bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance Characteristics of the Zn-Ce Hybrid Redox Flow Battery
Authors: Berlouis Leonard , Nikiforidis Georgios 
Published: February 2020

Redox flow batteries (RFB) offer a potential solution to the implementation of medium to large scale energy storage (10 kWh - 10 MWh) since they have the advantage of cost, flexibility, rapid response and safety over other alternatives such as the lithium ion and sodium-sulfur batteries. The zinc-cerium hybrid RFB is one of the most promising RFB systems due to its high open circuit cell voltage (Ecell
= 2.4 V) and moderately high energy density (20 – 35 kWh dm-3). The investigations here examined the impact of operating parameters such as charging/discharge current density, electrolyte composition, flow velocity, temperature and the use of different carbon composite electrodes on the performance of the Zn-Ce RFB. The chemical stability of the positive electrode material in the strongly oxidising Ce(III)/Ce(IV) is an issue here and although certain treated carbon surfaces have shown some promise, long term electrode stability has only been achieved so far with Pt or Pt/Ir coatings on titanium. On the negative electrode side, the impact of charging current density (0.5 mA cm-2 to 100 mA cm-2) and temperature (25°C to 60°C) on the nature and morphology of the zinc deposit from concentrated (~2.5 M) Zn2+ solutions in methanesulfonic acid (MSA) were initially investigated using an electrochemical Hull cell. The measurements revealed that on a number of carbon composite electrodes (BMA5, PPG86 and BPP4) from the SGL Group, the best compact and adherent deposits were produced over a narrow current density range. Flow cell investigations were then carried out to evaluate the influence of these parameters on the cell performance. The RFB used here comprised the carbon composite electrode (100 cm2) as the negative terminal in contact with the Zn2+/MSA solution. A Pt/Ti mesh served as the positive electrode in contact with an electrolyte containing 0.8 M total cerium content in 3.5 M MSA. A Nafion® 117 cation exchange membrane separated the two electrolytes in the flow cell. The reservoirs containing the two electrolytes were immersed in a water bath whose temperature was maintained constant through a Gallenkamp water circulator. Consistently, high (>90%) coulombic efficiencies (ηC) were obtained from the charge-discharge cycles. High zinc concentrations yielded energy efficiencies of ~64% at currents of 1 A over the temperature range 45°C - 60°C. Under these conditions, the duration of the charging cycles, from 10 min to 2 hours, had little impact on the energy efficiency. Nevertheless, variations in ηC and in particularly, the voltage efficiency (ηV) were observed on charging at different current densities although flow velocity had little impact on these efficiencies. Investigations are also currently under way to examine the kinetics of the cerium half-cell so that the cell capacity can be improved by using additives as well as mixed anion electrolytes.
Relating Anode Gaps to the Positioning of the Reference Electrode in PEM Fuel Cells
Authors: Berg Peter , Kulikovsky Andrei 
Published: February 2020

We present analytical solutions for the potential and current density distributions in the vicinity of inactive (“dead”) regions inside a PEM fuel cell anode. For simplicity, the dead region is modeled as a step function for the anode exchange current density, representing membrane gaps or delamination. The solutions exhibit a large peak of the anode current density just outside the dead region. This overshoot can substantially exceed the average current density, thereby accelerating membrane degradation. In the limit of large gap sizes, we demonstrate how these findings relate to the positioning of a reference electrode which can independently measure the anode and cathode overpotential, respectively.
[1] A. A. Kulikovsky and P. Berg, Analytical description of a dead spot in a PEM fuel cell anode, ECS Electrochem. Lett., 2, pp. F64-F67 (2013)
[2] P. Berg and A. A. Kulikovsky, A model for a crack or a delaminated region in a PEM fuel cell anode: Analytical solutions, Electrochim. Acta, submitted.
Manganese Oxides As Anode Catalysts for Electrolysis: In Situ Raman and Corrosion Studies
Authors: Ranjan Chinmoy 
Published: February 2020

