bluuebunny/crossref_metadata_2025_split huggingface dataset:
First-Principles Modeling Approach Towards Quinone-Derivatives for Li Ion Battery: Effect of Molecular Architecture on Electrochemical Properties
Authors: Jang Seung Soon 
Published: February 2020

Electrochemical energy storage (EES) systems such as battery and capacitor are important because of their short charge/discharge time, high energy storage efficiency, long cycle life, and ease of integration into renewable energy sources. Currently, lithium-ion batteries have become the dominant power sources for portable electronic devices through the utilization of transition metal oxides or metal phosphates as the positive electrode (Cathode) materials. Now organic electrode materials have obtained great amount of attention because organic electrode materials are composed of inexpensive and earth abundant elements such as carbon, oxygen, nitrogen, sulfur, and hydrogen, and additionally the structural change of organic materials associated with redox reactions is very small compared to significant volume change of conventional metal and metal oxide materials. More importantly, their properties can be finely tuned by well-established principles of organic chemistry. To develop more cost-effective and sustainable battery technology, organic electrode materials have received lots of attention since organic electrode materials are composed of earth abundant elements such as carbon, oxygen, nitrogen, sulfur, and hydrogen and their properties can be finely tuned via well-established principles of organic chemistry.
In this study, we aim at establishing an integrated design framework to identify high-performance organic electrode materials through the first-principles modeling approach. Thus, various DFT methods are used to obtain the redox potentials of various quinone-derivatives 1) to identify accurate computational method and process; 2) to achieve the structure-property relationship by investigating effect of molecular architectures such as aromaticity and functional groups on electrochemical properties, which can guide the development of new organic materials for battery applications. We compare our computational results with experimental data for validating our approach.
Multiscale Modeling of a Proton Exchange Membrane Fuel Cell: Macroscopic Fuel Cell Model and Experimental Validation
Authors: Castañeda Ramírez Sergio , Carmona Juan , Pérez Mendoza Alejandro Esteban , Ribadeneira Paz Rafael Esteban 
Published: February 2020

Nowadays, Proton-exchange membrane fuel cells (PEMFCs) show drawbacks associated with their high costs and sluggish kinetics, [1,2]. One of the most attractive alternatives for the improvement of the PEMFCs is the development of mathematical models. Those models allow to analyze the effects of variables such as temperature, pressure, humidity and flow of reactive gases on the operation of the fuel cell [3]. Therefore, the number of publications related with fuel cell models has increased in the past years and several models are available in the literature with different approximations, several kinds of transport approaches and kinetic models, also different detail levels and complexity [4]. However, most of those models still rely on a lot of empirical parameters and quantities, which in most cases do not have a physical meaning or are difficult to obtain.
For these reasons, considering the increase of computer capacity, analysis at different scales have been made in order to obtain a better understanding of the physicochemical phenomena involved in the operation of a fuel cell [5], specially the phenomena directly related with the catalytic layers, where the device has its main drawbacks. Also, methodologies to integrate results from different simulation scales are very attractive and they are an active area of study nowadays [5,6].
Considering these issues, a PEMFC multiscale model is presented in this research. This model integrates a kinetic model for the oxygen reduction reaction, an electric double layer description and a macroscopic transport model. The kinetic model consists of a reaction mechanism studied with density functional theory - DFT. The effects of the formation of water adlayers at the electric double layer of the cathode were studied by molecular dynamics. Finally, the transport through the gas diffusion layers and the membrane was described with a diffusion model based on the Stefan-Maxwell equation.
Results for output flows of reactive gases and water, and also current-voltage curves (i-V) are obtained for different operation conditions. They are discussed and compared with experimental data with the aim of support the applied multiscale methodology and to make a contribution to the area of modeling of the PEMFCs.
References:
[1] Y. Wang, K.S. Chen, J. Mishler, S.C. Cho, X.C. Adroher, Appl. Energy 88 (2011) 981.
[2] E. Antolini, E.R. Gonzalez, J. Power Sources 195 (2010) 3431.
[3] A.Z. Weber, J. Newman, J. Electrochem. Soc. 150 (2003) A1008.
[4] A.Z. Weber, J. Newman, Modeling Transport in Polymer-Electrolyte Fuel Cells., 2004.
[5] K.-D. Kreuer, S.J. Paddison, E. Spohr, M. Schuster, Chem. Rev. 104 (2004) 4637.
[6] R.F. de Morais, P. Sautet, D. Loffreda, A. a. Franco, Electrochim. Acta 56 (2011) 10842.
Diagnostic Criteria for Identifying Electrode Reaction Mechanisms By Cyclic Square Wave Voltammetry
Authors: Bottomley Lawrence A , Mann Megan A 
Published: February 2020

