bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrically Conducting Membranes - Challenges and Opportunities
Authors: Jassby David
Published: February 2020

Humans have been expending energy to clean water for millennia. While boiling water to kill pathogens or collect and use vapor are viable methods to produce potable water, water's large heat capacity makes this process energetically expensive, and economically unfeasible on a large scale. Membrane-based separation methods have emerged as the preferred water treatment technology, as membrane processes consume significantly less energy to produce water. However, membranes are prone to fouling, a fact that increases the cost of water and leads to significant operational complexity. We have developed a range of electrically conducting carbon nanotube - polymer composite membranes suitable for a range of water treatment applications ranging from ultrafiltration to reverse osmosis. The polymer composites maintain the transport properties critical for water treatment, with the additional benefit of electrical conductivity. We use the membrane’s intrinsic electrical conductivity to solve many of the fouling problems associated with membrane processes. For example, we demonstrate how an alternating current applied to an RO membrane surface prevents the growth of a biofilm; how the application of a DC potential prevents the nucleation and growth of CaSO4 and CaCO3 mineral scale; and, how membrane surface potentials can be manipulated to prevent the deposition of organic foulants during the ultrafiltration of concentrated waste streams, such as the effluent from anaerobic reactors. Furthermore, we discuss the energy requirements of our technology, and its potential application in real-world water treatment processes.
Electron and Ionic Transport in Microbial Anode Respiration and Their Importance in Microbial Electrochemical Cell Applications
Authors: Popat Sudeep , Parameswaran Prathap , Torres César
Published: February 2020

Anode-respiring bacteria (ARB) catalyze the complete oxidation of organic compounds (e.g. acetate, glucose) into electrical current and carbon dioxide. ARB produce a biofilm at the electrode surface, where even cells on the outer part of the biofilm are participating in current production. Our team uses a variety of electrochemical techniques in order to characterize electron transport responses from various ARB. Through these experiments, we have observed a complex response to anode potential that allows ARB, such as G. sulfurreducens, to optimize their efficiency in electron transport. Identifying this complex behavior allows us to better understand and predict the response of ARB to different conditions in microbial electrochemical cells (MXCs).

While the topic of electron transport is the focus of most ARB research, ionic transport is the most important factor in determining rate-limiting and potential loss processes. ARB require near-neutral pH in the medium to grow, differing from chemical fuel cells commonly employed, which run under acidic or alkaline conditions. This pH requirement results in a major transport limitation, as H+ ions (now in mM range) should be transported from anode to cathode to achieve electron neutrality. In an MXC anode, H+ ions accumulate in the ARB biofilm, creating an acidification that limits current generation. We have identified and characterized ARB that work outside the neutral pH range, including Geoalkalibacter ferrihydriticus and Thermoanaerobacter pseudethanolicus, that allow us to operate MXCs at either acidic or basic conditions. Meanwhile, at the cathode, local gradients leading to pH > 12 is typical in MXC operation. As a consequence, the pH gradient results in Nernstian concentration overpotential of > 300 mV. Thus, understanding and controlling ionic transport in MXCs is essential to ensure an efficient operation. I will discuss our current efforts to characterize and overcome ionic transport limitations in order to develop efficient MXC processes.
Biofilms in Water-Energy-Nexus
Authors: Beyenal Haluk
Published: February 2020

Biofilms are used to clean wastewater, convert chemical energy in wastewater to electrical energy, and are ubiquitous in water bodies. Therefore they play a crucial role in the water-energy nexus. In addition, biofilms on electrodes acting as anodic or cathodic biocatalysts can be used to improve water quality. This section invites papers describing the use of biofilms relevant to the water-energy nexus. Specifically, we welcome papers describing 1) the use of biofilms to clean water, 2) the use of biofilms to convert chemical energy in wastewater to electrical energy, 3) the use of biofilms on electrodes to enhance water treatment, 4) the use of biofilms in energy producing devices in natural waters (i.e. sediment/benthic microbial fuel cells), 5) the use of biofilms on electrodes for water desalination, and 6) biofilms used to monitor water quality. Basic science approaches describing mass and electron fluxes operating inside these biofilms that are within the context of the water-energy nexus are especially welcome. We also welcome innovative applications of biofilms not explicitly described above that may be of interest to biofilm researchers.
Morphology Controlled Magnetic Interactions of Porous Silicon Embedded Nanostructures
Authors: Rumpf Klemens , Granitzer Petra , Koshida Nobuyoshi , Poelt Peter , Michor Herwig
Published: February 2020

In the frame of this work porous silicon templates with different morphologies, especially with respect to the roughness of the pore-walls are filled with diverse ferromagnetic metals to fabricate self-assembled three dimensional arrays of nanostructures (wires, particles) with distinct magnetic properties. The fabricated templates offer a quasi-regular self-assembled pore-arrangement with oriented pores. Also the pore-filling is self-assembled by electrochemical deposition and there are multiple possibilities to tailor the magnetic behavior of these systems such as material, morphology, inter particle distance or interfaces. One critical parameter for this purpose is the roughness of the pore walls and the surface of the metal structures, respectively. To vary the morphology of the templates also magnetic field assisted etching has been employed and a remarkable decrease of the dendritic pore growth has been achieved resulting in smoother pore walls. Within the pores of these templates ferromagnetic metals are deposited and the modification of the magnetic properties compared to metal structures embedded in conventional etched (without magnetic field) porous silicon templates has been figured out. The magnetic anisotropy between easy axis and hard axis magnetization could be increased significantly and furthermore the magnetic behavior becomes comparatively hard magnetic. These properties can be ascribed to less magnetic coupling between nanostructures of adjacent pores and modified stray fields due to less dendritic metal nanowires. The magnetic behavior of three dimensional metal nanowire/nanoparticle arrays with regard to morphological parameters as well as to the influence of the inner interfaces of the composites will be presented. The presented system is of interest due to the silicon base material and the broad tunability of the magnetic properties for integrated magnetic and magnetooptic devices.
Correlation Between Theoretical Data and Experimental Propierties of Selective PtAg Core-Shell Nanoparticles for Oxygen Reduction Reaction
Authors: Cuevas-Muñiz Francisco Mherande , TéllezVázquez Oswald , Esparza Rodrigo , Ledesma-García Janet , Arriaga Luis Gerardo , Guerra-Balcázar Minerva
Published: February 2020

