bluuebunny/crossref_metadata_2025 huggingface dataset:
The Predicted Crystal Structure of Metastrengite I FePO4∙2H2o and Its Importance in Li-Ion Battery Systems
Authors: Kim Soo , Ward Logan , Michel Kyle , Wolverton Chris , Shin Eun Jung , Kim Hyung-Sun , Cho Byung-Won
Published: February 2020

The demands for large-scale energy storage devices have increased significantly for the past decade [1]. Olivine structured lithium iron phosphate, LiFePO4, has been recognized as a promising cathode material for lithium ion batteries because of its advantages of high power capability, low cost, non-toxicity, excellent thermal safety, and high reversibility [2]. In addition to LiFePO4, various amorphous and crystalline phases of iron phosphates, FePO4 and FePO4·nH2O have been proposed as the cathode materials in lithium ion batteries [3].

Among various phases of iron phosphates, the exact crystal structure of crystalline FePO4·2H2O (metastrengite I) is still unknown as first mentioned by Rémy et al. [4]. It was determined that an orthorhombic olivine-type LiFePO4 (Pnma) and metastrengite I FePO4·2H2O (Pbnm) belong to the same space group #62. Here, we use the recently developed genetic-algorithm-based FPASS method [5] to determine the crystal structure of crystalline FePO4·2H2O (metastrengite I) and discuss the possible applications of the crystalline FePO4·2H2O (metastrengite I) for the LIBs system.

References

[1] J. M Tarascon and M. Armand, Nature, 414, 359 (2001).

[2] A. K. Padhi, K. S. Nanjundaswamy, and J. B Goodenough, J. Electrochem Soc., 144, 1188 (1997).

[3] C. Delacourt, P. Poizot, D. Bonnin, and C. Masquelier, J. Electrochem. Soc.,
156, A595 (2009).

[4] P. Rémy, Ph.D. Thesis, University of Paris, France (1971).

[5] B. Meredig and C. Wolverton, Nature Mater., 12, 123 (2013).
Advanced Redox Flow Battery Technology
Authors: Wang Wei , Nie Zimin , Vijayakumar Murugesan , Wei Xiaoliang , Li Bin , Cosimbescu Lelia , Xu Wu , Liu Tianbiao , Reed David , Sprenkle Vincent
Published: February 2020

This presentation describes the recent progress of the advanced redox flow battery research and development including both aqueous and non-aqueous systems. Recent development on the single cell components including high selective membrane, high energy density electrolyte, and new nonaqueous redox flow chemistries will be reported. Varied electrochemical, chemical and physical evaluations were carried out to assist the component screening and optimization. The mass transport mechanisms of the redox flow battery will be discussed, which allowed us to optimize the related cell operation parameters and continuously operate the system for more than three months without any capacity decay. Particularly, a series study to correlate the Nafion structure (Figure 1) with the flow battery performance (Figure 2) will be presented in details.

Acknowledgements

The authors would like to acknowledge financial support from the U.S. Department of Energy’s (DOE’s) Office of Electricity Delivery and Energy Reliability (OE) (under Contract No. 57558). Pacific Northwest National Laboratory is a multi-program national laboratory operated by Battelle for DOE under Contract DE-AC05-76RL01830.
Phosphorus @ Porous Carbon for Na-Ion Batteries
Authors: Wen Yang , Wang Chunsheng
Published: February 2020

Sodium ion battery has drawn significant attention recently due to its low cost and it can be potentially used in large-scale electric energy storage. Elemental phosphorus has a high theoretical capacity of 2596 mAh g-1 which is one of the most promising anode materials. However, due to high volume expansion caused by Na+ insertion (~490% from phosphorus to Na3P), it is hard to achieve stable cycling. In this study, P @ porous carbon sample will be prepared through a vaporization/adsorption strategy. The conductive mesoporous carbon serves as host material which can improve the electronic conductivity as well as good structure material to confine the nano-P. The P @ porous carbon material will be evaluated by vary electrochemical measurements, including cycling stability, rate capability and impedance. And the obtained results will be compared with phosphorus in other carbon host materials.
Harvesting High Loading Electrode with Nanosized Particles for Rechargeable Lithium Batteries
Authors: Lv Dongping , Lozano Terence , Shao Yuyan , Bennett Wendy D , Zhang Ji-Guang , Liu Jun , Xiao Jie
Published: February 2020

Contributed by significantly improved solid/liquid interface and kinetics of Li+ diffusion, nanostructured electrode materials offer wide and promising applications in Li-ion and rechargeable lithium batteries, especially for the high power demand.[1] For example, by embedding electronic insulating sulfur into the nanostructured carbon frameworks, the obtained sulfur/carbon composites deliver high capacity and greatly improved cycling stability as cathode.[2, 3] Similarly, silicon exhibits outstanding properties as promising anode for Li-ion batteries after reduced to nanosize or combined with carbon by forming Si/C composites.[4] Despite these superiorities of nanosized novel structures, materials in nano-scale still face the challenge with respect to the practical applications in batteries. Besides side reactions initiating on the high surface electrode, it is difficult to achieve high loading electrode with nanosized active materials through slurry coating technique due to the generation of sever cracking or pinholes during the drying process. One of the reasons behind this phenomenon is the large volume shrink of nanosized materials accompanying the solvent removing from slurry. These downsides have plagued the practical application of nano-sized materials in energy storage systems. Attempts have been made to address these issues by increasing the particle size through spray drying, introducing conductive polymer or other self-assemble approaches, which are either complicated with special equipment or not cost-effective for large scale applications. We herein propose a facile and up-scale available approach to coat nano particles into electrodes with practically usable thickness and active mass loadings. Successful demonstration of this approach was shown in sulfur and silicon nano particles. High loading but crack-free coating for sulfur (loading: 2-8 mg sulfur/cm2) and Si (loading: 2-4 mg Si/ cm2) electrodes have been displayed. In addition, we did detailed screen for the binder selection and slurry composition modification. Base on the obtained high loading electrodes, systematical study was performed on the relationships of electrode loading, pressure, energy density and rate capability. All these obtained results will be presented at the meeting.

