bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Standing Hierarchically-Structured Electrodes for Energy Storage Devices
Authors: Kalra Vibha
Published: February 2020

Fabrication of novel three-dimensional material architectures is essential for successful development of energy storage devices that allow high rate operation along with sufficient energy capacity. We will present our work on development of nanofiber-based hierarchically structured materials for applications in electric double layer capacitors and lithium-based batteries using a simple and scalable electrospinning methodology. As a first step, a comprehensive study on fabrication and structure-control of porous carbon nanofibers exhibiting specific surface areas of >1500 m2/g and multi-levels of pore sizes in the range of micro (<2 nm), meso (<50 nm) and macropores (>50 nm) was conducted. In particular, blends of polyacrylontritrle (PAN) and a sacrificial polymer in dimethyl formamide (DMF) were electrospun into non-woven nanofiber mats with diameters in the range of 200-300 nm. Fast evaporation of solvent (~200 nl/s) and high elongational flow rate (~105 s-1) during electrospinning allowed us to prevent phase separation and develop a co-continuous morphology of PAN and the sacrificial polymer in the nanofibers. Electrospun nanofiber mats were subjected to stabilization and carbonization processes to obtain porous carbon nanofibers (CNFs) as PAN converted to carbon and the sacrificial polymer decomposed out to create intra-fiber pores (Figure 1). These materials exhibit specific surface area of up to 1600 m2/g without any activation process. We exhibit the tunability of the pore sizes within CNFs by varying material composition. These materials were tested as free-standing electrodes (without any binder) for electric double-layer supercapacitors. Our study shows that they exhibit a large specific capacitance (210 F/g and 80 F/cm3), possibly due to the presence of a large fraction of meso-pores (2-4 nm) and macropores (>50 nm) compared to state-of-the-art activated carbons (pores <2 nm), which leads to an increase in the accessible carbon surface, thereby improving specific capacitance. These electrodes exhibit near-ideal rectangular CV curve even at a high scan rate of 2V/s (Figure 2). This again is attributed to the relatively larger pore size in these materials compared to most activated carbons, which allows faster ion transport and charge/discharge. Note that activated carbons often deviate from ideal behavior even at a scan rate of 100 mV/s scan rate.These materials retain 75% performance at a large current density of 20 A g1indicating excellent power handling capability. Preliminary data on use of these hierarchically structured materials for high energy density lithium-based batteries – Lithium-sulfur and Lithium-air, will be presented.
Electrochemical Characteristics of Li4Ti5O12 - Coated MCMB as an Anode Material for Hybrid Capacitor
Authors: Lee Jong Dae , Choi Jeong Eun
Published: February 2020

In recent years, the over consumption of fossil fuels leads to critical environmental problems and increasing attentions are being paid on energy security issues. The green energy sources, such as solar and wind, are typically periodic or intermittent and therefore requires an electrical energy storage for utilization purposes. Great research effort has been focused on the energy storage systems of capacitors and batteries. The hybrid capacitor incorporates a faradaic lithium ion battery system in combination with a non faradaic electric double layer capacitor system in a unit cell. This combination called hybrid capacitors can be used to obtain better performance in power/energy demands.

In this research, we coated Li4Ti5O12 onto meso - carbon micro beads (MCMB) to form a core - shell structure by a sol–gel process followed by calcinations. This MCMB-Li4Ti5O12 of core-shell structure was prepared to improve low electric conductivity of Li4Ti5O12 and cycling behavior. Prepared MCMB-Li4Ti5O12 composite was analyzed by XRD and SEM. The electrochemical performances of hybrid capacitor were investigated using MCMB-Li4Ti5O12 as the negative electrode and LiMn2O4, Active Carbon Fiber (ACF) as the positive electrode. The anodes were prepared by coating slurries containing the active materials (76wt%), Super P (17wt%), and polytetrafluroethylene (PTFE, 7wt%) on Al foil. The cathodes were made by dispersing 85wt% LiMn2O4, 10wt% Super P and 5wt% PTFE binder. The electrolyte consisted of 1M LiPF6in a mixture of ethylene carbonate(EC) / dimethyl carbonate(DMC) / ethyl-methyl carbonate(EMC) with a volume ratio of 1:1:1.