In previous reports PtAg core-shell catalyst has showed selective properties for the oxygen reduction reaction in presence of glucose 0.1 M as interference in basic media. This characteristic has allowed the operation of microfluidic fuel cell with only one feeding stream mixing fuel and oxidant. In this work Molecular dynamics (MD) and Density functional theory (DFT) were used to explain the nanoparticle stability and conductive properties. Also is reported the analysis by XRD, XPS and STEM characterization, and electrochemical tests for oxygen reduction reaction in absence and presence of glucose, and testing in a microfluidic fuel cell. The structural simulation agrees with the experimental data showing the core-shell formation from an alloy nanoparticle by heating. Also, the electronic properties of the PtAg core-shell nanoparticles are very similar to the Pt nanoparticles.
Aqueous Phase Synthesis of CuIn Alloy Nanoparticles and Its Application for CIGS Solar Cell
Authors: Takahashi Hideyuki , Fujiki Hironari , Yokoyama Shun , Tohji Kazuyuki
Published: February 2020

Among various low cost solar cells with high efficiency, CIGS (Cu(In,Ga)Se2) type solar cell shows attractive performances. These CIGS type solar cell is synthesized by gas phase method or liquid phase reduction method in organic solvents. However, in the case of former, productivity is relatively low, since vaporizing temperature of three or more elements is extremely different, which read the large amount of waste of resources. On the other hand, in the case of later, synthesis costs become increase because of the use of organic solvents. Thus, to decreasing the cost of CIGS type solar cell, synthesis method with high recovery rate and without the using of organic solvents is required.

Until now, we reported that the synthesis of uniform and well crystallized alloy nanoparticles, such as Pd20Te7 and Bi2Te3 by restrict controlling the homogenization of metallic complexes in the aqueous solution under room temperature [1]. In this method, reduction rate of the metal species can be controlled under the room temperature, nevertheless ternary, or more, alloy nano materials with uniform and well crystallized structure was not synthesized until now.

Therefore, in this study, CI nanoparticles were synthesized by obeying the calculation results and reduction potential measurements. CIS semiconductor was tried to synthesize through selenided reaction of CI nanoparticles synthesized. Solar cell ability was also investigated.

Metallic complexes in the aqueous solution was restricted to homogenized species by utilizing the theoretical calculation method using the critical stability constants. Detailed calculation procedure was summarized in Ref. 1. Amine-based and/or carboxyl-based complexing reagent, were used for the complex reagents. Reduction potential of Cu (and/or In) complexes was measured, and synthesized materials were analyzed by XRD.

Calculation was performed for various system, such as the Cu-NO3-OH-glycine system (dissolution of Cu(NO3)2 and glycine). By obeying the calculation results and also electrochemical potential measurement, various copper complexes was successfully restricted to single species, such as [(Cu2+)(Gly)2], at the pH range over 10, and relationship between stability constants of complex reagents and reduction potential were summarized. As a results, CuIn nanoparticles can be successfully synthesized.

CuInSe semiconductor materials were also synthesized by gas phase selenided reaction of the CuIn thin film on the substrate. XRD mesurments shows that synthesized materials were single phase of CuInSe alloy. Synthesized CuInSe thin film on the substrate shows the voltage under the irradiation of light. Thus, by using this easy methods, solar cell can be constructed.

This work was supported by the Grant-in-Aid for Challenging Exploratory Research (No. 25550085).

References: [1]H. Takahashi, et.,al; Applied Catalysis A: General 392, 80-85 (2011)
Gas Permeation Property of Polyimide-Poly(ethylene glycol) Copolymer Membranes
Authors: Nam Sang Yong , Park JungHo , Kim DeukJu
Published: February 2020

The CO2 removal process using polymeric membranes has been developed and received a great attention because of global warming. However, polymeric membranes still have low permeability and selectivity. Many researchers have been studied to resolve this weakness. Among various polymer membranes, polysulfone and polyimide have several advantages such as good chemical resistance, mechanical properties and gas separation performance. These kinds of glassy polymers are affected by diffusivity-selectivity. The high diffusivity of glassy polymer can be achieved easily by control of the fractional free volume (FFV) which relates to rotational and flexural mobility of polymer chain. Polymer membranes introduced fluorene bulky groups into polymer backbone showed high FFV and diffusivity. Permeability of rubbery polymer membranes such as poly(ethylene glycol) (PEG) influenced by solubility-selectivity. Rubbery polymer membranes have high CO2 permeability and high polar/nonpolar gas selectivity. In this work, we synthesized fluorene-based polysulfone-PEG and polyimide-PEG random copolymer and prepared copolymer membranes. Molecular weight and mole percent of PEG were controlled to investigate the effect of PEG. Finally, thermal properties, fractional free volume (FFV) and gas permeability PEG-containing random copolymer membranes were investigated.
Electrochemical Study of the Effect of Adsorbates and Precursors in the Synthesis of Well-Defined Platinum Nanoparticles Using Water-in-Oil Microemulsion
Authors: Martínez-Rodríguez Roberto Alexis , Vidal-Iglesias Francisco José , Solla-Gullón José , Montiel Vicente , Cabrera Carlos R , Feliu Juan
Published: February 2020

