bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Modeling of Carbon Dioxide Exposure and Mitigation in Hydroxide Exchange Membrane Fuel Cells
Authors: Setzler Brian P. , Shi Lin , Wang Teng , Yan Yushan 
Published: February 2020

Despite rapid advancements in performance and durability of hydroxide exchange membrane fuel cells (HEMFCs), the performance loss caused by carbon dioxide in air is unacceptable for transportation applications1. In this paper an expanded model2 of carbon-dioxide-induced performance loss will be presented. The model predicts performance loss under dynamic and steady-state conditions, considering effects of temperature, carbon dioxide concentration, fuel and air stoichiometry, anode recycle, and down-the-channel concentration gradients.
There are two major causes of performance loss upon CO2 exposure: lowered anode pH and reduced ionic conductivity. CO2 reacts with hydroxide to form carbonate and bicarbonate, which are pushed to the anode by the ionic potential gradient. At the anode, these anions accumulate, lowering the pH. At a sufficiently low anode pH, bicarbonate decomposes, establishing a steady state. The pH gradient shifts the half-cell potentials of the anode and cathode reactions, which reduces the cell voltage by an amount that depends on the transference number of hydroxide, but can be approximated as 70 mV per pH unit over most of the pH range. Accumulation of bicarbonate also causes an increase in Ohmic losses due to reduced ionic conductivity, but this effect is generally secondary to the concentration polarization caused by the pH gradient.
The anode pH is determined primarily by the kinetics or thermodynamics of bicarbonate decomposition, which in practice, means that even very high values of ionomer conductivity cannot mitigate the performance loss under CO2. Figure 1 shows the modeled performance loss caused by 400 ppm CO2 in air for HEMFCs with ionomer hydroxide conductivity values of 5-40 S/m. Except at very low current density, increasing hydroxide conductivity does not render the HEMFC less sensitive to CO2.
Figure 2 shows the transient performance loss caused by CO2 uptake at 1 A/cm2 and a range of CO2 concentrations from 0.1 to 10 ppm. At 1 ppm, performance drops by 10 mV in the first 0.5 h and 30 mV at steady state. Even at 0.1 ppm, the modeled performance loss is 10 mV at steady state. These simulations provide a first indication of the level of CO2 removal required for systems operating on air and should be supplemented with experimental measurements.
The model results lead to the disappointing conclusion that a CO2-tolerant HEMFC cell is unlikely. However, modeling also supports the viability of CO2 removal using electrochemical pumping, which could be significantly more compact and less costly than conventional scrubbing. Proof-of-concept experiments will be presented, and future prospects will be discussed.
References

S. Gottesfeld et al., J. Power Sources, 375, 170–184 (2018).

B. P. Setzler and Y. Yan, Meet. Abstr. , MA2017-01, 1654 (2017).

Figure 1
(Invited) Stable and Conductive Anhydrous Proton Conducting Membranes Based on Polycations Blended with Polybenzimidazole
Authors: Arges Christopher George , Venugopalan Gokul , Kole Subarna 
Published: February 2020

This talk primarily focuses on anhydrous, mild temperature (100 to 250 °C) proton conductors composed of polycation polymers, typically used as anion exchange membranes, blended with polybenzimidazole (PBI). These moderate temperature membranes are envisioned for fuel cell systems that operate with hydrogen from steam-reformed methane. Evaluating polycation membrane variants alone demonstrated lower proton conductivity when compared to PBI doped with phosphoric acid (H3PO4) and sulfuric acid. PBI doped with phosphoric acid, on the other hand, was observed to be unstable above 160 °C because of H3PO4 boiling and evaporation. Plus, the PBI-H3PO4membrane loses its acid due to leaching if condensed water is present (i.e., lack of robust operation if the cell drops below 100 °C).
To overcome these problems, polycation polymers, were blended with polybenzimidazole (PBI) and these membranes routinely showed conductivity values as high as 0.18 S cm-1and were stable under dry and wet conditions and with thermal stability up to 250 °C. These membrane composites were also assessed with other types of doped acids (e.g., phosphoric acid, methanesulfonic acid, p-toulenesulfonic acid, trifluoroacetic acid, and sulfuric acid) to promote the Faradaic reaction kinetics at low pH (i.e., pH values below 0).
The talk will close with our recent efforts to pattern polymer electrolyte membrane surfaces to make high surface area bipolar junction interfaces. It is envisaged that an acidic anode and alkaline cathode with a bipolar membrane offers a pathway forward for very low platinum loading fuel cells.

