bluuebunny/crossref_metadata_2025 huggingface dataset:
Thin Film Silicon-Based Intermetallic Systems for Lithium Ion Battery Application
Authors: Schmuelling Guido , Renger Katrin , Reyes Jimenez Antonia , Meyer Hinrich Wilhelm , Winter Martin
Published: February 2020

The demand for high energy lithium-ion battery systems has increased tremendously in the last few decades.[1] The most common anode material nowadays is graphitic carbon due to its long cycle life, low cost and abundant availability. Its drawback comes within a rather low specific capacity of 372 mAh/g. [2] To meet the requirements of next generation lithium ion batteries, new anode systems with a higher theoretical capacity are needed. A promising candidate to replace graphite is silicon, as it offers a capacity exceeding 3500 mAh/g at room temperature, while still being environmentally friendly and easily available. The main challenge before implementing Si as anode material is its enormous volume expansion upon lithiation causing the electrode material to collapse, thus resulting in a short cycle life. [3]

One approach to address this issue is the use of a stabilizing matrix, in which silicon is embedded. Therefore, several different alloy or intermetallic phase systems consisting of Cr, Ni, Ti or Mg in combination with Si are investigated on their use as a stabilizing matrix for Si based anode systems. Thin films of the binary systems are obtained via a co-magnetron sputter deposition process, in which we are able to steer the composition of the system by varying different parameters like the applied RF power during deposition. The as prepared thin films are electrochemically characterized by galvanostatic cycling as well as cyclic voltammetry. Embedding silicon in different alloys or intermetallic phases drastically changes the electrochemical performance, increasing capacity retention and cycle life of the anode system in lithium ion battery application.

References:

[1] J.B. Goodenough, Accounts Chem Res, (2012).

[2] M. Winter, Chem Unserer Zeit, 33 (1999) 320.

[3] U. Kasavajjula, C.S. Wang, A.J. Appleby, J Power Sources, 163 (2007) 1003-1039.
3-D Conformal Silicon/Carbon Nanofiber-Graphene Composites for Next Generation of Li Batteries
Authors: Nazri Gholam-Abbas , Nazri Maryam
Published: February 2020

Next generation of lithium battery may use new electrode materials with significantly higher energy density to meet more demanding applications for, auto, space and marine. Silicon anode material has the highest known specific capacity, 4,200 mAh/g, more than an order of magnitude higher than the current graphite anode (372 mAh/g). We have engineered a 3-D conformal anode based on silicon anode technology with capacity exceeding 1000 mAh/g, and high capacity retention during charge-discharge cycles. The capacity retention of the composite has been optimized by engineering of support/Si interface as well as Si/electrolyte interface. Our technology includes incorporation of a nano composite of silicon coated carbon nanofiber and graphene sheets embedded in electronically conductive polymers. In this presentation we reports electron microscopy, electrochemical performance and mechanical properties of our anode composite before and after multiple electrochemical charge-discharge cycles. Applications of our new electrode in structural battery containing sulfur cathode for auto and space and marine will be discussed.
Mesoporous Carbon-Sulfur Composite Microspheres with Multiscale Morphology Control to Achieve High Areal Capacity for Lithium-Sulfur Battery Cathodes
Authors: Xu Terrence , Song Jiangxuan , Wang Donghai
Published: February 2020

Lithium-sulfur (Li-S) batteries are widely regarded as the next-generation energy storage technology, due to their high potential in energy density and a low projected cost. Practical applications of such batteries are plagued with radical challenges that mainly stem from two factors. First, both sulfur and its final lithiation product, Li2S, are insulating. Thus, the reaction kinetics is slow and often leads to a low attainable capacity. Second, active material dissolve in the electrolyte in the form of lithium polysulfides. This dissolution causes a series of problems, including loss of cathode materials by diffusion away from the cathode, collapse of the cathode structure, and the polysulfide shuttle effect. As a result, Li-S batteries commonly show fast capacity decay and low coulombic efficiency.

Herein, we report the exceptional battery performance of porous carbon-sulfur composite microspheres, PSC-S, that benefited from simultaneous control of nanostructure and microscale particle morphology. The porous carbon microspheres (PSC) was synthesized as the sulfur host,by combining emulsion polymerization and evaporation-induced self-assembly (EISA) process, with a good control of both pore structure and microscale particle morphology. Such material not only demonstrated superioty in attainable capacity, but also in several other critical parameters for the development of high-energy Li-S batteries. PSC-S composite boasts a high tap density of 1.08 g/ml and contains 75 wt.% sulfur embedded into the mesopores of its carbon framework. At a high sulfur loading of 5 mg-S/cm2 and 60wt.% sulfur content in the electrode, this material delivers both high gravimetric and high volumetric capacity with excellent retention. Carbon nanotubes (CNTs) can also be readily incorporated into the microspherical structure in the synthesis process to form a porous spherical carbon-carbon nanotube-sulfur composite (PSC-CNT-S). CNT incorporation effectively raises the conductivity of the composite, and thus significantly improves its high-rate performance. At a high current density of 2.8 mA/cm2, an initial capacity of 1100 mAh/g and a reversible capacity of 700 mAh/g after 200 cycles were achieved in PSC-CNT-S. The resultant areal capacity of over 3.5 mAh/cm2 is much higher than in previous reports of Li-S cathodes fabricated using coating techniques.
Electrochemical Characteristics of PEO-Based Ternary Polymer Electrolyte for Lithium-Oxygen Batteries
Authors: Kim Yong-Han , Jadhav Harsharaj S. , Kalubarme Ramchandra S. , Park Chan-Jin
Published: February 2020