Intensive research has been focused on the study of the production of well-defined structured nanoparticles. This is due to the different properties possessed by these materials according to their size/shape. One of the most studied noble metals is Platinum (Pt) due to its catalytic properties and different methods have been reported to prepared. However, it is of great importance to find easy new ways as well as cost effective and scalable method to synthesize them. In a recent communication [1] we have reported, for the first time, the synthesis of cubic Pt nanoparticles with a very high yield using a water-in-oil (w/o) microemulsion method in which HCl was added in the aqueous phase of the w/o microemulsion. This method, unlike others such as the colloidal method, fulfils these previous requirements. This works pretends to explain the effect on the shape of the nanoparticles of different surface modifiers added in the aqueous phase using also different Pt precursors. In addition, bimetallic nanoparticles have been prepared with similar methodology and the effect of the adsorbates will be evaluated. The nanoparticles have been electrochemically characterised by hydrogen and Ge ads/desorption processes, CO monolayer oxidation and ammonia electro-oxidations have been also studied as test reactions in order to determine the efficiency in the catalytic activity.

References

[1] R. A. Martínez-Rodríguez, F. J. Vidal-Iglesias, J. Solla-Gullón, C. R. Cabrera, J. M. Feliu, Synthesis of Pt Nanoparticles in Water-in-Oil Microemulsion: Effect of HCl on Their Surface Structure, J. Am. Chem. Soc. 136 (2014) 1280.
Oxidation State and Local Structure of a High-Capacity LiF/Fe(V2O5) Conversion Cathode for Li-Ion Batteries
Authors: Pohl Alexander , Guda Alexander , Shapovalov Viktor , Witte Ralf , Das Bijoy , Scheiba Frieder , Rothe Jörg , Soldatov Alexander , Fichtner Maximilian
Published: February 2020

Electrical energy storage becomes increasingly important to extend the range of electric vehicles and to buffer the electricity generated by intermittent energy sources. Recently a lot of effort has been put into finding novel materials with higher energy density and longer cycle life. Especially conversion materials based on fluorides offer a 3-5 fold increase of capacity compared to current state-of-the-art Li-ion batteries based on Li-intercalation [1]. Fluorides have the advantage of a high cell voltage vs. Li due to a large band gap compared to other conversion materials such as oxides and nitrides. For example, FeF3converts reversibly to Fe and LiF upon discharge transferring up to 3 electrons according to

FeF3 + 3Li ↔ Fe + 3LiF E0 = 2.96 V (weighted average), Cth= 712 mAh/g

The traditional approach to enable metal fluorides as cathode materials for Li-ion batteries is to coat the insulating fluoride particles with a conducting carbon shell by high-energy ball milling [2]. The FeF3/C nanocomposites show a very high capacity up to the theoretical maximum in the first few cycles, but cyclic stability is poor due to a pulverisation of the core-shell FeF3/C particles upon prolonged cycling.

We recently prepared an improved LiF/Fe(V2O5) nanocomposite by high-energy ball milling, which shows a high reversible capacity of 420 mAh/g in the first 20 cycles and 270 mAh/g after 50 cycles [3]. The cyclic stability was much improved compared to FeF3/C composites due the addition of V2O5. We used in situ XAS, Mössbauer spectroscopy, ab initio calculation of model XANES spectra and principle component analysis to identify highly amorphous V[FeV]O4 nanograins, which form during ball milling [4]. From the calculations we also identified LixVO2-xFx. Both phases have open crystal structures and the ability to reversibly store lithium in interstitial lattice sites. As the V[FeV]O4 and LixVO2-xFx nanograins are in close contact with LiF and Fe particles, they help to maintain electrical and ionic contact upon prolonged cycling.

J. Cabana, L. Monconduit, D. Larcher, M.R. Palacín, Adv. Mater.
22 (2010), E170.

F. Badway, F. Cosandey, N. Pereira, G.G. Amatucci, J. Electrochem. Soc.
150 (2003), A1318.

B. Das, A. Pohl, K. Chakravadhanula and M. Fichtner (2014), submitted.

H. Pohl, A. A. Guda, V. V. Shapovalov, R. Witte, B. Das, F. Scheiba, J. Rothe, A. V. Soldatov and M. Fichtner, Acta Materialia
68 (2014), 179.
Vanadium Oxide 3-D Nanostructures for Lithium Ion Battery Cathodes
Authors: Gillette Eleanor , Liu Chanyuan , Rubloff Gary W , Lee Sang Bok
Published: February 2020

Nanostructured electrodes have been a popular area of research in energy storage, where their high surface area and shortened diffusion pathways can provide increased energy and power density over bulk electrodes of the same materials. While a variety of nanostructures have been demonstrated, often these structures are disordered and randomly interconnected, or they must be held together by polymer binder which essentially constitutes a dead weight and volume in the electrode. It can be difficult to draw broadly applicable conclusions to pursue optimized electrode geometries without the ability to test electrodes with systematically variable geometries. As 3-D structures have become of greater interest in energy storage, there is a need to be able to explore the relationship between structure and performance systematically.

