bluuebunny/crossref_metadata_2025 huggingface dataset:
Doubling up: Increasing Charge Storage in Organic Donors and Acceptors for Non-Aqueous Redox Flow Batteries
Authors: Odom Susan A , Kaur Aman Preet , Casselman Matthew D , Milshtein Jarrod David , Kowalski Jeffrey A , Elliott Corrine F , Parkin S R , Risko Chad , Anthony John , Brushett Fikile R.
Published: February 2020

Redox flow batteries (RFBs) are promising candidates for grid storage, with a few large-scale systems currently in operation. However, current systems have not met the stringent cost and/or safety requirements needed for widespread implementation. Replacing vanadium with organic compounds may lower materials cost, and utilizing non-aqueous (aprotic) electrolyte solvents, in place of water, could enable a 2- to 3-fold increase in operating voltage. Both features make non-aqueous RFBs candidates for large-scale stationary storage. Currently a limited number of organic compounds have been reported as stable electron donors and acceptors, with even fewer materials being studied as small molecule two-electron donors and/or two-electron acceptors. Yet if the amount of charged stored within an individual molecule were raised without significantly increasing the molecular weight, then electrolyte capacity could be increased proportionally, assuming solubility of neutral and charged species is retained. Our recent efforts have focused on the development of highly soluble electron donors and acceptors with stable oxidized and reduced states. This presentation will focus on design strategies utilized to increase molecular stability in all relevant states of charge as well as solubility. In particular, we highlight the design, synthesis, and electrochemical analysis of phenothiazine and napthoquinone derivatives designed to serve as two-electron donors and two-electron acceptors, respectively. We show that tactical placement of substituents leads to improved stability of doubly oxidized and doubly reduced species, whilst retaining atom economy and that high solubility.
Performance of a Non-Aqueous Flow Battery System with a Mushroom-Derived Electrolyte
Authors: Agar Ertan , Cappillino Patrick J , Nourani Mahnaz , Huang Haobo , Howland Rachael
Published: February 2020

Recently, a significant emphasis has been placed on non-aqueous electrolytes for use in redox flow batteries due to their wider electrochemical potential windows, offering higher energy and power densities. To date, several non-aqueous electrolytes using organic molecules [1-2] and metal-ligand complexes [3] have been evaluated for use as electrolytes in non-aqueous redox flow battery (NRFB) systems. With these efforts, substantial performance enhancements, including a several-fold increase in energy density and improved operating temperature range, are possible compared to state-of-the- art vanadium/sulfuric acid flow batteries; however, NRFB progress has been hampered by poor electrolyte stability [4]. Thus far, development has been limited to systems with short cycle-life that exhibit capacity-fade and low current density. This underscores a key challenge currently limiting the advancement of these technologies – the stability.

We employ a bio-inspired approach to address the problem of redox-couple instability that impedes commercialization of NRFB. Our strategy of molecular design is based on naturally occurring chelating molecules that have evolved to bind metal ions extraordinarily tightly and with high-specificity. With this approach we have targeted Amavadin, a vanadium compound found in mushrooms of the Amanita genus. This molecule, and its analog, calcium vanadium(iv)bis-hydroxyiminodiacetate (CVBH) (Figure 1 inset) are among the most stable vanadium chelates ever elucidated. Initial, static-cell investigations have demonstrated that CVBH is stable to exhaustive, deep redox cycling (Figure 1), making it an excellent candidate for implementation in an NRFB system.

In this presentation we will demonstrate the performance of such an NRFB system, using this mushroom-based (CVBH) electrolyte. Results include battery cycling as well as capacity fade and efficiency analyses. The results of these analyses with respect to various operating conditions and flow cell components will also be reported.

References:

[1] Milshtein, J. D., Kaur, A. P., Casselman, M. D., Kowalski, J. A., Modekrutti, S., Zhang, P. L., Harsha Attanayake, N., Elliott, C. F., Parkin, S. R., Risko, C., Brushett, F. R., Odom, S. A. Energy Environ. Sci. 2016, 9 (11), 3531-3541.

[2] Wei, X., Xu, W., Vijayakumar, M., Cosimbescu, L., Liu, T., Sprenkle, V., Wang, W. Adv. Mater. 2014, 26 (45), 7649-7653.

[3] Suttil, J. A., Kucharyson, J. F., Escalante-Garcia, I. L., Cabrera, P. J., James, B. R., Savinell, R. F., Sanford, M. S., Thompson, L. T. J. Mater. Chem. A 2015, 3 (15), 7929-7938.

[4] Carino, E. V., Staszak-Jirkovsky, J., Assary, R. S., Curtiss, L. A., Markovic, N. M., Brushett, F. R. Chem. Mater. 2016, 28 (8), 2529-2539.

Figure 1
Modeling Slurry Electrodes for Redox Flow Batteries Using Kinetic Monte Carlo
Authors: Franco Alejandro A. , Shukla Garima , del Olmo Diaz Diego , Thangavel Vigneshwaran
Published: February 2020

A new technological avenue, that allows utilization of conventional rechargeable battery material at grid scale, has opened up with the development of slurry redox flow batteries (SRFBs) [1]. These can offer volumetric capacity of up to 5-20 times greater than conventional redox flow batteries based on aqueous solutions [1]. However optimization and commercialization of SRFBs requires better understanding of suspension stability, non-Newtonian fluid flow behavior, electrochemical cycling phenomena, and consequent particle dynamics of the solid material in suspension.