The biggest advantage of metal-air batteries is their high theoretical energy density. Furthermore, they use oxygen from nature and exhibit eco-friendly characteristics. Lithium-air battery is recognized as a potential candidate for the application in EV. In particular, lithium-air battery shows a similar theoretical energy density (11,140 wh/kg) to that of gasoline (13,000 wh/kg). However, its performance has still been limited by problems such as the stability of lithium metal. In practical applications for electric vehicles, air containing moisture should be used. The exclusion of water from air is difficult using a conventional filter, hence lithium metal can react vigorously with the water from moisture and make the battery unsafe for use. Thus, the protection of Li-metal from water is the critical problem for rechargeable Li-air batteries. The other prominent problem for rechargeable lithium-air batteries is the lithium dendrite formation during repeated charge and discharge cycles; the dendritic Li-metal causes an internal short circuit. To overcome this problem, the key component of aqueous type lithium-air batteries is the water stable LISICON type lithium conducting solid electrolyte, since lithium metal reacts severely with water. However, the LISICON type solid electrolytes are not stable in contact with Li-metal. Thus, interlayers are needed between the solid electrolyte and Li-metal, which must be chemically stable in contact with Li-metal during operation and should have high lithium ion conductivity. PEO-based polymer electrolytes are best candidates as an interlayer. However, conductivity of PEO-based electrolytes is still much lower compared to that of liquid and inorganic solid electrolytes. The PEO-LiTFSI electrolyte has the ionic conductivity of the order 10-6 S×cm-1 at room temperature. In order to use PEO-LiTFSI as an interlayer, its ionic conductivity needs to be improved. In the present study, an ionic liquid has been added to PEO-based polymer electrolyte to increase its ionic conductivity.

The ionically conducting polymer membrane was prepared by casting technique. Microstructure and morphology of surface were obtained by FE-SEM and optical microscope. The samples were obtained by optimizing the ratio of PEO, Li salt and ionic liquid. The ac impedance of symmetric cells were measured in frequency range of 1 Hz ~ 1 MHz. The stability test indicates that the PEO based polymer electrolyte improves the stability between the Li-metal and solid electrolyte with improved conductivity. The ac impedance and charge discharge performance measurements for Li-O2 cell employing the polymer and LAGP solid electrolyte layers for the protected lithium electrode were also carried out. The Li-O2 cell with the developed polymer electrolyte exhibited a favorable discharge-charge performance.
Magnesiothermic Reduction of Structured Silica As Anode for Lithium Ion Batteries
Authors: Schrandt Matthew , Smirnova Alevtina , Cook Rob , Rhine Wendell , Kolla Praveen
Published: February 2020

In lithium ion batteries, Si-based anodes possess the highest specific capacity from four to 10 times greater than graphite [1, 2]. However, up to 400% volume expansion of Si during lithiation results in anode pulverization due to mechanical stresses. To avoid mechanical degradation of silicon, the critical value of the silicon particle size/wall thickness should be below the required threshold of <50nm [3,4]. Thus, it is crucial to maintain the silicon particle size in this range. The second major requirement for silicon anode in lithium ion batteries is to have the second conductive phase, e.g. graphite or graphene, in the form of a flexible coating that can withstand lithiation-delithiation without deterioration of the carbon phase. The goal is to develop a silicon-based anode that can withstand lithiation-delithiation cycles without mechanical degradation.

Through using structured silica precursors, the goal is to reduce the silica to silicon while maintaining its structure and porosity and thus mitigate the degradation during cycling. Two types of silicon oxide precursor materials that meet these requirements have been evaluated, among them hollow silica microspheres from 3M and silica aerogel from Aspen Aerogels. The major steps including silica synthesis and magnesium vapor reduction will be discussed.

Preparation of Si precursor materials has been performed by magnesium reduction followed by the removal of unnecessary impurities such as magnesium oxide and silica by washing the material in 1M HCl followed by 1% HF. Preliminary data from XRD confirms Si formation from the magnesiothermic reduction. SEM, TEM, EDS, BET, XRD, and Raman spectroscopy will be presented to analyze the structure and morphology of the materials. Structure dependent electrochemical properties such as cyclic voltammetry, cycleability, galvanostatic discharge, and cycle stability will be discussed.

Fig. 1: (A) TGA for 3M silica microspheres (iM30K) and (B) TGA for Aspen Aerogels’ SiO2 aerogel with Mg with the corresponding SEM images (C) 3M microspheres and (D) Silica aerogel precursors. (E) XRD for reduced SiO2 aerogel: top profile is fully washed reduced Si, middle profile is after reduction but before washing, and bottom profile is for a Si nanopowder reference to vindicate successful Si reduction from SiO2.

References:

[1] A. Kraytsberg, Y. Ein-Eli, J. of Power Sources, 196 (2011) 886.

[2] W. J. Zhang, J. of Power Sources, 196 (2011) 13.

[3] X. H. Liu, L. Zhong , S. Huang, S. X. Mao, T. Zhu, J. Y. Huang, ACS Nano, 6 (2012) 1522.