Here we present electrodes produced by controllably interlinking an array of uniform nanotubes. The aspect ratio of the nanotubes and the number of interconnecting points can be modified systematically. 3-D branched anodized aluminum oxide (AAO) membranes are used as templates for the atomic layer deposition of vanadium oxide (V2O5). AAO templates have frequently been used to produce uniform high aspect ratio arrays of materials, and the systematic introduction of branch points allows our templates to be expanded into three dimensional networks. The use of an ALD deposition process allows these templates to be uniformly and conformally coated with V2O5, creating nanostructured cathodes whose morphology can be carefully and systematically controlled.

We successfully produced a series of V2O5 cathodes with varying aspect ratios as well as the number and spacing of branch points. These cathodes were then characterized by a variety of electrochemical methods, including cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge. These studies will lay the groundwork for rationally designed 3-D electrodes and full battery devices in the future.
Catalytic Polymer Membranes for Improved Oxygen Evolution Reaction in Lithium-Oxygen Batteries
Authors: Ryu Won-Hee , Gittleson Forrest S , Taylor André D.
Published: February 2020

Owing to the decline in our fossil fuels reserves and the growing worldwide demand for energy, sustainable energy storage systems are unquestionably needed. The lithium-oxygen battery, an emerging next generation energy storage system, demonstrates an exceptionally high theoretical energy density which is comparable to the available energy density of gasoline.[1] However, the insufficient round trip efficiency and poor cyclability of current lithium-oxygen batteries must be solved before commercialization for large scale energy storage systems (i.e. smart grid) and electric vehicles. A critical step towards advancing the performance is to develop highly efficient catalytic electrodes for oxygen reduction and oxygen evolution reactions, corresponding to the formation and decomposition of insulating Li2O2 products.[2,3] The insulating solid products formed during discharging often deactivate the surface of catalysts on the oxygen electrode, making reversible decomposition of the Li2O2products during charging difficult. Therefore, tailored design and effective positioning of catalyst materials in the oxygen electrode are key to avoiding deactivation.[4]

In this presentation, we report the design of a new cell system including catalytic polymer membranes to improve lithium-oxygen battery performance. The catalytic polymer membrane can be inserted between the oxygen electrode and separator, thereby affording more catalytic sites by geometric positioning of catalyst nanoparticles decorated on the polymer membrane. The polymer membrane scaffold can effectively preserve their catalytic activity after the formation of Li2O2products on the oxygen electrode (discharging), and consequently faciliate oxygen evolution reaction (charging). Here, we will further discuss the unique effects of the catalytic membrane on the performance and charge/discharge characteristics of the lithium-oxygen battery.

[1] Peter G. Bruce, Stefan A. Freunberger, Laurence J. Hardwick, and Jean-Marie Tarascon, Nature Materials 11 (2012) 19.

[2] Won-Hee Ryu, Taek-Han Yoon, Sung-Ho Song, Seok-Woo Jeon, Yong-Joon Park, and Il-Doo Kim, Nano Letters, 13 (2013) 4190.

[3] Forrest S. Gittleson, Ryan C. Sekol, Gustavo Doubek, Marcelo Linardi and André D. Taylor, Physical Chemistry Chemical Physics, 16 (2014) 3230.

[4] Ryan C. Sekol , Xiaokai Li , Peter Cohen , Gustavo Doubek , Marcelo Carmo, and André D. Taylor, Applied Catalysis B: Environmental, 138 (2013) 285.
Sulfur-TiO2 Yolk-Shell Nanoarchitecture for Long-Cycle Lithium-Sulfur Batteries
Authors: Seh Zhi Wei , Li Weiyang , Cui Yi
Published: February 2020

Sulfur is an attractive cathode material with a high specific capacity of 1,673 mAh g-1, but its rapid capacity decay due to polysulfide dissolution presents a significant technical challenge. Although much effort has been devoted to encapsulating sulfur particles with conducting materials to limit polysulfide dissolution, relatively little emphasis has been placed on dealing with the large volumetric expansion of the sulfur core during lithiation (~80%), which will lead to cracking and fracture of the protective shell. Here, we demonstrate the design of a sulfur–TiO2 yolk–shell nanoarchitecture with internal void space for stable and prolonged cycling over 1,000 charge/discharge cycles in lithium–sulfur batteries. Compared to bare sulfur and sulfur–TiO2 core–shell nanoparticles, the yolk–shell nanostructures were found to exhibit the highest capacity retention due to the presence of sufficient empty space to accommodate the volume expansion of sulfur, resulting in a structurally-intact TiO2 shell to minimize polysulfide dissolution. Using the yolk–shell nanoarchitecture, an initial specific capacity of 1,030 mAh g-1 at 0.5C and Coulombic efficiency of 98.4% over 1,000 cycles was achieved. Most importantly, the capacity decay after 1,000 cycles was found to be as small as 0.033% per cycle, which represents the one of the best performance for long-cycle lithium–sulfur batteries so far.
Electrocatalytic Activity of Copper–Palladium Nanopaticles for Formic Acid Oxidation
Authors: Montes de Oca-Yemha Maria Guadalupe , Palomar-Pardavé Manuel , Romero-Romo Mario , Licona-Sánchez Teresa de Jesús , Torres-Rodríguez Miguel , Medina-Rojano Victor Alberto , Gónzalez Martínez Erika
Published: February 2020