In this work we present a multiphysics mesoscopic modeling tool resolved using an kinetic Monte Carlo algorithm [2,3] in three dimensions. This model simulates the phenomena which take place during the discharge of a SRFB in static mode with a silicon-carbon based slurry in organic electrolyte [4]. It captures the dynamics of electronic percolation networks of carbon particles created during Brownian motion. These percolation networks form electron conduction pathways for silicon particles to discharge and eventually undergo volume expansion [Fig.1]. Results are discussed in contrast to in-house experimental data [4]. Our model offers a first look into the complex interplay of intrinsic parameters that need to be understood to achieve optimization based on factors like carbon volume fractions and C-rates [5].

Fig. 1. Snapshot of the channel during galvanostatic discharge slurry containing carbon (in red) and silicon particles (in blue). When silicon is in contact with carbon percolation networks (in yellow), it can discharge. The channel thickness is 1.5 μm and the area of the current collector is 6.25 μm2.

References :

[1] M. Duduta, B. Ho, V. C. Wood, P. Limthongkul, V. E. Brunini, W. C. Carter, and Y. Chiang, Adv. Energy Mater., 1(2011) 511

[2] M. A. Quiroga, and A. A. Franco, J. Electrochem Soc.
161(7) (2015) E73.

[3] G. Blanquer, Y. Yin, M. A. Quiroga, and A. A. Franco, J. Electrochem Soc., 163(3) (2016) A329

[4] S. Hamelet, D. Larcher, L. Duport, and J. M. Tarascon, J. Electrochem Soc., 160(3) (2013) A516.

[5] G.Shukla, D. del Olmo Diaz, V. Thangavel, and A. A. Franco, in preparation (2016)

Figure 1
New Process to Synthesize Rh2S3 Precursor for Rhxsy Catalyst for HER/HOR in HBr Solution By Na2S and Pretreated Carbon
Authors: Li Yuanchao , Nguyen Trung Van
Published: February 2020

There has been growing interest in electrical energy storage because of the challenge of integrating intermittent renewable energy sources such as wind and solar into the electrical grid. The hydrogen-bromine reversible fuel cell system serves as a promising technology to meet this need because of its high round-trip conversion efficiency and low cost. Since the commonly used catalyst, platinum, is not stable in the corrosive HBr and Br2 environment, an alternative catalyst which is durable and active is needed. RhxSy catalyst has been found to be stable in the HBr/Br2 environment1,2.

The conventional synthesis of RhxSy/C has been developed by De Nora3, where (NH4)2S2O3 serves as sulfur source and XC72R is the carbon support. This kind of catalyst, however, has large and broad particle sizes (12-40 nm) and consequently low mass specific active area (< 10 m2/g) for HOR. Moreover, the exchange current density for the HOR/HER is also relatively lower than the commercial RhxSy catalyst from BASF, which can be seen from Figure 1. Other research groups4,5 have shown that smaller particle size can be achieved if preferable surface for precipitation of Rh cation is provided. Figure 2 shows the mass specific active surface area (ECSA) of the catalyst prepared with pretreated carbon and the commercial Rh2S3 synthesis process. In addition to the ECSA/mass enhancement, Na2S also serves as an appropriate sulfur source to modify the crystal structure of RhxSy, as shown in Figure 3. The modified crystal structure leads to improved exchange current density. This presentation will discuss the attempt to synthesize the RhxSy catalyst with pretreated carbon and Na2S. The characteristics and performance of this catalyst will also be presented.

Reference

1. J. Masud, T. Van Nguyen, N. Singh, E. McFarland, M. Ikenberry, K. Hohn, C.J. Pan, and B.J. Hwang, Journal of the Electrochemical Society, 162, F455 (2015).

2. A. Ivanovskaya, N. Singh, R.-F. Liu, H. Kreutzer, J. Baltrusaitis, T. Van Nguyen, H. Metiu, and E. McFarland, Langmuir, 29, 480 (2013).

3. De Nora Elettrodi S.P.A, Synthesis of Noble Metal, Sulphide Catalysts in A Sulfide Ion- Free Aqueous Environment, US6967185 B2, 2005.

4. A. Eguizabal, L. Uson, V. Sebastian, J.L. Hueso, and M.P. Pina, RSC Advances, 5, 90691 (2015).

5. M.S. Shafeeyan, W.M.A.W. Daud, A. Houshmand, and A. Shamiri, Journal of Analytical and Applied Pyrolysis, 89, 143 (2010).

Acknowledgments

The work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000262 and the National Science Foundation under Grant No. EFRI-1038234 and No. 1416874, as a sub-award from Proton Onsite.

Figure 1
Scaling Considerations in All-Iron Flow Batteries
Authors: Sinclair Nicholas S. , Murphy Joseph , Savinell Robert F. , Wainright Jesse S.
Published: February 2020

In recent years, the deployment of renewable energy sources, development of smart grid technology and advances in electrified transportation have resulted in a surge in markets for large-scale stationary energy storage. Several factors contribute to the demand for large-scale energy storage, including capital costs of managing peak demands, integration of renewable energy sources and investments needed for grid reliability. Although hydroelectric is one of the most common types of energy storage, flow batteries offer a much more desirable alternative, due to scalability and location flexibility. A number of studies and demonstration projects have been carried out in the field of flow batteries, in particular with the vanadium [1,4], and iron/chromium[2-4] chemistries and these and other systems are in the first stages of commercial deployment. In this presentation we will discuss the scale-up an all iron flow battery, focusing on two issues in particular, flow distribution and hydrogen generation/recombination.

