bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using Ion Exchange Capacity to Control Water Uptake in Electrodes of Low-Temperature Anion Exchange Membrane Electrolyzers
Authors: Huang Garrett , Mandal Mrinmay , Dobbs Alexandra , Groenhout Katelyn , Kohl Paul A 
Published: December 2020

Hydrogen today is mainly produced by steam reforming natural gas or other fossil fuels. However, this method produces low purity hydrogen with a high concentration of carbonaceous species and ultimately does not relieve dependencies on fossil fuels or reduce harmful greenhouse gasses. Hydrogen production from water electrolysis is a low-carbon or carbon-free alternative to steam reforming and can be utilized as a chemical means of storing excess energy from intermittent sources such as wind and solar.
Solid polymer electrolyte electrolysis based on anion exchange membranes (AEM) seeks to combine the benefits of more established water electrolysis technologies such as alkaline electrolysis (AEL) and proton exchange membrane electrolysis (PEMEL). The high pH environment in AEM electrolysis (AEMEL) promotes facile oxygen evolution reaction kinetics and enables the use of electrodes with little to no platinum group metals. AEMEL systems also have the advantage of a compact design without the need for constant circulation of a concentrated KOH electrolyte.
The polymer membranes used in AEM devices have seen significant advances in recent years, with the development of highly conductive, stable and low-cost membranes for AEM fuel cells (AEMFC). Less attention has been paid to the ionomers in the gas diffusion electrodes. Proper water management has been a key factor in obtaining maximum performance in AEMFCs and it is reasonable to infer that water management will also play an important role in achieving high performance in AEMEL.
In this study, a series of high performance polynorbornene tetrablock copolymer ionomers were synthesized and used to understand the effects of hydrophobicity and ionic conductivity on the performance of low-temperature AEMEL. The ion exchange capacity (IEC) of the ionomers was used to control the amount of swelling and water uptake within the catalyst layer. Teflon was also used to add hydrophobicity to the catalyst layer without sacrificing ionic conductivity. It was found that low IEC at the oxygen evolving electrode and high IEC at the hydrogen evolving electrode enables more efficient water electrolysis.
Financial support for the authors provided by the EERE H2@Scale program (U.S. Department of Energy) is gratefully acknowledged.
Theory Driven Catalysts Design for Hydrogenation Reactions in Solid Oxide Electrolyzer
Authors: Li Meng , Hua Bin , Wang Lu-Cun , Ding Dong 
Published: December 2020

Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds. CO2 and N2 can be transformed into carbonates and NH3 through hydrogenation reactions. Metal oxides supported metals/alloys are the most investigated catalytic materials in heterogeneous electrochemical catalysis. The strong metal-support interaction (SMSI), which determines the catalytic activity, largely depends on chemical conditions of the support and particle size of dispersed metal nanoparticles (NPs). In this work, we studied the SMSI in doped CeO2 supported noble metal NPs systems and their activities for CO2 and N2 hydrogenation reactions in solid oxide electrolyzer. By using a combination of high-throughput density functional theory (DFT) calculations and electrochemical measurements in solid oxide electrolyzer, we developed highly active catalysts for CO2 and N2 hydrogenation reactions.
The reactions of CO2 and N2 hydrogenation normally require large energy input because both CO2 and N2 are quite stable and inert molecules with strong chemical bonds and low polarizability. The adsorption of CO2 and N2 molecules on metal-oxide composite surfaces is normally quite weak, which results in large energy barriers for their activation processes. We performed DFT calculations to determine the key properties for selected doped CeO2 supported noble metal NPs systems to achieving high performance under solid oxide electrolyzer operating conditions. The predictions were further confirmed by the experiments. The highly predictive DFT calculations played a great role in determining the development of electrochemical catalysts for hydrogenation and reactions. Atomic-level materials properties and reaction pathways based on different reaction mechanisms from DFT paved the way for searching for highly active catalysts. The experimental evidence indicated that it is applicable to several hydrogenation reactions.
(Invited) Ruthenium/Samaria-Doped Ceria Cermet Anode through Plasma Enhanced Atomic Layer Deposition
Authors: Kim Hyong June , Kye Seunghyeon , An Jihwan 
Published: December 2020

