bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anthraquinone Derivatives in Aqueous Flow Batteries
Authors: Gerhardt Michael R. , Tong Liuchuan , Chen Qing , Gordon Roy G. , Aziz Michael J. 
Published: February 2020

Aqueous quinone/hydroquinone couples exhibit rapid redox kinetics, require no electrocatalyst, and are potentially very inexpensive, making them attractive candidates for large-scale energy storage devices such as flow batteries [1-3]. We evaluate four anthraquinone derivatives for use as the negolyte in aqueous flow batteries. These anthraquinones are shown to undergo reversible two-electron reduction and oxidation in acidic aqueous solution, with tunable reduction potentials. When paired with a posolyte containing bromine and hydrobromic acid, three of these quinone derivatives exhibit cell voltages above 1 V. These derivatives are evaluated for chemical stability against bromination and stability upon reduction. Two anthraquinone derivatives stable under both conditions are cycled in a flow cell, showing greater than 98% current efficiency at 0.25 A/cm2cycling current. Mechanisms for capacity loss and energy inefficiency are discussed to guide further research.
Figure 1. (a) Cyclic voltammetry of four anthraquinone derivatives, showing two-electron redox events at a range of potentials. (b) Open circuit potential of flow batteries employing quinone/hydroquinone negolytes and bromine/bromide posolyte.
[1] B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon and M.J. Aziz, “A metal-free organic-inorganic aqueous flow battery”, Nature 505, 195 (2014), http://dx.doi.org/10.1038/nature12909
[2] B. Huskinson, M.P. Marshak, M.R. Gerhardt and M.J. Aziz, “Cycling of a quinone-bromide flow battery for large-scale electrochemical energy storage”, ECS Trans. 61, 27 (2014)
[3] B. Yang, L. Hoober-Burkhardt, F. Wang, G.K. Surya Prakash, and S.R. Narayanan, J. Electrochem. Soc. 161, A1371 (2014)

Figure 1
(Invited) Ab Initio Studies of Strain Effects on Perovskite Oxygen Vacancy Formation and Migration Energetics
Authors: Morgan Dane , Mayeshiba Tam 
Published: February 2020

Oxygen active materials are capable of rapidly transporting oxygen and exchanging it with the environment and have a wide range of applications, including solid oxide fuel cells, gas separation membranes, oxygen sensors, chemical looping devices, and memristors. Recent work has shown that epitaxial strain can play a significant role in altering the transport of oxygen through oxygen active materials, particularly in fluorite structured compounds. However, transition metal perovskites are an important class of oxygen active materials that have received only limited attention. In this work we use ab initio methods to model the coupling of biaxial epitaxial strain with oxygen vacancy formation and migration energetics in a range of transition metal perovskites. We focus on materials of the form LaBO3, where B = [Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga]. We predict the formation volume and strain response of oxygen vacancy formation energy, demonstrating that non-linear coupling of strain and vacancy formation can yield responses qualitatively different than those expected from simple elasticity arguments. In particular, as first observed in Ref. [1], we show that in some cases the vacancy can weaken the bonding and lower the elastic constants, which allows the formation of a vacancy to reduce the strain energy. This effect leads to stabilization of the vacancy under both compressive and tensile strain, even though the vacancy has positive formation volume.
We also predict the migration volume and the strain response of oxygen migration energetics, here finding that values are quite consistent with a simple elastic strain model.[2] We find that tensile (compressive) biaxial strain reduces (enhances) the oxygen vacancy migration barrier approximately linearly across the systems studied (Figure 1). The average decrease in migration energy is 66 meV per percent strain for a single selected hop, with a low of 36 and a high of 89 meV decrease in migration barrier per percent strain across all the systems studied. In general we find that the oxygen transport kinetics can be altered by orders of magnitude in perovskites through strain effects on both vacancy content and migration energetics. These effects could play a significant role on materials performance at interfaces and in thin-film devices.
[1] W. Donner, C. L. Chen, M. Liu, A. J. Jacobson, Y. L. Lee, M. Gadre, and D. Morgan, Epitaxial Strain-Induced Chemical Ordering in La0.5Sr0.5CoO3-delta Films on SrTiO3, Chemistry of Materials 23, p. 984-988 (2011).
[2] T. Mayeshiba and D. Morgan, Strain Effects on Oxygen Migration in Perovskites, Phys. Chem. Chem. Phys. 17, p. 2715-2721 (2015 ).

