bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Electrochemical Performance of Mn- and Y-Codoped CeO2 under Pure and Impure Hydrogen Fuels
Authors: Handal Hala Talaat , Thangadurai Venkataraman
Published: February 2020

Currently, research has been focusing on the development of mixed ionic electronic conductors (MIECs) for applications in catalysis, gas separation membranes and solid oxide fuel cells (SOFCs). The present anode Ni/Y-doped ZrO2 (YSZ) is suffering from coking, sulfur poisoning under hydrocarbon fuels. Doped ceria has shown mixed ionic electronic characteristics under reducing atmosphere that could be potentially promising anode for solid oxide fuel cells. Using MIEC electrode materials is expected to enlarge electrochemical reaction zone (ERZ) over the entire electrode-gas interfacial area and alleviate or inhibit anode poisoning.

Here, we report synthesis and electrochemical properties of novel nanostructured CYMO (Ce0.8Y0.1Mn0.1O2-δ) prepared by autocombustion method using metal salt precursors. The investigated samples were characterized using several solid state techniques such as powder X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX), and infrared spectroscopy (IR). The electrochemical performance of the prepared anode was tested using a symmetrical cell CYMO/YSZ/CYMO at 600-800○C in humidified H2 / N2 under open circuit and polarization conditions using ac electrochemical impedance spectroscopy (EIS) and DC method. Area specific resistance (ASR) of 0.3 Ωcm2 at 800oC was observed for CYMO and is comparable to that of Ni-YSZ / Ni-ScSZr (0.185 Ωcm2)1 and La0.65Ce0.1Sr0.25Cr0.5Mn0.5O3-δ (0.2 Ωcm2) .2 Interestingly, a noticeable enhancement in the performance of the symmetrical cell was observed upon exposing the cell to 10 ppm H2S in H2 / N2 (Fig.1). In this talk, a detailed analysis for electrochemical results will be presented.
Versatile Ternary Manganese-Nickel-Cobalt Compounds in Multi-Shell Spherical Structures As Electrode Materials for High-Capacity Lithium Ion Batteries
Authors: Zhao Jianqing , Wang Ying
Published: February 2020

Electrochemical performance of rechargeable lithium ion batteries significantly relies on electrochemical properties of both cathode and anode materials. Nanostructured electrode materials have been demonstrated to improve cycling stability and rate capability for lithium ion batteries. Here, ternary manganese-nickel-cobalt carbonate (Mn0.54Ni0.13Co0.13(CO3)0.8, marked as MNCCO3) was first synthesized by hydrothermal method, which shows multi-shell spherical structure from numerous agglomerated nanoparticles. MNCCO3 as anode material can deliver very high initial charge capacity of 997.8 mAh/g at a current density of 50 mA/g, and 821.2 mAh/g at 250 mA/g, respectively. Furthermore, the versatile ternary transition metal carbonate enables to produce two different derivates: manganese-nickel-cobalt oxide (0.54Mn3O4-0.13Co3O4-0.13NiO, marked as MNCO) in multi-shell caged structure after sintering and lithium-excess layered cathode material (Li[Li0.2Mn0.54Ni0.13Co0.13]O2, marked as LMNCO) in yolk-shell structure after lithiation. The yielding MNCO as anode material shows outstanding cycling stability, which can retain charge capacity of 270.6 mAh/g after 100 electrochemical cycles at 250 mA/g. Simultaneously, LMNCO as cathode material delivers high initial discharge capacities of 250.7, 173.0 and 80.9 mAh/g at 25, 250 and 1250 mA/g, and can retain 156.3 mAh/g at 250 mA/g after 100 cycles, with remarkable corresponding capacity retention of 90.3%. The potential full battery from multifunctional ternary manganese-nickel-cobalt compounds, in which MNCCO3 or MNCO as anode material and LMNCO as cathode material, can be fabricated for next generation high-capacity lithium ion batteries.
Amorphous LiLaTiO3 As Solid Electrolyte for Lithium Ion Batteries
Authors: Wang Yan , Zheng Zhangfeng
Published: February 2020

Amorphous lithium lanthanum titanate (LLTO) thin films were successfully prepared by a sol-gel method with an all-alkoxide based route. The thin film resistance was determined from the complex spectra by fitting experimental data to the equivalent circuit. The ionic conductivities of amorphous LLTO thin films were 4.5×10-6, 6.9×10-6, 1.3×10-5, and 3.8×10-5 S/cm at 30°C, 50°C, 70°C, and 90°C, respectively. The activation energy of lithium ion conduction in the thin film was evaluated to be 0.36 eV in the temperature range of 30-90°C. The amorphous structure of LLTO was predicted by ab-initio molecular dynamics (AIMD) silumations and analyzed by partial pair distribution functions and coordination numbers. It is observed that the local atomic environment of Ti in amorphous LLTO is quite similar to that in the crystal state but the atomic packing is much less dense. The ionic diffusivities were derived from the mean square displacements obtained from the AIMD simulation results, and the ionic conductivities were evaluated through the Einstein’s relation, showing good agreement with experimental data. The good ionic conductivity of amorphous LLTO is attributed to its open and disordered structure with large excessive volume.
Magnetic Studies of Conversion Processes in Iron (Oxy)Fluoride Based Electrodes
Authors: Chernova Natasha A. , Omenya Fredrick , Pereira Nathalie , Amatucci Glenn G , Whittingham M. Stanley
Published: February 2020