Direct methane-fueled solid oxide fuel cells (DM-SOFCs) operating at low temperature range (<450 C) are promising next-generation energy conversion devices, in which, however, anode reactions should be facilitated for high performance even at low temperatures. Obtaining catalyst with high activity, thermal stability and carbon coking resistance is essential for high-performance SOFC operating with hydrocarbon fuel. Noble metal catalyst, e.g., Ru, can be effective for direct methane oxidation in DM-SOFC anode. However, their high costs prevent them from being extensively applied to such devices as SOFCs, and, therefore, significant efforts have been made to lower the noble metal loading in designing fuel cell electrodes.
Herein, we report the design and fabrication of heterogeneous catalyst with ultra-low-loading Ru nanostructures via plasma enhanced atomic layer deposition (PEALD) on SDC backbone anode. We confirmed the presence of highly dispersed PEALD Ru particles over the SDC backbone compared to sputtered Ru deposited on only porous sputtered SDC surface. We found out that PEALD Ru of 100 ALD cycles, or approximately 5nm in thickness with Ru loading of only 0.004 mg/cm2, was sufficient for the use of anode catalyst with methane fuel. Furthermore, compared to the cell with 100 nm-thick sputtered Ru/sputtered SDC anode, the cell with PEALD Ru/sputtered SDC anode showed 45 % higher peak power density with only 1/20 of Ru loading. Moreover, after 4 hours operation with dry methane at 450 C, the activation resistance of the cell with the sputtered Ru composite anode increased by 7 times, while that of the cell with the PEALD Ru composite anode increased by only 2 times. This result suggests that, using PEALD, one can simultaneously reduce Ru loading, thereby reducing cost, and improve the performance and the thermal stability of the anode for DM-SOFC.
(Invited) Engineering the Charged Defects at the Perovskite Oxide Surfaces for the Stable Operations at the Elevated Temperatures
Authors: Choi Mingi , Lee Wonyoung 
Published: December 2020

Perovskite oxide is one of the most promising materials for the energy conversion devices including the solid oxide cells (SOFC/SOEC), photovoltaics, and others. However, operations at the elevated temperatures induce the considerable cation re-arrangement at the perovskite oxide surfaces, resulting in the chemical heterogeneities. Since re-arranged cations typically form the undesired secondary phases, destroying the ideal stoichiometry of the perovskite oxides near the outermost surface, the surface exchange reaction rates are significantly retarded. Therefore, the underlying mechanisms of cation re-arrangements should be systematically conducted based on in-depth fundamentals.
Here, we present the relationship between the re-arrangements of the charged defects such as oxygen vacancy and doped-Sr in the perovskite oxides and the chemical and electrochemical stability at the elevated temperatures. Sr-doped perovskite oxides were employed as model electrodes, and doped ceria was additionally deposited onto the perovskite oxides to make the hetero-interface for controlling the distribution of charged defects. The hetero-structured electrodes maintained the initial surface exchange reactivity at 650 °C with substantially suppressed cation rearrangements. Systematic characterizations revealed that the space charge layers established near the hetero-interfaces with re-arranged charged defects reduce the electrostatic interactions for cation rearrangements. The experimental evidences for the charge transfer near the hetero-interfaces and the chemical and electrochemical stability at the elevated temperatures will be discussed.
(Invited) HT-PEM Fuel Cell Development for Product Definition and Scaleup
Authors: Primdahl Soeren , Alfaro Silvia M. , García Héctor R. , Terkelsen Carina , Steenberg Thomas , Hjuler Hans Aage 
Published: December 2020