[4] U. Kasavajjula, C. S. Wang, A. J. Appleby, J. of Power Sources, 163 (2007) 1003.
The Interface Kinetics of La2NiO4+
δ-Coated La0.6Sr0.4Co0.2Fe0.8O3-
δ Cathode
Authors: Zhang Xinxin
Published: February 2020

Infiltration technique was widely used in SOFCs electrode to enhance the cell performance. However, the oxygen transport in the cathode, especially between the extra interfaces, was still not well understood. The oxygen surface and interface exchange kinetics of La2NiO4+
δ(LNO)-coated La0.6Sr0.4Co0.2Fe0.8O3-
δ (LSCF) have been detected by electrical conductivity relaxation method. The dense LNO layer was coated on LSCF surface to simulate the infiltrated cathode. The electrical conductivity relaxation behaviors of LNO-coated LSCF were measured at high temperature under different oxygen partial pressure from 0.2-0.02 atm. The ECR data showed that both the oxygen surface and interface exchange coefficient increased with oxygen partial pressure. The reaction rate constants for surface oxygen reduction and interface oxygen transfer were investigated based on the oxygen exchange coefficient data under different conditions, which were the fundamental knowledge for the infiltrated cathode surface and interface reaction mechanism.
Nb2O5 anchored-Graphene Hybrid Nanocomposites As High Performance Anode for Lithium Ion Batteries
Authors: Arunkumar P , Ashish A. G , Sarang Som , Abhin S , Shaijumon Manikoth M
Published: February 2020

With the ever-increasing demand for energy storage, lithium ion battery has been an attractive technology, which has revolutionized the portable electronic industry and has recently become popular in the electric vehicle market, due to their superior energy density [1]. Innovative materials chemistry has been the key to various advancements in lithium rechargeable battery [2]. Various transition metal oxides have been widely studied as electrode materials for rechargeable lithium-ion batteries because of their high theoretical capacity, safety, environmental benignity and low cost [3]. Recently, there is great interest in developing graphene-based nanocomposites as high performance electrodes, owing to the multifunctional attributes of such electrodes [4]. Such materials designs are expected to offer marked improvements in energy and power densities.

Here, we present the synthesis of Nb2O5 anchored graphene hybrid nanocomposites through simple hydrothermal method and their application as high performance anodes for lithium ion battery. Self-supported nanostructured electrode with graphene as support and with homogenously anchored Nb2O5 nanoparticles has been obtained as shown in Figure 1a. Nanostructured hybrid electrodes have been characterized by X-ray diffraction (XRD), Scanning and Transmission Electron Microscopy (SEM/TEM). Cyclic voltammetry and Galvanostatic charge-discharge cycling measurements have been performed using hybrid nanocomposites as positive electrodes in 1 M LiPF6 –EC/DMC electrolyte vs.Li metal negative electrodes. Electrochemical studies of these hybrid electrodes show improved reversible capacities and power capabilities.

Conducting graphene sheets improves the kinetics of the lithium ion and electron transport, and conductivity of the metal oxide by the enhanced particle-particle contact and buffering action during lithiation. Synergistic effect of both Nb2O5 nanocrystals anchored onto conducting graphene layers showed reversible capacity of 192 mAhg-1 up to 50 cycles with C/10 rate, indicating two electron transfer process in LixNb2O5
(Figure 1b). Nb2O5anchored graphene sheets with superior electrochemical performance of high reversible capacity, enhanced rate capability, including an improved electronic and ionic conductivity, can be ideal anodes for high performance lithium ion battery.

Figure1: (a) TEM image of Nb2O5-anchored graphene nanocomposites; (b) Charge-discharge galvanostatic curves for Nb2O5-anchored graphene electrtodes cycled at a rate of C/10 versus Li and using a charge cut off voltage of 1 V.

References

J. -M. Tarascon, M. Armand, Nature, 414 (2001), 359.

P. G. Bruce, B. Scrosati, J. -M. Tarascon, Angewandte Chemie International Edition, 47, (2008), 2930.

P. Poizot, S. Laruelle, S. Grugeon, L. Dupont & J-M. Tarascon, Nature 407, (2000), 496.

Z.-S. Wu, W. Ren, L. Xu, F. Li, H.-M. Cheng, ACS Nano 5, (2011), 5463.
Mn(II) Deposition on Anodes and Its Effect on Capacity Fade in Spinel LiMn2O4-Carbon System
Authors: Lu Jun , Zhan Chun , Kropf Jeremy , Wu Tianpin , Jansen Andrew N. , Sun Yang-Kook , Qiu Xinping , Amine Khalil
Published: February 2020

Dissolution and migration of manganese from cathode lead to severe capacity fading of Li2MnO4-carbon cells. Overcoming this major problem requires better understanding of the mechanism of manganese dissolution, migration, and deposition. Here, we apply a variety of advanced analytical methods to the study of LiMn2O4 cathodes cycled with different anodes. We provide solid evidence, for the first time, that oxidation state of manganese deposited on the anodes is +2, which differs from the results reported earlier. The results also indicates that a metathesis reaction between Mn(II) and some species on the solid-electrolyte interphase takes place during the deposition of Mn(II) on the anodes, rather than a reduction reaction that leads to the formation of metallic Mn otherwise, as speculated in earlier studies. The concentration of Mn deposited on the anode increases gradually with cycles; this trend is well correlated with anode’s rising impedance and capacity fading of the cell.
Understanding the Role of Ni in Stabilizing the Lithium Rich Cathode Material, Li[Nixli(1-2x)/3Mn(2-x)/3]O2 (0 ≤x≤0.5)
Authors: Hy Sunny , Cheng Ju-Hsiang , Pan Chun-Jern , Chen Jing-Ming , Hwang Bing-Joe
Published: February 2020