This presentation will demonstrate the utility of cyclic square wave voltammetry for determining the mechanism of an electrode reaction. The impact of theoretical and empirical parameters on the shape of the current-voltage curve was evaluated computationally. Simulations were conducted for single and consecutive reversible electron transfer reactions as well as those that are kinetically controlled and/or chemically coupled. The simulation involved systematic variation in alpha, k0, Keq, kf + kb, amplitude, increment, period and switching potential. Trends in peak potentials, currents, and widths with variation in each of these parameters were elucidated. From these trends, diagnostic criteria for assigning each mechanism was identified and, in many cases, experimentally verified. Our goal is to facilitate the use of cyclic square wave voltammetry as a mechanistic tool by both experts and non-experts in electrochemistry. These criteria enable accurate diagnosis of the electrode reaction mechanism and measurement of pertinent kinetic and thermodynamic quantities.
First Principles Calculations of Transition Metal Containment in Li-Ion Cathode Materials with Surface Coatings
Authors: Snydacker David Henry , Kirklin Scott J. , Wolverton Chris 
Published: February 2020

In Li-ion cells, transition metal (TM) dissolution from the cathode active material into the electrolyte can accelerate degradation of capacity and power.[1-4] Containment of TMs in cathode particles using surface coatings is one strategy for improving durability. To achieve TM containment, coatings must have low TM solubility and must not react with the cathode active material to form new phases that contain TMs. We use Density Functional Theory to investigate TM containment in cathode particles composed of an active material and a coating material. We consider LixMn2O4, LixNiO2, LixMnO2, Li2MnO3, and LixMPO4 (M = Mn, Fe, and Ni) active materials, and we consider Al2O3, MgO, ZnO, Li3PO4, Li4P2O7, and LiMPO4 (M = Mn, Fe, and Ni) coating materials. For each particle type, we calculate transition metal solubility in the coating, and we identify reactivity or stability between the coating and the active material. We find that TM containment is somewhat sensitive to temperature and is very sensitive to the cathode state of charge. Although most cathode-coating combinations are not stable either during heat treatment or during battery operation, we identify several combinations that are stable under both of these conditions.
[1] A. Blyr, C. Sigala, G. Amatucci, D. Guyomard, Y. Chabre, and J. M. Tarascon, J. Electrochem. Soc.
145, 194-209, (1998).
[2] J. Vetter, P. Novak, M.R. Wagner, C. Veit, K.-C. Moller, J.O. Besenhard, M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, and A. Hammouche, J. Power Sources, 147, 269–281 (2005).
[3] K. Amine, J. Liu, and I. Belharouak, Electrochem. Comm., 7, 669–673 (2005).
[4] C. Zhan, J. Lu, A. J. Kropf, T. Wu, A. N. Jansen, Y.-K. Sun, Q.Qiu, and K. Amine, Nature Comm., 4, 1–8 (2013).
Oxygen Reduction Reaction Kinetics at Elevated Temperatures and Pressures
Authors: Tse Edmund C. M. , Gewirth Andrew A. 
Published: February 2020