References

[1] A. S. Arico; P. Bruce; B. Scrosati; J. M. Tarascon; W. Van Schalkwijk, Nature Materials
2005,
4, 366.

[2] X. Ji; K. T. Lee; L. F. Nazar, Nature Materials
2009,
8, 500.

[3] J. Zheng; M. Gu; M. J. Wagner; K. A. Hays; X. Li; P. Zuo; C. Wang; J.-G. Zhang; J. Liu; J. Xiao, Journal of the Electrochemical Society
2013,
160, A1624.

[4] C. K. Chan; H. Peng; G. Liu; K. McIlwrath; X. F. Zhang; R. A. Huggins; Y. Cui, Nature Nanotechnology
2008,
3, 31.
Synthetic Strategies Impacting Voltage, Capacity, and Current Capability of Energy Storage Materials
Authors: Takeuchi Kenneth J , Marschilok Amy C , Takeuchi Esther S
Published: February 2020

Low temperature synthetic strategies for direct control of crystallite size and composition of energy storage materials will be discussed. This ability to synthetically control material properties enabled the systematic exploration of the fundamental properties of the materials, which reveals a dependence of electrochemical reversibility, current capability, and delivered capacity on chemical or physical properties, likely crystallite size. In a more general sense, fundamental studies involving the impact of physical and chemical properties of materials on their electrochemical properties are critical in the rational development of materials, which may address the present and future requirements for stationary and portable power.

Results

Materials from several structural types could be synthetically controlled to achieve variation in crystallite size. For example, magnetite, Fe3O4, a densely packed structure could be made where the crystallite size is tightly controlled.1,2 Correlation of the electrohemical performance to crystallite size was observed where the cell using the smallest crystallite size, delivered higher capacity under pulse type testing.

A second category of materials is represented by AgxMn8O16 (silver hollandite) a tunnel structure.3 Remarkably, as the Ag:Mn ratio was varied via the synthetic approach developed for the system, concomitant changes in the crystallite size were observed.4 This enabled systematic investigation of this variable on the resultant electrochemistry. The delivered capacity, reversibility, and loaded voltage improved significantly for the small crystallite size material.5

References

1. S. Zhu; A.C. Marschilok; E.S. Takeuchi; K.J. Takeuchi. Electrochemical and Solid State Letters, 2009,
12(4), A91-A94.

2. S. Zhu; A.C. Marschilok; E.S. Takeuchi; G.T. Yee; G. Wang, G.; K.J. Takeuchi. J. Electrochem. Society,
2010,
157(11), A1158-A1163.

3. S. Zhu; A.C. Marschilok; C.-Y. Lee; E.S. Takeuchi; K.J. Takeuchi. Electrochem. Solid-State Lett.
2010,
13(8), A98-A100.

4. K.J. Takeuchi; S.Z. Yau; M.C. Menard; A.C. Marschilok; E.S. Takeuchi. ACS Applied Materials and Interfaces.
2012,
4(10), 5547-5554.

5. K.J. Takeuchi; S.Z. Yau; A. Subramanian; A.C. Marschilok; E.S. Takeuchi. J. Electrochem. Soc.
2013
, 160(5), A3090-A3094.
Effect of Solid Electrolyte Distribution in Composite Cathode on Electrochemical Properties of Solid-State Li-Air Batteries
Authors: Kim Tae Young , Ma Sang Bok , Lee Dong Joon , Choi Wonsung , Im Dongmin , Doo Seok-Kwang
Published: February 2020

Li-air batteries have increasing attention as energy sources for automotive application due to high theoretical energy density over 3000 Wh/kg which is about 10 times greater than that of Li-ion battery [1-2]. Typical nonaqueous Li-air batteries used organic liquid electrolyte and oxygen from the air in atmosphere as active cathode material. Oxygen can be reduced and oxidized at three phase boundary in electrolyte filled-porous electrode. Excess organic liquid electrolyte may be needed to fill porous electrode and occupy nearly 70% of total weight, which makes the specific energy density of practical Li-air batteries reduced [3].

Recently, the studies for solid-state Li-air batteries with solid electrolyte have been reported [4]. Using solid electrolytes such as polymer and inorganic ionic conductors makes it possible to control proper amount in composite cathode and keeps the electrolyte from being squeezed out compared with organic liquid electrolyte. However, lithium ion conductivity of solid electrolyte is lower than that of liquid one and it is difficult to make a good interface between solid electrolyte and carbon in composite cathode. The design and internal structure in composite cathode is important to maintain the performance of solid-state Li-air batteries.

In this study, the electrochemical properties and pore structure in various composite cathodes were measured from solid-state Li-air batteries. PEO (polyethylene oxide)-based electrolyte containing LiTFSI (lithium bis(trifluoromethanesulfonyl) imide) was used as a solid electrolyte in composite cathode. The mixture of carbon and PEO was directly coated on LATP (Ohara Inc.) by screen printing method. Solid-state Li-air cell was assembled by stacking Li metal, interlayer, LATP with composite cathode and GDL (gas diffusion layer), respectively.

