bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Simulations of Proton and Hydroxide Transport in Fuel Cell Membranes
Authors: Tse Ying-Lung Steve , Savage John , Chen Chen , Knight Chris , Voth Gregory
Published: February 2020

Acid/base reactions are ubiquitous in nature and they have received extensive experimental and theoretical attention over the past several decades. Even though we now understand reasonably well how the Grotthuss hopping mechanism is responsible for the rapid charge diffusion in aqueous acidic and basic solutions, the mechanisms for long-range proton and hydroxide transport in fuel cell membranes are not nearly as well understood. While there is similarity in the solvation structures for the hydroxide and the hydronium ions, the underlying hopping mechanisms in both cases have significant differences. Through careful parameterization based on ab initio calculations, accurate and efficient multistate reactive molecular dynamics (MS-RMD) models are constructed to study proton and hydroxide transport in both proton-exchange and anion-exchange membrane (PEM and AEM) systems. These MS-RMD models allow for the calculations of statistically converged properties and reveal important transport mechanisms in these energy materials. In this talk, the mechanistic pictures of proton and hydroxide transport in PEM and AEM will be discussed and compared.

Figure Caption: The left figure shows the typical solvation structures around hydronium ions (green) in the 3M PEM and illustrates how a hydronium bridges two sulfonates. The right figure shows the solvation around hydroxide ions (green) in poly(vinyl benzyl trimethylammonium) AEM.

Acknowledgment: This research used resources of Research Computing Center (RCC) at the University of Chicago, the Innovative and Novel Computational Impact on Theory and Experiment (INCITE), ASCR Leadership Computing Challenge (ALCC) programs, and the Argonne Leadership Computing Facility (ALCF) at Argonne National Laboratory (Supported by DOE contract DE-AC02-06CH11357).

Figure 1
First-Principles Based Modeling of Structures and Processes at Electrochemical Electrode-Electrolyte Interfaces
Authors: Gross Axel
Published: February 2020

In spite of its technological relevance in the energy conversion and storage,

our knowledge about the microscopic structure of electrochemical

electrode-electrolyte interfaces and electrical double layers is still rather

limited. The theoretical description of these interfaces from first

principles is hampered by three facts. i) In electrochemistry, structures and

properties of the electrode-electrolyte interfaces are governed by the

electrode potential which adds considerable complexity to the theoretical

treatment since charged surfaces have to be considered. ii) The theoretical

treatment of processes at solid-liquid interfaces includes a proper

description of the liquid which requires to determine free energies instead of

just total energies. This means that computationally expensive statistical

averages have to be performed. iii) Electronic structure methods based on

density functional theory (DFT) combine numerical efficiency with a

satisfactory accuracy. However, there are severe shortcomings of the DFT

description of liquids, in particular water, using current functionals.

Despite these obstacles, there has already significant progress been made in

the first-principles modeling of electrochemical electrode-electrolyte

interfaces. In this contribution, I will present our attempts to contribute to

this progress by systematically increasing the complexity of the considered

systems [1, 2].  Different approaches to describe aqueous electrolytes at

electrodes using first-principles calculations will be compared: the

electrolyte can be described either as a thermodynamic reservoir or using

implicit of explicit solvent models. The equilibrium coverage of specifically

adsorbed anions such as halides will be addressed which is an integral part

of the realistic modeling of electrochemical double layers. Finally,

first attempts to model the structure of battery electrodes using electronic

structure calculations will be presented.

[1] Axel Gross, Florian Gossenberger, Xiaohang Lin, Maryam Naderian, Sung

Sakong, and Tanglaw Roman, Water structures at metal electrodes studied by

ab initio molecular dynamics simulations, J. Electrochem. Soc. 161, E3015-E3020 (2014).

[2] Nicolas Hoermann, Markus Jaeckle, Florian Gossenberger, Tanglaw Roman,

Katrin Forster-Tonigold, Maryam Naderian, Sung Sakong, and Axel Gross,

Some challenges in the first-principles modeling of structures and processes

in electrochemical energy storage and transfer, J. Power Sources 275, 531-538 (2015).
Defect Chemistry of CeO2 Surfaces from First Principles and Space Charge Theory
Authors: Bjoerheim Tor Svendsen , Kotomin Eugene , Maier Joachim
Published: February 2020