Fundamental understanding of the oxygen reduction reaction (ORR) in aqueous medium at temperatures between 100 and 200 °C is challenging due to practical limitations related to the harsh experimental conditions. By using a high-temperature, pressurized electrochemical cell, we obtain a 150-fold improvement in the kinetics of the electrocatalytic reduction of O2 on Pt relative to room temperature and pressure under an O2 pressure of 3.4 MPa at 200 °C in basic solution.
Figure 1 demonstrates that the ORR kinetics is a function of both temperature and pressure. To deconvolute their combined effect, we examine the underlying variables that dictate the observed ORR kinetics individually. In the Temkin region, we observe temperature-insensitive Tafel slopes, suggesting that the transfer coefficient (α) is temperature-dependent. Another factor contributing to this temperature dependence is a change in the surface morphology of Pt at 200 °C, likely reflecting instability of Pt at elevated temperatures during ORR. O2 availability at the electrode-solution interface is controlled by the interplay between the diffusion coefficient and the concentration of O2 in bulk solution.
ORR kinetics measured on a glassy carbon (GC) electrode yields similar temperature-dependent behavior of the Tafel slopes and α values. GC electrode reduces O2 via a 2 e– process even at elevated temperatures. We conclude that correctly accounting for the many temperature- and pressure-dependent variables is necessary to accurately describe the enhanced ORR kinetics observed at intermediate temperatures under pressurized conditions.

Acknowledgements. E.C.M.T. acknowledges a Croucher Foundation Scholarship. We thank the US Department of Energy (DE-FG02-95ER46260) for support of this research. This work was carried out in part in the Frederick Seitz Materials Research Laboratory Central Facilities, which are partially supported by the US Department of Energy (DE-FG02-07ER46453 and DE-FG02-07ER46471).

Figure 1
Methanol Tolerant Oxygen Reduction Activity of Nitrogen-Iron Doped Carbon in a Hollow Core Mesoporous Shell Structure
Authors: Chan Kwong-Yu , Zhou Ming 
Published: February 2020

A well-defined porous carbon structure with tunable parameters in different length scales can provide a platform for systematic study of transport and confinement effects on electrochemical conversion. For example, the carbon structure with tunable hierarchical porosity composed of a hollow core within a mesoporous shell (HCMS) is used to investigate transport limitations in electrochemical capacitance [1, 2]. Recently, we synthesized the same HCMS carbon structure with doping of nitrogen and iron and investigated the electrocatalytic activity for oxygen reduction in acid medium [3]. As shown in Fig. 1, the electrocatalyst has a mesoporous shell of 50 nm thick around a hollow core of 350 nm. The pores have uniform diameter of 8 nm. The synthesis follows the procedure described in [1] and the introduction of iron nitrate and ethylene diamine as nitrogen and iron precursors [3, 4].
Despite having no precious metals, the Fe-N-HCMS electrocatalyst displays excellent performance for oxygen reduction reaction. The better mass transport of the HCMS structure leads to higher diffusion limitation currents compared to other carbon structures. The Fe-N doped HCMS catalyst also performs better at high current than a similar HCMS carbon with Pt nanoparticles but no Fe-N doping. This is attributed to uniformly distributed activity of Fe-N doped carbon as opposed to localized activity Pt nanoparticles which is vulnerable to diffusion limitation. Furthermore, Fe-N/HCMS carbon electrocatalyst is inactive towards methanol oxidation, thus rendering it ideal for methanol tolerant oxygen reduction. As shown in Fig. 2, platinum containing electrocatalysts has an overall anodic current between above 0.6 V/RHE due to methanol oxidation, whereas Fe-N-HCMS carbon is insensitive to presence of methanol. The Fe-N-HCMS electrocatalyst also display good durability in accelerated degradation tests (ADTs) of over 1000 cycles of voltage scan between 0.6 and 1.0 V/RHE. Under the same ADTs, Pt containing electrocatalysts all show large increase in overpotential at the end of 1000 cycles.