Flow distribution is a scaling concern in all flow battery systems both on a cell to cell level within a stack and within an individual cell. This investigation utilizes the all iron chemistry to investigate the effects of flow distribution within a single cell on cell performance and the pressure drop associated pumping costs of achieving a more even flow distribution within a cell. These effects are considered in the context of transitioning from a 50cm2 lab scale cell to a 1100cm2 commercial scale prototype. An optimization can be achieved between flow uniformity and pumping losses.

Hydrogen evolution is a parasitic reaction in many chemistries that can have a significant effect on lifetime. We have developed a simple in-tank system that captures and re-oxidizes hydrogen to maintain electrolyte stability and demonstrated this concept on a laboratory scale.[5] This investigation looks into scaling considerations and their effect on the hydrogen recombination system. Specifically, the relationship between head space, gas recirculation and the effectiveness of the reactor are considered.

[1] G. Codina, J. Perez, M. Lopez-Atalaya, J. Vasquez, and A. Aldaz, J. Power Sources, 48, 293 (1994).

[2] S. Takahashi and T. Hiramatsu, J. Power Sources, 17, 55 (1986).

[3] M. Futamata, S. Higuchi, O. Nakamura, I. Ogino, Y. Takada, and S. Okazaki, J. Power Sources, 24, 137 (1988).

[4] M. Skyllas-Kazacos, M. H. Chakrabarti, S. A. Hajimolana, F. S. Mjalli and M. Saleem, J. Electrochem.Soc., 158, 8 (2011).

[5] S, Selverston, R. F. Savinell and J. S. Wainright, J. Power Sources., 324, 674, (2016).
A New Membrane-Less Porous Electrode Cell Design for Zinc-Iodide Redox Flow Battery
Authors: Shakeri Hosseinabad Fatemeh , Fofana Daouda , Li Jialang , Roberts Edward P.L.
Published: February 2020

A new flow field using a flow through porous electrode for membrane-less flow battery has been evaluated using the zinc-iodide redox system. The flow through the porous electrode enables good mass transport at the zinc electrode, and thus good performance was obtained. The flow through arrangement also allowed separation of the charged species without the use of a membrane. An electrolyte system of zinc-iodide, iodine, and zinc chloride was used. A 5cm2 carbon paper (39AA SIGRACET) was used as the electrode. Cyclic voltammetry studies were carried out for the electrolyte system using a glassy carbon working electrode in the range of -2 to 2V (versus Ag/AgCl) , and the effect of zinc-iodide concentration and different range of scan rate was investigated. Mass transfer modeling of the zinc iodine system during the discharge process was carried out and the concentration profile was obtained. The variation of zinc-iodide concentration along the length of the cathode, resulted in spatial variation in mass flux and current density. The 2-D model is reduced to an equivalent 1-D model for the concentration profile by using realistic boundary conditions at the electrode along with using similarity technique. The effect of Péclet number, zinc-iodide concentration and flow rate on columbic and energy efficiency of the new cell will be presented.
Development of an Advanced Zinc-Air Flow Battery
Authors: Mahlendorf Falko , Müller Christoph , Fuchs David , Heinzel Angelika
Published: February 2020

In recent years, zinc-air flow batteries have regained importance as promising energy storage system for mobile and stationary applications. This revived importance is driven by the increased demand of high-performance, efficient, safe and environmentally friendly energy storage solutions to meet the challenges of modern energy supply systems with high amounts of renewable energy. These energy storage systems need to address variable power, capacity and profitability requests. Zinc-air batteries with a specific energy density higher than lithium-ion and low cost, highly available, eco-friendly active materials are suitable to fulfill these requirements. The use of a flow battery type with zinc-particles suspended in alkaline solution (zinc-slurry) in addition with oxygen reduction electrodes developed for the chloralkali process allows the development of high-power zinc-air batteries. This setup also enables the independent scaling of capacity and power.

The cooperative research project ZnMobil, supported by the Federal Ministry of Economic Affairs and Energy in Germany, combines the experience of industrial and academic partners (Covestro Deutschland AG; Grillo-Werke AG; VARTA Microbattery GmbH; Accurec Recycling GmbH; Technical University Freiberg, Gottfried Wilhelm Leibniz University Hannover; University of Duisburg-Essen; The fuel cell research center ZBT GmbH) to develop a low-cost zinc-air flow battery with high performance.

Here we present the electrochemical performance of the new zinc-air flow battery with respect to different zinc-slurry compositions. The battery system consists of a 100 cm² copper plate as current collector for the zinc-suspension electrode and an oxygen reduction electrode with gas-diffusion layer (supplied by Covestro). The zinc-slurry contains zinc particles (supplied by Grillo) suspended in alkaline solution (30 wt-% KOH) and stabilized with polyacrylic acid.