Figure 1
Photoelectrosynthesis of 2,5-Furandicarboxylic Acid (FDCA) and Impact of Band-Gap on Conversion Yield
Authors: Hosseini Seyyedamirhossein , Peters Dennis G 
Published: February 2020

Electrooxidation of water to oxygen is a kinetically slow reaction; hence, a large overpotential is required to drive this process at a desired rate and to generate adequate electrons for hydrogen reduction at a platinum cathode. A possible alternative is to replace water with another species whose oxidation needs lower overpotentials. In this regard, electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) has shown fast kinetics at low overpotentials Figure 1).1 Furthermore, this reaction features great industrial significance; HMF is a byproduct of the food industry (estimated annual production of 50 million tons) and its conversion to FDCA is an important process in the field of degradable polymers.2,3 FDCA is a cheap and green alternative for polyethylene terephthalic acid (PET) that has been used for fabrication of plastics.4–6

In the present work, we studied the electro- and photoelectrooxidation of HMF to FDCA with application of an anode made of NixCu1-xWO4 (0 ≤ x ≤ 0.1). In experiment 1, electrooxidation of HMF was carried out in the absence of light. The conversion yield has been reported for this experiment by measurement of the amount of hydrogen gas evolved and FDCA formed at the end of the electrolysis. Finally, the yield of the reaction was correlated to the doping amount of copper incorporated within the host of nickel tungstate.
For photoelectrochemical conversion of HMF, a similar setup to experiment 1 has been utilized; however, electrolyses were carried out in the presence of light (experiment 2). Conversion yield and oxidation overpotential in both experiments have been compared to evaluate the effect of doping on the photoelectrochemical properties of modified nickel tungstate. Present data revealed that lower oxidation overpotential is needed in experiment 2 in comparison with experiment 1. Moreover, we observed that, by enhancement of the copper amount (experiment 2), conversion yield was improved significantly.

References

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Rosatella, A. A.; Simeonov, S. P.; Raquel, F. M.; Afonso, C. A. M. Green Chem. 2011, 13, 754.

Howard, J.; Rackemann, D. W.; Bartley, C.; Samori, C.; Doherty, W. O. S. ACS Sustainable Chem. Eng.
2018, 6, 4531.

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2018
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Macedo, N. G.; Gouveia, A. F.; Roca, R. A.; Assis, M.; Garcia, L.; Andres, J.; Leite, E. R.; Longo, E. J.
Phys. Chem. C
2018, 122, 866.

Figure 1
Use of Imidoxyl Radical Mediators for Electrochemical Oxidation/Depolymerization of Lignin
Authors: Rafiee Mohammad , Stahl Shannon S. 
Published: February 2020

Lignin is an abundantbiopolymer with aromatic subunits in itsbackbone, and depolymerizationof this polymer could provide a source of valuable aromatic chemicals. The beta-O-4 unit, which features secondary benzylic and primary aliphatic alcohols (Figure 1), is the most prevalent linkage in the structure of lignin, and its cleavage provides high yields of aromatic monomers. The hydroxyl functional groups within this linkage are susceptible to oxidation, and their controlled oxidationprovides the basis for lignin depolymerization.[i]We have shown previously that the benzylic alcohol in lignin undergoes selective oxidation with an aminoxyl/NOxcocatalyst system under aerobic conditions. Subsequent treatment of the oxidized lignin with formic acid affords high yields of aromatic monomers.[ii]This talk will describe a complementary electrochemical method for selective oxidation of the benzylic alcohols in lignin.
N-Hydroxyimide derivatives undergo facile proton coupled electron transfer at electrode surfaces to generate an imidoxyl radical that promotes efficient hydrogen atom transfer from the of benzylic hydroxyl groups.[iii]Our advances in the use of electrochemically generated imidoxyl radicals for chemoselective oxidation of hydroxyl groups in the structure of lignin will be presented. Benzylic alcohol oxidation proceeds efficiently to the corresponding ketones using imidoxyl radicals as electrocatalyst in water/acetone as solvent and with acetic acid/acetate as buffer and supporting electrolyte. Treatment of the oxidized lignin with formic acid affords more than 30 wt% of monomeric aromatic compounds.
[i]. Li,C.; Zhao,X.; Wang,A.; Huber, G.W.; Zhang T. Chem. Rev.
2015,115, 11559.
[ii]. Rahimi, A.; Ulbrich, A.; Coon, J. J.; Stahl S. S.Nature
2014, 515, 249.
[iii]. Nutting, J. E.; Rafiee, M. R.; Stahl, S. S. Chem. Rev.
2018, 118, 4834.

Figure 1. Imidoxyl catalyzed electrochemical oxidation of lignin followed by formic acid catalyzed depolymerization.