CeO2 (ceria) is a diverse oxide with numerous technologically important functional properties. It is one of the most studied oxygen incorporation materials, and exhibits remarkable catalytic properties towards hydrocarbon and CO oxidation, and water splitting reactions.1-3 Further, acceptor doped ceria is of great interest as electrolyte for solid oxide fuel cells due to its considerable oxide ion conductivity at intermediate temperatures.4 Recently, nanocrystalline CeO2 ceramics were shown to display significant proton conduction even at room temperature,5 suggested to be due to surface, or sub-surface proton migration. The majority of these functional properties are affected by, or even originate from the rich surface, or interface defect chemistry of ceria, and corresponding space charge layers.3
,
6

In this contribution, we explore the defect chemistry of various surface terminations of CeO2 at finite temperatures, by combining first principles calculations and space charge theory. Plane-wave based electronic/atomic structure calculations at the GGA+U and hybrid HF-DFT levels are used to determine bulk defect formation energetics and the defects' surface segregation energies in CeO2. The first principles results are further combined with space charge theory through numerical evaluation of the space charge potential profiles and corresponding defect concentration profiles.

The charged oxygen vacancies and protonic defects exhibit highly favorable surface segregation energies, and therefore tend to accumulate on CeO2 surfaces. Although such accumulation is partly charge compensated by oxide and hydroxide ad-ions and Ce3+ species at the surface, the surface turns out to be overall positively charged, and charge-compensated by a negative sub-surface space charge region, at least for low defect concentrations. Under humid conditions, especially at lower temperatures, the surfaces are saturated by protonic species, forming water layers. Finally, the effect of such surface saturation by protonic species, and also H2O monolayer and film formation on the sub-surface space charge potential and defect concentration profiles are discussed.

1.         A. Trovarelli, Catalysis Reviews, 1996, 38, 439-520.

2.         E. P. Murray, T. Tsai and S. A. Barnett, Nature, 1999, 400, 649-651.

3.         Z. A. Feng, F. El Gabaly, X. Ye, Z.-X. Shen and W. C. Chueh, Nat Commun, 2014, 5.

4.         H. L. Tuller and A. S. Nowick, Journal of The Electrochemical Society, 1975, 122, 255-259.

5.         E. Ruiz-Trejo and J. Kilner, Journal of Applied Electrochemistry, 2009, 39, 523-528.

6.         G. Gregori, M. Shirpour and J. Maier, Advanced Functional Materials, 2013, 23, 5861-5867.
Confinement in Soft Materials for Novel Energy Applications
Authors: Mossa Stefano
Published: February 2020

Confinement at the nano-scale characterizes electro-chemistry and physics of soft materials for energy applications. Consider Nafion, the ionomer used as the proton-conducting membrane in fuel cells. Phase separation upon hydration controls the formation of ionic domains, delimited by the polymer backbone matrix. Details of this self-organized charged confining environment, whose typical nano-metric channels sizes strongly interfere with the correlation length scales of bulk water, and of the consequent degradation of transport properties, still have not been completely elucidated. External confining environments are also ubiquitous in configurations of technological interest, as the solid-state boundaries at the electrodes, with the resulting formation of complex hard/soft materials interfaces. In this talk I will address these aspects of confinement, and describe some recent molecular dynamics simulation work on two different systems. First, I will focus on model hydrated polymer electrolyte supported ultra-thin films. We have studied hydrated Nafion thin films in contact with unstructured supports, characterized by their global wetting properties only, and found evidence of strongly heterogeneous structural and dynamical behavior of water in different regions of the film. Next, I will introduce a coarse-grained model for ionic surfactants in explicit aqueous solutions. We have studied both the impact of water content on the morphology of the system, and the consequent effect of the formed interfaces on the structural features of the adsorbed fluid. Finally, I will discuss the implications of our work on the current understanding of a large range of systems, where the behaviour of water at the interface with nano-structured soft materials is crucial.
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
Magnetoelectrocatalysis of the Oxygen Reduction Reaction (ORR)
Authors: Knoche Krysti L. , Leddy Johna
Published: February 2020

Fundamental kinetic studies of the catalytic effect of localized magnetic fields on the oxygen reduction reaction (ORR) are conducted at platinum electrodes in the organic solvent acetonitrile with tetrabutylammonium tetrafluoroborate (TBABF4) electrolyte. Electrodes are modified with magnetic particles suspended in a Nafion film. The magnetic particles are SiMag C1 (ChemiCell Gmbh) superparamagnetic maghemite particles coated with methyl silane to make them chemically inert. Cyclic voltammetric results for a Nafion film in oxygen free and oxygen saturated conditions are shown. For the composite of magnetic particles in Nafion, data for saturated oxygen are shown. Enhanced heterogeneous electron transfer kinetics are observed. Currents increase by 20% and the peak splitting is reduced by 400 mV (from 1.8 V to 1.4 V). The overpotential as measured at current half height is decreased by 200 mV. Particles with different magnetic field strengths are examined as well as demagnetized particles.