Figure 1
Stress/Strain Effect on Non-Stoichiometry of La0.6Sr0.4Co0.2Fe0.8O3-
δ
Authors: Qiu Miaolong , Arai Yoshio , Araki Wakako 
Published: February 2020

La0.6Sr0.4Co0.2Fe0.8O3-δ
(LSCF) is a mixed ionic-electronic conductor and one of the candidates to be used for oxygen separation membrane and cathode material for solid oxide fuel cell. The ionic conductivity of LSCF, which is still by several orders of magnitude lower than its electronic conductivity, needs to be further improved for higher performance of those devices.
LSCF has a cubic perovskite structure. The oxygen vacancies are formed at elevated temperatures above 873 K, while the transition metal ions are reduced for the charge neutrality, accompanied by a sudden volume expansion, i.e., an increase in lattice constant. This implies that the oxygen vacancies could be introduced by applying mechanical strain or stress, as has been discussed in recent reports. In the present study, the oxygen-nonstoichiometry in LSCF was examined under uniaxial compression using coulometric titration technique.
The test cell consisted of polycrystalline LSCF placed between 8 mol%-yttria stabilized zirconia (YSZ) plates with the platinum paste on the interfaces and on the surfaces, i.e., Pt/YSZ/Pt/LSCF/Pt/YSZ/Pt. The side of LSCF was covered with borosilicate glass. A constant voltage (25 mV to 100 mV) was applied to YSZs using a galvanostat in order to control the oxygen partial pressure in the cell (from 0.0678 to 0.0026). After the measured current reached a constant value (e.g., zero in case there is no leakage), the circuit was opened and the decay current was subsequently measured. The change in the oxygen deficiency was calculated from the integration of the measured decay current. Then, the oxygen non-stoichiometries in LSCF under various oxygen partial pressures were examined. The measurement was conducted under uniaxial compressive stress ranging from 0 to 10 MPa, and all the tests were performed at 1073 K in air. In addition to the above experiment, the relationship between the uniaxial strain and the oxygen non-stoichiometry was estimated based on the mechanical property as well as thermo-chemical-mechanical property at 1073 K based on the literature data, assuming that the oxygen deficiency merely depends on the volume change.
The oxygen deficiency increased as the oxygen partial pressure was decreased, and there was almost no leakage from the test cell. The obtained results showed a good agreement with the previous reports. There was no significant effect of the applied stress up to 10 MPa on the measured decay current or the oxygen non-stoichiometry, whereas the stress above 20 MPa caused the fracture of the test cell. According to our estimation based on the mechanical and thermo-chemical-mechanical properties, the oxygen deficiency could be decreased by ~0.006 when the uniaxial compressive stress of 100 MPa is applied, which is being examined using a modified experimental setup.
(Invited) Enhancing Cathode ORR Kinetics and Durability through Low-Cost Surface Modification
Authors: Chen Yu , Ding Dong , Wei Tao , Chen Dongchang , Zhang Lei , Rainwater Ben Harris , Liu Meilin 
Published: February 2020

One of the key technical challenges facing the commercialization of SOFC technology is to ensure high performance and long-term stability and reliability. Under realistic operating condition, the cathodes are exposed to various contaminants commonly encountered in air (e.g., CO2 and/or H2O) as well as impurities from other cell components (e.g., a Cr-containing interconnect), which may lower the SOFC performance and accelerate cathode degradation. To develop durable, high-performance SOFC cathodes, we have investigated the mechanism of cathode degradation due to contaminant poisoning and developed strategies for mitigating the problem. It is found that surface modification of La0.6Sr0.4Co0.2Fe0.8O3(LSCF) cathodes with robust perovskite catalyst coatings through a solution infiltration method is the most effective and economical approach. Electrochemical impedance spectroscopy, cathode polarization measurement, Raman spectroscopy, and modeling and simulation have been used to quantify the tolerance of catalysts-coated cathodes against various contaminations, including steam, CO2, Cr-containing species, and a combination of them. We have further characterized the kinetics of oxygen reduction reaction (ORR) and long-term stability of homemade cells with blank and catalyst-modified LSCF cathodes exposed to different concentrations of contaminants, demonstrating that surface modification through solution-infiltration is a low-cost approach to enhancing both ORR kinetics and stability of the LSCF cathodes.
Rational Design of Stable Cathode Materials for Solid Oxide Fuel Cells
Authors: Cetin Deniz , Poizeau Sophie , Gopalan Srikanth 
Published: February 2020