The electrochemical behaviors of hybrid capacitor using organic electrolytes were characterized by charge/discharge, cyclic voltammetry, impedence and cycle tests. The hybrid capacitor using MCMB-Li4Ti5O12/LiMn2O4 electrodes had better capacitance than MCMB hybrid systems and was able to deliver a specific energy as high as 67 Wh/kg at a specific power of 781 W/kg. Also, it was found that MCMB-Li4Ti5O12 composite exhibited very good cycle life performance.
VASP Calculation on Lithium Reaction to Tin Phosphides
Authors: Doh Chil-Hoon , Lee Won-Jae , Pervez Syed Atif , Song Jae-Sung
Published: February 2020

Studies on electrochemical reaction of SnPx materials were carried out by VASP ab initio calculation, where. SnPx having four different crystalline compositions, SnP0.75(Sn4P3), SnP0.94(SnP17/18), SnP and SnP3. The reaction potential of the lithiation of SnP0.94(SnP17/18) material was compared between intercalation and conversion reaction. The total-energy calculation and full structural optimization of SnPx, SnPx related materials and Li materials were performed using the Vienna ab initio Simulation Package (VASP)[1]. The possibility of intercalation of lithium to SnP0.94 was analyzed to obtain reaction potential of 1.853 V (Li/Li+) accommodating lithium to 6i site. 6i site is a vacant site in Sn18P17 (SnP0.94). Through further intercalation of lithium, reaction potential of Li0.5SnP0.94, Li1.5SnP1.56 and Li6.06SnP0.94 can also be calculated as 0.9026, 0.705 and -1.5 V(Li/Li+), respectively.Considering conversion reaction, SnP0.94 can react to produce 2 kinds of products such as LiP and Li3P as shown in Eq. 1.

SnP0.94 + (0.94z+y) = 0.94LizP + LiySn ---------(1)

At LiySn formation, y of zero means that only conversion reaction takes place without the formation of LiySn. Reaction potential of y=0 were 1.35 V and 0.948 V for the formation of LiP and Li3P. Reaction potential of the hole reaction [SnP0.94 + xLi = products], including intercalation and conversion, was plotted against reacted lithium extent of x in Fig. 1. It is observed that the reaction potential of conversion is higher than that of the lithium intercalation. In case of conversion reaction to form LiP with reacted lithium extent of 0.94 was 1.35 V which was higher than 0.937 V of lithium intercalation to form Li0.56SnP0.94 . Therefore, conversion reaction is labile compared to intercalation. Moreover, the reaction potential of conversion to form Li3P with reacted lithium extent of 2.833 was 0.948 V which is higher than that of the conversion reaction potential of 0.704 V to form LiP with reacted lithium extent of 3.28. Therefore conversion reaction to form Li3P is easier than to form LiP. We will discuss VASP calculation on lithium reaction to Tin Phosphides in details

[1] Kresse,G.; Hafner, J. Phys. Rev. B
,
47 (1993) 558; 49(1994) 14251.
Preparation of Carbon Coated MoS2 Flower-like Nanostructure with Self-Assembled Nanosheets As High-Performance Lithium-Ion Battery Anodes
Authors: Hu Shan , Chen Wen , Cao Guozhong
Published: February 2020