Non noble metal "earth abundant" electrocatalysts will significantly reduce the costs and make it possible to use electrochemical water splitting (electrolysis) on a very large scale. Non noble metal catalysts can be an effective replacement even if their electrochemical activities are a fraction of their noble metal counterparts. If these catalysts can be developed to an extent where their operational lifetime would become comparable to their noble metal counterparts, a large part of the problem would be solved. MnO2 is earth abundant and well known for catalyzing oxygen evolution. A form of MnOx cluster is known to catalyze water oxidation in photosynthesis. These catalysts although with immense potential remain a long way from successful implementation within electrolysers. Catalyst stability remains an extreme challenge. MnO2-x naturally exists in various polymorphs, with various amounts of defects each of which is known to have a different electrocatalytic performance. In such a scenario the true nature of the electrocatalyst needs to be well established.
In order to understand the limitations of this catalyst under the operational conditions, it is important to study this material in situ. Setup for in situ Surface Enhanced Raman Spectroscopy is used for tracking the structural changes of hydrous MnOx. Electrodeposition of MnOx on the surface of Au was achieved by passing an anodic current of 50 mC/cm2 at 1,6V. Besides in-situ study of catalyst structure, ex situ analysis of corrosion using flow cells combined with Inductively Coupled Plasma-Optical Emission Spectroscopy and explicit oxygen detection using Rotating Ring Disc Electrode allows us to develop.
The structural integrity of the MnOx was studied by following the Mn-O-Mn stretching various potential ranges in various electrolytes. Onset of phase changes and corrosion could be clearly established. Beside this, other methods such as XRD, SEM, TEM were applied to study these thin films.

Figure 1
Exploring Phase-Change-Induced Flow in Fuel Cells through X-Ray Computed Tomography
Authors: Shum Andrew , Hatzell Kelsey B. , Connolly Liam G , Burheim Odne Stokke , Parkinson Dilworth Y. , Weber Adam Z , Zenyuk Iryna V 
Published: February 2020

Effective liquid-water management is critical for optimal polymer-electrolyte fuel-cell (PEFC) operation. At lower operating temperatures and during startup, there is a need to remove liquid water from the cathode electrode to ensure reactant delivery1. At higher operating temperatures, large thermal gradients from catalyst layer to flow-field channel in the system promote water removal in the vapor phase due to the exponential dependence of water vapor pressure on temperature (i.e., phase-change-induced (PCI) flow). To achieve maximum water permeation and consequently higher current densities, it is necessary to understand the interplay between PCI flow, capillary-driven liquid water transport, and evaporation/condensation in PEFC porous diffusion media. PCI flow causes the liquid water to evaporate in hotter locations (electrode) and condense in cooler locations (PEFC’s land). Simultaneously, the heat redistribution occurs because heat is consumed during evaporation and released during condensation.
Currently there is little understanding of how water is redistributed under PCI flow. Although water transport in diffusion media has been investigated with modeling and experiments,2-3 evaporation and PCI flow are poorly understood. The basic fundamental knowledge is lacking primarily due to a challenge of experimental measurements and visualization of the evaporating water front within these porous materials. In this talk, we will examine the water distribution and quantify local evaporation/condensation within diffusion media subjected to thermal gradients using synchrotron-based X-ray micro computed tomography (XCT). The novel experimental in-situ setup is presented that allows for precise temperature control and simultaneous water injection. Conditions studied include varying liquid pressure, thermal gradients, and GDL materials.

Acknowledgments

We thank Prof. Jeff Gostick for helpful insights and discussions. We thank Dr. Felix Büchi, Dr. Jens Eller and Dr. Adrien Lamibrac for experimental concept of evaporation experiment. This work was supported by EERE, Fuel-Cell Technologies Office, of the U.S. DOE under contract number DE-AC02-05CH11231. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

References

1. Weber, A. Z., et al., A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells. J Electrochem Soc
2014, 161, F1254-F1299.
2. Zenyuk, I. V.; Parkinson, D. Y.; Hwang, G.; Weber, A. Z., Probing Water Distribution in Compressed Fuel-Cell Gas-Diffusion Layers Using X-Ray Computed Tomography. Electrochemistry Communications
2015, 53, 24-28.
3. Zenyuk, I. V.; Weber, A. Z., Understanding Liquid-Water Management in Pefcs Using X-Ray Computed Tomography and Modeling. ECS Transactions
2015, 69, 1253-1265.
Furfuryl Alcohol-Derived Vitreous Carbon Coating on Si/ Silicide Nanocomposite Anode of Li-Ion Batteries:
Authors: Jang Juyoung , Kang Inyeong , Kim Moon-Soo , Kim Jae-Hun , Yi Kyung-Woo , Cho Young Whan 
Published: February 2020