In this study we consider several heretofore unexplored composite cathode materials systems for solid oxide fuel cells (SOFCs), whose compositions and microstructures have been optimized for high electrocatalytic activity for oxygen reduction reaction and for chemical stability. The design approach takes into account the need for combining facile oxygen surface reactions with bulk transport.
The new composite cathodes in this study consists of carefully tailored composition of perovskite type MIECs and fluorite type ionic conductors.
In this study, all components of the button cells with composite MIEC cathode functional layer (CFL) were prepared via tape casting. Electrochemical performance of these button cells were analyzed through polarization modelling and impedance spectroscopy at temperatures between 700 and 900°C and at cathode side oxygen partial pressures between 1 and 5x10-2 atm. The effect of cathode microstructure on the cell performance is also discussed.
Understanding Morphology and Ion Transport in Novel Poly (cyclooctene) Based Membranes Under Humidified Conditions
Authors: Sarode Himanshu , Zhang WenXu , Yang Yuan , Coughlin E. Bryan , Herring Andrew M 
Published: February 2020

Anion Exchange membranes have been gaining popularity for their applications in fuel cells, CO2electrolysers, redox flow batteries, etc. The main focus has been in the area of synthesizing new polymers for these applications and understanding their morphological and transport properties under humidified conditions of operations. The main aim is toward increasing the ion transport and minimizing degradation over time. Phase separated morphology is one of the pathways to create defined ionic pathways to increase ion conductivity of the AEMs. Here we report morphological study performed on a polycyclooctene based triblock copolymer AEM, for electrochemical applications.
We have performed in situ SAXS under humidified conditions on these AEMs of importance to understand the swelling and morphological behavior. AEMs in this study show lamellar morphology with a d spacing of 39-41nm. We also studied the mechanical properties of these AEMs. Mechanical properties of these membranes are good under dry and low temperature, but above 60°C and hydration the AEMs become soft. Our initial results show that the AEM is stable under alkaline conditions of operation and offers reasonable hydroxide conductivity (70mS/cm @ 60°C) under humidified conditions. Conductivity of these AEMs increases by 4 fold when humidity is increased from 80% to 95%. Overall we report a functional AEM with reasonable properties for electrochemical applications.

Acknowledgements:

We would like to thank the Army Research Office for funding this Multidisciplinary University Research Initiative under contract #W911NF-10-1-0520 and the Colorado School of Mines NMR facility, funded by National Science Foundation under the grant CHE-0923537.
Spectroelectrochemical Insights into the Formation of Robust Interfaces for the Immobilization of Biological and Molecular Electrocatalysts
Authors: Harris Tomos Gwilym Ab Alun , Heidary Nina , Sokolowski Anja , Tzschucke Christoph , Hildebrandt Peter , Zebger Ingo , Fischer Anna 
Published: February 2020

The immobilization of enzymatic and molecular catalysts on conductive surfaces is of interest in many different fields of electrocatalysis. The interface between these catalysts and the electrode surfaces plays hereby a critical role for the catalysts efficiency, stability and applicability (e.g. affecting electron transfer).
Surface immobilization strategies hereby involve the functionalization of the electrode surface. In this work the covalent modification of various electrodes for the tailored immobilization of molecular and biological catalysts is presented. Crucial information regarding the surface functionalization process, the interface structure and it’s behavior have been obtained using a combination of electrochemical techniques as well as in-situ Surface Enhanced Infrared Absorption Spectroscopy (SEIRAS). In this way catalyst immobilization, stability and mechanistic aspects could be probed in a large electrochemical window due to the remarkable stability of these covalent interfaces.
Development of Nanostructured Metal Oxides-Platinum Electrodes for Enhanced Electrocatalytic Oxidation of Ethanol
Authors: WANG Youling , Aoul Amel-Tabet , Mohamedi Mohamed 
Published: February 2020