In this work, the catalytic activity of copper-palladium (Cu-Pd) nanoparticles (NPs) is studied for formic acid oxidation. The Cu-Pd NPs were synthesized in a toluene/water system at room temperature. The synthesis of organic phase containing the metal ions was carried out as follows: the aqueous solutions containing the cooper and palladium metals ions, Cu(NO3)2 and PdCl2. Cu and Pd were mixed in appropriate amounts to obtain aqueous solution with 1:1 molar ratios of Cu:Pd. The toluene solution of hexadecylamine (C16H33NH2) was added to the Cu and Pd aqueous solution under strong stirring. For the mixture solution, an immediate two-layer separation was produced, with a light yellow organic phase on the top and a yellow tinted aqueous phase on the bottom. Ions were allowed to diffuse gradually into the organic phase by complexing them with the amine. Cu-Pd NPs were characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive X-ray (EDX) analysis. The catalytic activity of Cu-Pd NPs was evaluated for formic acid oxidation, using the anodic current density. The electrochemical result shows that Cu-Pd NPs present a higher catalytic activity than Pd NPs.
Electrochemical Properties of Gold-Palladium Core-Shell Nanostructures for Ethanol Oxidation
Authors: Palomar-Pardavé Manuel , Romero-Romo Mario Alberto , Montes de Oca-Yemha Maria Guadalupe , Licona-Sánchez Teresa de Jesús , Torres-Rodríguez Miguel , Aldana-González Jorge , Herrera-Toribio Rey David
Published: February 2020

Gold-palladium nanoparticles (NPs) have been used as catalysts due to their catalytic activity, selectivity and stability for a variety of reactions, such as the small organic molecule oxidations (i.e. ethanol). In the present contribution, the catalytic activity of Pd and Au-Pd core-shell (CS) NPs is investigated towards the ethanol oxidation (Figures 1A and 1B). The Au-Pd CS NPs were synthesised by a seed-mediated growth method, where PdCl4
2- is reduced at the surface of Au NPs in the presence of ascorbic acid. This method allows adjusting the average Pd shell thickness between 1 (CS1) and 10 (CS10) nm, by varying the amount of palladium chloride. Electrochemical studies in potassium hydroxide (KOH) containing electrolyte solutions with ethanol show that the current density of ethanol oxidation decreases as the shell thickness decreases. Correlation between catalytic activity and shell thickness will be discussed in terms of the structural parameters.
Investigation of the Performance Improvement of Silicon Electrodes Cycled with Electrolyte Containing FEC or VC
Authors: Lucht Brett L. , Nguyen Cao Cuong
Published: February 2020

Silicon is one of the most promising candidates for an anode material in LIBs due to the high theoretical capacity, 3580 mAh/g. This theoretical capacity is ~10 times that of commercial graphite (372 mAh/g) currently used in lithium ion batteries. However the silicon electrodes have a very large volume expansion (300–400%) during lithiation resulting in instability of the solid electrolyte interphase (SEI) and poor capacity retention. The two most frequently utilized SEI stabilizing additives are vinylene carbonate (VC) and fluoroethylene carbonate (FEC). A systematic comparison of the effects of added FEC or VC at multiple concentrations is being conducted with uniform silicon nano-particle electrodes.

Capacity retention of Li/silicon nano-particle cells with different concentrations of VC and FEC in 1.2 M LiPF6 in 1:1 EC/DEC have been investigated. The capacity fades very rapidly for the baseline electrolyte. Incorporation of FEC at any of the concentrations investigated (5, 10, 15, or 25 %) results in significant improvements in capacity retention. Interestingly, intermediate concentrations of FEC 10-15 % give the best capacity retention suggesting that lower concentrations do not generate a sufficiently stable SEI while higher concentrations may results in increased cell resistance. Cells containing added VC do not have significantly better performance than the cells containing the baseline electrolyte. Incorporation of 3 % VC results in cells with very similar capacity fade to the baseline electrolyte, while cells containing 6 % VC have an odd intermittent behavior which may be due to high cell impedance as evidenced by electrochemical impedance spectroscopy. The cycling efficiencies correlate very well with the capacity retention. Cells containing 10-15 % FEC have the best efficiencies (~99 % for cycles 10-50), while cells containing the baseline electrolyte or electrolyte with added VC have lower efficiencies (<98 % for cycles 10-50).

Ex-situ surface analysis of the electrodes after cycling via a combination of SEM, XPS and FT-IR will be reported. Structural characterization of the SEI will lead to a better understanding of the source of performance enhancement due to the incorporation of added FEC.

Acknowledgements

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, Subcontract No 6879235 under the Batteries for Advanced Transportation Technologies (BATT) Program.
Electrolytes for Li-Ion Batteries Based on High Voltage Cathodes
Authors: Jow T. Richard , Delp Samuel A. , Allen Joshua L. , Borodin Oleg , Allen Jan L.
Published: February 2020

The electrolyte is a critical part of today’s Li-ion batteries. The state-of-the-art Li-ion batteries, which are made of cathodes such as 4.1 V LiCoO2 and 3.4 V LiFePO4 and graphite anode, function well in the state-of-the-art electrolytes made of LiPF6 in carbonate solvent mixtures such as EC and EMC with additive such as VC. The reason for this compatibility is attributed to the facts that the cathodes are within the stability range of the electrolytes and the ability of the electrolyte for forming a solid electrolyte interphase (SEI) layer on graphite, protecting the graphite anode from reacting with the electrolytes.