Fundamental studies of reaction mechanisms in Li-ion batteries are driven by a demand for high energy density and safe electrodes capable of fast lithiation/delithiation reactions. While the current intercalation systems are mostly limited to one Li per red-ox center, conversion systems do not have this limitation. Conversion electrodes are usually nanostructured, which facilitates phase transformations, but makes their characterization quite challenging. In this work we use magnetic methods to investigate conversion and reconversion mechanisms in FeF2, FeOyF2-y and FeF3-based electrodes, which form nano-network of metallic Fe upon Li insertion. Bulk Fe is ferromagnetic at room temperature, while small (< 6-8 nm) nanoparticles become superparamagnetic, meaning that the magnetic moment of the whole particle can flip under the influence of thermal energy. The amount of Fe can be determined from the saturation magnetization (Ms), and the particle size can be estimated from the blocking temperature Tb below which the magnetic moments cannot flip. The crystallinity and presence of defects can be estimated from their effects on the magnetic ordering transition, i.e. antiferromagnetic ordering of FeF2 at 82 K. Magnetization studies have confirmed the initial intercalation processes upon lithiation of FeO0.7F1.3 and FeF3 electrodes, followed by the conversion reaction accompanied by linear magnetization increase due to metallic iron formation. FeF2 system reveals the presence of metallic Fe already at 10% lithiation, meaning that intercalation is minimal, if any, in this system. Upon delithiation, FeO0.7F1.3 shows the best reversibility, i.e. Ms dependences on Li content are essentially the same upon lithiation and delithiation. The studies of superparamagnetic behavior in lithiated samples reveal that small Fe nanoparticles (2-5 nm) observed in the TEM studies are magnetically interacting, forming an interconnecting network over the whole initial (oxy)fluoride crystallite, i.e. 10-15 nm. Evolution of the magnetic properties over long cycling (2nd, 10th and 20th cycles) will be reported and correlated with the electrochemical cycling stability. The differences between these three systems will be discussed, involving the results obtained by other techniques (TEM, PDF, XAS, electrochemistry). This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-SC0001294.
Electrocatalytic Activity and Electroanalytical Performance of Nanodiamond-Derived Carbon Nano-Onions
Authors: Kim Doo Young , Yang Juchan
Published: February 2020

Carbon nano-onions (CNOs) are an emerging, novel class of carbon nanomaterials. A CNO is a 0-D carbon analogue of a 1-D carbon nanotube (CNT) and a 2-D graphene. It is composed of sp2-bonded, concentric carbon shells surrounding a hollow core. The curved morphology of a CNO loosens the conjugation along the graphene sheet and results in the change in electronic structure. The unique structure as well as surface chemical functional groups of CNOs will significantly influence physicochemical, electronic, and electrochemical properties.

In this talk, the physicochemical and electrochemical properties of CNOs will be presented. First, morphology and microstructure of CNOs were characterized by scanning and transmission electron microscopies (SEM, TEM), X-ray diffraction (XRD), and Raman spectroscopy. Chemical composition and chemical functional groups were probed by X-ray photoelectron spectroscopy (XPS). Raman spectra of CNOs showed a large value of ID/IG ratio, indicating that carbon concentric shells of CNOs include defects, i.e., exposed edge planes. Second, heteroatomic doping of CNOs and its electrocatalytic activity toward oxygen reduction reaction will be presented, in comparison with other carbon nanomaterials. Last, redox activities and electron transfer kinetics of CNOs were studied. CNOs showed remarkable electrochemical activities for the detection of biologically important molecules (such as high sensitivity, high selectivity and fast ET kinetics). Electrochemical measurements were carried out with standard redox couples such as Ru(NH3)6
3+/2+, Fe2+/3+, IrCl6
2
-
/3
- and Fe(CN)6
3-/4- as well as redox-active biomolecules such as dopamine, epinephrine, and norepinephrine. The results showed a stable and fast electrochemical response of CNOs for all of the redox analytes and often surpassed the performance of other carbon electrodes like carbon nanotubes, graphite nanoflakes, and glassy carbon.
Studies of Metal Electrodeposition in Adiponitrile
Authors: Cheek Graham T.
Published: February 2020

Introduction

Electrodeposition of certain metals, particularly active metals and some noble metals, sometimes employ nonaqueous solvents (1,2,3), among other reasons, to obtain wider potential limits than those provided by water. Recent work in this laboratory has involved the use of adiponitrile [NC(CH2)4CN] as an electrochemical solvent (4). It is evident that adiponitrile has desirable properties such as a moderately high dielectric constant, high boiling point, and an extremely wide potential range (5, 6). The present abstract represents work involving the use of adiponitrile as an electrochemical solvent for electrodeposition of metals, particularly silver, onto various substrates.

Experimental

Adiponitrile was obtained from Aldrich Chemical Co. Tetraethylammonium tetrafluoroborate [TEA BF4] was purchased from Southwestern Analytical Chemicals (SACHEM). Voltammograms were taken with a PAR283 potentiostat using PowerSuiteTM
software. Potentials are reported with respect to a Ag/AgCl (0.1M EMICl in EMI BF4) reference electrode (Cypress Systems). Vitreous carbon and platinum electrodes were obtained from Cypress Systems. All experiments were carried out in a Vacuum Atmospheres drybox.