The class of lithium rich cathode material, Li[NixLi(1−2x)/3Mn(2−x)/3]O2 (0≤x≤0.5), shows great potential as a positive electrode for the next generation of high-energy materials for lithium ion batteries. These materials exhibit capacities exceeding 270 and over 300 mAh/g depending on the transition metal incorporated into the material structure[1]. However, over several cycles the material exhibits severe capacity deterioration and voltage decay. [2]. This is attributed to the instability of the material to change from layered to more spinel-like and the separation of the transition metals inducing migration of these transition metals to the bulk[3]. It has been suggested that Ni plays an important role in stabilizing this class of material [4]. In this study we try to elaborate further on the role of the secondary transition metal in stabilizing the structure and its relationship to oxygen by using soft and hard x-ray absorption spectroscopy to probe the electronic and local structural changes at different charged and discharged states for the Li[NixLi(1−2x)/3Mn(2−x)/3]O2 for x=0 ,0.2, and 0.5. The O K-edge, transition metal L II,III- edges were performed both in partial electron yield and fluorescent yield modes that probe the surface and bulk, respectively. The transition metal K-edges were performed to observe the oxidation states. Observation of the O-K edge pre-edge intensity increase can be attributed to the Ni redox couple. Closer examination of the lower and higher photon energy bands reveals a decrease of the 3d versus 4sp intensity bands at the charged state for the oxygen activated stoichiometry, x=0 and x=0.2 indicating hybridization from the reductive coupling mechanism. Mn L II,III-edges (figure) shows that with decreasing Ni content, the changes of the electronic structure from layered to more spinel-like occurs much earlier on and Mn redox couple participation. The results of the soft and hard x-ray absorption spectroscopy suggest the oxidation of oxygen will induce the reduction of Mn with an oxidation state between 3 – 4+ in order to stabilize the distorted structure and maintain the overall charge balance. When a secondary metal, nickel in this case, is incorporated, it will alleviate the changes by reducing in lieu of Mn thus maintaining the original non-distorted 4+ oxidation state.

[1] H. Yu, H. Zhou, The Journal of Physical Chemistry Letters, 4 (2013) 1268-1280.

[2] M. Gu, I. Belharouak, J. Zheng, H. Wu, J. Xiao, A. Genc, K. Amine, S. Thevuthasan, D.R. Baer, J.-G. Zhang, N.D. Browning, J. Liu, C. Wang, ACS Nano, 7 (2012) 760-767.

[3] S. Hy, W.-N. Su, J.-M. Chen, B.-J. Hwang, The Journal of Physical Chemistry C, 116 (2012) 25242-25247.

[4] D. Kim, J.R. Croy, M.M. Thackeray, Electrochemistry Communications, 36 (2013) 103-106.
Silicon-Immobilized Ferrocenyl Monolayers for All-Solid Molecular Charge Storage and Logic
Authors: Fabre Bruno , Zuilhof Han , Hapiot Philippe , Pujari Sidharam , Scheres Luc , Li Yan
Published: February 2020

The functionalization of technologically relevant conducting surfaces, such as oxide-free, hydrogen-terminated silicon (H-Si), with high-quality ferrocene (Fc) [1] and metal-complexed porphyrin [2] -terminated monolayers has been demonstrated to be a powerful bottom-up approach for the fabrication of electrically addressable charge-storage devices with low-power consumption.

Compared with metalloporphyrins, Fc is a much smaller molecule (average diameter of tetraphenylporphyrin and Fc are about 18 and 6.6 Å, respectively), and consequently is immobilized on silicon with a higher surface coverage, which gives rise to higher charge densities. Indeed, the surface coverages reached for high-quality ferrocenyl monolayers are in the range of (2.0–5.0) ×10-10 mol cm-2. This does not only allow for an extremely fast electron communication between the electroactive groups [3], but also yields charge densities in the range of 20–50 mC cm-2. These values are thus much higher than those measured for Si/SiO2 capacitors currently used in Dynamic Random Access Memories (5–10 mC cm-2).

Very recently, we also demonstrated that tailor-made micrometer-sized patterns of such redox-active monolayers could behave as light-activated molecular memory cells operating at low voltages with unprecedented capacitance performances [4]. The characteristics of this stimuli-responsive device are of great scientific interest for data-processing applications, such as redox-based Boolean logic gates [5]. In our system, the switching of the capacitance upon light irradiation that is observed only at a certain electrical potential constitutes the principle of all-solid two-input AND logic gate without the need of chemical inputs in solution. Such performances can be ascribed to the judicious combination between a photoswitchable conducting/insulating silicon substrate and high-quality microstamped redox-active assemblies.

[1] Fabre, B. Acc. Chem. Res.
2010, 43, 1509–1518.

[2] Lindsey, J. S.; Bocian, D. F. Acc. Chem. Res.
2011, 44, 638–650.

[3] a) Hauquier, F.; Ghilane, J.; Fabre, B.; Hapiot, P. J. Am. Chem. Soc.
2008, 130, 2748–2749. b) Zigah, D.; Herrier, C.; Scheres, L.; Giesbers, M.; Fabre, B.; Hapiot, P.; Zuilhof, H. Angew. Chem. Int. Ed.
2010, 49, 3157–3160.

[4] Fabre, B.; Li, Y.; Scheres, L.; Pujari, S. P.; Zuilhof, H. Angew. Chem. Int. Ed.
2013, 52, 12024-12027.