Acknowledgement

The work was supported by a grant from Hong Kong Research Grants Council GRF HKU 700209P) and funding from ICEE via SRT Clean energy and UDF of University of Hong Kong.
References:
[1]. F. Li, M. Morris and K.Y. Chan*, J. Mater. Chem.21 (2011) 8880-8886.
[2] C. Yang, C.-Y. V. Li, F. Li, K.-Y. Chan*, .J. Electrochem. Soc. 160(4) (2013) H271-H278.
[3] M. Zhou, C. Yang, and K.Y. Chan, Adv. Energy Mater. DOI: 10.1002/aenm.201400840, Aug 2014.
[3] H. W. Liang, W. Wei, Z. S. Wu, X. Feng, K. Müllen, J. Am. Chem. Soc. 2013, 135, 16002.
[4] T. Palaniselvam, B. P. Biswal, R. Banerjee, S. Kurungot, Chem. Eur. J. 2013, 19, 9335.

Figure 1
Enhanced Oxygen Reduction Activity of N-Doped Multiwalled Carbon Nanotubes in Alkaline Media
Authors: Tammeveski Kaido , Vikkisk Merilin , Kruusenberg Ivar , Joost Urmas , Shulga Eugene , Kink Ilmar 
Published: February 2020

A great deal of work has been made to develop new electrocatalysts for oxygen reduction reaction (ORR) in acid and alkaline media. In order to replace expensive and scarce Pt-based catalysts that have been primarily employed as cathode catalysts in low-temperature fuel cells, different carbon-based materials that possess lower price, better availability and improved chemical stability have been studied. Nitrogen-doped nanocarbons can be used as alternatives to Pt-based cathode catalysts. Previously, we have investigated the reduction of O2 on CVD grown nitrogen-doped carbon nanotubes,1 on CNTs heat-treated in the presence of urea2 and on N-doped graphene3 and few-layer graphene/multiwalled carbon nanotube (FLG/MWCNT) composites.4

In this work the electrocatalysis of oxygen reduction on nitrogen-doped carbon nanotube (NCNT) catalysts has been investigated. These NCNT materials were prepared from two different nitrogen precursors and acid-treated MWCNTs. Cyanamide (CM) and dicyandiamide (DCDA) were used as nitrogen precursors and the doping was achieved by pyrolysing MWCNTs in the presence of these nitrogen-containing compounds at 800 °C. The MWCNT-to-nitrogen precursor mass ratio was 1:20.
The N-doped carbon nanotube catalyst samples were characterized by scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, the latter method revealed successful nitrogen doping. The electrocatalysis of the ORR was studied in 0.1 M KOH on glassy carbon (GC) electrodes modified with N-doped CNT electrocatalysts employing the rotating disk electrode (RDE) method. The NCNT-DCDA material showed a better ORR performance than the NCNT-CM catalyst. Fig. 1 presents the ORR polarization curves on NCNT-DCDA at various rotation rates and Fig. 2 shows the Koutecky-Levich plots for this catalyst. As can be seen, the number of electrons transferred (n) is close to 4, which is advantageous from the point of view of fuel cell application. A comparison of the RDE results indicated that these metal-free NCNT catalysts possess remarkable electrocatalytic activity toward the ORR in alkaline media similar to that of commercial Pt/C catalyst (Fig. 3). The results obtained in this work are important for the development of Pt-free cathode catalysts for alkaline membrane fuel cells (AMFC). In the next stage of work these materials will be tested in AMFC conditions.
References
1. N. Alexeyeva, E. Shulga, V. Kisand, I. Kink, and K. Tammeveski, J. Electroanal. Chem.,
648, 169, 2010.
2. M. Vikkisk, I. Kruusenberg, U. Joost, E. Shulga, and K. Tammeveski, Electrochim. Acta, 87, 709, 2013.
3. M. Vikkisk, I. Kruusenberg, U. Joost, E. Shulga, I. Kink, and K. Tammeveski, Appl. Catal. B: Environ.,
147, 369, 2014.
4. S. Ratso, I. Kruusenberg, M. Vikkisk, U. Joost, E. Shulga, I. Kink, T. Kallio, and K. Tammeveski, Carbon, 73, 361, 2014.