Figure 1
Versatility of Time-Resolved Raman Spectroelectrochemistry: From the Resolution of Mixture of Vitamins to the Detection Pesticides
Authors: Fanjul Pablo , Ibáñez David , Junquera-Pérez Alejandro , González-García María Begoña , Hernández-Santos David 
Published: February 2020

Electrochemical Surface-enhanced Raman scattering (EC-SERS) is a powerful analytical tool for the sensitive and selective detection of different molecules adsorbed on a nanostructured metal. This methodology consists of the electrochemical generation of metal nanostructures with excellent SERS properties and the analytical detection of different molecules in a unique experiment.
Detection of pesticides in food is an essential step in regulating and monitoring the levels of pesticides. However, there is currently a clear demand in the development of new and easy methodologies that allow a quick detection. In order to demonstrate the utility of EC-SERS in this field, two pesticides have been selected. Imidacloprid and permethrin are widely used for controlling different insects in agricultura and their detection is completely required. EC-SERS allows the fast and simple detection of these pesticides, opening new gates for future application in this field.
However, the versaility of EC-SERS has been demonstrated in this work since this technique can be also used in a different, way, and for example is really useful in the resolution of mixtures. As proof of concept, mixtures of different vitamins (B1, B2, B3, B6 and B12) have been studied by time-resolved Raman spectroelectrochemistry. Raman spectra show the characteristic bands of each vitamin, allowing us to differeciate between them. However, apart from differenciate the vitamins present in the mixture, this methodology allows the calculation of the chemical composition of different samples.
Clear-to-Black Dynamic Windows with Minute-Long Switching Using Reversible Metal Electrodeposition
Authors: Islam Shakirul M. , Hernandez Tyler S. , McGehee Michael , Barile Christopher J. 
Published: February 2020

Dynamic windows possess electronically tunable transparency, which allows them to transition from clear to dark on demand. By controlling the flow of light and heat into buildings, dynamic windows can substantially increase the energy efficiency of homes and offices. Installing these "smart" windows in automobiles could also extend the battery range of electric vehicles by attenuating energy-intensive air conditioning use. Smaller versions of these windows have applications in actively switchable sunglasses as opposed to current passive photochromic transition lenses.
We are developing next-generation dynamic windows based on the reversible electrodeposition of metals. In this approach, window tinting is controlled via the electrochemical movement of metal between a transparent conducting working electrode and a counter electrode metal frame. This strategy offers several advantages over current windows based on electrochromic materials including minute-long switching times, neutral color, and the potential to be manufactured at low cost. To enable uniform electrodeposition over a large working electrode area, transparent conducting oxides are modified with a self-assembled monolayer of Pt nanoparticles, which serves as an inert metal seed layer for metal nucleation and enhances electrodeposit morphology. An aqueous electrolyte separates the two electrodes and consists of Ag+, Cu2+, and/or Bi3+ ions. We interrogated several electrodeposition chemistries and derived relationships between electrolyte composition and device performance.
The 25 cm2 or 100 cm2 device prototypes we developed display clear-to-black transitions with ~80% optical contrast in 1 minute and cycle thousands of times without significant deterioration. Future improvements in electrode and electrolyte design will increase the scalability and functionality of these devices.
Drop-on-Demand 3D Printed Lithium-Ion Batteries
Authors: Ben Barak Ido , Schneier Dan , Kamir Yosef , Goor Meital , Shekhtman Inna , Golodnitsky Diana , Peled Emanuel 
Published: February 2020

The recent trend of accelerated miniaturization of electronic devices has increased the demand for microbatteries of different geometries and chemistries, with high customizability and low manufacturing cost. Devices for applications such as personal wearable electronics, medical implants and remote sensors require small-size, but high-energy-density batteries, often with extraordinary design restriction and highly specific requirements.
To facilitate the production of microbatteries of this type, we plan to use drop-on-demand dispensing, a highly robust printing method already used for various types of functional materials. This method, based on piezoelectrically actuated mechanical droplet formation, enables high accuracy and repeatability in the printing of active-material inks with different properties and rheology parameters.
We have used this method to print various types of active materials for lithium-ion batteries, including cathode (lithium iron phosphate, LFP) and anode (silicon-nickel-based nanoparticles). Both yielded repeatable printability at a resolution below 200µm, which allows customization of the printing to various geometries, including 3D construction of upright electrodes.
We found that the electrochemical performance of printed active materials is highly competitive with traditional manufacturing methods. Cathodes show very high specific capacity, up to 160mAh/g LFP, close to its theoretical capacity and good cyclability. Electrochemical impedance spectroscopy of cathodes shows that cathode chemistry and performance are unaffected by the printing process. Hence, direct implementation of well-established equivalent-circuit models is enabled for data analysis.
Anodes also show high capacity – up to 1200mAh/g anode – and electrochemical behavior consistent with that of anodes prepared by traditional methods. We studied the adhesion of printed anodes to several current collectors and present methods of improving it. The anodes with improved adhesion gave longer cycle life and better performance of microbatteries printed in nonconventional geometries.
Our results inspire further studies, development of manufacturing protocols, and designs for highly customizable batteries. Such development is of particular importance for small-scale and flexible production in many fields of applications, such as in-situ 3D printing of embedded batteries during the assembly process of electronic devices.
Evaluation of Changes in Bond Parameters in Sulfolane Under the Influence of Electron-Withdrawing Substituents
Authors: Yasko Andrey , Khamitov Edward , Kuzmina Elena , Kolosnitsyn Vladimir 
Published: February 2020