“High Temperature” Proton conducting Electrolyte Membrane (HT-PEM) fuel cells offer an attractive method of converting renewable energy carriers (e.g. methanol) to electricity, especially remotely and in transportation. A particular advantage is their ability to digest reformates containing a few % CO, thus not requiring high purity hydrogen.
Membranes of polybenzimidazole (PBI) allow for operation in the 150-200 °C range, as they do not require liquid water for continuous moisturizing as do fluorinated polymer membranes. This temperature range is advantageous for the typically used Pt catalyst, as the passivation by CO is limited.
A central challenge is cost reduction, with particular focus on Pt loading of electrodes. The critical trade-off is against lifetime and electrode performance while maintaining adequate tolerance to CO and fuel trace impurities. These limitations are sensitive to system and customer parameters via selection of fuel, reformer characteristics and operation mode.
Results will be presented and discussed on single cell lifetime in the 10.000 h range; objectives and results in electrode development and Pt loading, as well as results on methanol slip testing, start-stop testing and testing at elevated pressure. Lessons from early upscaling will be shared.
A Zero-Dimensional Electrochemical Model for Organic Flow Cells
Authors: Modak Sanat Vibhas , Kwabi David G. 
Published: December 2020

We develop and experimentally validate a zero-dimensional model of the electrochemical performance of a flow cell. The model takes into account voltage losses due to Faradaic charge transfer, ohmic and mass transport resistance, as well as the effect of spatial variations in state-of-charge between the cell and electrolyte reservoir. We validate the model by comparing voltage-current data during cycling to equivalent electrochemical measurements from a symmetric cell with organic reactants. With the exception of the mass transfer coefficient, all relevant model parameters are determined independently prior to the experiment using electrochemical impedance spectroscopy and cyclic voltammetry measurements. We find excellent agreement between the model and experiment for constant-current and constant-voltage cycling, across a wide range of current densities (40 – 200 mA/cm2) and volumetric flow rates (~ 10 – 140 mL/min). The relationship between the fitted mass transport coefficient and flow rate conforms to expectations from the literature [1-3], and reasonably approximates the analogous relationship from single-reservoir cell measurements. This work supports the notion that zero-dimensional electrochemical models can yield simple but predictive frameworks for optimizing organic flow battery performance and understanding how reactant decomposition and crossover contribute to capacity fade.

References

[1] M. Pugach, M. Kondratenko, S. Briola, and A. Bischi, "Zero dimensional dynamic model of vanadium redox flow battery cell incorporating all modes of vanadium ions crossover," Applied Energy, vol. 226, pp. 560-569, 2018/09/15/ 2018, doi: https://doi.org/10.1016/j.apenergy.2018.05.124.
[2] J. L. Barton, J. D. Milshtein, J. J. Hinricher, and F. R. Brushett, "Quantifying the impact of viscosity on mass-transfer coefficients in redox flow batteries," Journal of Power Sources, vol. 399, pp. 133-143, 2018/09/30/ 2018, doi: https://doi.org/10.1016/j.jpowsour.2018.07.046.
[3] J. D. Milshtein, K. M. Tenny, J. L. Barton, J. Drake, R. M. Darling, and F. R. Brushett, "Quantifying Mass Transfer Rates in Redox Flow Batteries," Journal of The Electrochemical Society, vol. 164, no. 11, pp. E3265-E3275, 2017, doi: 10.1149/2.0201711jes.
Optimized SrVOx/Ag/SrVOx Multilayers As High Transparency Electrodes for UV Optoelectronic Devices
Authors: Kim Su-Kyung , Seong Tae-Yeon 
Published: December 2020