Silicon has been widely studied as an anode material for lithium ion batteries because of high gravimetric and volumetric capacity. However, lithium ion insertion and extraction results in a volumetric expansion of about 400%, which leads to pulverization of the silicon anode during electrochemical cycling. One of the methods to mitigate this problem is to coat a thin carbon layer on silicon particles. It can effectively increase the electrical conductivity, improve the chemical and/or physical properties of the surface layer. In addition, the anode particles can be protected from direct contact with electrolyte, leading to enhanced cycle life. Most of the carbon coating layer tried so far is graphitic starting from different types of aromatic hydrocarbon sources.
Here, we have adopted a new carbon coating with vitreous carbon derived from furfuryl alcohol. The vitreous carbon structure, formed after carbonization heat treatment at relatively lower temperatures, with inherently higher strength, hardness, resistance to chemical reaction, as well as lower porosity and permeability may result in better carbon coating layer. For the anode material, we combined chemically inert phase such as silicides with silicon into nanostructured composite particles which should have a much lower volumetric expansion after lithiation than pure silicon particles.
The specific surface area which would affect the irreversible capacity and charge retention ratio of the cell could be controlled by change of the heat treatment condition. The specific surface area was changed between 7m2/g and 70m2/g after coating of the alloy powder with the specific surface area of 3m2/g. By optimizing heat treatment conditions, we could obtained much improved initial capacity as well as significantly better charge retention ratio after 20 cycles.
Hydrocarbon Blended Membrane for Redox Flow Battery
Authors: Kim Haekyoung , Park Su Mi 
Published: February 2020

With the expanding need for large electrical energy storage systems in connection with renewable energy sources, flow batteries, have been enormously considered due to their high flexibility in upgrade and low cost associated with scale-up. Of all the flow batteries, vanadium redox flow battery (VRFB) use of same element in both half-cell solutions that overcomes the inherent issue of cross contamination by diffusion of different ions across the membrane. Together with the absence of any toxic emissions, the vanadium redox flow battery has demonstrated its uniqueness in terms of safety and long life cycle. Typical charge-discharge reactions of a VRFB involve two vanadium redox couples, V(II)/V(III) and V(IV)/V(V), in the negative and positive half-cells, respectively. In a fashion similar to most batteries, electrons are transferred between the two electrodes through the external circuit during the charge and discharge processes. In a VRFB, the ion exchange membrane is a key component as an ionic conductor and separator: it not only provides an ionic conduction pathway between the two electrolytes but also prevents mixing of the negative and positive electrolytes. The crossover of ions through the membrane, with the diffusion of vanadium ions from one half-cell to the other due to the concentration gradients between the two electrolytes, will result in self-discharge and thus the loss of the chemical energy.
In this study, the blended membrane of hydrocarbon polymer with perfluorinated organic membrane were fabricated and characterized in terms of ionic conductivity and permeability. The ionic conductivity was measured with four point probe method and the permeability was measured with UV spectroscopy. The blended membrane exhibited comparable ionic conductivity with perfluorinated organic membrane and 30 – 40 % lower permeability than perfluorinated organic membrane. With performances of VRFBs, the energy efficiencies of VRFBs will be discussed.
Advanced Lead Batteries for Automotive and Storage Applications
Authors: Monahov Boris North Carolina , Ellis Timothy 
Published: February 2020