Ethanol is an attractive fuel for direct ethanol fuel cells (DEFCs) because it has high theoretical energy density (8.0 kWh/kg) [1], it is nontoxic and can be produced from biomass, which could make DEFCs beneficial low greenhouse gas emission power sources. Platinum is known to be the most active catalyst for the ethanol oxidation reaction (EOR). Nevertheless, at Pt catalyst, the complete oxidation of ethanol to CO2 is not attained, because of CO poisoning and the difficulty in breaking the C-C bond at low temperature, which has a detrimental effect on the fuel cell efficiency [2].
A promising strategy to improve the catalytic activity of DEFC reaction can be obtained by integrating metal oxides with Pt to form platinum-metal oxides-composites. Indeed, due to certain intrinsic properties and functions of their own, several nanostructured metal oxides (MOx) such as CeO2, SnO2, TiO2, MnO2, WOx... are emerging as a distinctive class of electrode materials in energy conversion fields. In such applications, MOx can perform as the electroactive material itself, or as a supporting matrix to enhance catalyst dispersion and its stability against sintering and particles aggregation; or advances certain electrocatalytic reactions when combined with other catalysts. In this presentation, we will discuss our recent advances in the development of nanostructured MOx-Pt catalysts anodes for low temperatures DEFCs. Both nanostructured Pt and Pt-MOx (M: Ce, Sn, Mn, Ti) composites of various surface morphologies (smooth, semi-porous and highly porous) were synthesized at room temperature by adapting and optimising the pulsed laser deposition (PLD) method.
Such composites are systematically characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), microRaman spectroscopy, and transmission electron microscopy (TEM) techniques and insights into the physical interaction of MOx with Pt are discussed. Afterwards, we study the electroactivity and durability performances with post-mortem surface morphology of MOx-Pt composites as well as catalytic promoting properties of MOx to Pt towards the EOR.
[1] G. Hoogers, Fuel cell technology handbook, CRC press, Boca Raton, FL, 2003.
[2] F. Vigier, C. Coutanceau, F. Hahn, E.M. Belgsir, C. Lamy, J. Electroanal. Chem. 563 (2004) 81-89.
Phenanthroimidazole Mediators - Immobilization on Electrodes and Mechanistic Studies
Authors: Johnson Bruce , Berben Louise , Little R. Daniel , Römelt Michael , Francke Robert 
Published: February 2020

The use of redox mediators is a well-established approach in electrosynthesis to lower kinetic barriers, to improve product selectivity and to suppress electrode fouling.[1] Recently we have developed a new series of metal‐free and easy-to-synthesize redox mediators based on the phenanthro[9,10-d]imidazole framework (see figure below, left).[2] Upon anodic oxidation these compounds form stable radical cations which can be used to catalyze the oxidation of benzylic alcohols and ethers. By selection of a suitable substitution pattern the oxidation potential of the mediator can be adapted to the redox potential of a specific redox reaction.
Our efforts are currently focused on the immobilization of alkyne-modified phenanthroimidazoles on carbon electrodes via Cu(I)-catalyzed azide-alkyne cycloaddition (see figure below, right). Our goal is to simplify the product separation after an electrolysis and to improve the long-term stability of the mediator. By attachment to the electrode surface we were able to increase the turnover numbers by several orders of magnitude while maintaining reasonable reaction rates.
Further studies are directed towards a better understanding of the mechanism of the charge transfer between mediator and substrate as well as the chemical follow-up reactions. A combination of spectroelectrochemical experiments and computational studies will be used to discuss possible intermediates and transition states.

References:

[1] R. Francke, R. D. Little, Chem. Soc. Rev.
2014,43
, 2492.
[2] R. Francke, R. D. Little, J. Am. Chem. Soc.
2014, 136, 427.

Figure 1
Electroorganic Construction of Pyrazolidine-3,5-Diones
Authors: Gieshoff Tile , Waldvogel Siegfried R. 
Published: February 2020

Pyrazolidin-3,5-diones are an important motif in heterocyclic chemistry, which is highly interesting for pharmaceutical applications. One example is Phenylbutazone, an anti-rheumatic drug in human and veterinary medicine. Additionally, many pyrazolidin-3,5-dione derivatives are regularly tested on their pharmaceutical activity.[1]