Current voltage curves and depth of discharge were measured as a function of slurry composition (e.g. zinc content, additives) and different flow velocities of the zinc slurry. Corresponding zinc-slurry conductivities were evaluated in a flow-through conductivity measurement setup. Depending on the selected parameters, it is possible to achieve discharge current densities higher than 4 kA/m².
Free-Standing Two Dimensional MoS2 nanosheet/Acitvated Carbon Clothes Composite for High Performance of Supercapacitor
Authors: Sari Fitri Nur Indah , Ting Jyh-Ming
Published: February 2020

Two dimensional (2D) MoS2 nanosheet has been successfully grown on Activated Carbon Clothes (ACC) by facile method, microwave-assisted hydrothermal at a shorter time. We have investigated the growth mechanism at different time reactions and their performance as electrode material of supercapacitor. Scanning electron microscopy (SEM) confirmed that time reaction controls the morphology and growth orientation of MoS2. On the other hand, it was found from the X-Ray Photoelectron Spectroscopy (XPS) that the additional phase which is MoO3 was formed during the reaction. This phase contributed to the performance by giving an additional pseudocapacitance. Furthermore, the intimate contact between MoS2 and ACC favor for fast electron transport during the charge and discharge. As a result, MoS2/ACC composite shows an excellent performance with specific capacitance of 230 F g-1 at a scan rate of 5 mV s-1 in 1M H2SO4  and high energy density of 79.9 W h kg-1 at high power density of 1044 W kg-1. Noteworthy, by growing MoS2 on ACC, the specific capacitance of MoS2 is 913.7 F g-1 which is the highest that ever been reported. Furthermore, this free-standing material is a promising material for a flexible supercapacitor.

Keywords: MoS2, microwave-assisted hydrothermal, supercapacitor, energy density.
Production of Ethanol in Electrochemical Cell Using Saccharomyces Cereviseae and Wickerhamomyces Anomalous As Counter Microbes
Authors: Joshi Jarina , Shrestha Rejeena , Manandhar Krishna , Sreerama Lakshmaiya , Bhattarai Tribikram
Published: February 2020

Ethanol production by the yeast strains Saccharomyces cerevisiae and Wickerhamomyces anomalous was done by simultaneously cultivating the yeasts in the anode and the cathode of an electrochemical cell alternatively on either side of the electrolytic compartments. When Saccharomyces cerevisiae was cultivated on a platinum plate anode and Wickerhamomyces anomalus was cultivated in graphite rod cathode and an external electric potential of 4V was applied to induce the electrochemical redox reaction in the anode and cathode compartment of an electrochemical cell using glucose as a substrate, 27.61±0.35 mg/ml ethanol was produced. However counter combination produced only 24.78±0.45 mg/ml ethanol. Electrochemical oxidation potential inhibited Wickerhamomyces anomalus but showed a reduced effect on Saccharomyces cerevisiae. Graphite rod when modified by the immobilization of neutral red as a mediator of electron transfer showed improvement in ethanol production. The Wickerhamomyces anomalus when cultured with modified graphite rod and Saccharomyces cerevisiae when cultured in the anode 11.67% more than the neutral red non-immobilized combination of Saccharomyces cerevisiae and Wickerhamomyces anomalusand 64.28% more than that of the control maintained without the supply of external voltage.

Key words: Saccharomyces cerevisiae, Wickerhamomyces anomalus, Electrochemical cell, Neutral red, Platinum, Graphite rod

References

D.H Park, “Microbial Utilization of Electrically Reduced Neutral Red as The Sole Electron Donor for Growth and Metabolite Production.1999, Applied and environmental Microbiology, July1999, p.2912.

Jeon, Bo Young and Doo Hyun Park (2009), “Improvement of Ethanol Production by Electrochemical Redox Combination of Zymomonas mobilis and Saccharomyces cerevisiae,” 2010, J. Microbiol. Biotechnol., 20(1), 94.

Korneel Rabaey et al, “A microbial fuel cell capable of converting glucose to electricity at high rate and efficiency,”, 2003, Biotechnology letters25: 1531.

Abril D and Abril A., Ethanol from lignicellulosic biomass. 2009, Cien. Inv. Agr., Vol. 36(2), 177.

Delaney, G. M.; Bennetto, H. P.; Mason, J. R.; Roller, S. D.; Stirling, J. L.; Thurston, C. F. "Electron-transfer coupling in microbial fuel cells. Performance of fuel cells containing selected microorganism-mediator-substrate combinations". 2008, Journal of Chemical Technology and Biotechnology. Biotechnology 34: 13.

Jarina Joshi, Rejeena Shrestha, Rojlina Manandhar, Dinita Sharma, Krishna Manandhar, Lakshmaiah. Sreerama, Doo Hyun Park , Tribikram Bhattarai (2014). Optimization of External Potential for Ethanol Production by yeasts in electrochemical Cell. Rentech Symposium Compendium, Volume 4:44.
Thermodynamic Properties Determination in LiF-CaF2 using Electrochemistry in High Temperature Fused Salts: Application to CeF3
Authors: Gibilaro Mathieu , Massot Laurent , Chamelot Pierre
Published: February 2020

Pyrochemical route is a promising option for spent nuclear fuel recycling. The major step of spent fuel reprocessing is the actinides-lanthanides separation performed by electrochemical processes. In this partitioning strategy, the most radiotoxic elements (actinides) are separated from the lowest ones (lanthanides) to decrease the volume of high activity nuclear waste disposal. The knowledge of thermodynamic properties (such as activities, standard potentials…) of actinides and lanthanides in solution is then crucial to predict their electrochemical behaviour in a complex multi-element system.