Loosely packed MoS2 nanosheets with thin carbon coating were synthesized via a facile, one-pot hydrothermal growth method. In the resulted optimal-designed nanoarchitecture, the ultrathin nanosheets, with a wall-thickness of approximately 5-10 nm, provide large electrode-electrolyte interface, so as to facilitate faster lithium-ions intercalation and diﬀusion. The ﬂexible and conductive carbon overcoats accommodate and alleviate the volume variation of the composites and thus maintain the structural and electrical integrity. In favor of the synergy and interplay of the carbon eﬀect and intrinsic structural advantages, MoS2@C (1:2) composites with the precursor MoO3: D-glucose molar ratio of 1:2 exhibit high reversible speciﬁc capacity of 1419 mA h g-1 at 0.1 A g-1, retain 80 % of the capacity after 50 cycles, and excellent rate capability as high as 672 mA h g-1 at 10 A g-1 with almost 100 % Coulombic efficiency. The good electrochemical performance suggests that these MoS2@C composites with unique flower-like morphology give rise to high specific surface area and increased layer distance leading to the reduced diffusion path of lithium-ions and rapid electrons transport. The rational and optimal design of the MoS2@C composites with an excellent electrochemical performance in the report creates a new avenue to develop a high-performance anode material.
NaCl Inducing Phase Transformation in Interfacial Water Under Quasistatic-Loading Conditions
Authors: Khan Shah Haidar , Hoffmann Peter Manfred
Published: February 2020

From clay swelling to geological transformations, from the structure to functioning of living organism, and from metallic corrosion to the recovery of oil from deeply lying pores, the presence of ions in water at the interface plays an important role. Many studies have been performed to understand the role of ions in water at the interface between solid to solid, solid to liquid and soft matter to liquid media. However, the dynamics and mechanical properties of electrolytic water at the interface have not yet been completely understood. The present day literature still consists controversial results with some time contradictory explanations. Here we present a study of the effects of the concentration of NaCl on the stiffness and damping properties of interfacial water confined between mica substrate and an oxidized silicon cantilever. We have used a home-built Scanning Probe Microscope (SPM), which uses an optical fiber, based on Fabry-Perot interferometer principle, to monitor the amplitude and phase of the cantilever with <0.1 Å precision. Here we present the behavior of electrolytic water of various NaCl concentrations (0.001-1M) near the interface under different dynamical conditions. We have observed that even under nearly static condition (a compression rate of 2 Angstrom per second), the presence of NaCl introduces peaks in the relaxation time which were not seen in the case of pure water, suggesting a phase transformation of the electrolytic water from a liquid-like to more solid-like behavior at the interface. The critical concentration of NaCl suggesting the phase transformation seems to be lying around 0.1 M NaCl. Our detailed and systemic study of the effects of NaCl ions in pure water under different dynamical conditions may contribute to better understanding of the role of electrolyte in interfacial water as well as may help to clear some of the underlying controversies in its physics and chemistry.
Ag Ion Irradiation of Multi-Walled Carbon Nanotubes Modified ITO Induces Electrocatalytic Effects
Authors: Goyal Rajendra N , Agrawal Bharati
Published: February 2020

Energetic ion irradiation has been used as a tool to improve the electrocatalytic activity of multi-walled carbon nano tubes (MWCNTs) modified indium tin oxide (ITO). A thin film of MWCNTs was irradiated with Ag ions having energy of 120 MeV with fluences of 1x1012, 3x1012 and 1x1013 ions/cm2, using a palleteron accelerator. The structural differences between un-irradiated and irradiated thin films were characterized by SEM observation and energy dispersive x-ray analysis. The change in MWCNTs due to ion beam irradiation was determined by Raman spectroscopy. The effect of irradiation on the electrocatalytic activity was examined by voltammetric measurements on epinephrine and it was found that irradiation improved peak current response. The anodic peak current for epinephrine increased by ~10 times in the pH range 2.0 -10.0 over that for the original MWCNTs and the peak potential shifted to less positive values. The detection limit (3/slope) and sensitivity for epinephrine for the pristine material were found to be 100 nM and 0.1086 A/M as compared to 2 nM and 0.998 A/M for the Ag ion beam irradiated MWCNT.
Vibrational Spectroscopic Study of Nafion Ionomer and Its Model Molecules on Platinum Surfaces
Authors: Yagi Ichizo , Notsu Hideo
Published: February 2020