Results and Discussion

In order to investigate the effectiveness of adiponitrile as a solvent for electrodeposition, cyclic voltammograms of silver deposition, from dissolved silver nitrate, were carried out in adiponitrile / 1.00 M TEA BF4. The figure at the end of this abstract shows a well-defined reduction process at platinum, followed by a rather narrow stripping peak on the return sweep. At vitreous carbon, the deposition potential shifts to a less positive deposition potential, with significant oxidative activity ( silver stripping ) after the main stripping peak. The behavior observed at vitreous carbon apparently reflects the presence of active areas on the carbon surface (7), accounting for the extended stripping process. The facile electrodeposition of silver from adiponitrile gives hope that this solvent is a feasible choice for metal deposition. Attempts at electrodeposition of other metals, particularly aluminum, are also intended for presentation.

References

1. L. M. A. Monzon, F. Byrne, J. M. D. Coey, J. Electroanalytical Chemistry, 657,54–60 (2011).

2. P. Heoa, R. Ichino, M. Okido, Electrochimica Acta, 51, 6325–6330 (2006).

3. A. P. Abbott and K. J. McKenzie, Phys. Chem. Chem. Phys., , 8, 4265–4279 (2006).

4. G. Cheek, Abstract I1-2481, 224thElectrochemical Society Meeting, San Francisco, CA, 29 October 2013.

5. P. G. Sears, J. A. Caruso and A. I. Popov, Journal
of
Physical
Chemistry, 71(4), 905 (1967).

6. H. Duncan, N. Salem, and Y. Abu-Lebdeh,
J. Electrochem. Soc., 160 (6) A838-A848 (2013).

7. M. Miranda-Hernandez, I. Gonzalez, and N. Batina, J. Phys. Chem.
B,
105(19), 4214 (2001).

Figure : Cyclic voltammograms of 17 mM AgNO3 in adiponitrile (1.00 M TEA BF4) at 1 mm diameter electrodes, 25 mV/s.

(a) Platinum electrode [ black curve ].

(b) Vitreous carbon electrode [ red curve ].
In Situ X-ray Photoelectron Spectroscopy for Electrochemical Reactions at Solid/Liquid Interfaces
Authors: Masuda Takuya , Yoshikawa Hideki , Noguchi Hidenori , Kawasaki Tadahiro , Kobata Masaaki , Kobayashi Keisuke , Uosaki Kohei
Published: February 2020

X-ray photoelectron spectroscopy (XPS) is the most powerful technique for the determination of surface compositions, oxidation states and electronic structures of materials of interest with very high surface sensitivity. Since surface structure and oxidation states of materials in vacuum can be significantly different from those under operation, in situ analysis is strongly desired. However, because XPS requires vacuum, it is difficult to conduct in situ surface analysis at solid/liquid interface during electrochemical processes.

“Electrochemical photoelectron spectroscopy” has been developed1 and utilized for practical applications such as electrocatalysts for fuel cells.2 In this system, samples can be transferred from an electrochemical chamber in an ambient atmosphere to an analysis chamber kept in vacuum immediately after the electrochemical treatments without being exposed to air, so that any contamination of the surface from exposure to open air can be avoided. However, structure and oxidation state of the electrode surface may be changed during the transfer from the solution, where the electrode is under electrochemically controlled conditions, to vacuum, where potential control is not possible. Here, we constructed an in situ electrochemical XPS apparatus for the measurements at solid/liquid interface under electrochemical condition using hard X-rays and a micro-volume cell equipped with an ultrathin Si membrane.3

The conceptual design of the present in situ electrochemical XPS arrangement is illustrated in Figure 1. A micro-volume cell filled with a liquid is sealed by an ultra-thin Si membrane,4 which serves as a separator between vacuum and liquid, a window for X-rays and photoelectrons, and a working electrode for electrochemical reactions. The cell is placed in an analysis chamber for XPS and synchrotron radiation hard X-ray is irradiated to the vacuum side of the membrane. X-rays penetrate to the solution side through the membrane and photoelectrons emitted from Si exposed to the solution, i.e., at solid/liquid interface, can pass through the Si membrane, and can then be collected and analyzed by a hemispherical photoelectron analyzer. Its operation was demonstrated for potential-induced Si oxide growth in water.3 Effect of potential and time on the thickness of Si and Si oxide layers was quantitatively determined at sub-nanometer resolution.3

References

(1) Wieckowski, A. Interfacial Electrochemistry: Experimental, Theory and Applications; Marcel Dekker: New York, 1999.

(2) Wakisaka, M.; Udagawa, Y.; Suzuki, H.; Uchida, H.; Watanabe, M. Energy Environ. Sci.
2011, 4, 1662.

(3) Masuda, T.; Yoshikawa, H.; Noguchi, H.; Kawasaki, T.; Kobata, M.; Kobayashi, K.; Uosaki, K. Appl. Phys. Lett.
2013, 103.

(4) Kolmakov, A.; Dikin, D. A.; Cote, L. J.; Huang, J. X.; Abyaneh, M. K.; Amati, M.; Gregoratti, L.; Gunther, S.; Kiskinova, M. Nat. Nanotechnol.
2011, 6, 651.
Far- and Near-Field Spectroscopy and Imaging of Interfaces and Interphases in Li-Ion Battery Electrodes
Authors: Ayache Maurice , Jarry Angelique , Lucas Ivan , Syzdek Jaroslaw , Kostecki Robert
Published: February 2020

Development of new innovative experimental approaches and enabling methodologies to understand the function and mechanism of operation of materials, electrodes and electrochemical interfaces in electrical energy storage systems is critical for clean and/or renewable energy technologies. A better understanding of the underlying principles that govern these phenomena is inextricably linked with successful implementation of high energy density materials.