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

1. F. C. Nart, T. Iwasita, Electrochim. Acta, 37, 385 (1992).

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
Reduction Induced Surface Amorphization Enhances Oxygen Evolution Reaction Activity in Co3O4
Authors: Leng Xue , Zeng Qingcong , Wu Kuang-Hsu , Gentle Ian , Wang Dawei
Published: February 2020

Oxygen evolution reaction (OER) is one of the paramount steps in sustainable energy conversion and storage technologies.1-3
Spinel oxide Co3O4 has long been recognized as a promising alternative non-precious OER electrocatalyst for its good activity and low cost. Numerous nanostructured Co3O4 materials have been developed in order to acquire better OER performance.4-6 Herein, we have adopted thermal H2 annealing and air exposure to modify the surfaces of crystalline Co3O4. Our results demonstrate the remarkably enhanced OER activity of the surface modified Co3O4 electrocatalyst despite its increased crystal size and reduced surface area. The improved OER performance is believed to be relevant to the very surficial amorphous layer consisting of mixed hydrated cobalt oxyhydroxide/carbonate species on the reduced Co3O4.

REFERENCES

1. H. B. Gray, Nat. Chem.,
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2. M. G. Walter, E. L. Warren, J. R. McKone, S. W. Boettcher, Q. Mi, E. A. Santori, N. S. Lewis, Chem. Rev.,
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3. H. Wang, H. Dai, Chem. Soc. Rev.
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4. M. Hamdani, R. N. Singh, P. Chartier, Int. J. of Electrochem. Sc
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Fabrication of Multi-Metallic Frameworks with Specific Surface Areas Tailored for Catalysis of Surface Based Reactions
Authors: Oppedisano Daniel Keith Joseph , Jones Lathe A , Bhargava Suresh Kumar
Published: February 2020

Fabrication of catalysts is important with regards to the extraction of energy from future fuel sources. In order to enhance the understanding and improve reactions associated with this extraction, the control of size, shape, morphology and composition is crucial. Noble metals such as platinum, palladium, gold, and ruthenium are active for both electrocatalysis and heterogeneous catalysis, however the price of materials containing these metals is high, hence the creation of catalysts with large specific surface areas is essential.

Electrodeposition at high overpotential is able to create open surfaces of a 3-D high surface area nature. Here we use the dynamic hydrogen bubble templating method to fabricate highly porous and stable multi-metal frameworks. By using, copper, a relatively cheap metal, as the major component and incorporating precious noble metals, frameworks of both varying compositions and morphologies can be produced. Most importantly the porous and nanostructured nature results in increased roughness factors and therefore increases in the specific surface area and material utilisation. Through variation in the deposition parameters composition, shape and pore size is able to be controlled.

These frameworks of materials were tested for surface based catalysis reactions and have shown enhanced ability towards the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR). It is shown that subtle variations in surface chemistry greatly affect catalytic activity. This is linked to both structural and electronic effects from the combination of the metals.

Figure 1
Patterned Electrodeposition of Cobalt Selenide Nanostructure Arrays As a Highly Efficient Bifunctional Catalyst for Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER)
Authors: Masud Jahangir , Swesi Abdurazag , Nath Manashi
Published: February 2020

There is a growing interest in oxygen electrode catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as they play a key role in a wide range of renewable energy technologies such as fuel cells, metal-air batteries, and water splitting. Nevertheless, the development of highly-active bifunctional catalysts at low cost for both ORR and OER still remains a huge challenge [1]. Herein, we report, a cost effective alternative, viz. cobalt selenide Co­x­Se­­y nanotube and nanorod arrays which shows considerable catalytic activity afor OER and/or ORR., The CoxSey nanostructure arrays were produced by a protocol developed recently in the Nath laboratory [2] which involves confined electrodeposition on lithographically created nanoelectrodes. ORR activity of catalysts were evaluated in acidic medium (Fig. 1). Coating the CoxSey nanostructures with a thin layer of Pt (CoxSey-Pt) also exhibits enhanced catalytic efficiency. ORR current densities of CoxSey and CoxSey-Pt are comparable with Pt which indicate the four electron reduction process of all catalysts. Besides ORR, CoxSey exhibits excellent activity towards OER. The polarization curve (inset of Fig. 1) for CoxSeyin linear sweep voltammetry (LSV) conditions show higher current and earlier onset (ca. 330 mV) of catalytic current in comparison with Pt in 1M KOH solution. Detailed characterization and analysis of ORR/OER activity of catalyst will be presented along with structural and morphological characterization of the active catalyst surface and the relationship between morphology and the observed catalytic activity.