[5] de Ruiter, G.; van der Boom, M. E. Acc. Chem. Res.
2011, 44, 563–573.
Nonlinear Vibrational Study of Solvent Adsorption on the Cathode Surface of Li-Ion Batteries
Authors: Ye Shen , Yu Le , Liu Huijin , Qiao Yu , Osawa Masatoshi , Kuwata Naoaki , Kawamura Junichi
Published: February 2020

To improve the performance of Li-ion batteries, it is important to understand the structures on the electrode/solution interface. In the present study, a surface sensitive nonlinear vibrational spectroscopic technique, sum frequency generation (SFG),1 was employed to evaluate the molecular structures of the solvent adsorption at the LiCoO2 cathode surface of the Li-ion battery, rather than those of the solvent in the bulk solution obtained by previous studies.

A LiCoO2 thin film was deposited on the CaF2 substrate surface. A broadband SFG system using a tunable infrared pulse (2.5~10mm) and a visible pulse (800nm) was used to characterize LiCoO2 surface in contact with electrolyte solutions consist of carbonate solvents, such as ethylene carbonate (EC), propylene carbonates (PC), diethyl carbonate (DEC) and dimethyl carbonate (DMC).2,3

Figure 1a shows the sps-polarized SFG spectrum at the LiCoO2 contacting with EC (middle panel, circles) and the fitting result (solid trace) in the infrared frequency region between 1700 and 1850 cm−1. As SFG does not occur in a homogenous bulk solution with inversion symmetry, the present result suggests that the EC molecules align on the LiCoO2 surface with a certain structure. The bottom panels are deconvoluted bands for the SFG spectrum. The upward and downward peaks represent the modes with reversed orientations as the schematic model shown in inset. These modes optically interfere with nonresonant signal cNR
(2) as well as themselves, generating constructive (upward) and destructive (downward) peaks depending on the adsorption geometry of the molecules. The top panel in Fig. 1a shows SFG spectrum after removing contribution from cNR
(2). Based on the spectral analyses, two adsorption geometries of EC molecules on LiCoO2 surface have been observed by the present SFG measurement, by pointing the C=O groups away from or towards the electrode surface, respectively.

Solvent adsorption has also been investigated in the other solvent solvents or their mixtures. Figure 1b shows the SFG spectra of different carbonate solutions after removal of cNR
(2). It is found that the SFG spectra of the mixed solvents containing EC molecule are quite similar to that of EC solvent. This implies that the preferential adsorption of EC molecules on the LiCoO2 surface compared to the linear carbonates of DEC and DMC, with a largely different molecular proportion from that in the mixed solution bulk.3 The present results is expected be useful to understand the initial stage for the solid electrolyte interphase (SEI) formation on the cathode surface.

References

[1] Shen, Y. R. The Principles of Nonlinear Optics; Wiley: N. Y., 1984; [2] Liu, H.; Tong, Y.; Kuwata, N.; Osawa, M.; Kawamura, J.; Ye, S. J. Phys. Chem. C
2009, 113, 20531. [3] Yu, L.; Liu, H. J.; Wang, Y.; Kuwata, N.; Osawa, M.; Kawamura, J.; Ye, S. Angew. Chem. Int. Ed.
2013, 52, 5753.
Oxygen Reduction for Fuel Cells: Mechanistic Studies and the Design of New Catalysts
Authors: Gewirth Andrew , Barile Christopher , Tse Edmund , Hoang Thao
Published: February 2020

In this talk, we discuss aspects of our work related to the structure and reactivity of electrode surfaces. We report on our efforts directed at establishing the mechanism of oxygen and peroxide reduction on many different metal surfaces.

First, we evaluate Pt-Pt bond strains developing during the oxygen reduction reaction (ORR) as determined by in situ EXAFS measurements obtained with and without the presence of O2 The change in Pt-Pt bond distance in carbon-supported nanoclusters under O2 is found to be a maximum of 0.23 (±0.15) % to 0.40 (±0.20) % larger than under a N2 atmosphere. The Pt-Pt surface bond strains are discernible at macroscopic scales in cantilever-based bending measurements of Pt thin films under O2 and Ar over the same potential range. EXAFS - measured Pt-Pt bond strains correspond to a stress thickness and are well matched to the experimentally determined values obtained using the cantilever bending method. The electrochemical stress method is useful in evaluating reactivity in other contexts, such as the oxygen evolution reaction (OER).

The understanding derived from the mechanistic work provides directions for synthesis of advanced catalysts for oxygen reduction. In particular, we have synthesized a series of bio-insipired metal coordination polymers exhibiting oxygen reduction activity. Complexes exhibit modest activity in acid, but have good activity in base where the per metal activity at maximum power is greater than that afforded by Pt. Extension of our initial synthetic work shows that a µ-η1-η1 motif for oxygen coordination gives a lower overpotential relative to the more structurally defined µ-η2-η2 geometry, probably because dioxygen coordinated in the former way is more susceptible to nucleophilic attack. Recent efforts directed at mimicking the trinuclear site in the multicopper oxidases will be described.