In polymer electrolyte fuel cells (PEFCs), perfluorosulfonated polymers such as Nafion are usually utilized as electrolyte membrane and ionomers in catalyst layers. Recently, molecular structure and ion-conducting mechanism in the ultrathin ionomer films covering catalysts’ surfaces have been interested and various measurements at ultrathin Nafion films were carried out by means of electrochemical methods,[1-3] in situ vibrational spectroscopy,[3,4] and DFT calculations. However, the evaluation of the molecular conformation and orientation of perfluorosulfonated polymers are very difficult, since the molecular weights of these molecules are much larger and the vibrations of C-F bonds included in both the backbone and side-chains overlap with those of sulfonic acid groups, which can provide useful information to speculate the orientation of side-chains.

Recently, we have performed homodyne vibrational sum frequency generation (VSFG) spectroscopic measurements at Nafion-covered Pt surfaces. By comparing the VSFG spectra and ATR-IRRAS spectra of the same samples, where the thicknesses of Nafion film were controlled, VSFG spectroscopy selectively detect the vibrational bands, especially the stretching band of sulfonate terminal in Nafion at the Pt/Nafion or Nafion/air interface. Since the relative hydrophobicity was confirmed at the top most layer of the samples, sulfonate groups were considered not to be adsorbed at Nafion/air interface. However, the picture is just a speculation from the indirect experimental results. Ex situ heterodyne VSFG [5.6] measurements have proved that the direction of sulfonate groups in Nafion ultrathin films is downward toward Pt surfaces. However, in situ and dynamic behaviors of sulfonate terminals

In the present study, in situ surface enhanced infrared absorption spectroscopy (SEIRAS) at Pt electrode[7] immersed in diluted Nafion dispersion and Nafion-model electrolyte solutions are applied to follow the dynamic behaviors of sulfonates.

Acknowledgement

This work was supported by New Energy, Industrial Technology Development Organization (NEDO), Fuel Cell Promotion Office of the Agency of Natural Resources and Energy, Ministry of Economy, Trade and Industry (METI).

References

[1] R. Subbaraman et al., J. Phys. Chem. C, 114, 8414 (2010)

[2] M. Ahmed et al., J. Phys. Chem. C, 115, 17020 (2011)

[3] A.N. Gomez-Marin et al., J. Phys. Chem. C, 114, 20130 (2010)

[4] J. Zeng et al., Langmuir, 28, 957 (2012)

[5] S. Nihonyanagi et al., J. Chem. Phys., 130, 204704 (2009)

[6] S. Nihonyanagi et al., J. Am. Chem. Soc., 132, 6867 (2010)

[7] M. Osawa et al., J. Phys. Chem. C, 112, 4248 (2008)
Shape-Controlled Nanocrystals and Core-Shell for Oxygen Reduction Reaction
Authors: Shao Minhua
Published: February 2020

The slow kinetics of oxygen reduction reaction (ORR) is one of the main obstacles hindering the commercialization of low-temperature fuel cells.1 Platinum is by far the most effective electrocatalyst for ORR, but it is an extremely rare and expensive element. One way to address this problem is to increase the ORR activity of a metallic catalyst by optimizing the shape of constituent nanoparticles and thus maximizing the expression of facets most reactive towards ORR reaction.2-3 Another approach is to increase the utilization of expensive noble metal atoms by developing core-shell catalysts.4-5

In this study, the structural dependence of palladium nanocrystals for ORR, as well as the impact of the structure of the Pd core on the ORR activity of Pt shells in core-shell catalysts was studied in details. The carbon supported Pd nanocubes and octahedra with an edge length of 5-6 nm were synthesized and their ORR activities were measured using a rotating disk electrode technique.6 The activity enhancement of cubic Pd in a HClO4 solution was about 10 and 6 times over octahedral and conventional Pd, respectively. Interestingly, no difference in ORR activity was observed in an alkaline solution among the three samples (Figure 1). Two (octahedral and conventional) of the three Pd samples showed an increase in activity when an atomic thick Pt shell was deposited on their surfaces. Surprisingly, the activity decreased slightly for the Pd cubes after the deposition of a Pt shell.