In the steadily growing battery market, low emission hybrid electric vehicles (HEV) and energy storage systems (ESS) for supporting utility and decentralized grids linked to renewable energy power are supposed to form the major segments in the coming decade or two. In these applications the requirements to the batteries (which have to be cycled by increasingly high currents and at partial state of charge (HRPSoC)) are challenging for every chemistry. Like other advanced power sources, lead batteries are steadily improving and are matching today to the requirements of the advanced applications. Performance parameters like charge acceptance and dynamic charge acceptance, specific energy and specific power, cranking ability and energy efficiency, as well as cycle life at HRPSoC and deep cycling are subject of steady enhancement by the lead battery community. The ALABC members are achieving this by optimizing the design of the cells or by adding various forms of carbon to the negative and to the positive plates.
Carbon is added as micro or nano sized particles of graphite, carbon black, activated carbon, nano tubes or graphene; as separate plates operating in parallel to the negative plate, or as a replacement of the grids. Efficient cell design optimization includes thin plates, height to footprint aspect ratio, bipolar and pseudo bipolar design, electrolyte concentration and a variety of additives. Optimizing of the recharge profiles at HRPSoC is another method of significantly prolonging the life of the battery.
A number of companies in the US, in Europe, Asia, Australia and New Zeeland are offering batteries with the above enhancements, following the first lead-carbon battery – the Ultrabattery - which is now available by several battery manufacturers in Japan, USA, Europe and China. Along with lowest production costs and full safety, advanced lead batteries have the lowest carbon dioxide prodution footprint and are fully recycled, what makes them the most environmentally friendly battery chemistry on the market.
The presentation reviews these innovations and provides a summary of the new program of the ALABC for further basic battery electrochemistry research and technology advancements.
Capacitance Improvement of Semiconductor Electrode By LbL Modification
Authors: Gonzalez Zoilo , Ferrari Begoña , Sanchez-Herencia Antonio , Caballero Alvaro , Morales Julian 
Published: February 2020

In the last decades, supercapacitors have been considered as one of the most promising energy storage devices due to their large power density and their long cycle life. Carbon and binder-free technologies have been recently proposed based on the consolidation of semiconductor nanostructures to use as device electrodes [1, 2] due to its wider mechanical and thermal stability. Among oxide films, NiO has been intensively investigated in supercapacitors based on their high theoretical specific capacity values (2584 F/g), high chemical stability, ready availability and lower cost. Electrodes requirements of a supercapacitor, and consequently their delivered capacitance, are largely dependent on the microstructure characteristics. In particular, it strongly depends on the increase of the active surface area avoiding electronic conductivity fall. In fact, a well-connected mesoporous structure, with a high and narrow pore size distribution exhibits greatly improved electrochemical performance. The processing of those ceramic films through inexpensive and ecofriendly powder technologies is challenging. Among different approaches, the use of the colloidal techniques allows nanostructures tailoring, strengthening the control over the specific final properties.
In this work, colloidal routes have been explored to improve the electrochemical response of a pseudocapacitor electrode based on a NiO nanostructure consolidated at low temperature (325°C) [3]. At this time, we have considered the surface modification of Ni(OH)2 nanoplatelets synthesized by ultrasound through the addition of polyelectrolytes to the suspension. The formation of different layers with polycationic and polyanionic electrolytes was studied. Polyethylenimine (PEI) and Polyacrylic Acid (PAA) were used as polyelectrolytes to form a Layer by Layer system. As a result the modified Ni(OH)2 nanoplatelets were stabilized in suspension and shaped by Electrophoretic Deposition (EPD) on Ni substrates, for later sinterization of films which were electrochemically tested.
[1] D.-H. Ha, M.A. Islam and R.D. Robinson, Binder-free and carbon-free nanoparticle batteries: A method for nanoparticle electrodes without polymeric binders or carbon black, Nano Lett .12, 2012, 5122–5130.
[2] S.Cabanas-Polo, Z. González, A.J. Sanchez-Herencia, B.Ferrari, A.Caballero, L.Hernan and J.Morales. Cyclability of binder-free β-Ni(OH)2 anodes shapes by EPD for Li-ion batteries, J. Eu. Cer. Soc., 35, 2015, 573-584
[3] Z. González, B.Ferrari, A.J. Sanchez-Herencia, , A.Caballero and J.Morales. A One-Step and Binder-Free Method to CoatStructures with NiO nanoplatelets. Influence of the Particle Packing in Supercapacitor Electrodes. J. Electrochem. Soc.
(Invited) Charge Generation in Bulk-Heterojunctions Based on Fullerene Heterodimers
Authors: Dyakonov Vladimir , Sperlich Andreas , Poluektov Oleg G. , Niklas Jens , Delgado Juan Luis , Martin Nazario 
Published: February 2020