Finally, we use the catalyst motif developed for ORR studies in a novel proton transfer switch, the operation of which will be described.
Polyaniline-Supported Atomic Gold Electrodes: Comparison with Macro Electrodes
Authors: Josowicz Mira A , Jonke Alex P , Janata Jiri , Schwartz Ilana T.
Published: February 2020

Under precisely controlled conditions, atomic gold electrodes with even or odd number of Au atoms per polyaniline repeat unit (Pt/PANI/AuN for 0 \ N \ 7) were prepared. The electrochemical behavior of these new electrodes is compared with that of macro gold and PANI coated platinum electrodes by testing electrochemical oxidation of n-propanol and iso-propanol. This study allowed us to separate the behavior dominated by that of macroscopic gold in strongly alkaline medium and by that of the quantized odd–even effect of atomic gold. Within this overarching scope, there is a specific oxidation pattern attributable to the structural differences between the two isomers of propanol. The significance of this research lies in the recognition of high specific catalytic activity of atomic gold, which is at least three orders of magnitude higher than that of bulk gold for the oxidation of alcohols. It points to a substantial saving of the precious metal without the loss of catalytic activity, which is important in fuel cells and in other energy conversion device applications.
Theoretical and Experimental Studies on Electrocatalytic Activities of Boron Nitride
Authors: Uosaki Kohei , Elumalai Ganesan , Noguchi Hidenori , Masuda Takuya , Lyalin Andrey , Nakayama Akira , Taketsugu Tetsuya
Published: February 2020

Oxygen reduction reaction (ORR) is one of the most important processes in fuel cells as well as in biological system. Pt based electrocatalyst is the most prominent ORR catalyst showing low over potential. Major challenges to commercialize the Pt based electrocatalyst are its high cost, less abundance, and still sluggish kinetics. These problems can be addressed by using metal-free carbon materials doped with various elements such as N and B. N- and B-doped carbon materials have been demonstrated to be effective metal free ORR catalyst. Therefore, one may expect that the consecutive substitution of carbon atoms in graphene by B- and N-atoms will result in an increase of ORR activity. In extreme case, if all the carbon atoms in graphene are substituted by B- and N-atoms, hexagonal boron nitride (h-BN) monolayer, which is an insulator with a wide band gap (˜5.8eV), can be obtained. Theoretical investigations show that atomically thin h-BN becomes semiconducting if some defects are introduced or it is placed on metal substrates and may acts as electrocatalyst for ORR.1, 2 Here, we studied the electrocatalytic behavior of BN of several shapes such as nanotube and nanosheets (BNNS) supported on Au toward ORR by using typical three electrode rotating disk electrode (RDE) in O2 saturated 0.5M H2SO4solution. The overpotential for ORR at Au electrode was reduced in all cases, confirming the electrocatalytic activity of BN, but the most significant effect was observed when BNNS was used as an electrocatalyst where ca. 280 mV reduction of overpotential was achieved.

References

1. A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, Phys. Chem. Chem. Phys., 15, 2809-2820 (2013) .

2. A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, J. Phys. Chem. C., 117, 21359-21370 (2013).
Bio-Inspired Electrocatalysis of Oxygen Reduction
Authors: Chlistunoff Jerzy , Sansiñena José-María
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are clean power sources, where a fuel is “burned” by means of two electrocatalytic reactions occurring simultaneously on the anode (fuel oxidation) and the cathode (oxygen reduction reaction, ORR) of the cell. Platinum is the most frequently used cathode catalyst, but its world resources are limited and the platinum market is volatile. These factors virtually prevent commercialization of PEFCs for transportation purposes.

In biological environments, oxygen reduction is catalyzed by enzymes and some enzymatic oxygen reduction catalysts, e.g., copper laccase exhibit the catalytic activity superior to that of platinum.1While practical application of copper laccase is not possible due to temperature, pH, and other limitations, its excellent catalytic activity demonstrates that it is possible to develop non-precious metal based ORR electrocatalysts with higher activities than Pt.

It is well known that the biological function and activity of heme proteins, which contain Fe coordinated by a porphyrin ring, can be modified through axial coordination of the metal center. These phenomena have become a foundation of our approach to create an effective bio-inspired oxygen reduction catalyst. As opposed to copper laccase, porphyrin based ORR catalysts exhibit quite reasonable stability in strongly acidic environments, such as those in PEFCs. In our talk we will present new results in our recent study on the effects of axial coordination of the iron center on oxygen reduction catalysis by selected iron porphyrins.2Special emphasis will be placed on the correlations between redox and electronic properties of the porphyrins determined using spectroelectrochemical techniques (Fig. 1) and their catalytic activity in ORR.

Acknowledgements

The financial support from the University of California is gratefully acknowledged.

References

1) H. Schweiger, E. Vayner, and A. B. Anderson, Electrochemical and Solid-State Letters, 8(11) A585-A587, 2005

2) J. Chlistunoff, J.-M. Sansiñena, Effects of Axial Ligation and Electron Donors on Oxygen Reduction Catalysis by Metalloporphyrins, 224th ECS Meeting, San Francisco, CA, 10/27/2013-11/01/2013
Characterization and Functional Improvements of Roll-to-Roll Manufactured Biofuel Cells
Authors: Tuurala Saara Anniina
Published: February 2020

A power source integrated with printed electronics could have a remarkable market potential in several mass-marketed consumer products, e.g. as package integrated functionalities or as part of diagnostic devices. One important requirement is that the power source should be biodegradable or possible to incinerate with normal household waste. This demand is not easily met by traditional battery technology. In addition, the material costs of the power source should be reasonable, should not significantly increase the price of the product, and the cells should be made from roll-to-roll (R2R) in a cost effective way.

Enzymatic biobatteries are a potential alternative to traditional batteries for low power applications. Due to the use of enzymes as catalysts and harmless organic fuels, biobatteries are non-toxic, disposable and renewable. Hence, they have potential to be developed to meet the demands that were addressed before.

In the past years we have studied printing of enzymatic layers, their electrochemical performance, functionality, and stability [1-5]. Mass manufacturing of printed enzymatic electrodes was presented in 2012 by Smolander et al. [6]. We demonstrated R2R processability of biologically active materials and the manufacturing of anodic and cathodic layers by rotary screen printing using VTT’s ROKO pilot scale printing line. The R2R manufacturing was successful and functional enzymatic power sources were constructed using these electrodes.