Several analytical techniques have been implemented for the physico-chemical characterization of the materials, interfaces and interphases. In many cases limitations in studying the real system are imposed by ex situ methods that require excitation or detection of electrons or ions in vacuum environment and/or they suffer from inadequate sensitivity, selectivity and specificity in the in situ environment.

The advent of femtosecond (fs) lasers and near-field optical methods during the past decades has led to the development of new advanced techniques for chemical analysis. This presentation provides a brief overview of novel in and ex situ experimental approaches aimed at probing battery materials and electrodes in electrical storage systems at an atom, molecular or nanoparticulate level.

The presented methodologies exploit the micro and nano-manipulation techniques and single particle model electrodes to provide sufficient sample definition suitable for advanced far- and near-field Raman, FTIR , fluorescence spectral microscopy, pumped laser probes and micro- and nano-electrochemical characterization techniques.

Examples of detailed in situ molecular characterization of electrode surface and bulk processes at the nano-level scale exceeding the diffraction limit will be discussed. These include elemental and molecular depth profiling at nanometer-scale depth resolution of a solid electrolyte interface (SEI) layer formed on Sn polycrystalline and monocrystral model electrodes in an organic carbonate-based electrolyte.

Acknowledgement

Part of 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. It has also been supported in part by the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under award number DESC0001294. This work was also supported in part by the Chemical Science Division, Office of Basic Energy Sciences, Office of Nuclear Nonproliferation, and the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Electrocatalysis from First Principles: Mechanistic Insights into the Oxygen Reduction Reaction
Authors: Neurock Matthew
Published: February 2020

Electrocatalysis is controlled by the elementary reactions that occur at the interface between the electrode and the solution phase along with the electrochemical potential that results across this interface. Elucidating the electrochemical behavior at this interface, however, presents a considerable challenge due to complexity of the surface chemistry, the explicit atomic and molecular structure of the solution phase at the interface, the presence and formation different ions and their specific location in solution or on the surface, and the surface potentials and electric fields that results as a function of the surface reactivity. Professor Andrzej Wieckowski has been one of the leading pioneers in the development and application of in-situ methods to follow the atomic and electronic scale features in electrochemical systems under working conditions and establish fundamental principles that govern surface reactivity in electrochemical and electrocatalytic systems. His persistent encouragement and nurturing also helped to establish first principle theory and simulation within the electrochemistry community. While theory has become an invaluable partner together with in-situ experiment, there are still a number of challenges in simulating more realistic materials and interfaces and modeling constant potential systems. Herein, we present an approach to simulate the elementary pathways and kinetics for constant potential systems and highlight the opportunities and challenges of this approach. The results are used to construct first principles based kinetic Monte Carlo simulations to model different electrochemical systems. We discuss the application of the approach to simulate the electrocatalytic reduction of oxygen over transition metal surfaces as well as nitrogen doped carbon-based substrates.
Size Effect of Pt Nanoparticles Deposited By Plasma-Enhanced Atomic Layer Deposition on the Electrocatalytic Activity Toward the Methanol Oxidation Reaction
Authors: Liu Chung Hsuan , Ting Chao Cheng , Tai Chun Yen , Hsu Shih Chieh , Pan Fu Ming
Published: February 2020

Platinum is the most important catalyst used for direct methanol fuel cells (DMFC) because its excellent electrocatalytic activity toward the methanol oxidation reaction (MOR). Most of recent research on DMFC focuses on the size minimization of the Pt catalyst, which can reduce the use of the precious Pt catalyst and increase the electroactive surface area. Moreover, nanosized Pt catalyst can significantly enhance the electrocatalytic activity toward MOR. In this study, we used plasma-enhanced atomic layer deposition (PEALD) to deposit Pt nanoparticles of different sizes on the TiO2substrate, and studied the electrocatalytic activity of Pt nanoparticles toward MOR as a function of the particle size.

Pt nanoparticles were deposited on the TiO2 substrate by PEALD with a plasma power of 5W at 200oC using (methylcyclopentadienyl) trimethyl platinum (MeCpPtMe3) as the Pt precursor. Due to the self-limiting growth kinetics of ALD reactions, the size of Pt nanoparticles can be controlled by the number of the PEALD cycle, which was varied from 8 to 50 cycles in this study. The TiO2 was the nature oxide layer on a 100 nm thick Ti thin film sputter-deposited on the Si(100) wafer. Transmission electron microscopy (TEM) reveals that Pt nanoparticles has a size in the range between 3 nm and 7 nm depending on the number of the PEALD cycle. Cyclic voltammetry (CV) and CO stripping analysis were performed to study the electrocatalytic activity of the Pt/TiO2 electrode toward MOR in acidic media. The Pt/TiO2 electrode prepared with 15 PEALD cycles has a Pt particle size distribution peaking at ~4 nm, and has the best electrochemical performance, including electrocatalytic activity and CO tolerance. With the PEALD cycle number increased to 50, Pt nanoparticles trend to coalesce, and the electrode exhibits an electrochemical performance similar to a continuous Pt thin film. The better electrocatalytic activity of Pt nanoparticles prepared with a smaller number of the PEALD cycle can be ascribed to the synergistic effect of the nanosized Pt catalyst and the electronic interaction between Pt nanoparticles and the TiO2support. A schematic model describing the role of Pt nanoparticle size in the synergistic effect will be presented at the meeting.

