. Reduced CTE trends with increased titanium loading. We will discuss possible opportunities to use these new properties for various applications.
This project is supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
(Digital Presentation) Cost-Effective Processing of Nickel-Rich Layered Cathodes for Li Batteries
Authors: Fung Kuan-Zong , Tsai Shu-Yi 
Published: November 2022

The layered structured cathode material can provide a higher capacity and stable cycle retention, which is a desired property for lithium-ion batteries. Among them, NMC composed of Ni, Mn and Co as transition metals is considered a promising positive electrode. However, because Co is slightly toxic and an expensive strategic resource, reducing the Co content and maintaining the capacitance and cycle stability are the objectives of this study.
In this study, LiNi0.8Mn0.1Co0.1O2 were investigated. Adjust the amount of Li2CO3 and the temperature of calcination to control the size of the crystal grains to achieve better retention. The value of the I(003) and I(104) ratio in XRD pattern represent cation mixing in layered structure. And this parameter is closely related to its electrochemical properties. Discussion will be carried out based on the results of XRD analysis and the charge–discharge profiles and cycling performance.
The layered structured cathode material may provide a high capacity and stable cycle retention, which is a desired property for lithium-ion batteries. Among them, NMC composed of Ni, Mn and Co as transition metals is considered a promising positive electrode. However, because Co is slightly toxic and an expensive strategic resource, reducing the Co content and maintaining high capacity and cycle stability are the objectives of this study. In addition, the fabrication of NMC adopting single-crystal (grain size: 1~6 mm) process tends to give better long-term performance than ones with particles in nanometer range.
In this study, LiNi0.8Mn0.1Co0.1O2 (NMC811) with substitution of Ni/Mn for Co were selected as the Ni-rich layered cathode investigated. Due to the low melting point of Li2CO3, the heating temperature/time of powder mixture become crucial to control the adequate grain size of to achieve better retention. The value of the I(003) and I(104) ratio in XRD pattern represent cation mixing in layered structure. And this parameter is closely related to its electrochemical properties. Discussion will be carried out based on the results of XRD analysis and the charge–discharge profiles and cycling performance.
The Role of Ion-Correlation in Reducing the Lithium Transference Number in Lithium-Ion Polyelectrolyte Solutions
Authors: Bergstrom Helen K. , Fong Kara D. , McCloskey Bryan D. 
Published: November 2022

Non-aqueous polyelectrolyte solutions (PESs) have been suggested as a promising route to high conductivity, high transference number (t+) electrolytes.1–3 State-of-the-art liquid electrolytes suffer from low t+, meaning the majority of ionic conductivity results from motion of the anion rather than the electrochemically active Li+ ion. Increasing t+ requires decreasing the mobility of the anion, which is dictated by both the diffusion of the anion as well as its net charge. PESs are intuitively appealing because anchoring the anion to a polymer backbone slows down the motion of the electrochemically inactive anion while maintaining higher ion conductivity through improved ion dissociation and solvent-mediated Li+ transport. However, in polyelectrolyte systems, increasing molecular weight both decreases polymer diffusion and increases charge, which will act as competing effects for t+.Recent molecular dynamic simulations of PESs have highlighted the critical importance of correlated ion motion in these systems and have called into question oligomeric PESs as a feasible strategy to achieving high t+ and conductivity electrolytes4,5

In this work we discuss complete studies of transport properties in lithium-ion and lithium metal battery-relevant PESs- specifically lithium triflimide appended polystyrene (PS-LiTFSI) and polymethacrylate (PM-LiTFSI) dissolved in carbonate blends. All prior PES experimental work in the literature has relied on ideal solution assumptions for measuring transport properties. This work represents the first rigorous characterization of transport properties for a battery-relevant polyelectrolyte solution. Using electrophoretic NMR and electrochemical experiments, we characterized the transport properties, including the electrophoretic ion mobilities, conductivity, diffusion coefficients, and t+ of these model PESs. While previous studies that rely on ideal assumptions predict that PESs will have higher t+ than monomeric solutions, we demonstrate that below the entanglement limit, t+ decreases with increasing degree of polymerization. For higher degrees of polymerization, we directly observe Li+ move in the “wrong direction” in an electric field, evidence of a negative transference number due to correlated motion through ion clustering. Using calculated Onsager transport coefficients and insights from molecular dynamics modeling, we demonstrate that despite selectively slowing anion motion using polyanions, anion-anion correlation through the polymer backbone and cation-anion correlation through ion aggregates reduce the t+ in non-entangled PESs.
References

Diederichsen, K. M. et al. ACS Energy Lett. (2017).

Diederichsen, K. M. et al. Macromolecules (2018).

Dewing, B. L., et al. Chem. Mater. (2020).

Fong, K. D. et al.
ACS Cent. Sci. (2019).

Fong, K. D., et al. Macromolecules (2020).