The AC impedance was conducted to get internal resistance in fresh composite cathode at non faradic condition. The activation energy for each resistance components was calculated by fitting the impedance spectra. The activation energy of Rinf (interface resistance between LATP and cathode) is higher than those of Rel (resistance of LATP) and Rion(resistance of Li ion transfer in cathode), which indicates kinetic barrier for Li ion transfer between LATP and solid electrolyte in cathode.

We also have studied the change of internal resistance in composite cathode with various carbons and electrolyte composition and will present our investigation.

References

[1] K. M. Abraham, Z. Jiang, J. Electrochem. Soc. 143 (1996) 1.

[2] A. Ogasawara, A. Debart, M. Holtzapfel, P. Novak, P. G. Bruce, J. Am. Chem. Soc.129 (2006) 1390.

[3] J.-G. Zhang, D. Wang, W. Xu, J. Xiao, R.E. Williford, J. Power Sources 195 (2010) 4332.

[4] H. Kitaura, H. Zhou, Energy Environ. Sci. 5 (2012) 9077.
Electrodeposition of Pd-Based Binary Catalysts on Carbon Paper Via Surface-Limited Redox-Replacement Reactions for Oxygen Reduction Reaction
Authors: Modibedi Remegia Mmalewane , Mathe Mkhulu K. , Motsoeneng Rapelang Gloria , Khotseng Lindiwe Eudora , Ozoemena Kenneth I.
Published: February 2020

Direct alcohol fuel cells (DAFCs) continue to extensive attention as potential power sources for portable and stationary applications [1]. The oxygen reduction reaction (ORR) involving the four electron transfer remains a challenge for DAFCs due to its slow kinetics. Research activities worldwide are focussed on improving the performance of ORR catalysts, reducing the amount of Pt required in DAFCs and in addition, developing catalysts tolerant to alcohol (alcohol crossover). Pd has attracted enormous attention as it is more abundant and also cheaper than Pt [2-5].

In this presentation, Electrochemical Atomic Layer Deposition (ECALD) was used in the preparation of binary ORR catalysts. The binary nanoclusters were synthesised via surface-limited redox-replacement reaction (SLR3) with Cu as a sacrificial metal. Co-deposition of the two metals on carbon paper was also performed. ECALD is the appropriate fabrication methodology because the resultant catalysts showed good dispersion of the nanoclusters on the carbon paper. This will reduce the amount of Pt and increase the utilization of the catalyst. The prepared binary nanoclusters were evaluated for the ORR.

References:

F. Barbir, PEM Fuel Cells: Theory and Practice, Elsevier Academic Press, 2005, Oxford: p. 1-16

A. Kiani, E.N. Fard, Fabrication of palladium coated nanoporous gold film electrode via underpotential deposition and spontaneous metal replacement: A low palladium loading electrode with electrocatalytic activity, Electrochim. Acta. 54 (2009) 7254-7259.

T.S. Mkwizu, M.K. Mathe, I. Cukrowski, Electrodeposition of Multilayered Bimetallic Nanoclusters of Ruthenium and Platinum via Surface-Limited Redox− Replacement Reactions for Electrocatalytic Applications, Langmuir. 26 (2009) 570-580.

L.B. Sheridan, D.K. Gebregziabiher, J.L. Stickney, D.B. Robinson, Formation of Palladium nanofilms using Electrochemical Atomic Layer Deposition (E-ALD) with Chloride complexation, Langmuir 29 (2013) 1592

R.M. Modibedi, M.K. Mathe, R.G. Motsoeneng, L.E. Khotseng, K.I. Ozoemena, E.K. Louw, Electro-deposition of Pd on Carbon paper and Ni foam via surface limited redox-replacement reaction for oxygen reduction reaction, Electrochimica Acta (2013), accepted for publication
Evidence for Oxygen Reduction Reaction Activity of a Ni(OH)2/Graphene Oxide Catalyst
Authors: Farjami Elaheh , Rottmayer Michael , Deiner L Jay
Published: February 2020

Effective catalysis of the oxygen reduction reaction in alkaline solution is crucial to a variety of electrochemical energy storage and conversion devices like metal-air batteries and alkaline fuel cells. While Pt-based catalysts exhibit excellent activity, their high cost and lack of stability motivates the search for alternative electrocatalysts. Non-noble metal oxides like MnxOy have shown particular promise, especially when supported by carbon nanomaterials like graphene. Most recently, the performance and stability of a MnxOy has shown additional improvement with the doping of Ni(OH)2. The performance improvement is typically ascribed to stabilization of the Mn3+/Mn4+ couple, but it is also possible that Ni(OH)2 itself displays significant oxygen reduction reaction catalytic activity. This work provides the first report of the oxygen reduction reaction activity of a Ni(OH)2nanoparticle catalyst supported by graphene oxide in basic media.