The density functional theory (DFT) calculations were conducted to explain this observation and will be discussed in the meeting.

References

Electrocatalysis in Fuel Cells: A Non- and Low- Platinum Approach; Shao, M., Ed.; Springer: London, 2013.

N. M. Markovic, R. R. Adzic, B. D. Cahan and E. B. Yeager, J. Electroanal. Chem. 1994, 377, 249.

V. R. Stamenkovic, B. Fowler, B. S. Mun, G. Wang, P. N. Ross, C. A. Lucas and N. M. Markovic, Science 2007, 315, 493.

Adzic, R. R.; Zhang, J.; Sasaki, K.; Vukmirovic, M. B.; Shao, M.; Wang, J. X.; Nilekar, A. U.; Mavrikakis, M.; Valerio, J. A.; Uribe, F. Topics in Catalysis 2007, 46, (3-4), 249.

Shao, M. H.; Shoemaker, K.; Peles, A.; Kaneko, K.; Protsailo, L. J. Am. Chem. Soc. 2010, 132, (27), 9253.

Shao, M.; Yu, T.; Odell, J.; Jin, M.; Xia, Y. Chem
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Commun. 2011,
47, 6566.
Polymers Based on Sulfonated Polyanillines for Direct Electron Transfer with (PQQ)GDH and Application in Carbon Nanostructure-Based Biofuel Cells
Authors: Lisdat Fred , Sarauli David , Scherbahn Vitali , Göbel Gero , Putze Marie , Heinlein Thorsten , Schneider Jörg J.
Published: February 2020

Dopant-functionalized anilines with improved electrocatalytic properties are promising building blocks for the construction of bioelectronic devices [1]. The present study is devoted to the use of polyanillines possessing different substitution patterns in the interaction with the enzyme PQQ-GDH (pyrroloquinoline quinone dependent glucose dehydrogenase). The aim is to obtain an electron transfer from the substrate reduced enzyme to the polymer without additional shuttle molecules. This has been first studied in solution and then transferred to a surface in order to build a reagentless enzyme electrode.

6 polymers have been prepared from different mixtures of sulfoxy-, methoxy- and carboxy-substituted aniline by chemical synthesis and characterized by UV/VIS, IR and NMR spectroscopy. The substitution pattern influences the reactivity of the different polymers with the enzyme in solution, however when fixed on electrode surfaces the potential can be effectively used to enforce the reaction [2].

One of the polymers (poly(3-aminobenzoic acid-co-2-methoxyaniline-5-sulfonic acid) has been applied in modifying carbon nanotube based electrode structures and coupling (PQQ)GDH for construction of a bioanode. The first fuel cell uses MWCNT-based bucky paper as electrode material. The PQQ-GDH has been covalently coupled to the polymer. The glucose oxidation of this electrode achieves a current density of 700μA/cm2. As cathode PQQ modified bucky paper with covalently bound BOD (bilirubin oxidase) is applied. For this electrode a start potential of about 0.5V vs. Ag/AgCl and a maximum current density of 1mA/cm2 can be observed. The biofuel cell resulting from the bucky paper electrodes shows current densities up to about 100μW/cm2 in a 10mM glucose solution.

In a second approach vertically aligned carbon nanotubes (vaCNT) have been used for the electrode construction. Both enzymes have been immobilized in a similar way as compared to bucky paper. The vaCNT-based fuel cell achieves a maximum power density of 125µW/cm2. Even after three days and several runs of load a power density of more than 110µW/cm2 is retained (quiescent solution, 10mM glucose, room temperature). Furthermore it can be shown that this biofuel cell operates in human serum samples.