When developing higher energy density Li-ion batteries based on higher voltage cathodes such as 4.7 V LiNi0.5Mn1.5O4 (LNMO) and 4.8 V LiCoPO4 (LCP), the oxidative stability of the state-of-the-art electrolytes is in question. Furthermore, the stability of the high voltage cathodes themselves is also not certain. Efforts in improving the stability of LNMO and LCP through substitutions have yielded better performing cathodes in terms of improved capacity retention and coulombic efficiency.1, 2

The search for electrolytes that work with the high voltage cathodes has been intensive. Molecular modeling to understand the oxidative stability of Li-ion electrolytes has been active.3 This paper will review our recent efforts on electrolyte development for improving the electrochemical performance of the high voltage cathodes in Li-ion batteries.

References

A. Manthiram, Phys.Chem. Lett. 2011, 2, 176-184.

J. L. Allen, T. R. Jow, J. Wolfenstine, J. Power Sources 2011, 196, 8656.

O. Borodin, W. Behl, T. R. Jow, J. Phys. Chem. C 2013, 117, 8661-8682.
BASF - Lithium Ion Battery Electrolytes
Authors: Schmidt Michael , Chesneau Frederick Francois , Garsuch Arnd , Meini Stefano , Schmitz René
Published: February 2020

Research and development efforts of BASF are stimulated by the future energy demand of our society. Thus we investigate and evaluate energy storage systems for mobile and stationary applications.

BASF develops products for the battery industry with its knowledge and experience in chemicals and materials. Our research activities are focused on the development of new materials for improved lithium ion battery performance. Currently, we are focusing on the development of next generation cathode materials and high performance electrolyte systems.

The first part of the talk will give an overview on BASF’s growing activities in the field of lithium ion battery materials. The second part will concentrate on lithium ion battery electrolytes with a special focus on electrolyte and electrolyte additives for high voltage cathodes.
Atomic Force Microscopy Study of Ionic Liquid Structure at Carbon Interface
Authors: Black Jennifer , Feng Guang , Okatan M. Baris , Hillesheim Patrick C , Dai Sheng , Cummings Peter T , Kalinin Sergei V. , Balke Nina
Published: February 2020

Ionic liquids are attractive electrolytes for electrochemical capacitors because of the large operational voltage windows leading to an increased energy density in these systems. The charge storage mechanism and structure of ionic liquids at the interface is still poorly understood. Atomic force microscopy (AFM) force spectroscopy is capable of probing the layered structure of ionic liquids which forms at the electrode interface. Figure 1 shows the ion density profiles from molecular dynamics for the cation (a) and anion(b) of the ionic liquid 1-ethyl-3methyl-imidazolium bis(trifluoromethanesulfonyl)imide (Emim+Tf2N-) as a function of potential and distance from a carbon surface. Molecular dynamics predicts an alternating structure of anions and cations extending several nm from the surface. A histogram of 50 force distance curves on a highly oriented pyrolytic graphite (HOPG) for the same ionic liquid is shown in Figure 1c. Distinct steps are observed during the approach of the AFM tip due to interaction with the ion layers present at the interface. By combining this technique with insights from molecular dynamics simulations the effect of applied potential on the structure of the ionic liquid within the electrical double layer is investigated and we are able to observe reconstruction of ions in response to an applied bias. This technique is also used to map the structure of the ionic liquid over the carbon surface to investigate the effect of defects such as step edges on the structure of the ionic liquid.

Figure 1: Molecular dynamics ion density profiles as a function of potential and distance from a carbon surface for the Emim+ cation (a) and Tf2N- anion (b). Histogram of 50 consecutively measured force distance curves at a single location on an HOPG surface in Emim+Tf2N- ionic liquid (c).
Electroactive Polymer Based Porous Membranes for Energy Storage Applications
Authors: Costa C. M. , Lanceros-Méndez Senentxu
Published: February 2020

The market of portable batteries will reach $30.5 billion dollars in 2015 with an annual growth rate of 8.5% [1]. This growth is interconnected with advances of the portable electronic products (mobile-phones, computers) and with the development of new products such as e-labels, e-packaging, disposable medical testers and drug delivery patches.

Wide ranges of materials properties for cathode, anode and battery separator/electrolyte are being developments for improving characteristics and performance of the battery.

The battery separator is essential in electrochemical cells, separating the anode and cathode and controling the number and mobility of the lithium ions.

Among the materials most investigated for battery separators are the PVDF and its copolymers poly(vinylidene fluoride-co-trifluoroethylene), PVDF-TrFE, poly(vinylidene fluoride-co-hexafluoropropylene), PVDF-HFP, and poly(vinylidene fluoride-cochlorotrifluoroethylene),PVDF-CTFE [2].

These materials show strong advantages for their use as separator membranes in comparison to polyolefins due to their high dipolar moment and large dielectric constant for a polymer material, which can assist ionization of lithium salts.

In this work, PVDF and its copolymers have been processed by solvent cast technique with varying solvent evaporation temperature and the polymer/solvent ratio with the objective to tailor degree of porosity, mechanical, thermal and electrical properties.

Degree of porosity, uptake, tortuosity, degree of crystallinity and ionic conductivity of the different membranes are evaluated and their influence in lithium-ion battery performance presented and discussed.

Acknowledgments

This work is funded by FEDER funds through the “Programa Operacional Factores de Competitividade—COMPETE” and by national funds from FCT—Fundação para a Ciência e a Tecnologia, in the framework of the Strategic Project PEST-C/FIS/UI607/2011, project F-COMP-01-0124-FEDER-022716 and grant SFRH/BD/68499/2010 (C.M.C.). The authors also thank funding from Matepro –Optimizing Materials and Processes”, ref. NORTE-07-0124-FEDER-000037”, co-funded by the “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte), under the “Quadro de Referência Estratégico Nacional” (QREN), through the “Fundo Europeu de Desenvolvimento Regional” (FEDER).