Thermodynamic calculations have been done on cerium fluoride in the LiF-CaF2 eutectics from 1113 to 1233K with FactSage and HSC 6.1 database. From electrochemical measurements (linear sweep voltammetry, equilibrium potential measurements…), the main thermodynamic properties needed for the electrochemical separation evaluation were determined: standard potentials and activity coefficients in different reference states (liquid or solid reference state, and infinite dilution reference state) and for different composition scales (molarity, molality, or molar fraction), and also standard enthalpy and standard entropy of formation in the 1113-1233K temperature range.

Finally, constants which interconnected the infinite dilution reference state and the solid and liquid reference states were evaluated.
Combined Anodic Oxidation and Hydroxyapatite-Magntite Composites Adsorption Treatments for Aqueous Solution Containing Antibiotic Ciprofloxacin- a Novel Approach
Authors: Sivarasan G , Prabha D , Sabarathinam Shanmugam , Haneesh C M
Published: February 2020

In this study, electrochemical degradation of the widely used antibiotic Ciprofloxacin (CIP) was investigated using commercial mixed metal oxide anodes (RuO2/IrO2/TaO2 coated Ti- mesh). Here, one of the secondary inorganic by-products namely, Fluoride ions (F-), was removed from the aqueous medium by means of an adsorption process using Fe2O3/HAp nano composites. A general hydrothermal process was used to prepare Fe3O4 nanoparticles dispersed on the hydroxyapatite nano rods. The obtained nano composites were characterized by XRD, FESEM, BET, VSM and FTIR analysis. The synthesized Fe3O4/HAp Nano composites were further explored to study the maximum removal of F- (99.9%) by optimizing various conditions. The effects of the oxidative potential, current density, initial concentration of CIP, electrolysis time, electrolyte concentration and initial pH on the formation and evolution of F- ions released to the medium during the process were evaluated. The degradation efficiency of CIP was further confirmed by HPLC and GC-MS analysis. At the optimum conditions (current density = 5 mA/cm2, initial CIP concentration = 5mg/L, pH = 3.4, electrode gap = 1.5 cm, and electrolyte concentration = 0.1M Na2SO4), after 30 min, the removals of CIP concentration, COD and TOC were about 99.9%, 75.4%, and 85.6%, respectively. The reaction exhibited a pseudo first-order kinetics model. The results showed that combined electrochemical oxidation, using a RuO2/IrO2/TaO2 coated Ti-mesh as anodes along with adsorption, using adsorbent Fe2O3/n-Hap composites were highly effective for the degradation of CIP.
Platinum Electrodeposition Methods to Enable Incorporation of Low Density Foam-Lined Hohlraums
Authors: Horwood Corie , Stadermann Michael , Bunn Thomas
Published: February 2020

A low density foam liner, in place of a tamping gas, inside a hohlraum will reduce laser plasma interactions and possibly result in more uniform X-ray illumination on the capsule. Hohlraums made of gold are incompatible with a new chemical process to produce very low density, templated foams that possess excellent mechanical properties. Therefore, platinum is of interest for high-Z hohlraums because it is inert to the chemical etchants used to produce the low density foams. Platinum can be electrodeposited using commercially available aqueous electrolytes; however, published work on platinum electrodeposition has focused on thin films with high surface area. We will discuss electrochemical process developments that enabled non-porous, 3 - 20 μm thick Pt coatings on gold hohlraums, electroformed Pt hohlraums of thicknesses greater than 50 μm and a foam-lined hohlraum, where Pt was electrodeposited directly onto the foam starting material.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Energy Saving Chlorine Electrolysis with Gas Diffusion Electrodes
Authors: Trieu Vinh , Bulan Andreas , Eiden Stefanie , Kintrup Juergen , Rittermeier André , Weber Rainer
Published: February 2020

Chlorine is needed for some two-thirds of all chemical products, including plastics. And that comes at a cost. The production of this important basic chemical is one of the most energy-intensive processes in the chemical industry. In Germany the annual production of around 4.5 million tons of chlorine accounts to about 3% of the overall German electricity consumption. Thus, process innovation in chlorine manufacturing provides an important lever for tremendous savings of energy and their related carbon dioxide emissions.

The existing state-of-the-art chlorine processes of brine or hydrochloric acid electrolysis are already highly developed. A significant improvement is only possible by a major technology change. For conventional chlor-alkali electrolysis the reactions can be described as:

Anode: 2 NaCl = Cl2 + 2 e- + 2 Na+ (E0 = +1.36 V)

Cathode: 2 H2O + 2 Na+ + 2 e- = H2 + 2 NaOH (E0 = -0.83 V)

Replacing the cathode reaction of hydrogen evolution reaction by oxygen reduction reaction (ORR) would bring a drastic decrease of the overall electrolysis voltage due to thermodynamics.

Cathode: ½ O2 + H2O + 2 Na+ + 2 e- = 2 NaOH (E0 = +0.4 V)

Electrodes for efficient ORR are well known from fuel cell technology in form of gas diffusion electrodes. However, the implementation of gas diffusion electrodes in a chlorine evolving electrolysis is a challenge when it comes to industrial scale.