A Ni(OH)2/graphene oxide material was synthesized using a single step microwave reduction method. Cyclic voltammetry shows that the Ni(OH)2/graphene oxide material has a peak potential of -310 mV vs. Ag/AgCl, a shift of + 110 mV as compared to the unsupported Ni(OH)2 nanoparticles and + 90 mV as compared to the graphene oxide support alone. Rotating disk electrode studies confirm that the activity of the Ni(OH)2/graphene oxide catalyst is greater than either the graphene oxide support or the Ni(OH)2 nanoparticles alone. Significantly, the limiting current density of the oxygen reduction reaction on the Ni(OH)2/graphene oxide catalyst is 1.3 mA/cm2 (as normalized by electrochemically active surface area) and the electron transfer number is 3.5. Chronoamperometry demonstrates that the Ni(OH)2/graphene oxide material is relatively stable, with the oxygen reduction current density sustaining a steady state value of 60 % of its initial value. Electrochemical impedance spectroscopy shows that the charge transfer resistance of the Ni(OH)2/graphene oxide catalyst is lower than either the Ni(OH)2 nanoparticles or the graphene oxide support. Taken together, these data indicate that the Ni(OH)2/graphene oxide catalyst exhibits significant oxygen reduction reaction activity which may be related to the interaction of the support and the nanoparticles.
Fragmentation of Carbon Nanotube Macro-Films By Ultrasound As Conductive Binder for Lithium-Ion Batteries
Authors: Cao Zeyuan , Wei Bingqing
Published: February 2020

Fragmentation carbon nanotube macro-films (FCNT) with the structure of irregular laterally 2-D distributed CNT segments is found not only have high conductivity but also adhesive force. A conceptual idea to exploit FCNT alone as both binder and conductive additive for lithium-ion batteries was first-time proposed and demonstrated by constructing composite electrodes with a typical positive material, LiMn2O4 (LMO), in half cells. The new composite electrodes exhibit superior high-rate capabilities compared to the electrodes employing conventional binder, poly(vinylidene fluoride) (PVDF), and carbon black (CB). LMO with 30 wt% FCNT has specific capacity as high as 100 mAgh-1 at 150 mAg-1 and 78 mAhg-1 at 1500 mAg-1, which are about 87% and 70% of the 115 mAhg-1 at an extremely low current density of 15 mAg-1. In the contrast, the capacity of LMO with 15 wt% PVDF and 15 wt% CB drops over 55% of the initial capacity 87 mAhg-1 when the current density rises 100 times from 15 mAg-1 to 1500 mAg-1. Electrochemical impedance spectra indicate 30 wt% FCNT contributes both the lowest series and charge transfer resistance out of the electrodes with 5 wt%, 15 wt% and 30 wt% FCNT, which determine its best high-rate performance. LMO with 30 wt% FCNT also maintains 100% retention for 100 cycle at 150 mAg-1. An in-situ tribology method combining the wear track imaging and force measurement (shown in Figure 1) is introduced to evaluate the adhesion strength of electrodes comprising LMO with different mass fractions of FCNT and PVDF. The results show LMO with 30 wt% has adhesion strength of 7-10 MPa on the aluminum substrate which is at least comparable with the 6.3-8 MPa of 30 wt% PVDF. In addition, we further confirm the feasibility of this concept in two demo-systems, the half cells involving the negative materials Li4Ti5O12 (LTO) and the full cells combining LMO-FCNT as cathodes with LTO-FCNT as anodes. FCNT could be a competent substitute for polymer binders and conductive additives to maintain mechanical integrity and electrical connectivity of active materials in the composite electrodes.
Tin Oxide Nanowires As High Energy Density Anodes for Lithium-Ion Batteries
Authors: Nguyen Tu Quang , Thapa Arjun K , Vendra Venkat Kalyan , Jasinski Jacek B , Sunkara Mahendra Kumar
Published: February 2020

Recently, tin oxide has attracted great attention as an anode for lithium ion batteries due to their high theoretical capacity of 782 mAhg-1 which is two times higher than that of current commercial graphite anode. However, the main challenges for employing tin oxide as anode are the huge volume expansion during cycling leading to electrode pulverization and irreversible capacity loss due to SEI formation. In this presentation, we report two kinds of tin oxide nanowire structures: (1) tin nanocluster covered tin oxide nanowires, (2) titania coated tin oxide nanowires. Both structures showed high capacity retention and much less morphological degradation. In addition, we also demonstrated a new method called "Solvo-plasma" for large scale production of tin oxide nanowire powders. Even at lab scale, we demonstrated production rates of 8 grams per hour [1] (See Figure 1a).

The tin nanocluster covered tin oxide nanowires show an exceptional capacity of 814 mAhg-1 even after 100 cycles at a high current density of 100 mA/g [2]. Recently, thin protective coatings are of great interest for enhancing the durability. Here, we demonstrate that such a thin layer of protective coating of titania or alumina using atomic layer deposition technique could stabilize and improve cyclability. Figure 1b shows a 5 nm titania layer coated on tin oxide nanowires. Without coating, tin oxide nanowires exhibited a very low capacity of 300 mAhg-1. With a 5 nm titania layer, the capacity retention increased to 767 and 664 mAhg-1(Figure 1c) at the current density of 700 and 1500 mA/g after 30 cycles, respectively [3]. The protective coatings also reduced the irreversible capacity losses associated with SEI formation.

Figure 1: a) SEM image of SnO2 NWs using Solvo-plasma synthesis, b) TEM image showing a thin layer of titania on tin oxide nanowires, c) the capacity retention at different current densities compared with non-coating tin oxide nanowires

References

[1] Nguyen et al., manuscript in preparation

[2] P. Meduri, C. Pendyala, V. Kumar, G. U. Sumanasekera, M. K. Sunkara, Nano lett.
2009, 9, 612.