References:

N.I. Andersen, A. Serov, P. Atanassov Applied Catalysis B: Environmental, 2015, 163, 623.

S. Mishra and Manashi Nath, Nano Energy, 2013, 2, 1207

Figure 1
Confinement of Platinum Catalysts in Carbon Nanocontainers to Control the Durability in the Oxygen Reduction Reaction
Authors: Kurtoglu Abdullah , Walsh Darren , Khlobystov Andrei N , Gimenez-Lopez Maria del Carmen
Published: February 2020

Platinum and platinum alloys are widely used as catalysts for hydrogen fuel cells. However, several challenges need to be over come in order for Pt catalysts to reach their full potential. These include the high intrinsic costs, the fairly poor durability, wide nanoparticle size distributions, and a the lack of understanding of the precise nature of the contact between the catalyst and support materials.1 Moreover carbon black, which is the most commonly used support material in fuel cells is thermo chemically unstable under acid conditions which drastically limits its use. Recently, carbon nanotubes (CNTs) and graphitised carbon nanofibres (GNFs), both of which have a number of exciting properties including; high specific surface areas, high electrical conductivity and relatively good stability in acid and alkaline media, have been proposed as alternative catalyst supports.2 In addition, confinement of metal nanoparticles (NPs) inside these tubular structures potentially offers enhanced stability against sintering. As a consequence of this stabilisation the resultant catalysts will remain highly catalytically active for a significantly higher number of cycles making fuel cells financially more viable.3

In this study we have developed a series of GNF supported platinum composites for use as catalysts in the cathode side of the hydrogen fuel cell. Preformed free-standing platinum NPs (PtNPs) were deposited on either the external and internal surfaces of the GNFs using different conditions.4High resolution transmission electron microscopy (HRTEM) was used to characterise the composites, verifying the location of the PtNPs in each material (Figure1). The electrochemical active surface area of the composites materials, turn over numbers and the lifetime/stability of the materials was quantified using cyclic voltammetry, and the electrocatalytic activity of the catalyst towards the oxygen reduction reaction was assessed. It was found that depositing the PtNPs inside the GNFs (PtNPs@GNFs) rather than outside (PtNPs/GNF) resulted in a catalyst with higher catalytic activity, stability, and an increased electrochemical active surface area.

Figure 1: TEM images of the PtNPs@GNF (left) and Pt/GNFs (right) composites studied.

H. A. Gasteiger, S. S. Kocha, B.Sompalli, F. T. Wagner, Catal. B-Environ., 2005, 56, 9-35.

L. Li, Yangchuan Xing, J.Electrochem. Soc., 2006, 153, 1823-1828.

G. A. Rance, W. A. Solomonsz, A. N. Khlobystov, Chem. Commun., 2013, 49, 1067.

A. La Torre, M. C. Gimenez-Lopez, M. W. Fay, G. A. Rance, W. A. Solomonsz, T. W. Chamberlain, P. D. Brown, A. N. Khlobystov, ACS Nano, 2012, 6, 2000-2007.

Figure 1
Self-Assembled Monolayer Experiments in Undergraduate Laboratories
Authors: Suroviec Alice H
Published: February 2020

This talk will describe a junior/senior level undergraduate laboratory for analytical or physical chemistry that can be used to demonstrate how self-assembled monolayers (SAM) form and pack onto a surface.  The laboratory experiment will also introduce students to electrochemical techniques, instrumentation and surface analysis techniques.  This experiment uses both  chronocoulometry to determine the surface area of an electrode as well as using reductive desorption to determine the surface coverage and packing of the SAM.  Discussion of how molecules interact with the monolayers will also be discussed.
Structure and Dynamics at Ionic Liquid/Electrode Interfaces
Authors: Parr Daniel , Zibart Christina , Egan Bryce , Malik Kasim , Shadley Tyler , Haverhals Luke M.
Published: February 2020