The results of quantum-chemical calculations of the bond orders in the sulfolane molecule during the substitution of hydrogen atoms for fluorine atoms are presented. The change in the bond parameters were estimated.
Quantum chemical calculations were performed using the Gaussian09 software package. The optimization procedure and the calculation of the vibrational problem were performed using the TPSS/aug-cc-pVTZ method. Analysis of wave functions and calculation of bond orders by “fuzzy’ method were performed in MultiWFN software package.
The objects of study were sulfolane, monosubstituted and disubstituted fluorosulfolanes. A total of 15 structures. The nature of the change in bond orders shows the influence of the position of substituents on bond strength. It has been established that the substitution of hydrogen atoms for fluorine atoms has the greatest influence on the order of the C–S bond, reducing it, and the smallest on the S=O bond.
This work was performed as part of a Government Order to Ufa Institute of Chemistry of the Russian Academy of Sciences by the Ministry of Science and Higher Education of the Russian Federation (Theme No. AAAA-A17-117011910031-7).

Figure 1
(Invited) Nanostructured-Metal-Oxide Functionalized-Supports for Noble Metal Catalytic Nanoparticles: Enhancement of Electrooxidation of Simple Organic Fuels
Authors: Rutkowska Iwona Agnieszka , Kulesza Pawel J. 
Published: February 2020

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.
Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.
We pursue a concept of utilization of mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of methanol and ethanol. Among important issues is incorporation of Rh nanostructures capable of weakening, or even breaking, the C-C bond in the ethanol molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol is partitioned (at Rh) to methanolic residues further oxidized at PtRu cannot be excluded.
Purely Protonic Solar Cells Fabricated from Photoacid-Modified Ion-Exchange Membranes
Authors: Schulte Leanna , Ardo Shane 
Published: February 2020

Analogies have been drawn between electronic semiconductors and water since 1956 when Fuller explained the similarity between silicon ionization, which generates an electron and a hole as mobile charge carriers, and water ionization, which yields a hydroxide and a proton as mobile charge carriers.1 Since then our group has taken steps to produce a water-based pn-junction solar cell that uses water as a protonic semiconductor. Toward this, we have demonstrated photovoltaic action using photoacid-modified Nafion membranes alone2 and when laminated to an anion-exchange membrane,3 yet each demonstration required the membrane to be wetted by an aqueous acid–base gradient.
In this report, a liquid-electrolyte-free photoacid-modified ion-exchange membrane–electrode–assembly (MEA) driving reversible H2 redox chemistry is described. The cell architecture consists of a three-layer membrane (cation-selective Nafion membrane, aminopyrene-functionalized polyphenylene oxide, anion-selective X37 membrane) that was characterized using direct membrane contacts consisting of platinized platinum mesh. The MEA achieved V
oc = 10 mV and J
sc = 7.5 μA/cm2 under low-intensity 405 nm illumination, resulting in an internal quantum efficiency of ~0.2%.
The reported composite MEA overcomes the problem of co-ion crossover by eliminating co-ions altogether while still exhibiting photovoltaic action due to the charge-separating potential across the membrane interfaces. Because photovoltaic performance persists in the absence of electrolyte gradients and because the potentiometric measurements conducted here are only sensitive to the electrochemical potential of protons, we can conclude that the light-induced voltage and current originate from protons and/or hydroxides, and no other ionic species. This MEA thus serves as a robust proof-of-concept of water’s role as a protonic semiconductor. It also offers a promising format for fundamental studies on the origin of photovoltaic action in photoacid–polymer-electrolyte membranes in the absence of the convoluting effects of liquid electrolyte.
Acknowledgments: This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Research Award under award number DE-SC0019162 from the Solar Photochemistry Program.

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