Keywords: direct methanol fuel cells, DMFC, plasma-enhanced atomic layer deposition, PEALD, methanol oxidation reaction, Pt nanoparticles, TiO2.
Progress in Fuel Cell Electrocatalysis and PEMFC Performance
Authors: Spendelow Jacob S , Papageorgopoulos Dimitrios C
Published: February 2020

Fuel cells have been used in niche applications for many years, but they only recently began to be competitive with incumbent power generating technologies in more widespread applications. Since the invention of the modern PEMFC MEA around 20 years ago, significant investment in R&D by the public and private sectors has led to major improvements in fuel cell performance, with simultaneous reduction of precious metal content. This time span has seen a shift in attention from the work on liquid fuel onboard reforming in the 1990s and early 2000s to a focus on the use of direct H2PEMFCs for transportation and other applications in the last decade.

Since the 1990s, published accounts of state of the art MEA performance demonstrate that power density under conditions that approximate the rated power operating point (0.6 – 0.7 V) has nearly doubled, while typical operating pressures have decreased by more than 50% and typical precious metal loadings have decreased by an order of magnitude (Figure 1). Similar improvements are apparent at 0.8 V, which approximates the expected average voltage during a typical automotive drive cycle.

This improvement in performance under rated power and average power operating conditions has enabled fuel cells to more effectively compete with alternative technologies, such as batteries and combustion engines. It has also enabled major cost reductions due to the decrease in the required PEMFC stack size and the decrease in the precious metal catalyst loading.

This communication attempts to measure and compare, in as objective and quantitative a fashion as possible, PEMFC MEA performance since the early 1990s. Progress toward achieving key MEA performance targets is measured using published MEA performance data, primarily in the form of polarization curves. Along with a quantitative analysis of the improvement in performance results, several R&D advances that have led to these improvements will be discussed.

Figure 1. Power density at 0.7 V with operating pressures of 1-5 atm and PGM loadings of 0.12-8.0 mg/cm2. The area of each data point is proportional to the PGM loading.
Geobacter Sulfurreducens Biofilm Growth Kinetics on High Surface Area, Flow-through Anodes Under Ion-Transport Limitations
Authors: Harrington Timothy David , Beyenal Haluk
Published: February 2020

Anode-respiring bacteria like Geobacter sulfurreducens have been used to generate electrical current in many different bioelectrochemical systems, including microbial fuel cells and microbial electrolysis cells. Various cell designs have led to increases in the current densities of these systems when normalized to the projected surface area of the anodes by using 3D architecture and various convection mechanisms, with the result being an increase in current density by around five-fold. However, this increase does not nearly match the increase in available surface area. We hypothesized that the surface area is in excess in these systems, and that the current density is probably limited by ion-transport. To investigate this hypothesis, we designed a flow-through, 3D anode bioelectrochemical reactor to investigate the effect of the ion-transport limitation on the growth kinetics of G. sulfurreducens.

Using our three-electrode bioelectrochemical reactor system, we ran experiments to test how the current production, acetate utilization, hydrogen production, and biomass production were affected by changing Nernst-Planck variables, including ion transport and electrode spacing. In our system, we found that ion transport can become limiting after a 3D electrode is sufficiently colonized by Geobacter sulfurreducens, and that beyond this point the growth kinetics are no longer defined by the Nernst-Monod equation. Under these conditions, we found that the maximum current is controlled by mass transport of acetate when advection is absent, and by the mass transport of ions when advection is present. We also found that on a graphite felt electrode, in a system where ion transport is limiting (i.e., when addition of salt or convection increases the current), the acetate consumption and growth kinetics of Geobacter sulfurreducens are arithmetic, with the respective rates controllable using the variables in the Nernst-Planck equation. In this arithmetic growth regime, the acetate consumption rate, hydrogen productivity and the growth rate were decoupled from instantaneous biomass, and instead coupled solely to the steady-state current. Though arithmetic growth patterns in bacteria and algae have been described historically when the cells are under certain conditions, this the first time that an arithmetic growth regime of a microorganism has been demonstrated to be caused by ion transport in an electrochemical system, and should add to our understanding of the growth kinetics of anode-respiring biofilms. The presentation will discuss the implications of our results for future reactor designs.
Mechanistic Aspects of Multistep Bioelectrocatalytic Oxidation of Fuels
Authors: Calabrese Barton Scott
Published: February 2020

Quantitative models were developed for dihydroxyacetone (DHA) production from glycerol oxidation coupled with electrocatalysis. A two-step kinetic model was developed to describe the reactions in bioelectrocatalysis involving electrochemical NADH regeneration. Planar and porous bioelectronic interfaces are modeled to simulate, predict and evaluate kinetics and diffusion in the bioconversion (Figure 1). Key parameters involve diffusivity of cofactor/substrate, electrocatalytic activity and enzyme kinetics. Model-based analysis indicates that the bioreactor is controlled by glycerol dehydrogenase kinetics for enzyme loadings lower than 1 mM and shifts to mass transport and incipient NADH oxidation kinetic control at higher enzyme loadings.
Vertically Aligned Carbon Nanosheets As Immobilization Supports for Enzyme Bio-Electrocatalysis
Authors: Umasankar Yogeswaran , Brooks D. Bradford , Brown Billyde , Zhou Zhiguo , Ramasamy Ramaraja P
Published: February 2020

High performance laccase-based biofuel cell cathode has been developed using carbon nanosheet (CNS) with buckypaper (BP) as the substrate electrode. Compared to multi-walled carbon nanotubes (MWNT) based electrode, CNS based electrode exhibited better electrochemical activity for oxygen reduction reaction (ORR) at biologically relevant conditions. The scanning electron microscopy and Raman spectroscopy studies show that CNS was coated on the nano-tubule bundles within the BP. The attenuated total resonance Fourier transform infrared spectroscopy results show that laccase was intimately attached on to the CNS-BP. Electrochemical characterization including cyclic voltammetry and Tafel region sweep were performed to derive the kinetic parameters of ORR at the laccase-CNS-BP cathode. The onset potential obtained from the cyclic voltammogram for laccase ORR at CNS-BP is 20 mV higher than the MWNT based electrodes. The laccase-CNS-BP also exhibited steep ORR cathodic wave in the voltammograms with a Tafel slope of 19 mV decade-1. Steady state cathode polarization curves also reveal that laccase-CNS-BP cathode yielded higher current density than MWNT electrodes.