The characterization of the bio power sources indicated two main challenges: stability of the electrodes and moisture control of the power source. In this presentation the stability of the electrodes will be presented as well as improvements of the cell performance by adjusting the ink and activation electrolyte, as well as running conditions. The running life time was increased by adding moisture absorbing material into the power source. After these various optimization procedures app. 1.5 fold increase in the maximum power density and app. 4 fold increase in the energy output was achieved.

Acknowledgments

The support by Tekes, the Finnish Funding Agency for Technology and Innovation (co-funded by industrial companies) is acknowledged.

References

[1] M. Smolander et al., Enzyme and Microbial Technology 43 (2008) 93–102

[2] S. Tuurala et al., ECS Transactions, 25 (33) 1-10 (2010)

[3] P. Jenksins et al., Bioelectrochemistry 87 (2012) 172-177

[4] P. Jenkins et al., Enzyme and Microbial Technology 50 (2012) 181– 187

[5] S. Tuurala et al., Electroanalysis 2012, 24, No. 2, 229 – 238

[6] M. Smolander et al., Abstract #1453, 221st ECS Meeting, 2012
Functional Interfaces for Biomimetic Energy Harvesting: CNT-DNA Matrix for Enzyme Assembly
Authors: Hjelm Rachel M , Garcia Kristen , Babanova Sofia , Artyushkova Kateryna , Banta Scott , Atanassov Plamen
Published: February 2020

The development of 3D structures exploring the properties of nano-materials and biological molecules allows us to mimic natural metabolic processes such as Krebs or Calvin cycle by creating “artificial” metabolic pathways called metabolons. The utilization of metabolons in biomimetic energy-harvesting systems leads to increased fuel oxidation and as a result increased Columbic efficiency. The specific order and minimized distance between the enzymes from those metabolons are the main reasons for subsequent and more effective fuel consumption.

In this study a complex carbon nanotubes (CNTs) – DNA matrix for specific enzyme immobilization was created. It composed of “brush” type aligned CNTs covalently attached on electrochemically modified gold surface. This forest like CNTs structure was used as a substrate for the development of a DNA scaffold. This DNA scaffold had a designed sequence that allows strong attachment of DNA to the CNTs surface by wrapping the nanotubes through pi-pi stacking and at the same time has a unique nine base pair motif that was further hybridized. The hybridized part of the DNA was used to specifically attach zinc finger (Znf268) that was genetically fused to small laccase (SLAC).

Zinc fingers are small protein structural motifs that can recognize dsDNA and specifically bind to it. We used this property to control the SLAC immobilization by fusing the Znf268 to the enzyme and attaching it to the CNTs-DNA scaffold (Fig. 1). Due to the specific interactions of zinc fingers with DNA we will be able to immobilize enzymes in particular order and distance creating metabolons.

Figure 2 shows Atomic Force Microscopy (AFM) images of the gold surface at the different stages of its modification to the creation of the CNTs forest. The modification procedures were also confirmed with x-ray photoelectron spectroscopy (XPS).

To prove the concept we used SLAC, which is an enzyme from the family of well-known multi-copper oxidases that are able to reduce oxygen and form water [1]. The enzyme was immobilized by the described approach and characterized by XPS (Fig. 3). The presence of copper in the XPS spectrum unambiguously proofs the success of the immobilization procedure. The developed herein approach for specific enzyme immobilization can be applied for all types of enzymes for the development of bio-cathodes as well as bio-anodes in the design of energy-harvesting systems.

The developed herein approach for specific enzyme immobilization can be applied for all types of enzymes for the development of bio-cathodes as well as bio-anodes in the design of energy-harvesting systems.

[1] Szilvay, G., S. Brocato, D. Ivnitski, C. Li, P. De La Iglesia, C. Lau, E. Chi, M. Werner-Washburne, S. Banta P. Atanassov Chem. Commun., 2011, 47, 7464–7466.
Heterogeneous Proton Transfer As an Explanation for the Unusually Thick Cyclic Voltammograms and Unusually Small Second Redox Wave of Para-Quinones in Aprotic Solvents
Authors: Staley Patrick Andrew , Smith Diane K.
Published: February 2020

Quinones are well-known to undergo two reversible reductions at glassy carbon electrodes in aprotic solvents, first to a radical anion and then to a dianion, eq 1. Despite 50+ years of voltammetric investigation of this chemistry, two unusual features of quinone voltammetry—that the second redox wave is smaller than the first, and that the area between the two waves is thicker than CV simulations say it should be—was typically ignored until Gupta and Linschitz made note of the difference in height of the redox waves in 1997.1 The current explanation for the unequal wave heights, advanced by Macías-Ruvalcaba and Evans in 2010,2 is that some of the radical anion is trapped in the form of a pi dimer in solution. Macias-Ruvalcaba and Evans hypothesize that this dimer can be reduced at the same potential as the monomer radical anion, but only by 1 e- per dimer, resulting in smaller current than expected. There currently is no explanation in the literature for the thickness between the two waves.

In this study, concentration dependence of the CVs of differently substituted quinones showed that radical dimerization cannot be a general explanation for the small second redox wave. In some cases the thickness between the waves appears as its own quasi-reversible wave. Addition of phenols to a quinone solution produces a quasi-reversible wave at the same potential due to hydrogen bonding to the radical anion. The McCreery lab showed that oxide content of the surface of glassy carbon can change its chemistry through the presence of functional groups such as phenols.3 In low concentration duroquinone studies, different surface treatments show that with higher oxide content a new wave grows in that is at the same potential as the wave seen in a 1:1 addition of naphthol to the quinone redox system. This indicates that the odd thickness in quinone CV’s may be due to hydrogen bonding of the quinones to phenolic groups on the glassy carbon surface followed by proton transfer.