[3] T. Q. Nguyen, A. K. Thapa, V. K. Vendra, J. B. Jasinski, G. U. Sumanasekera and M. K. Sunkara. RSC Advances (accepted 2013)
Enhanced Ionic Conductivity of Microwave Processed LiO2-Al2O3-TiO2-P2O5 Glass Ceramics
Authors: Davis Calvin G. , Nino Juan C.
Published: February 2020

Glass-ceramics with a NASICON crystal structure are of great interest as solid state electrolytes because of their thermal stability and high room temperature ionic conductivities. It has been shown that the crystallization kinetics can greatly affect the activation energy and ionic conductivity of glass ceramic electrolytes. In this work, the effect of annealing conditions on the crystallization and ionic conductivity of glass ceramics will be presented. LiO2-Al2O3-TiO2-P2O5 (LATP) was prepared by melt quenching methods, and crystallization was induced by both microwave and conventional heating for comparison. Results from broadband impedance spectroscopy analysis combined with microstructural characterization will be discussed and processing avenues for enhanced conductivity via microwave heating will be demonstrated.
Symposium Keynote Address - Thoughts about Science and Life, Gathered from the Career of Andrzej Wieckowski
Authors: Faulkner Larry R.
Published: February 2020

This presentation will open the symposium honoring Andrzej Wieckowski and is intended to draw attention to his career as a committed scientist, ever attentive to the well-being of students, colleagues, and institutions. Brief comments will be made about high points and critical junctures in Professor Wieckowski’s professional life, and they, in turn, will furnish a basis for more general commentary about opportunity, pleasure, and duty in science.
Clean Energy from Ethanol: Efficient Oxidation of Ethanol in Solid Oxide Fuel Cell Via a New Reformer Catalyst
Authors: Kowal Andrzej , Adzic Radoslav , Parlinska-Wojtan Magdalena , Pokora Monika , Martyla Agnieszka , Nowak Ryszard
Published: February 2020

The possibility of obtaining electrical energy from bio-ethanol provokes an increased interest in Direct Ethanol Fuel Cells (DEFC). Commercial platinum nano catalysts do not facilitate a complete oxidation of ethanol. Ternary PtRhSnO2 catalysts are able to split the C-C bond and oxidize ethanol to CO2at room temperature [1- 2], but require further development.

In order to improve the efficiency of high-temperature solid oxide fuel cells (SOFCs), particularly those utilizing ethanol as a fuel (ESOFC), our recent research focused on the catalysts that increase the power density of such fuel cells. The systems studied were based on nano-oxides such as SnO2, SnO2/Sb2O5, CeO2 and TiO2. The structural properties of such synthesized oxides were evaluated using XRD and HRTEM. These oxides were then deposited on nickel foam and used in an external reformer converting ethanol to H2. Reformed ethanol was fed to an anode of the SOFC . The Ni/CeO2catalyst in the external reformer, combined with SOFC, gives the highest power density of ESOFC (Ethanol Solid Oxide Fuel Cell).

[1] Kowal A., et al., Nature Materials , 2009, 9, 325.

[2] Adzic R, Kowal A., (Brookhaven National Laboratory), Patent Application Publication , Pub. No. US2009/0068505 A1 (Mar. 12,2009).
Controlling Local Substrate Concentrations in Multi-Enzyme Complexes
Authors: Wheeldon Ian , Gao Yingning , Lin Jyun-Liang
Published: February 2020

In nature we find many examples of bifunctional enzymes that effectively process cascade reactions. For example, the bifunctional enzyme thymidylate synthase-dihydrofolate reductase (TS-DHFR) couples two active sites on the same polypeptide structure via an electrostatic patch. Interactions between the negatively charged cascade intermediate, dihydrofolate, and the positively charged enzyme surface create an environment for bounded diffusion between active sites, thus promoting substrate channeling. This is a useful example from which we can draw design inspiration for synthetic enzyme cascades for multi-step reactions in biofuel cells. To this end, our research group is designing new nanostructured multi-enzyme complexes to study the effects of cascade structure on reaction kinetics. Our overall goal is to turn our understanding of these relationships into a generalized set of design rules that can be used to engineer optimized cascade catalysis. The first step is to investigate interactions between multi-enzyme scaffolds and cascade substrates. The TS-DHFR example suggests that substrate-scaffold interactions are important and can be beneficial to cascade catalysis. Here, we demonstrate that DNA scaffolds can enhance the kinetics of assembled enzymes and that these enhancements are related to the binding energy of the substrate and DNA scaffold. A model system of horseradish peroxidase (HRP) with phenolic substrates and a triangular DNA scaffold (sides ~ 25 nm in length) showed increased enzyme activity with one, two, and three HRPs assembled on the scaffold over freely diffusing HRP modified with short single stranded DNA. Interestingly, the enhancements in activity mimicked the Sabatier principle and a plot of the kinetic enhancement as a function of substrate-DNA binding energy followed the trends of a volcano plot commonly described in heterogeneous catalysis. No enhancement in enzyme activity was observed when the binding of the substrate to the scaffold was weak (kd = 10 mM). No enhancement occurred when binding was strong (kd = 4 mM). With intermediate binding (kd = 100 – 1000 mM) the enhancement in enzyme activity of HRP assembled on a DNA scaffold over freely diffusing enzymes was significant. We hypothesize that the enhancement was due to an increase in local concentration of the substrate resulting from substrate-DNA interactions. We confirm this hypothesis by demonstrating control over the apparent Michaelis constant of HRP-DNA nanostructures by tuning the interactions between substrates and DNA scaffold. These findings represent an important first step in designing multi-enzyme complexes and demonstrate that interactions between substrates and the scaffolds must be considered when engineering such structures. Our current work is focused on extending these findings to controlling the local concentration of enzyme co-factors used in biofuel cell anodes for multi-step oxidation cascades.
Investigating the Redox Abilities of DNA Aptamers Bound to Redox Cofactors for Possible Application in Biofuel Cells
Authors: Emahi Ismaila , Gruenke Paige R , Freitag Lucy , Baum Dana A
Published: February 2020