Fig. 1: Schematic representation of four electron transfer ORR at laccase-CNS interface.

Acknowledgements:

This work was partially supported by the United States Army under Contract No W911NF-13-C-0014.

References:

1. Ramasamy, R. P.; Luckarift, H. R.; Ivnitski, D. M.; Atanassov, P. B.; Johnson, G. R. (2010) High electrocatalytic activity of tethered multicopper oxidase-carbon nanotube conjugates. Chemical Communications., 46, 6045-6047.

2. Parimi, N. S.; Umasankar, Y.; Atanassov, P.; Ramasamy, R. P. (2012) Kinetic and mechanistic parameters of laccase catalyzed direct electrochemical oxygen reduction reaction. ACS Catal., 2, 38-44.

3. Umasankar, Y.; Brooks, D. B.; Brown, B.; Zhou, Z.; Ramasamy, R. P. (2013) Three dimensional carbon nanosheets as novel catalyst support for enzymatic bioelectrodes. Advanced Energy Materials, (accepted paper).
High Performance Porous Platinum Counter Electrodes for Co(II/III) Based Dye-Sensitized Solar Cells
Authors: Hu Yelin , Yella Aswani , Braun Artur , Graetzel Michael , Stefik Morgan
Published: February 2020

Cobalt-based electrolytes have significantly advanced the tunability and performance of dye-sensitized solar cells (DSC). Although these electrolytes hold much promise to advance DSCs, there remain challenges in developing suitable electrocatalytic cathodes. Platinum is the most widely used catalyst in DSCs due to its long-term stability in harsh environments and ability to transfer charge to numerous electrolytes. Unfortunately, the Pt-Co(II/III)BPY3 redox couple is hampered by slow electron transfer kinetics. Here, we present a host-guest synthesis route based upon atomic layer deposition (ALD) to create a high surface area platinum electrode supported upon a conductive scaffold of niobium doped tin oxide (NTO). This approach maximizes the catalytic surface area of platinum while minimizing the inactive platinum atoms in the bulk. The resulting nanocomposites had tunable performance with low charge transfer resistances towards Co(II/III)BPY3 electrolytes that are used in dye-sensitized solar cells. The new electrode led to DSCs with enhanced fill factors and improved power conversion efficiencies (>11%) as compared to conventional platinum cathodes.
Photo-Electrochemical Scanning Droplet Cell for Screening of Photocatalysts
Authors: Hassel Achim Walter
Published: February 2020

Reasearch on photocatalysts is rapidly increasing. They will hopefully help us solving or at least reducing our energy problems. Heterogeneous and homogeneous catalysts are considered in various approaches. The preparation of modified or entirely new photoactive materials requires an effective screening of the material. This is performed using the photo-electrochemical scanning droplet cell PE-SDC that was introduced in its initial form some 10 years ago [1]. The basic idea is using a glass capillary with a tip diameter of e.g. 100 µm that is wetting a small part of a substrate. An in build reference electrode guarantees a full 3 electrode arrangement. In the set up presented here various light sources can be randomly used to illuminate the investigated small spot. The light sources are either diode lasers with fixed wavelength or a continuous emitter for which the wavelength of interest is chosen using a monochromator [2].

The performance of this system is demonstrated using traditional semi conductors such as n-Si, p-Si and III-IV semiconductors proving that:

photo potential (continuous or chopped)

photo current (continuous or chopped)

photo impedance (full spectra and/or fixed frequency bias scanning)

can be automatically performed.

Material libraries of transition metal oxides have been prepared by multi source co-deposition and have been screened using the PE-SDC. This class of materials produces promising candidates for water splitting photo electrodes. In the comparison of MeOx-WOx libraries in which the metal Me is a ferrous metal like Fe, Ni or Co differences in the mechanisms are explained. There are striking differences which results form the differences in the watersplitting capacity of compositions within these libraries. What they do have in common is that they all show successful applications of a combinatorial photo-electrochemical approach in which samples are prepared and investigated in the CALMAR.