By interdisciplinary cooperation of industry partners and research institutes, significantly supported by public funding, the development of suited gas diffusion electrodes for chlorine electrolysis - also known as oxygen depolarized cathodes (ODC) - was successfully realized. The process has been operating on an industrial scale at Covestro’s plant in Krefeld-Uerdingen in Germany since 2011 and has been commercialized worldwide since 2013. As a result, up to 30 percent less electricity than for the conventional process is required.

The talk will highlight the technical requirements and the corresponding developments as well as the ecological and economic aspects of the use of gas diffusion electrodes for chlorine production.

Furthermore, the developed gas diffusion electrodes are the platform for future applications in the field of power generation, energy storage, water purification/disinfection and electrosynthesis.

Figure 1
Numerical Analysis of the Effect of Diaphragm Length, Position and Porosity on the Electric Field and Mass Transport inside a Lithium Electrolysis Cell
Authors: Oliaii Elaheh , Desilets Martin , Lantagne Gaétan
Published: February 2020

Lithium is commercially produced by the electrolysis of lithium chloride. This process is expensive due to the high energy consumption of the electrolysis process. A noticeable part of the energy lost in this electrochemical cell is caused by back reactions, essentially between chlorine bubbles produced at the anode and liquid lithium produced at the cathode. The diaphragm has two opposite effects on the cell energy consumption: it increases the current efficiency through its preventive effect on back reactions; however, it increases the energy consumption of the cell by introducing extra ohmic overpotential. Furthermore, in a lithium electrolysis cell, the diaphragm characteristics significantly influence the mass transfer, electric and velocity fields.

A 2D axisymmetric electrochemical model of a lithium production cell is solved using a finite element method and used to minimize the cell energy consumption by optimizing the diaphragm characteristics and its position in the cell. The model is considering the coupled effect of momentum, electric, kinetic and mass transfer phenomena. The diaphragm separates the cell in two regions: 1- a turbulent region, between the anode and the diaphragm, and 2- a laminar region between the diaphragm and the cathode. The k-ε model is used to solve the turbulent flow resulting from bubbles generation at the anode. The bubbles cause an ohmic overpotential and hyperpolarization, considered through the resistive layer and bubble coverage at the surface of the anode. Furthermore, the effects of the diaphragm length, position and porosity on the electric field are simulated. In fact, the diaphragm position and length influence the current distribution at the surface of electrodes and the velocity distribution in the cell all of which influence ohmic and kinetic overpotentials.

The experimental cell, simulated as a base case on which the model has been validated, contains a dense alumina diaphragm. The results show that up to 40% energy is saved when running a lithium electrolysis cell with a smaller porous diaphragm located as far as possible from the anode. Moreover, the diaphragm deteriorates the current density distribution along the electrodes with a detrimental effect to the integrity of the electrodes. The maximum current density, found at the bottom corner of anode, is higher when the diaphragm is longer and when it is closer to the anode.

Finally, but not least, the results of this research are not only useful for improving the design of lithium production cells. They also could be extended and applied to the study of other molten salts electrochemical cells equipped with diaphragm.
Quantifying Potential Contributions in the Hybrid Sulfur Electrolyzer at Elevated Temperatures
Authors: Garrick Taylor R , Wilkins Cody H , Pingitore Andrew T , Gulledge Alexander , Benicewicz Brian , Weidner John W.
Published: February 2020

The hybrid sulfur thermochemical cycle has seen much attention recently due to its potential to enable the production of clean hydrogen on a large scale with a higher energy efficiency than water electrolysis. The two step hybrid sulfur (HyS) process involves the high temperature decomposition of sulfuric acid to produce sulfur dioxide, oxygen, and water, as well as a low temperature electrochemical oxidation of sulfur dioxide in the presence of water to produce sulfuric acid and gaseous hydrogen. Due to the internal recycling of sulfur compounds in the HyS process, the overall balance is the decomposition of water to form gaseous hydrogen and oxygen. This process is interesting because the high temperature decomposition step could be coupled to next generation solar power plants or high temperature nuclear reactors in order to produce hydrogen for other applications.

Using a proton exchange membrane such as Nafion in the HyS electrolyzer has been thoroughly examined via the prediction of mass transport through the membrane as a function of operating potential and other design variables. However, Nafion presents several drawbacks, such as the inability to operate at elevated temperatures and the decreased performance seen when exposed to high acid concentrations. Previously, we showed that acid doped polybenzimidazole (PBI) membranes are an alternative to Nafion because they do not rely on water for proton conductivity, and therefore offer the possibility of operating at higher acid concentrations in order to minimize energy requirements necessary for water separation, as well as operation at higher temperatures in order to minimize voltage losses. Through the successful operation of the HyS electrolyzer using sulfuric acid doped PBI membranes, we have determined that despite the relative thickness of s-PBI, the area-specific resistance of s-PBI compares favorably with Nafion and is not adversely affected by the sulfuric acid concentration in the electrolyzer. Through further characterization of the membrane and the electrolyzer, we have been able to refine a model for high temperature and high pressure operation of the electrolyzer allowing for further analysis of the system in order to determine operating conditions that allow for economically viable operation of the HyS electrolyzer.