Aptamers are single-stranded RNA or DNA sequences that can bind to a target with affinity and specificity. Deoxyribozymes or DNA enzymes represent another type of functional, single-stranded DNA that can catalyze chemical reactions. Both aptamers and deoxyribozymes could find potential use in a number of applications, including biofuel cells. These functional DNAs are identified through an iterative process termed in vitro selection. This process allows one to develop customized catalysts made of DNA that can function under the desired application conditions. Compared to proteins, DNA is cheaper to synthesize, easily modified for attachment to surfaces such as electrodes, and stable under various conditions. It is therefore desirable to exploit these properties of DNA for use in various applications. For example, a deoxyribozyme capable of peroxidase activity has been identified, and our lab has demonstrated the ability of this deoxyribozyme to function in a biofuel cell.

As a long term goal, we are interested in replacing protein enzymes with DNA catalysts in enzymatic biofuel cells because of challenges encountered, such as limited enzyme lifetime and low power densities. We are therefore investigating whether we could identify DNA sequences that may bind to redox cofactors in order to create an active site and mimic oxidoreductases. Oxidoreductase protein enzymes contain cofactors in their active sites that allow the enzymes to do redox chemistry. In enzymatic biofuel cells, the redox cofactors act as electron-transfer shuttles to transport electrons between the enzymes’ active sites and electrode surfaces. We reason that binding of DNA aptamers to the cofactors could provide a stable environment that allows the cofactor to be easily accessible to the electrode’s surface with improved electron transfer. We are focusing our efforts on the three commonly used redox cofactors: flavin adenine dinucleotide (FAD), nicotinamide adenine dinucleotide (NAD+) and pyrroloquinoline quinone (PQQ).

Using in vitro selection, we have isolated DNA aptamers that bind to PQQ. To assess the usefulness of these aptamer-cofactor complexes in biofuel cells, we conducted spectroscopic redox assays which showed that PQQ’s redox ability is not affected upon aptamer binding. We are currently using electrochemical techniques to further investigate the redox abilities of the PQQ-DNA complexes. Aptamers for FAD and NAD+ have previously been reported. We are also testing their redox abilities to compare how each cofactor is affected by aptamer binding. The results of these experiments as well as progress towards incorporating these aptamer-cofactor complexes in biofuel cells will be presented.
Biobattery with Enzymatic Cathode and Zinc Anode for Powering Neurotransmitter Sensor
Authors: Bilewicz Renata
Published: February 2020

Renata Bilewicz, Dominika Majdecka, Michal Kizling, Krzysztof Stolarczyk, Paweł Krysiński, Jerzy Golimowski,

Faculty of Chemistry, University of Warsaw Pasteura 1, Warszawa 02-093, Poland

The advantages of biobatteries include easy miniaturization and utility for powering small devices e.g. sensors, switches, watches and other electronic devices. Recently, we have shown the biobattery parameters and its application for powering a clock [1]. Our aim was to optimize the construction of the biobattery and couple it with a biosensor for neurotransmitter detection. Arylated multiwall carbon nanotubes with bound laccase are used on the cathode for the reduction of oxygen and zinc disc covered with hopeite is the anode. Arylated carbon nanotubes increase the working surface of the electrode, and provide direct contact with the active sites of laccase. The electrode substrate is carbon paper. The zinc – air sandwich biobattery works under stationary or flow conditions. Parameters and time dependencies of the flow cell were evaluated. The system including the sandwich biobattery connected with the sensor was employed for monitoring selected neurotransmitters.

K. Stolarczyk; M. Kizling; D. Majdecka; K. Zelechowska; J. F Biernat; J. Rogalski; R. Bilewicz „Biobatteries and Biofuel Cells with Biphenylated Carbon Nanotubes” J. Power Sources
2014, 249, 263–269.
On the Structure-Function Relationship of Cobalt and Manganese Oxides as Oxygen Evolving Catalysts for Light-Driven Water Electrolysis: An In-Line Synchrotron Radiation Photoelectron Spectroscopy Study
Authors: Hillebrand Philipp , Ramirez-Caro Alejandra , Bogdanoff Peter , Fiechter Sebastian
Published: February 2020

The oxygen evolution reaction (OER) represents a bottle neck in the development of sustainable light-driven production of hydrogen from water using cheap and abundant electro-catalysts. Even though metal oxide catalysts have been used for decades, the mechanism of the OER has not been fully understood yet. We investigated Cobalt and Manganese Oxide thin films in their behavior during OER using photoelectron spectroscopy (PES) and synchrotron radiation. In an in-line system we could perform cyclic voltammetry as well as potentiostatic measurements in the anodic range under well-defined inert atmospheric conditions and afterwards transfer the samples into the UHV system for PES studies, without breaking the atmosphere. The electrochemical experiments have been interrupted at several potentials by removing the electrolyte drop and XPS as well as UPS spectra have been recorded successively. Despite the fact that the cyclic voltammetry curves (CV) of amorphous CoOx layers - deposited potentiostatically on FTO glass – and crystalline α-Mn2O3 – prepared by reactive sputtering and galvanostatic deposition – differ significantly in the low potential range before the onset of the OER, the differences in the PES spectra are little. Nevertheless, we could find some shifts in the peaks that have been interpreted as a change in the oxidation state of the metal ions at the surface depending on the potential applied and associated with the appearance of new oxo-bondings.
Direct Observation of Virtual Electrode Formation By Spectromicroscopy
Authors: Siegel David A , El Gabaly Farid , Bartelt Norman , McCarty Kevin F.
Published: February 2020

Novel electrochemical solutions to problems in energy storage and transportation can drive renewable energy to become an economically viable alternative to fossil fuels. In many electrochemical systems, the behavior of a device can be fundamentally limited by the surface area of a triple phase boundary, the boundary region where a gas-phase species, electrode, and electrolyte coincide. When the electrode is an ionic insulator the triple phase boundary is typically a one-dimensional boundary with nanometer-scale thickness: ions cannot transport through the electrode, while electrons cannot be transported through the electrolyte.