Ionic liquids (ILs) are potentially ‘game changing’ electrolytes for energy conversion applications such as capacitors
[i]

,[ii]
, batteries
[iii]

,[iv]
, fuel cells
[v]

,[vi]
, and solar cells.
[vii]

,[viii]
  Significant progress has been made towards utilizing these remarkably adaptable materials for specific applications however, much work remains to generate technologically and economically relevant devices and processes.[ix]  Characterizations of interfaces between IL-based electrolyte/electrode systems are crucial to continued development for these enterprises.  In specific, detailed descriptions and understanding of structure and dynamics at electrolyte/electrode interfaces are necessary to realize engineered progress because device efficiencies are often largely determined by processes that occur at the interface.
[x]

,[xi]
  Our presentation will focus on initial efforts to employ spectroscopic techniques that characterize interfacial structure and dynamics between ionic liquid media and electrode surfaces during simultaneous electrochemical perturbation.  In specific, we will present surface enhanced infrared absorption (SEIRA) spectroscopy data for ILs composed of imidazolium-based cations with bis(trifluoromethylsulfonyl)imide anions at nanostructured noble metal electrodes (i.e, Au).

[i].      T. Sato, G. Masuda, K. Takagi, Electrochim. Acta, 2004, 49, 3603-3611.

[ii].     A. Orita, K. Kamijima, M. Yoshida, J. Power Sources, 2010, 195, 7471-7479.

[iii].    A. S. Best, A. I. Bhatt, A. F. Hollenkamp, J. Electrochem. Soc., 2010, 157, A903-A911.

[iv].    J.-K. Kima, A. Matica, J.-H. Ahnb, P. Jacobsson, J. Power Sources, 2010, 195, 7639-7643.

[v].     S.-Y. Lee, A. Ogawa, M. Kanno, H. Nakamoto, T. Yasuda, M. Watanabe, J. Am. Chem. Soc., 2010, 132, 9764-9773.

[vi].    M. Guo, J. Fang, H. Xu, W. Li, X. Lu, C. Lan, K. Li, J. Membr. Sci., 2010, 362, 97-104.

[vii].   P. K. Singh, N. A. Jadhav, S. K. Mishra, U. P. Singh, B. Bhattacharya, Ionics, 2010, 16, 645-648.

[viii].  C.-P. Lee, P.-Y. Chen, R. Vittal, K.-C. Ho, J. Mater. Chem., 2010, 20, 2356-2361.

[ix].    M. Armand, F. Endres, D. R. MacFarlane, H. Ohno, B. Scrosati, Nature Materials, 2009, 8, 621-629.

[x].     A. J. Bard, L. R. Faulkner, Electrochemical Methods: Fundamentals and Applications, 2nd ed., 2002, John Wiley & Sons, Inc., New York, NY.

[xi].    M. Yoshida, A. Yamakata, K. Takanabe, J. Kubota, M. Osawa, K. Domen, J. Am. Chem. Soc., 2009, 131, 13218-13219.
Development of Transition Metal Complexes As Electrocatalysts for Small Molecules
Authors: Swavey Shawn
Published: February 2020

In this presentation I will describe the work performed in my laboratory over the past decade (including our most recent work) involving undergraduate researchers. We have synthesized a number of transition metal complexes and have characterized them by spectroscopic and electrochemical techniques. In addition many of these complexes have been adsorbed onto graphite electrodes and studied by rotating disc electrochemistry for the reduction of oxygen and the evolution of hydrogen.
Electrocatalytic CO2 Reduction with Homogeneous Transition Metals: Early Metals
Authors: Grice Kyle A , Saucedo Cesar , Sovereign Mark
Published: February 2020

Homogeneous electrocatalysts for CO2 reduction have been explored by many groups. However, the focus has been on systems based on groups 7 or later in the periodic table. Recently, a few examples of catalytic CO2 reduction have been observed at group 6 metals (Cr, Mo, and W) or earlier groups. Group 6 is notable as it is present in biological oxoreductase enzymes such as Formate Dehydroganse, which can convert between CO2 and formate. The electrochemical response of the homoleptic group 6 carbonyls was explored at a glassy carbon electrode.  In addition, other “early” metal systems were examined. The complexes were examined under aprotic conditions as well as in the presence of proton donors under argon and carbon dioxide. The results of the work with undergraduate researchers will be discussed. The integration of research and teaching chemistry concepts to undergraduates using electrochemistry will also be discussed.