Screening of homogeneous or immobilized catalysts is an alternative application. Complex bi-functional materials with an intramolecular donor acceptor pair are rather difficult to synthesize and therefore may exist only in several 10 mg amounts in the beginning. Here it is necessary to have an efficient method for fully characterizing such materials under these limited conditions [3]. Examples will be given to prove the effectiveness of PE-SDCs

[1] A. W. Hassel, M. Seo, Localised Photoelectrochemical Measuremnets with the Scanning Droplet Cell in Passivity and Localised Corrosion, Proc. Electrochem. Soc. (1999) 337

[2] J. P. Kollender, A. I. Mardare, A. W. Hassel, “Photoelectrochemical Scanning Droplet Cell Microscopy (PE-SDCM)”, ChemPhysChem 14 (2013) 560-567

[3] J. Gasiorowski, A. I. Mardare, N. S. Sariciftci, A. W. Hassel, “Electrochemical characterization of sub-micro-gram amounts of organic semiconductors using scanning droplet cell microscopy”, J. Electroanal. Chem. 691 (2013) 77-82
Coated Tubular Ion-Selective Electrode Units in Process Systems
Authors: VAN Staden Jacobus Frederick
Published: February 2020

Dick (Richard) Buck made his mark in 1968 in the activity on ion-selective electrodes (ISEs) on the response of solid-state membrane electrodes under zero current conditions1 and in 1974 on concentration dependent selectivity coefficients for ion-selective electrodes2. I met Dick Buck in 1985 in the UK when I gave my first lecture on the new innovation on coated tubular ion selective electrodes in flow analysis. We became friends with our involvement in IUPAC in the late 1980’s and 1990’s with his involvement in the commission on electroanalytical chemistry and mine in the commission on general analytical chemistry3-5.

In this talk different scenarios regarding the innovation, development, design, behaviour, implementation and application of coated tubular ion-selective electrode units will be outlined. The hydrodynamic conditions in process systems and especially in the conduits of flow-through process systems required special probes to fulfill the needs of these systems. The coated tubular ion-selective electrode units were designed and successfully applied in various areas and the results and performance thereof will be discussed.

References

1. R. P. Buck, Anal. Chem, 40(1) 1968, 1432-1439.

2. R.P. Buck Anal Chim Acta, 73(2) 1974, 321-328.

3. R.P. Buck, V.V. Cosofret, Pure Appl Chem, 65(8) 1993, 1849-1858.

4. R.P. Buck, E. Lindner, Pure Appl Chem, 66(12) 1994, 2527-2536.

5. J.F. van Staden, Pure Appl Chem, 71(12) 1999, 2303-2308.

Acknowledgements

The present work was supported by the Romanian National Programme

PN II, Ideas, Contract Nr. 100/27.10.2011.
Invited Presentation: Single-Walled Carbon Nanotubes for Delivery of siRNA: Producing a Pharmaceutically Stable and Effective Drug Product
Authors: Kirkpatrick Lynn
Published: February 2020

siRNA has the potential to be a selective targeted cancer therapy but currently lacks an effective delivery mechanism. Ensysce has been exploring the use of single-walled carbon nanotubes (SWCNT) as delivery vehicles for siRNA and has extensively examined the safety, and in vitro and in vivo efficacy of this platform. We have determined that siRNA/SWCNT complexes are well tolerated, and can be administered on a multi-weekly intravenous (i.v.) dosing schedule over extended periods of time. Our work has explored formulation and processing to provide a drug product with a good pharmacokinetic half-life allowing distribution of the SWCNT to desired tissues in animals and that provides suitable pharmaceutic properties for use in a clinical setting. Complexes with various siRNA payloads have been evaluated in animal models with human tumor xenografts. Antitumor activity has been demonstrated with siRNA/SWCNT complexes targeting one or two growth driving proteins. Preclinical development has begun and a product has been selected to move through IND enabling toxicology. SWCNT offer a novel approach to safely and effectively deliver oligonucleotides, and by manipulating formulation of the complex we can alter the siRNA biodistribution to tissues of interest with resulting target inhibition for disease control.
Carbon Nanostructures Used for Screening in Biomedicine
Authors: Stefan-van Staden Raluca Ioana
Published: February 2020

Carbon nanotubes, carbon onions, and C60 fullerenes were used as matrices for stochastic microsensors design. Maltodextrins, cyclodextrins and porphyrins were immobilized in the matrices to improve the stochastic behavior of the microsensors.

The “signatures” of HER-1, NSE, leptin, PAI-1 and hormones were recorded using this microsensors in stochastic mode. The “signatures” were used to identify these analytes on the diagrams obtained when whole blood was screened. Quantitative analysis was also performed using these microsensors. The results obtained using the proposed microsensors were correlating very well with those obtained using the standard methods used in clinical analysis.

Acknowledgements This work was supported by UEFISCDI PNII Program Ideas 2011-2014, Contract nr. 123/05.10.2011 and by ERC-like-3/07.2012 program.
Three-Dimensional Mesoscale Modeling of Anisotropic Mechanical Deformation in Lithium-Ion Electrodes
Authors: Roberts Scott A. , Long Kevin N. , Brunini Victor E. , Grillet Anne M.
Published: February 2020

Capacity fade in Lithium-ion batteries is dependent on a number of processes, one of which may be physical deterioration of the electron transport network formed by the solid particles which make up the electrodes. One cause of progressive capacity deterioration is the evolution of inter-particle stresses caused by cyclic swelling processes from intercalation and phase transformations. Intercalation reactions as lithium insert into the crystal lattice lead to anisotropic deformation and complex mechanical behaviors on the mesoscale.

In this presentation, we demonstrate our recent efforts in performing three-dimensional simulations of Lithium-Ion electrode materials at the mesoscale, with hundreds of particles included. Our focus will be on anisotropic mechanical deformation, with additional physics (such as thermal and species transport) included to appropriately drive the mechanical deformation. The simulations will include anisotropy within individual particles and demonstrate stochastic initiation of lithiation. This simulation approach will be deployed on multiple configurations, including spherical particles packs generated from measured particle size distributions and reconstructed geometries from FIB-SEM cuts of actual electrode materials.

* Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
Simulation of Macro Scale Mechanical Behavior of Pouch Cell Lithium-Ion Batteries
Authors: Smith Kandler , Maute Kurt , Behrou Reza , Santhanagopalan Shriram
Published: February 2020

Electrochemical energy storage devices suffer from capacity fade due to mechanical, thermal and electrochemical interaction. This study focuses on mechanical phenomena in lithium ion pouch cell batteries. A finite element model is developed to predict swelling/shrinking in cathode/anodes due to thermal expansion and lithium intercalation, as well as in-plane and out-of-plane deformation. Transport of lithium, transport of heat and generation of heat are obtained through measurement or numerical simulations.

Pouch cell batteries are composed of a large number of individual thin layers which are stacked together. To correctly capture the plate-like behavior of individual layers while limiting the in-plane discretization, a computational mesh with large aspect ratio elements is needed. As such elements may suffer from spurious stiffening effects a high performance finite element formulation is developed. This small-strain, solid-shell finite element formulation accurately captures both the in-plane and out-of-plane behavior of individual layers.

Figure 1 below shows a cross section of the pouch cell mesh resolving indivdual layers and folder separator construction.
Synthesis of the Materials Used in All-Solid-State Lithium Secondary Batteries
Authors: Matsumoto Takuto
Published: February 2020

Conventional electrolytes in Li-ion batteries based on organic solvents or polymers with a dissolved Li-salt pose serious limitations such as flammability, difficulty of miniaturization, and serious impact to the environment if poorly disposed of or recycled.

As a replacement, stable inorganic solid electrolyteswith high Li conductivity and suppressed electronic conductivity has become increasingly appealing, with several advantages including nontoxicity, ease of preparation, and low cost.

So far, Li ion conductors with garnet-type structure are considered as promising electrolytes because of their high conductivity and excellent stability.

Li7La3Zr2O12 (LLZO) has recently become of high interest as a result of its potential as a solid state Li-ion conductor, because it has good ionic conductivity (>10−4 S/cm) and is stable against lithium. However, for the case of LLZO two phases exist; cubic and tetragonal.

The cubic phase is preferred, because reports estimate a theoretical lattice conductivity of ~5×10-4 S/cm compared to ~1.6×10−6 S/cm, for the tetragonal phase.

Thus, it is important to understand how to prepare the cubic phase.

In general, calcination temperatures in excess of 1180 °C are required to obtain cubic LLZO.

In this study, we aim to synthesis of cubic LLZO using a hydrothermal synthesis method.
Mechanical-Electrochemical Coupling in Materials for Solid Oxide Fuel Cells: Insights from Computer Simulations
Authors: Marrocchelli Dario , Bishop Sean R. , Tuller Harry L. , Yildiz Bilge , Watson Graeme
Published: February 2020

The coupling between the electrical, chemical and mechanical properties of materials, usually referred to as Electro-Chemo-Mechanics [1], has very important implications for energy related materials and devices. Indeed, this coupling can be beneficial, e.g. the ion conductivity enhancement observed in ceria and zirconia when these materials are strained [2], or detrimental, e.g. the lattice parameter expansion observed in ceria upon reduction [3]. For this reason a better understanding of this coupling is necessary in order to tailor the properties of these materials.

Atomistic computer simulations represent a powerful tool to study the mechanical-electrochemical coupling, as they can provide information that is complementary to experiments. In this presentation, I will review some recent computational work in this field. First I will talk about chemical expansion in ceria, an example of chemo-mechanical coupling. I will show how, by combining Density Functional Theory and Molecular Dynamics Calculations with experimental data, we concluded that chemical expansion is caused by two competing processes, the formation of a vacancy (leading to a lattice contraction) and the cation radius change (leading to a lattice expansion). This information was then condensed in a simple analytical model, which was then used to predict materials compositions that minimize chemical expansion. Then I will present two more examples from my work: the first one on the study of co-doping strategies in ceria as a means to enhance its ionic conductivity (electro-chemical coupling) and the second one on the effects of dislocations in SrTiO3 on the defect chemistry and mobility of this material (electro-chemo-mechanical) coupling.

References

[1] Tuller and Bishop, Annu. Rev. Mater. Res.
41 369 (2011)

[2] Kushima and Yildiz, J. Mat. Chem. 20 4809 (2011)

[3] Marrocchelli et al. Adv. Fun. Mat.
22 1958 (2012)
Effect of Anelastic Relaxation of Defect Complexes on Mechanical Properties of Stabilized Zirconias
Authors: Gao Peipei , Bolon Amy , Lara-Curzio Edgar , Radovic Miladin
Published: February 2020

Stabilized zirconias with high ionic conductivity are currently essential electrolyte materials for solid oxide fuel cells (SOFCs). Study of mechanical properties of oxide ceramics is significant to reliability and durability of SOFCs which work under harsh environment including high temperature, mechanical stress, electric fields, etc. In this paper, we report on the temperature dependent elastic properties of two stabilized zirconias, namely Yttria Stabilized Zirconia (YSZ) and Scandia-Ceria Stabilized Zirconia (SCZ). The elastic properties were studied using Resonant Ultrasound Spectroscopy (RUS), Dynamic Mechanical Analysis (DMA) and Cyclic Compression Testing. It was found that elastic moduli change with temperature in non-linear manner with large peaks in the mechanical loss coefficients (or mechanical damping) at different temperatures. A strong mechanical damping or attenuation is related to the stress induced anelastic relaxation due to hopping of the oxygen vacancies in dopant-vacancy defect complexes. Effects of applied stress, stress frequency, electric field and temperature on the changes of elastic moduli are discussed in more details in this paper.