In classic heterocycle chemistry, the hydrazinic bond is established by ring closure using the corresponding hydrazine derivatives.[2] Most of them are toxic and require an upstream preparation due to low availability. Therefore, we now present a novel and sustainable synthetic approach to pyrazolidin-3,5-diones using electric current as oxidizing reagent.
This electroorganic approach has some major advantages. Firstly, less or no reagent waste is produced.[3] Secondly, this transformation is an easy and elegant way to build the hydrazine moiety in pyrazolidin-3,5-diones. Thirdly, the required malonic acid diamides can be prepared in high yields from easy available starting materials.[4]

References:
[1] G. Deng, W. Li, J. Shen, H. Jiang, K. Chen, H. Liu, Bioorg. Med. Chem. Lett.
2008, 18, 5497–5502.
[2] U. Funke, H.-F. Grützmacher, Chem. Ber.
1989, 122, 1503–1508.
[3] H. J. Schäfer, A. J. Bard, M. Stratmann, Organic Electrochemistry, Encyclopedia of Electrochemistry, Wiley-VCH, Weinheim, 2004.
[4] C.-T. Chen, Y.-S. Chan, Y.-R. Tzeng, M.-T. Chen, Dalton Trans.
2004, 17, 2691–2696.

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Oxygen Reduction over Dealloyed Pt Layers on Glancing Angle Deposited Ni Nanostructures and Efficient Water Oxidation over Easily Prepared Ir-Ni Oxide Nanoparticles
Authors: Wang Chao , Moghaddam Reza B. , Sorge Jason B. , Xu Shuai , Brett Michael J. , Bergens Steven H. 
Published: February 2020

A challenge in the commercialization of proton exchange membrane fuel cells (PEMFC) is the large overpotential for the oxygen reduction reaction (ORR) at the cathode. Platinum is the most active single-component catalyst, but it has the inherent drawbacks of high cost and scarcity. Combining Pt with non-noble metals (eg. Ni, Fe, Cu etc.) has proven to enhance the ORR activity and reduce the Pt mass (1). We describe the use of glancing angle deposition (GLAD, developed by Brett et al. (2), a physical vapor deposition technique) to deposit Ni with controlled nanostructures on glassy carbon supports (Ni GLAD/GC). A unique electrodeposition method was utilized to deposit a thin layer of Pt over the surface of the Ni GLAD structure in a controlled and conformal way. The Pt loading was varied by interrupting the deposition at various coverages, and a series of the Ni GLAD{Pt}/GC deposits was evaluated towards the ORR in acid (3). These Ni GLAD{Pt}/GC deposits are remarkably more active and durable than {Pt}/GC during ORR in acid and in base (4). In addition, dealloying (selective electrodissolution of Ni to make a more robust and active resulting catalytic material) in acid further enhanced the activity of Ni GLAD{Pt}/GC towards the ORR.
Water electrolyzers (WEs) are used to store/transform energy from renewable sources. The sluggish kinetics for the water oxidation reaction (WOR) severely lowers the efficiency of WEs (5). Iridium is an active and stable catalyst for WOR in acid. Due to its high cost, Ir based catalysts with better activity and decreased loading are required for the widespread adoption of WEs. In this talk, we will present a one-pot synthesis of novel highly active and durable Ir-Ni oxide nanoparticles under mild conditions. A mass activity > 140 A g-1
Ir at 0.25 V overpotential was obtained for IrNi0.125 atomic composition. Long term galvanostatic polarization and duty cycles showed that the catalysts prepared by this procedure are remarkably stable (6).
References
1. I. Katsounaros, S. Cherevko, A. R. Zeradjanin and K. J. J. Mayrhofer, Angewandte Chemie International Edition, 53, 102 (2014).
2. K. Robbie and M. J. Brett, Journal of Vacuum Science & Technology A, 15, 1460 (1997).
3. C. Wang, R. B. Moghaddam, J. B. Sorge, S. Xu, M. J. Brett and S. H. Bergens, Electrochimica Acta, 176, 620 (2015).
4. S. Xu, C. Wang, S. A. Francis, R. T. Tucker, J. B. Sorge, R. B. Moghaddam, M. J. Brett and S. H. Bergens, Electrochimica Acta, 151, 537 (2015).
5. E. Fabbri, A. Habereder, K. Waltar, R. Kotz and T. J. Schmidt, Catalysis Science & Technology, 4, 3800 (2014).
6. R. B. Moghaddam, C. Wang, J. B. Sorge, M. J. Brett and S. H. Bergens, Electrochemistry Communications, 60, 109 (2015).

Figure 1