Figure 1
An Approach for Highly Porous Non-Precious Metal Catalyst Synthesis for Polymer Electrolyte Fuel Cell Cathodes
Authors: Chung Hoon T , Higgins Drew Christopher , Kim Donghun , Wu Gang , Tylus Urszula , More Karren L. , Cullen David A , Zelenay Piotr 
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are electrochemical devices that convert chemical energy into electricity for a variety of applications, the most notable of which is transportation. The integration of PEFCs at scale for transportation applications however has been hindered due to the high price of platinum (Pt) that is the state-of-the-art catalyst for the oxygen reduction reaction (ORR) on the cathode. Replacing Pt with non-precious metal catalysts (NPMCs) synthesized from earth abundant elements (C, N, Fe, etc.) is therefore essential to deploy PEFCs for transportation applications.
Recently, many advances have been realized towards the development of NPMCs. One of the most important advances is the synthesis of highly porous (HP)-NPMCs. HP-NPMCs allow for improved active site accessibility as well as facilitated mass transport. This is especially important as the relatively low volumetric activity of NPMCs leads to a significantly larger electrode thickness for NPMCs in comparison to Pt/C catalysts, i.e., ca. 70 μm vs. 10 μm, respectively. Two main strategies that have been employed to achieve HP-NPMCs are the use of: (i) metal-organic frameworks (MOFs) [1] and (ii) template agents such as silica [2]. MOFs however are generally very expensive, with only very few commercially available, and a silica template approach requires using highly corrosive and hazardous reagents such as hydrofluoric acid for a silica template removal. These approaches are therefore far from ideal for efficient catalyst production.
In this work, we adopted a more proficient technique that uses combined nitrogen precursors. With this method, a lower decomposition temperature nitrogen precursor, cyanamide (CM), and higher decomposition temperature nitrogen precursor, polyanniline (PANI), are concurrently used. Under this circumstance, during heat-treatment, CM works as an efficient foaming agent. Indeed, we can synthesize HP-NPMCs with a microporous surface area of 1585 m2/g, and demonstrate record H2-air fuel cell performance (Fig. 1). In this talk, more detailed microscopic features and electrochemical and fuel cell performances of these HP-MPMCs will be presented.

Acknowledgements

Financial support for this has been provided by the DOE-EERE through the Fuel Cells Technologies Office.

References

Proietti et al., Nat. Commun. 2, 416 (2011).

Serov et al., Appl. Catal. B: Environmental, 127, 300 (2012).

Figure 1
(Keynote) Effects of Catalytic Site Size on Activity of Model Electrodes Prepared By Mass-Selected Cluster Deposition
Authors: von Weber Alexander , Baxter Eric T. , Anderson Scott L. , White Henry S 
Published: February 2020

Model size-selected electrodes were prepared by deposition of mass-selected metal cluster ions on electrode substrates, cleaned and characterized in ultra-high vacuum (UHV). After analysis by X-ray photoelectron spectroscopy (XPS), the electrodes were transferred and mated to a small electrochemical cell without air exposure, and then studied by cyclic voltammetry. Electrodes with small Ptn (n = 1 - 16) on glassy carbon and indium tin oxide substrates were studied. The ethanol oxidation reaction (EOR), the oxygen reduction reaction (ORR), and carbon oxidation by water were all found to depend strongly on cluster size, with peak currents varying by factors of up to 1000. For oxidation reactions, the activity was found to be anticorrelated with Pt core level binding energies measured by XPS, i.e., the dominant factor appears to be the electronic properties of the metal centers. For ORR, the dominant factor appears to be the physical size of the active site for O2 binding.
Electrocatalysis at Nanoelectrode Ensembles of Ultramicroelectrode Dimensions
Authors: Zoski Cynthia G 
Published: February 2020