The dependence of the individual potential contributions on temperature and pressure will be discussed, as well as trends seen in the membrane conductivity as a function of operating conditions and produced acid concentrations. A discussion of model results illustrating future membrane design considerations will also be presented.
A Multiplexed Electrochemical Probe for Glutamate and Dopamine Detection
Authors: Tan Chao , Hossain Imran , Dutta Gaurab , Siddiqui Shabnam , Arumugam Prabhu
Published: February 2020

Electrochemical detection of excitatory neurotransmitters (NTs) such as glutamate (GLU) and dopamine (DA) have generated much interest in the field of chemical neuroscience. These NTs have several important functions in mammalian brain, e.g. activating “reward-mechanism” center in the brain, learning and memory. DA deficiency causes depression, ADHD and Parkinson’s disease. Abnormal GLU levels are associated with Epilepsy, Alzheimer’s disease, dementia, insomnia and insufficient adrenaline function. New electrode materials (e.g. carbon nanotubes, boron-doped nanocrystalline diamond, platinized platinum) and probe designs (e.g. high density arrays) are much needed to better understand the neurological disorders that costs at least $100B annually in US alone. The probes are expected to near simultaneously measure multiple NTs in real-time with high spatial-temporal resolution. In our experiments, we use a commercial platinum (Pt) microelectrode array with eight individually addressable sites. Pt is well-known for its high selectivity towards hydrogen peroxide, a common by-product of enzyme-based GLU biosensor. The Pt microelectrodes are suitably modified with multi-walled carbon nanotubes (CNTs) for DA and enzymes for GLU detection and nafion for improved selectivity. Fast scan cyclic voltammetry and amperometry techniques are used to detect the NTs. We report increase in sensitivities of GLU and DA and their suitability for long-term in vitro measurements. The development of electrochemical models to explain the progression of surface fouling and sensor performance using impedance techniques will be elucidated in some detail.
Fast Scan Cyclic Voltammetry with Microdialysis for Quantitative Measurement of Dopamine
Authors: Shin Hojin , Blaha Charles D , Bennet Kevin E , Lee Kendall H , Jang Dong Pyo
Published: February 2020

Microdialysis methods have been widely used for the quantitative measurement of neurotransmitter concentrations in vivo. Because neurotransmitter efflux happens rapidly, microdialysis has a limit to detect neurochemical changes in the brain in real time. Fast-scan cyclic voltammetry (FSCV) is one of the electroanalytical methods to monitor neurotransmitter efflux such as dopamine, serotonin, adenosine, and ascorbic acid in the brain. Because conventional FSCV analyzes voltammagram differences to detect chemical substances, measuring concentrations of neurotransmitters is desirable. In a previous study we introduced a new method using multi-waveform cyclic voltammetry to reduce voltammogram differences and enhance sensitivity and selectivity.

In this study, we demonstrated FSCV with a carbon fiber microelectrode (CFM) adjacent to a microdialysis probe to measure concentration changes during microdialysis. Experiments were performed in agarose gel (0.1%) with a known concentration of dopamine inside, and perfusion of the dialysis probe with Tris-buffered saline (TBS, pH7.4, 5ul/min) decreased the baseline. After stabilization, a series of known concentrations of dopamine (200nM to 1uM) was perfused and concentration changes were monitored by FSCV until the decreased baseline was recovered. These results indicate that the amount of dopamine injected when decrease baseline is fully recovered reflects the concentration of dopamine inside the agarose gel. FSCV combined with microdialysis was also performed in the striatum of a rat, to monitor basal level of dopamine in the extracellular space of the brain.
Heparin Contained Multilayer Composite Coatings on NiTi Alloy By Electrochemical Methods for Reducing in-Stent Restenosis
Authors: Yen Shiow Kang , Liang Yu- Hsin , Zheng Po- Yin , Kao Chen- Yuan , Lai Yu-Liang , Lin Chien- Chung
Published: February 2020

Although the initial success of bare metal stents (BMS) has significantly reduced the restenosis rate from 35% for Percutaneous transluminal coronary angioplasty (PTCA) to 25%, the biological mechanism such as smooth muscle cell proliferation and neointimal hyperplasia may still induce in-stent restenosis (ISR). Therefore, some drug eluting stents have been introduced to reduce ISR. In this study, heparin (Hep) combined with calcium phosphate (CaP) and gelatin (Gel) was co-deposited on NiTi alloy by electrochemical methods in order to fabricate the sustained heparin releasing system for promoting the hemo-compatibility of NiTi substrate. Polarization tests were carried out in several solutions to investigate deposition mechanisms. Heparin contained composite coatings are characterized by X-ray diffractometry (XRD), Field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), toluidine blue colorimetric assay, UV-visible spectrometer and kinetic clotting tests. The consequences indicate that heparin accompanied with CaP, and Gel through ionic bonds can be loaded on the NiTi alloy, respectively. The post porous HA coating can enhance the drug content from 147.06±68.66 of the single layer coating (CaP-Hep) to 191.58±11.87 of the bilayer coating (HA/CaP-Hep) and further to 324.87±4.94 μg/cm2 of the trilayer coating (HA/CaP-Hep/Gel-Hep) by adding the third layer which also results in the in vitro heparin release prolonging from 1 day burst to more than 35 days sustaining release. As the result of clotting tests, drug loaded composite coatings reveal good anticoagulant property which is proportional to the cumulative content of drug release in an hour, indicating no denaturalization of heparin found during the electrochemical process.