REFERENCES

1. Gupta, J. ;Linschitz, H. Hydrogen Bonding and Protonation Effects in Electrochemistry of

Quinones in Aprotic Solvents. J. Am. Chem. Soc., 1997, 119(27), 6384-6391.

2. Macías-Ruvalcaba, N.; Evans, D. Association Reactions of the Anion Radicals of Some

Hydroxyquinones: Evidence for the Formation of π and σ–Dimers As Well As a Neutral-Anion

Radical Complex. J. Phys. Chem. C, 2010, 114(2), 1285-1292.

3. Kuo, T.; McCreery, R.L. Surface Chemistry and Electron-Transfer Kinetics of Hydrogen-Modified Glassy Carbon Electrodes. Anal. Chem. 1999, 71, 1553-1560.
PBI-Based Membranes for High Temperature Pemfcs: Proton Transport and Functional Properties
Authors: Mustarelli Piercarlo
Published: February 2020

High-temperature (100-200C, HT) PEMFCs are attracting for their applications in automotive. The development of devices operating in this temperature range likely requires the substitution of NafionTM with other polymers which are chemically and electrochemically stable, and can offer the required proton conductivity level (>10-2 ohm-1 cm-1) under low humidity conditions.

Polybenzimidazole and its derivatives are good candidates to work as the electrolyte in HT-PEMFCs. In the last years we developed several PBI-based membranes, including moieties with more nitrogen atoms in the main chain (1, 2), with ether oxygens (3), sulphonic groups (4), fluorine atoms and also (nano)composites (5-8). In this paper, we report on the functional properties of this class of electrolytes, and discuss the proton transport mechanisms at different doping conditions.

Carollo, E. Quartarone, C. Tomasi, P. Mustarelli, F. Belotti, A. Magistris, L. Garlaschelli and P.P. Righetti, J. Power Sources, 160 (2006) 175-180.

E. Quartarone, A. Magistris, P. Mustarelli, S. Grandi, A. Carollo, G.Z. Żukowska, J.E. Garbarczyk, J.L. Nowiński, C. Gerbaldi, S. Bodoardo, Fuel Cells 9 (2009) 349-355.

S. Angioni, P.P. Righetti, E. Quartarone, E. Dilena, P. Mustarelli, A. Magistris, International Journal of Hydrogen Energy, 36 (2011) 7174-7182.

S. Angioni, D. C. Villa, S. Dal Barco, E. Quartarone, P. P. Righetti, P. Mustarelli, J. Mater. Chem. A, accepted. DOI: 10.1039/C3TA12200J

P. Mustarelli, E. Quartarone, S. Grandi, A. Carollo and A. Magistris, Advanced Materials 20 (2008), 1339-1343.

E. Quartarone, P. Mustarelli, A. Carollo, S. Grandi, A. Magistris, C. Gerbaldi, Fuel Cells 9 (2009) 231-236.

V. Kurdakova, E. Quartarone, P. Mustarelli, A. Magistris, E. Caponetti, M.L. Saladino, Journal of Power Sources, 195 (2010) 7765-7769.

V. Di Noto, M. Piga, G.A. Giffin, E. Quartarone, P.P. Righetti, P. Mustarelli, A. Magistris, Physical Chemistry Chemical Physics, 13 (2011) 12146-12154.
Redox-Gated Molecular Memory Devices Based on Dynamic Doping of Polythiophene
Authors: McCreery Richard Louis , Das Bikas , Pillai Rajesh , Pekas Nikola , James David B
Published: February 2020

A solid state electrochemical cell resembling a field effect transistor will be described which can act as a nonvolatile memory element. “Write” and “Erase” pulses cause oxidation of a polythiophene to its conducting form, while the conductance is monitored by a “read” circuit. Raman and UV-Vis spectroelectrochemistry were used during device operation to investigate redox reactions which underlie memory operation. Important electrochemical concepts which control device operation include activated electron transfer, ion motion, and extended conjugation. In particular, internal ion transport creates ohmic potential losses which slow W/E operation, but can be significantly improved with higher mobility solid electrolytes. Applications seeking to augment existing silicon electronics with molecular components will be described.

Recent references:

(1) Yan, H.; Bergren, A. J.; McCreery, R.; Della Rocca, M. L.; Martin, P.; Lafarge, P.; Lacroix, J. C.; Activationless charge transport across 4.5 to 22 nm in molecular electronic junctions; Proceedings of the National Academy of Sciences
2013, 110, 5326.

(2) McCreery, R.; Yan, H.; Bergren, A. J.; A Critical Perspective on Molecular Electronic Junctions: There is Plenty of Room in the Middle; Phys. Chem. Chem. Phys.
2013, 15, 1065.

(3) Sayed, S. Y.; Fereiro, J. A.; Yan, H.; McCreery, R. L.; Bergren, A. J.; Charge transport in molecular electronic junctions: Compression of the molecular tunnel barrier in the strong coupling regime; Proceedings of the National Academy of Sciences
2012, 109, 11498.

(4) Kumar, R.; Pillai, R. G.; Pekas, N.; Wu, Y.; McCreery, R. L.; Spatially Resolved Raman Spectroelectrochemistry of Solid-State Polythiophene/Viologen Memory Devices; Journal of the American Chemical Society
2012, 134, 14869.