The authors thank Celgard LLC, Timcal, Solvay, Arkema and Clariant for kindly supplying their high quality membranes and excellent materials, respectively.

References

[1] P. R. Consulting, Advanced Batteries for Portable Power Applications, 2011.

[2] C.M. Costa, M.M. Silva, S. Lanceros-Mendez, RSC Advances, 3 (2013) 11404
Single Crystal, Cuprous Oxide Nanowire Arrays for Highly Stable Photocathodic Water Splitting
Authors: Banerjee Sriya , Wu Fei , Myung Yoon , Banerjee Parag
Published: February 2020

Cuprous oxide (Cu2O) is a favorable material for solar water splitting because of its suitable band gap for solar energy absorption (2.2eV) and conduction and valence band edges which straddle the hydrogen and oxygen reduction potentials, respectively. Further, Cu2O is earth abundant and can be synthesized by a variety of techniques. However, Cu2O has its reduction potential within its band edges, leading to considerable photocorrosion and degradation. Thus, there is a pressing need for the fabrication of stable and efficient Cu2O photocathodes.

Here, we investigate the photoelectrochemical (PEC) properties and stability of dense (108 cm-1) single crystalline Cu2O nanowire (NW) arrays grown by a combination of thermal and carbo-thermal reduction method from pristine copper foils (Fig 1a-d). Our data shows that single crystalline Cu2O NW arrays, show good photoresponse (Fig 1e) and higher stability as compared to thin film Cu2O (Fig 1f,g).

We will present structural investigation of the Cu2O NWs using SEM, HRTEM and Raman spectroscopy (Fig. 1a-d). Photoelectrochemical activity of Cu2O NW arrays for water splitting will be reported and stability towards photocorrosion will be tested with extended and accelerated reliability tests.
A Comprehensive Electrochemical Solution to Climate Change: STEP, the Solar Thermal Electrochemical Pressure Process for the Production of Societal Staples
Authors: Licht Stuart
Published: February 2020

The solar thermal electrochemical pressure process is capable of the production of societal staples with little or no carbon footprint, and can directly capture & convert carbon dioxide from the air that can be stored as useful graphite.In STEP the efficient formation of metals, fuels, cement, chlorine, and carbon capture is driven by solar thermal heated endothermic electrolyses of concentrated reactants occurring at voltage below that of the room temperature energy stored in the products. As one example, CO2 is reduced to either fuels, or storable carbon, at solar efficiency higher than the best photovoltaics. This is due to a synergy of efficient solar thermal absorption and electrochemical conversion at high temperature and reactant concentration. CO2-free STEP iron production, from iron ore, occurs via Fe(III) in molten carbonate. Water is efficiently split to H2 by molten hydroxide electrolysis, and chlorine, sodium and magnesium from molten chlorides. STEP cement uses a novel molten electrochemistry for the production of calcium oxide (lime from limestone).1-7

The solar electrochemical generation of societal staples and fuels decreases society's dependence on grid-based electricity. A pathway is provided for the STEP decrease of atmospheric carbon dioxide levels to pre-industrial age levels in 10 years.

Selected STEP references:

(1) S. Licht, "STEP generation of energetic molecules: A solar chemical process to end anthropogenic global warming," J. Phys. Chem., C, 2009, 113, 16283-16292.

(2) S. Licht, B. Wang, S. Ghosh, H. Ayub, D. Jiang, J. Ganley, "A New Solar Carbon Capture Process: STEP Carbon Capture," J. Phys. Chem. Lett., 2010, 1, 2363-2368, with online 2 page supplement.

(3) S. Licht, "Efficient Solar-Driven Synthesis, Carbon Capture, and Desalinization, STEP: Electrochemical Production of Fuels, Metals, Bleach," Advanced Materials, 2011, 47, 5592-5612.

(4) S. Licht, H. Wu, C. Hettige, B. Wang, J. Lau, J. Asercion, J. Stuart, " STEP Cement: solar thermal electrochemical production of CaO without CO2 emission " Chem. Comm., 2012, 48, 6019-6021, with online 20 page supplement.

(5) B. Wang, Y. Hu, H. Wu, S. Licht, "STEP Pollutant to Solar Hydrogen: Solar driven thermal electrochemical wastewater treatment with synergetic production of hydrogen," Electrochemical Science Letters,
2013, 2, H34-H36.

(6) B. Cui, S. Licht, ”Critical STEP advances for sustainable iron production,” Green Chemistry
,
2013, 15(4), 881-884, with 16 page online supplementary information

(7) S. Licht, B. Cui, B. Wang, ”STEP Carbon Capture: the barium advantage,” Journal of CO2 Utilization,
2013, 2, 58-63.
New Visible Semiconductors for Photoelectrochemical Water Splitting
Authors: Sunkara Mahendra Kumar
Published: February 2020

New semiconductors with appropriate band gap and band edge energetics are needed for making serious advances in solar fuels research. This presentation will highlight our efforts in the search for new semiconductor materials specifically toward photoelectrochemical water splitting: (a) New alloys of GaN with antimony and (b) a generic informatics strategy for band gap prediction.