Keywords: Ni-Ti alloy; in-stent restenosis (ISR); heparin; calcium phosphate; gelatin
Multi-Scale Modeling of Cathode Performance in Solid Oxide Fuel Cells (SOFCs)
Authors: Geisler Helge , Joos Jochen , Weber André , Ivers-Tiffée Ellen
Published: February 2020

A finite element method (FEM) based model was developed for performance simulation in SOFC, using a homogenized electrode microstructure at the cell level. The model was parametrized with electrode kinetics determined by electrochemical impedance spectroscopy (EIS) on planar anode supported cells and validated by current/voltage characteristics (C/V) over the technical relevant operating condition range of SOFC [1]. Model calculations on planar stack layer level have demonstrated that (i) cathode layer thickness and (ii) cathode layer porosity is key to avoid gas transport limitations and performance loss [2].

The model has been advanced by adopting mixed-ionic/electronic cathode (MIEC) kinetics, thus enabling the simulation of stack layer performance depending on the cathode’s chemical composition. Furthermore, it will be demonstrated how a functional gradient in pore and particle size distribution enhances stack performance compared to state-of-the-art cathodes. These simulations are not based on artificial, but on “real” microstructures, which were determined using a combined focused ion beam/scanning electron microscopy (FIB/SEM) and X-ray tomography reconstruction of a two-layer cathode.

[1] H. Geisler, A. Kromp, A. Weber and E. Ivers-Tiffée, JES 161 (6) F778-F788 (2014)

[2] H. Geisler, J. Joos, A. Weber and E. Ivers-Tiffée, ECS Transactions, 68 (1) 3043-3050 (2015)
The Investigation of Flow Channel Design on the Performance of PEM Fuel Cell
Authors: Wei Guanghua , Wang Chao , Jiang Chuanyu , Zhang Junliang
Published: February 2020

The flow channel is very important to the performance of proton exchange membrane fuel cells (PEMFCs), it is believed that the PEM fuel cell performance is greatly affected by the flow patterns besides the operating temperature, gas inlet humidity, and so on [1,2,3]. The channel or rib width and channel cross-sectional area determine the pressure drop, thus directly influence on the water removal, and then affect the oxygen supply and oxygen reduction reaction. In this study, two flow pattern, four different channel designs are investigated mainly by three-dimensional simulation, effects of different design on cell performance are validated by the experiments. After analyzing the differences between the four kinds of flow channels, the situations of current density distribution, water distribution and oxygen distribution in the cell are studied and the performance are analyzed. We found out how the flow channel width and cross sectional area on the performance of PEM fuel cell: the narrower the width is, the better the cell’s performance is when current is low. The larger the cross sectional area is, the better the cell’s performance is when current is high.

Acknowledgements

This work was supported in part by National Natural Science Foundation of China (Grant No. 21533005) and Science Foundation of Ministry of Education of China ( Grant No. 413064).

References

[1] Bonghwan Lee, Kiwon Park and Hyung-Man Kim. Numerical Optimization of Flow Field Pattern by Mass Transfer and Electrochemical Reaction Characteristics in Proton Exchange Membrane Fuel Cells[J]. Int.J. Electrochem. Sci., 8 (2013) 219 – 234

[2] A. Arvay, J. French, J.-C. Wanga, X.-H. Peng, A.M. Kannan. Nature inspired flow field designs for proton exchange membrane fuel cell[J]International Journal of Hydrogen Energy 38(2013):3717-3726

[3] Sungho Lee, Heeseok Jeong, Byungki Ahn, Taewon Lim, Youngjin Son. Parametric study of the channel design at the bipolar plate in PEMFC performances[J].International journal of hydrogen energy 33 ( 2008 ) 5691–5696

Figure 1
Structure of Polymerized Ionic Liquids from Neutron Scattering Perspective
Authors: Liu Hongjun , Paddison Stephen
Published: February 2020

Recent enthusiasm in polymerized ionic liquids (polyILs) with enhanced mechanical characteristics of polymers and unique physicochemical properties inherent in ionic liquids is fueled by their ability to selectively transport ions. Experiments suggest the morphology of polyILs has a significant effect on ion transport. Despite significant interest in the morphology of polyILs, investigation by traditional experimental techniques remains elusive. Few X-ray scattering experiments yield structural information, and provide little atomistic details. Neutron scattering has not been done on this important class of materials. In our recent ACS Macro Letters work, we reported a comparison of results from atomistic simulations with X-ray scattering experiments on 3 homologous polyILs that strongly support the capability of simulations to provide fundamental understanding of the structure and morphology. Herein, we extend the analysis of morphology to a complete homologous series of poly(CnVim Tf2N) (2 <= n <= 8) with emphasis on selective neutron scattering. We have demonstrated that neutron scattering with isotopic labeling along with X-ray scattering provides versatile ways to vet the intrinsic structure. The neutron scattering profiles markedly depend on the isotopic substitution pattern and that isotopically labeled neutron and X-ray scattering data do not necessarily lead to the same characteristic correlation length. Such an unintended consequence has a nontrivial implication on exploitation of scattering experiments. Moreover, the experimentally accessible difference scattering spectra based on common factor analysis offer a complementary view to the detailed decomposition of the total structure factor provided in molecular simulation and ESPR modeling. We hope the current work might stimulate experimentalists to explore polyILs using selective neutron scattering.