[1] Wallace GG, Kane-Maguire LAP. Manipulating and monitoring biomolecular interactions with conducting electroactive polymers. Adv Mater 511 2002;14:953–60.

[2] Sarauli D et al. Differently substituted sulfonated polyanilines: The role of polymer compositions in electron transfer with pyrroloquinoline quinone-dependent glucose dehydrogenase Acta Biomater 2013; 9: 8290-8298
Silica By Chemical Vapor Deposition (CVD): Towards Functional and Durable Bio-Interfaces
Authors: Gupta Gautam
Published: February 2020

It has clearly been demonstrated over the years that electricity can be derived from fuel cells that employ biological species such as enzyme, organelle or cells as the catalytic element. These fuel cells offer several advantages including high specificity, bio-friendly, ease of synthesis, and more over do not employ precious metal catalyst. Although bio based fuel cells possess these numerous advantages, however they are marred with issues such as lack of long-term stability, poor transport characteristics, and partial oxidation of most fuels resulting in overall low output of electrons. The design of fuel cells today is governed by obtaining parameters including minimal over potential, high current density, minimum transport losses and most importantly long-term stability. In order to achieve the desired properties we need to (a) control electron transport (mediated or direct) (b) effective immobilization technique for enzyme stabilization (3) high surface area and porous electrodes for high energy density and optimum fuel transport.

In this talk, I will go over the promising new sol-gel based techniques to encapsulate biological entities that range from a few nm (enzymes, lipid bilayers) up to micron-sized species (cells and organelles) We have developed two novel techniques that are compatible and have been integrated with fuel cell technologies. The two approaches mainly are (a) CVD approach: chemical vapor deposition of inorganic silica precursors onto the electrodes that contain biological species (b) microwave approach: a rapid biocompatible approach that results in bulk-immobilization of biomolecules in solution and substrates. These process allows precise temporal and spatial control of silica polymerization kinetics through the control of precursor delivery at room temperature and does not require or produce high concentrations of injurious chemicals that can compromise the function of biomolecular assemblies therefore result in optimum immobilization of desired species.

Secondly, I will talk about recent development in our lab of use of paper-based fuel cell that can power real devices including clock and LED. I will discuss the compatibility of immobilization techniques with paper based fuel cells and microbial fuel cells.
The Thermodynamics of Mesoporous Electrodes: Links Between Surface Morphology, Electrolyte Composition and Capacitance
Authors: Kobrak Mark
Published: February 2020

Recent developments in materials science have led to the creation of electrodes with an enormous range of morphologies. There has been considerable interest in the behavior of electrolytes confined in nanoscale domains, and there is a long-standing literature involving kinetic models of macroporous interfaces. Relatively little attention has been paid to mesoscale domains, however, and we use simple thermodynamic arguments to predict a novel phenomenon that links the distribution of ions near the interface with the composition of the electrolyte and mesoscale surface morphology. The results have significant implications for device design.
Fundamental Studies of Interfacial Phenomena at LiNi0.5Mn1.5O4/Graphite Electrodes in Organic Carbonate Electrolytes
Authors: Jarry Angelique , Lux Simon Franz , Kostecki Robert
Published: February 2020

The LiNi0.5Mn1.5O4 spinel exhibits a charge capacity of 148 mAh/g and operates at potential ca. 4.7 V vs. Li+/Li i.e., at the edge of the electrochemical stability window of standard carbonate-based electrolytes [1,2]. These conditions can result in electrolyte decomposition, electrode surface film formation, which can lead to impedance rise and overall degradation of the battery cell.

A variety of spectroscopy and microscopy techniques have been used to investigate basic properties of LiNi0.5Mn1.5O4 and its interfacial behavior in Li-ion cells. In fact, a thin surface layer of electrolyte decomposition products has been detected on LiNi0.5Mn1.5O4 composite electrodes by FTIR, XPS, and TEM [3-6].