Electrocatalysis studies at nanoelectrode ensembles (NEEs) of ultramicroelectrode dimensions (UME-NEEs) have a number of advantages that are related to the ability to access kinetics under high mass transport, steady-state diffusion which is difficult to achieve at macro-NEEs where convection is traditionally used. Of particular interest is the use of UME-NEEs as platforms for nanoparticle (NP) deposition in forming UME-NPEs. The use of NP electrodes in the study of electrocatalysis is of fundamental interest, ranging from nanoparticle ensembles (NPEs) to single NP electrodes and single NP collision experiments. Electrocatalysis at UME-NPEs permit direct investigation of NP interaction under high mass transport, steady-state diffusion that is comparable in magnitude to a single NP, thereby bridging the gap between classical ensemble studies on large platforms and isolated single NP investigations. Applications of UME-NEEs, UME-NPEs, and NP collision experiments to oxygen reduction (ORR) and hydrogen evolution (HER) electrocatalysis in acidic solution will be described.
Determination of Phosphoric Acid Coverage on Pt/C for High Temperature-Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC) Using in-Situ X-Ray Absorption Spectroscopy
Authors: Park Hee-Young , Cha In Young , Chung Young-Hoon , Cho Min Kyung , Yoo Sung Jong , Kim Hyoung-Juhn , Henkensmeier Dirk , Kim Jin Young , Nam Suk Woo , Jang Jong Hyun 
Published: February 2020

High temperature-polymer electrolyte membrane fuel cell (HT-PEMFC) utilizing polybenzimidazol (PBI) membrane doped with phosphoric acid has been considered to be a promising alternative for stationary power supplies. However, high-level of phosphoric acid doping is known to significantly decrease active sites for oxygen reduction reaction (ORR) on Pt surfaces and, therefore, diminish performance of the PBI based HT-PEMFCs (phosphoric acid poisoning). Thus, mitigating the phosphoric acid poisoning on Pt/C, which is the most common electrocatalyst for the HT-PEMFC, is crucial to improve the performance of HT-PEMFC. For this, measurement of phosphoric acid coverage at various electrode potentials would be highly required for practical Pt/C electrocatalysts.
FT-IR has been widely utilized to characterize the relative coverage and adsorption site of phosphoric acid on bulk Pt surfaces1, but could not analyze Pt/C catalysts. The characteristics of the phosphoric acid poisoning on Pt/C can be analyzed by X-ray absorption near edge structure (XANES) analysis, but quantitative evaluation is not available2. As an electrochemical method, cyclic voltammetry (CV) has been utilized to measure the amount of electrochemically adsorbed phosphoric acid amount3. However, the CV technique is insensitive to the chemically adsorbed phosphoric acids, and therefore total coverage cannot be measured.
In this study, we utilized the extended X-ray absorption fine structure (EXAFS) and CV together to measure the phosphoric acid coverage on Pt/C. For this, coordination numbers (CN) of Pt was determined from the curve fitting of EXAFS spectra using bulk model structures, such as Pt metal, rock salt structured PtO, and β-PtO2. Then, a conversion constant was estimated from adsorption charge density of phosphoric acid and the CN changes at 0.35 V ~ 0.60 V. Utilizing those values, the phosphoric acid coverage (θ) could be determined as a function of electrode potentials.

References
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2. Q. He, B. Shyam, M. Nishijima, D. Ramaker, S. Mukerjee, J. Phys. Chem. C, 117, 4877 (2013).
3. J. Mostany, P. Martínez, V. Climent, E. Herrero, J. M. Feliu, Electrochim. Acta, 54, 5836 (2009).

Figure 1