Here we present direct experimental measurements of a novel electrolyte-to-electrode transition with photoemission electron microscopy, and observe that the surface of an ionically conductive, electronically insulative solid oxide electrolyte undergoes a transition into a mixed electron-ion conductor in the vicinity of a metal electrode. Our direct experimental measurements allow us to characterize this system and address the mechanisms of ionic reactions and transport through comparisons with theoretical modeling to provide us with a physical picture of the processes involved.

Our results provide insight into one of the mechanisms of ion transport in an electrochemical cell that may be generalizable to other systems.
Lithium Ion Solvation and Diffusion in Bulk Organic Battery Electrolytes from First Principles Molecular Dynamics
Authors: Ong Mitchell T. , Lordi Vincenzo , Draeger Erik W. , Pask John E.
Published: February 2020

Lithium-ion secondary batteries are commonly used to power many consumer devices such as handheld phones, laptops, portable music players, and even electric vehicles. One of the key properties that influence the performance of lithium-ion batteries is the ionic conductivity of the electrolyte (i.e., the movement of Li ions from one electrode to another). This is dependent on the speed at which Li ions diffuse across the cell and related to the solvation structure of the Li ions. The choice of the electrolyte can greatly impact both solvation and diffusivity of Li ions. In this work, we use first principles molecular dynamics to examine the solvation and diffusion of lithium ions in several bulk organic electrolytes. We find that differences in the local environment throughout the liquid can lead to solvation of Li ions by either carbonyl or ether oxygen atoms. In addition, we examine the differences in solvation of associated and dissociated Li(PF6) salts, showing that the bulky PF6 group blocks complete solvation of Li+ by solvent oxygen atoms. Finally, we calculate Li diffusion coefficients in each electrolyte, finding slightly larger diffusivities in a linear carbonate such as ethyl methyl carbonate (EMC) compared to a cyclic carbonate like ethylene carbonate (EC). Results from this work can be used to design new bulk electrolytes that will improve the performance of current Li-ion batteries.
Effect of Pressure on the Deuteron Spin-Lattice Relaxation Times and the Self-Diffusion Coefficient in Ionic Liquids
Authors: Rua Armando , Pilar Kartik , Ostrovskiy Eugene , Hatcher Jasmine , Suarez Sophia , Wishart James , Greenbaum Steve
Published: February 2020

Ionic liquids (ILs) are of considerable interest for their physical properties: negligible vapor pressure, thermal and electrochemical stability, and high ionic conductivity, thus making them attractive for applications in radioactive material handling, batteries, capacitors, and electrochemical solar cells. A large variation of physical properties of ILs results from a corresponding variation of the structure and length of the cation sidechains and choice of anion, thus allowing tunability of properties for selected applications. In this context, there is much interest in the molecular motions that control transport properties and chemical processes. In this work we present investigations of a set of ILs based on the EMIM and BMIM cations and TFSI anion, in which the cation sidechains were partially deuterated. The 2H spin-lattice relaxation times (T1) have been measured at 47 MHz in the temperature range from 240 to 370 K (Graph 1) and under hydrostatic pressure from ambient to 250 Mpa. (Graph 2) with the deuteron T1 providing a particularly sensitive probe of alkyl side-chain reorientation. Additionally the self-diffusion coefficient (D) of both cation (using 1H NMR) and anion (using 19F NMR) were conducted as a function of temperature and Pressure (Graph 3). The Arrhenius plots of T1 exhibit T1 minima, and analyzed assuming an exponential decaying correlation function (BPP model). The high pressure T1 and D measurements were carried out to determine the activation volume of alkyl chain motion. Longer alkyl chain of BMIM exhibits a pressure invariance of the relaxation time after 80 Mpa possibly related to interactions between alkyl groups on adjacent cations. Hunter College acknowledges the U.S. Office of Naval Research for supporting the NMR portion of this project. The work at BNL was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract # DE-AC02-98CH10886.
Interfacial Electronic Structure of CO Absorbed on a Platinum Electrode in Electrochemical Environment Probed by Double Resonance Sum Frequency Generation Spectroscopy
Authors: Noguchi Hidenori , Yang Shuo , Uosaki Kohei
Published: February 2020