GaN-based ultraviolet LEDs are important for their use in various applications such as space-to-space communications, curing, sterilization, etc. For these applications, the development of high-efficiency UV LEDs is needed. However, UV LEDs show relatively lower external quantum efficiencies than visible LEDs. To enhance the performance of UV optoelectronic devices by increasing light extraction, it is essential to develop p-type transparent conducting electrodes (TCEs) with high transparency in the UV region. Sn-doped indium oxide (ITO) is typical material for transparent conducting electrodes (TCEs) because of its low resistivity (< 10-4 Ω·cm) and high transmittance (> 85%) in the visible range. However, ITO has large light absorption below 400 nm wavelength and the poor electrical properties when it is thinner than 50 nm. Thus, there is a need for alternative TCEs that have high transmittance in the UV light region (200 – 400 nm). Extensive studies have been conducted to develop TCEs such as graphene, CNT, metal nanowire, and oxide/metal/oxide (OMO) multilayer. Among them, the OMO structure can be a good candidate for TCEs, because the mid-metal layer acts as a conduction path and the oxide layers can lead to zero reflection conditions.
In this study, we used SrVOx (SVO) films to develop UV-transparent multilayer and investigated their structural, optical, and electrical properties as functions of SVO and Ag thickness by means of UV-VIS spectrometer, Hall-measurement, and transmission electron microscopy. Unlike ITO film, SVO film exhibited high transmittance (> 80%) up to 320 nm. It was shown that the SVO film showed larger optical bandgap (4.3 eV) than that of ITO (3.7 eV). For the OMO structures with Ag thickness of 15 nm, the sheet resistance was in the range 2.76 – 3.15 Ω/sq, depending on the SVO thickness. In particular, SVO (25 nm)/Ag (15 nm)/SVO (25 nm) sample exhibited the highest Haacke’s figure of merit (FOM) of 144.5 x 10-3 Ω-1 where the average transmittance of the OMO was 91.5% over the 360 – 400 nm wavelength. For the 25 nm-thick SVO-based OMO films, the transmittance and sheet resistance gradually decreased with increasing Ag thickness from 9 nm to 21 nm. For example, the sheet resistance of SVO/Ag/SVO samples was in the range 1.97 – 6.48 Ω/sq and the transmittance varied from 82.6 to 95.5%. Among these samples, SVO/Ag (15 nm)/SVO sample showed the highest FOM value. Rigorous coupled-wave analysis (RCWA) simulations were performed to understand the measured transmittance behavior and zero reflection condition in the SVO/Ag/SVO structure. These results imply that SVO-based OMO structure could be a potentially important TCEs for the fabrication of high-efficiency UV optoelectronic devices.

Figure 1
Electroreduction of Substituted Chlorobenzenes: Understanding Silver Catalysis
Authors: Scherschel Nicholas Franklin , McKenzie Eric C.R. , Couto Petro Ana G. , Peters Dennis G 
Published: December 2020

It has been well established that silver electrodes are remarkable catalysts for the reduction of carbon–halogen bonds. The mechanism of electron-transfer (concerted vs. stepwise) seems to be an important aspect for silver electrocatalysis, as catalysis is only observed for concerted electron-transfer processes.1,2 For several years, it has been understood that aliphatic halides prefer concerted transfer, whereas aromatic halides prefer stepwise transfer as a result of their low-lying π* orbitals.3 However, the effect of adding various substituents to the aromatic ring on silver catalysis has not been widely studied. Indeed, preliminary studies performed in our laboratory indicate a deviation from this standard behavior; reduction of 1,2- and 1,3-dichlorobenzene at carbon and silver cathodes display remarkable catalysis at a silver surface. Moreover, these results suggest that silver is only catalytic for the first cathodic process, not the second. As a result, we propose a change in the electron transfer mechanism after the first reduction event, which is believed to be cleavage of a carbon–chlorine bond.
To gain a deeper understanding of factors that influence catalysis at silver cathodes, more specifically for the reduction of substituted aromatic chlorides, the catalytic activity of silver for substituted chlorobenzenes was assessed by means of cyclic voltammetry. Voltammograms of chlorobenzene, 1,2-, 1,3-, 1,4-dichlorobenzene, and 1,2,3-, 1,2,4-, 1,3,5-trichlorobenzene were obtained at both glassy carbon and silver cathodes in dimethylformamide containing 0.10 M tetramethylammonium tetrafluoroborate. Analysis of reduction potentials reveals a moderate to significant positive potential shift, 50–200 mV, for these aromatic halides, which is indicative of electrocatalysis.

References

Isse, A.; Gottardello, S.; Durante, C. Dissociative electron transfer to organic chlorides: Electrocatalysis at metal cathodes. Phys. Chem. Chem. Phys. 2008, 10, 2409–2416.

Isse, A.; Mussini P.; Gennaro, A. New Insights into Electrocatalysis and Dissociative Electron Transfer Mechanisms: The case of Aromatic Bromides. J. Phys. Chem. C 2009, 113, 14983–14992.