Applicability of the Ga(Sbx)N1−x

alloys for practical realization of photoelectrochemical water splitting is investigated using first-principles density functional theory incorporating the local density approximation and generalized gradient approximation plus the Hubbard U parameter formalism. Prior results with calculations revealed that a relatively small concentration of Sb impurities is sufficient to achieve a significant narrowing of the band gap, enabling absorption of visible light.1 Theoretical results predict that Ga(Sb
x
)N1−x
alloys with 2 eV band gaps straddle the potential window at moderate to low pH values, thus indicating that dilute Ga(Sb
x
)N1−x

alloys could be potential candidates for splitting water under visible light irradiation. Theoretical computations with Sb composition beyond 7% change the band gap from direct to indirect.2 Experimental synthesis is carried out using metal organic chemical vapor deposition using trimethyl gallium (TMGa) and Trimethyl Antimony (TMSb) and ammonia. Crystalline GaSbxN1-xfilms were obtained at x values ranging from 0-8%.

In addition, highlights of our recent work3on informatics-aided predictions of band gaps for several new chalco-pyrite materials will be provided.

Acknowledgements: Financial support from US Department of Energy (DE-FG02-07ER46375) and NSF (DMS1125909).

References:

R.M. Sheetz, E. Richter, A.N. Andriotis, C. Pendyala, M.K. Sunkara and M. Menon, “Visible light absorption and large band gap bowing in dilute alloys of gallium nitride with antimony”, Phys. Rev. B, 84, 075304 (2011)

S. Sunkara, V.K. Vendra, J.B. Jasinski, T. Deutsch, A.N. Andriotis, K. Rajan and M.K. Sunkara, “New Visible Light Absorbing Materials for Solar Fuels, Ga(Sbx)N1-x”, In Press, Adv. Mater. (2013).

P. Dey, J. Bible, S. Datta, S. Broderick, J. Jasinski, M.K. Sunkara, M. Menon, and K. Rajan, "Informatics aided band gap engineering for solar materials", Accepted, J. Comp. Mater. Sci., (2013).
Cold Gas Sprayed Semiconductor-Based Electrodes for the Photooxidation of Water
Authors: Herrmann-Geppert Iris , Bogdanoff Peter , Emmler Thomas , Gutzmann Henning , Gärtner Frank , Dittrich Thomas , Klassen Thomas
Published: February 2020

Photoassisted water splitting for hydrogen generation requires the development of low cost, but highly efficient photoelectrodes. For the industrial hydrogen production with photoelectrochemical cells suitable catalysts and feasible photoelectrode preparation processes still need to be identified.

This contribution explores the potential of cold gas spraying (CGS) for the production of photoanodes employing semiconductors for the water oxidation reaction (OER). Conventional large area coating techniques usually employ wet chemical methods with subsequent calcination steps to obtain enhanced binding between the catalyst particles and the substrate. In the cold gas spraying process, particles are accelerated to high velocities by a pressurized gas. The nitrogen used as process gas is preheated and then expanded in a De Laval type nozzle. On impact with the substrate, the particles deform and break up and thus can build an efficient interface to the back contact.

For a first demonstration TiO2 aggregates delivered by EVONIK were probed for the preparation of TiO2 photoelectrodes. In photoelectrochemical experiments these cold gas sprayed TiO2 photoelectrodes showed seven times higher photocurrents in the photooxidation of water (at 1.23V(NHE)) than reference electrodes prepared by the established doctor blade technique. In systematic experiments it was observed that with increasing gas temperature in the coating process the obtained photocurrent is enhanced. The better performance can be mainly attributed to an improved bonding of the TiO2 particles to the substrate (back contact) due to their increased impact energy. Although the bulk characteristics of the particles remained unchanged incident photon to current efficiency (IPCE) and surface photovoltage measurements reveal the formation of surface-localized interband transitions at the TiO2 surface (1.2, 2 and 2.4 eV) during the CGS process. In order to study the influence of these defects on the photoreaction performance surface modification by plasma treatment is employed. For this structure-activity correlation analysis by Raman, XRD and XPS is performed.

From these initial experiments the preparation is extended to other potential metal oxides (e.g. WO3, Fe2O3 and BiVO4) for the photooxidation of water. Besides the relevant particle-substrate bonding and defect chemistry of the semiconductor layer due to the process, morphology investigation by SEM, gas sorption and 3D topography are considered for the optimization of the coating technique.
Using Metal Oxides for the Photo-Electrochemical Oxygen Evolution Reaction
Authors: Herring Andrew M , Pilli Satyander Kishore , Furtak Thomas E. , Deutsch Todd G , Turner John A
Published: February 2020

It is highly desirable that solar energy be efficiently and inexpensively directly converted to dispatchable fuels such as H2. Photoelectrochemical water splitting represents a clean, energy conversion technology, which still has many fundamental barriers that must be addressed before it can be reduced to widespread practice. Whilst much research effort has been applied to these systems and conversion efficiencies greater than the 10% desired by the US DOE have been achieved, these high efficiency systems remain too unstable to achieve 10 years of operation and the stable systems remain at non-viable efficiencies. New electrodes or electrode combinations, developed by a close coupling between theory and experiment, are needed to enable a robust, efficient system for direct solar-induced water splitting.In this paper we will summarize all the approaches we have taken to date to create efficent photo-active electrodes for the photo-electrocatalystic evolution of oxygen from water. Our first attempts were with heteropoly acid (HPA)modified titanium surfaces. DFT calculations indcated that lacunary HPA could shift the absorption of titania in to the visible. We then shifted our attention to sysytems usuing bismuth vanadate with the CoPI catalyst. We successfully showed that molybdenum doped bismuth vanadate was an extremely active oxygen evolution catalyst but to improve its utility we added siica to make the elecrode transparent. Laterly we have been investigating heterojuncyions with either tungsten oxide or copper tunngstate with bismuth vanadate.