Absorbed CO on Pt surface has attracted much interest among scientists in surface science, catalysis, and electrochemistry. Information about oxidation mechanisms of CO on Pt, which depends on geometric and electronic structures of CO/Pt interface, is important to design and develop new catalysts for various reactions including H2-O2 and direct methanol fuel cells. Small amount of CO present in H2 produced from fossil fuel readily adsorbs on Pt and inhibits H2 oxidation. Adsorbed CO is also formed when Pt is in contact with methanol solution and inhibits the methanol oxidation reaction. Compared to extensive study on CO/Pt system under ultrahigh vacuum (UHV), interfacial electronic structure of CO/Pt interface in electrochemical environment is less understood due to the difficulty in determining it in solution. Accordingly, it is very important to investigate interfacial electronic structure of CO/Pt under electrochemical condition. Because of the presence of solution, it is not possible to use techniques with electron probes, which are most powerful in UHV. Double resonance sum frequency generation (DR-SFG) spectroscopy, which is a highly surface-sensitive nonlinear optical technique with the tunable frequencies of both incident fundamental lights, i.e., visible and IR, can provide information of surface molecular and electronic structures, which is not obtained by traditional surface vibrational technique. Here, we employed DR-SFG technique to probe potential-dependent electronic structure of CO/Pt interface in methanol solution. SFG signal due to C-O stretching was observed and was dependent on frequency of visible light as a result of the energetic coupling of electronic transition with the input visible photon and/or output SF photon, i.e., double resonance effect. Furthermore, resonant visible energy linearly depended on electrode potentials. Thus, the electronic resonance could be explained by the transition from Fermi energy, Ef, of Pt to the unoccupied sigma anti-bonding state of CO.
Photocurrent Measurements at Quantum Dot Electrodes for Bioanalytical Applications
Authors: Riedel Marc , Tanne Johannes , Göbel Gero , Parak Wolfgang , Lisdat Fred
Published: February 2020

Quantum dots (QDs) allow the generation of electron-hole pairs upon illumination. When these particles are fixed to an electrode a photocurrent can be generated. This allows their use as a light-switchable layer on the surface. The QDs can not only exchange electrons with the electrode, but can also show reactions with donor or acceptor compounds in solution. This provides access to the construction of signal chains starting from an analyte molecule to be detected.

The direction and magnitude of the photocurrent depend on several factors such as electrode polarization, solution pH and composition. These defined dependencies have been evaluated with respect to the combination of QD-electrodes with enzyme reactions for sensorial purpose [1,2].

Thus, it has been found that the cofactor of many dehydrogenase-based reactions NADH can be oxidized at the illuminated QDs without applying high potentials. This provides the basis for a coupling strategy with the enzyme glucose dehydrogenase for the analysis of glucose concentrations in solution by photocurrent measurements.

CdSe/ZnS-QD-modified electrodes can also be used to follow enzymatic reactions in solution based on their capability to reduce molecular oxygen while being excited [3]. In order to develop a photoelectrochemical biosensor, glucose oxidase (GOD) is immobilized on the QD-electrode. One immobilization strategy applies the layer-by-layer-technique of GOD and a polyelectrolyte (polyallylamine hydrochloride). Photocurrent measurements of such a sensor show a clear concentration dependent behavior for millimolar glucose concentrations. Sensitivity can be influenced by the enzyme concentration and the number of layers deposited. The principle of combining QD electrodes with a layered protein architecture and light-triggered read-out can also be transferred to other enzymes such sarcosine oxidase and sarcosine detection. The sensing properties of quantum dot electrodes can be significantly influenced by additional nanoparticles giving access to the detection of other substances, but also by immobilizing multiple layers of the QDs.

In another direction of research it can be demonstrated that direct electron transfer from excited quantum dots can be achieved with the redox protein cytochrome c provided the QD surface is properly modified. This allows the detection of the protein in different concentrations and redox states, but also of interaction partners which show a defined reaction with the protein. Examples are the cyt c reduction by superoxide radicals resulting in an anodic photocurrent and the cyt c oxidation by nitrate reductase in the presence of nitrate resulting in a cathodic photocurrent .

[1] Ch. Stoll, S. Kudera, W.J. Parak, F. Lisdat, SMALL 2 (6) (2006) 741-743).

[2] K. Schubert, W. Khalid, Z. Yue, W. Parak, F. Lisdat, Langmuir 26 (2) (2010) 1395-1400

[3] J. Tanne, D. Schäfer, W. Khalid, W. J. Parak, F. Lisdat, Analytical Chemistry 83 (20) (2011) 7778–7785
From Molecular to Nanostructured Carbon Systems By Spectroelectrochemistry
Authors: Iurlo Matteo , Valenti Giovanni , Rapino Stefania , Paolucci Francesco , Marcaccio Massimo
Published: February 2020

The combination of electrochemistry and spectroscopy techniques has been widely used in different contexts both to complement physical chemical information or gain new data otherwise not so easily obtainable.

Thus, spectroelectrochemistry techniques, since the development in the 60’s of the last century has allowed to investigate the electron transfer processes in molecular systems with an increasing structure complexity as well as the electronic interactions among the various moieties in supramolecular species.1 The appearance of low-dimensional carbon nanostructures, such as nanotubes and graphenes, which represent a very promising class of new materials in the field of nanotechnology, has seen an even more frequent recourse to spectroelectrochemical investigations.2 This family of combined electrochemical and spectroscopy techniques has also been successfully used to develop sensor devices, as well as to study technological applications, as for example in the field of conducting polymers.

In this communication the interesting redox, luminescence and electrochemiluminesce properties of different species spanning from molecular species, mainly coordination complexes, to nanostructured carbon systems (single walled carbon nanotube – SWNT, graphene, planar and curved polycyclic hydrocarbons3) will be discussed together with the fundamental data obtained from the spectroelectrochemical investigations.

References:

1 Stagni, S. et al. Inorg. Chem.
2006, 45, 695.

2 (a) Iurlo, M. et al. Chem. Comm
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2008, 4867 ;

(b) Paolucci, D. et al. J. Am. Chem. Soc.
2008, 130, 7393 ;

(c) Dragin, F. ACSNano
2011, 5, 9892.

3 Valenti, G. et al. J. Phys.
Chem. C 2010, 114, 19467.