Isse, A.A.; Falciola, L.; Mussini, P.R.; Gennaro, A. Relevance of electron transfer mechanism in electrocatalysis: the reduction of organic halides at silver electrodes. Chem. Commun. 2006, 334–346.
Mechanistic Insight into the Catalytic Electroreduction of Tetrabromobisphenol-a at Carbon Cathodes
Authors: McKenzie Eric C.R. , Peters Dennis G 
Published: December 2020

Polyhalogenated phenols are a class of environmental pollutants that serve as precursors to dioxins and behave as endocrine disruptors.1,2 As a result, an efficient route of degradation is needed. Traditional methods of remediation include microbial, thermal, and chemical pathways; however, these typically require large amounts of toxic solvents, excessive amounts of energy, and can be tremendously time-consuming.3 Electrochemistry has become a growing area of research for the remediation of environmentally-harmful compounds, as the electroreductive behavior of carbon–halogen bonds is well understood.
Herein, we report the electrochemical reduction of the flame retardant 3,3',5,5'-tetrabromobisphenol-A (TBBPA), at carbon cathodes in the absence and presence of nickel(II) salen. Cyclic voltammograms at varying scan rates, coupled with voltammograms in the presence of a hydrogen-bonding stabilizer, suggest reduction proceeds by cleavage of a carbon–bromine bond, followed by reduction of a short-lived intermediate. Controlled-potential (bulk) electrolysis was performed to determine the extent of reduction that could be achieved; moreover, gas chromatography–mass spectrometry was utilized to separate and identify reduction products. Electrolyses performed in the presence of deuterium oxide and 1,1,1,3,3,3-hexafluoroisopropanol-OD reveal a carbanion intermediate present in the reduction mechanism.

References

M. Montaño, A. C. Gutleb, and A. J. Murk, Environ. Sci. Technol., 2013, 47, 6071–6081.

C. D. Klaassen, Casarett & Doull’s Toxicology the Basic Science of Poisons, McGraw-Hill Education, 2013.

E. T. Martin, C. M. McGuire, M. S. Mubarak and D. G. Peters, Chem. Rev., 2016, 116, 15198–15234.
Continuous Flow Synthesis of N-Phenylphenylglycine By Dehydration and Electrochemical Carboxylation
Authors: Naito Yuki , Tanaka Kenta , Atobe Mahito 
Published: December 2020

α-Amino acids and their derivatives are important and essential resources for human life such as foods, medical drugs, cosmetics and so on. The classical Strecker α-amino acids synthesis is a longstanding method although this classical method requires highly toxic cyanide reagents as the carbon source and these regents are unfavorable from the viewpoint of green chemistry. Carbon dioxide, on the other hand, would also be an abundant and favorable carbon source. There are several examples of synthesis of α-amino acids by direct carboxylation of imines with carbon dioxide. Because of chemical stability of carbon dioxide, this direct carboxylation requires stoichiometric quantities of hard to handle reagents such as magnesium metal and organotins under severe or harsh reaction conditions.
In this context, electrochemical carboxylation represents an attractive alternative to conventional chemical carboxylation methods because it is possible to readily generate highly reactive carbon nucleophiles that immediately react with carbon dioxide without handling sensitive, expensive, and toxic reagent. However, metal ions derived from sacrificial anode such as magnesium and aluminium anodes are generally required to stabilize the unstable carboxylate ions.
A flow microreactor enables fast generation and consumption of the unstable species. Therefore, it is attractive reaction system for electrochemical carboxylation involving unstable carboxylate ions without sacrificial anodes. Moreover, the electrochemical synthesis with a flow microreactor offers operational advantages over batch processes.
Under these backgrounds, we have demonstrated the electrochemical carboxylation of in situ generated imines in a continuous flow system. The present method enables an efficient synthesis for N-phenylphenylglycine derivatives using easily available aldehydes, amines, and CO2 without the use of toxic metal reagents and sacrificial anode.
As shown in Figure 1, the imine was smoothly generated from aldehyde and amine by dehydration using MS4A desiccant in a flow operation, and then reacted with carbon dioxide in the electrochemical flow microreactor to afford N-phenylphenylglycine derivatives with high to moderate yields.

Figure 1