Organic photovoltaic (OPV) cells remain to be one of the most attractive approaches for utilization of solar energy showing gradually increasing conversion efficiency of 11%. Significant efforts were directed to the improvement of the electron donating (polymer) part of the bulk-heterojunction (BHJ) solar cells. On the other hand, less advancement has been made on the acceptor side. Recently, a few examples of soluble fullerene hetero- and homodimers based on C60 and C70 linked through chemical bridges have been developed and were shown to competitively perform in solar cells. However, the electronic structure of these fullerene dimers is not well understood. Thus, it is not known how those two fullerene molecules are electronically coupled in the dimer, i.e., whether the excited neutral state or anion state of the dimer is delocalized over the whole dimer or still localized only on one fullerene cage. We have experimentally shown that fullerene molecules in the C60-C70-heterodimer in solid films are strongly electronically coupled and the spin densities of the anion and excited triplet states are delocalized over the whole molecular dimer. However, in the frozen diluted solutions the fullerene cages in heterodimers are instead weakly coupled. The anion and triplet states of the dimers show the signature of individual C60 or C70 molecules. We explain this phenomenon by the presence of two different conformers in the solid-state films and in frozen solutions. Since the electronic coupling between fullerene molecules in the dimers is influenced by their packing in the blends, our observation provides insight into how to tune the electronic properties of the fullerene acceptors by proper adjustment of molecular bridge structures between fullerene cages to fix the desired conformation, which in turn may have an impact on the charge carrier generation efficiency in organic solar cells.
(Invited) DNA As Supramolecular Template for the Assembly of Porphyrin Arrays
Authors: Stulz Eugen , Mames Iwona 
Published: February 2020

DNA has become very attractive as scaffold for functional molecules on the nanometre scale.1 The sequence specific insertion of modified nucleotides using automated DNA synthesis allows for the creation of new designer molecules with a wide range of potential applications. We have established a general synthetic route to porphyrin-nucleosides and their subsequent site specific incorporation into oligonucleotides to create multiporphyrin arrays. Up to eleven consecutive porphyrins could be incorporated into DNA giving access to a multiporphyrin array of approximately 10 nm in length, which corresponds to the highest amount of DNA modification with a large hydrophobic metal complex.2 The spectroscopic data and structure calculations indicate the formation of a stable helical array in the single strand porphyrin-DNA. The π-stack of the porphyrins leads to strong electronic interaction between the chromophores. A zipper array with induced stability and energy transfer properties has recently been realised, providing access to the first reversible photonic wire based on a DNA scaffold.3

We will present our latest results in terms of structure analysis of porphyrin modified DNA, which includes the stepwise built up of a porphyrin-DNA system and its detailed analysis using CD spectroscop and thermal analysis with absorption and fluorescence spectroscopy. In addition, a novel LNA derived porphyrin building block will be discussed which shows large differences in excitonic coupling depending on the DNA sequence.4 Several applications of porphyrin-DNA will also be described, including highly sensitive genosensors5 and DNA origami nanopores.6

References
1. T. J. Bandy, A. Brewer, J. R. Burns, G. Marth, T. Nguyen and E. Stulz, Chem. Soc. Rev., 2011, 40, 138-148.
2. L. A. Fendt, I. Bouamaied, S. Thöni, N. Amiot and E. Stulz, J. Am. Chem. Soc., 2007, 129, 15319-15329.
3. T. Nguyen, A. Brewer and E. Stulz, Angew. Chem. Int. Ed., 2009, 48, 1974-1977.
4. D. G. Singleton, R. Hussain, G. Siligardi, P. Kumar, P. J. Hrdlicka, N. Berova, E. Stulz, Org. Biomol. Chem., 2016, in print; DOI: 10.1039/C5OB01681A
5. I. Grabowska, D. G. Singleton, A. Stachyra, A. Gora-Sochacka, A. Sirko, W. Zagorski-Ostoja, H. Radecka, E. Stulz, J. Radecki, Chem. Commun., 2014, 50, 4196-4199.
6. a) J. R. Burns, E. Stulz and S. Howorka, Nano Lett., 2013, 13, 2351-2356; b) J. R. Burns, K. Gopfrich, J. W. Wood, V. V. Thacker, E. Stulz, U. F. Keyser and S. Howorka, Angew. Chem.-Int. Edit., 2013, 52, 12069-12072.

Figure 1