Interestingly, Raman signal from the electrode/electrolyte interface of cycled cathodes is often obscured by a strong fluorescent signal from the fluorescent products of electrolyte decomposition reactions. It has been also observed in LiNi0.8Co0.15Al0.05O2/graphite Li-ion cells after aging at 55 °C [7]. These fluorescent species, which originate from electrolyte side-reactions tend to spread out through the cell and interfere with the cell chemistry

Interfacial reactions at a LiNi0.5Mn1.5O4 spinel electrode in LiPF6-based organic carbonate-based electrolyte were investigated using FTIR, Raman and fluorescence spectroscopies. In situ fluorescence spectroscopy measurements at a carbon- and binder-free LiNi0.5Mn1.5O4 electrode showed formation of fluorescent species that coincides with the oxidation of Ni2+ in LiNi0.5Mn1.5O4. The majority of these electrolyte oxidation products tend to diffuse away into the electrolyte but some remain at the surface of the electrode and form an unstable layer. The formation of photoluminescent active species is not only influenced by the electrode material and the electrolyte but also by the crystalline orientation of the particle surface. The mechanism of these side reactions and their impact on the interfacial chemistry and electrochemical behavior of the graphite electrode will be discussed.

Acknowledgments

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy, under contract no. DE-AC02-05CH11231.

References

[1] J.B. Goodenough, Y. Kim, Chemistry of Materials, 22 (2010) 587-603.

[2] R. Santhanam, B. Rambabu, Journal of Power Sources, 195 (2010) 5442-5451.

[3] D. Aurbach, B. Markovsky, Y. Talyossef, G. Salitra, H.J. Kim, S. Choi, Journal of Power Sources, 162 (2006) 780-789.

[4] K.J. Carroll, M.-C. Yang, G.M. Veith, N.J. Dudney, Y.S. Meng, Electrochemical and Solid-State Letters, 15 (2012) A72-A75.

[5] N.M. Hagh, F. Cosandey, S. Rangan, R. Bartynski, G.G. Amatucci, Journal of the Electrochemical Society, 157 (2010) A305-A319.

[6] M. Matsui, K. Dokko, K. Kanamura, J. Electrochem. Soc., 157 (2010) A121-A129.

[7] R. Kostecki, L. Norin, X. Song, F. McLarnon, J. Electrochem. Soc., 151 (2004) A522-A526.
Spectroelectrochemical Behaviour of p-Aminobenzenethiol (p-ABT) on Platinum Group Metals
Authors: Vidal-Iglesias Francisco José , Solla-Gullón José , Pérez Juan Manuel , Feliu Juan
Published: February 2020

Researchers have particular interest in amino-terminated monolayers because they have been used for several applications. Among them, SAMs based on aromatic thiols have been vastly studied. The formation of organic monolayers by self-assembly is directed by a specific interaction between a terminal functional group and the surface, in this case the bond formed between the thiol sulphur and the metal. Aminobenzenethiols (ABTs) are frequently studied as SERS probe molecules and particularly the p-ABT is commonly used as molecular junction and building block in SAMs. Several contributions have been reported about the p-ABT adsorbed on Ag and Au due to the same specific behaviour under certain experimental circumstances. SERS from the self-assembled monolayer of p-ABT on Ag and Au is significantly different from the normal Raman spectrum of the molecule in solid state. In a normal Raman spectrum only bands that correspond to completely symmetric a1 vibrations are observed, but in its SERS spectrum, non-a1-type bands are also present (1143, 1390 and 1432 cm-1). However, the SERS from benzenethiol on these metals are substantially the same as the normal Raman spectrum. It was first speculated [1, 2] that the alteration of the spectrum of p-ABT could be due to the CT mechanism contribution, as a consequence of the alteration of the electronic states of benzenethiol by the introduction of an -NH2 group on the benzene ring. Alternatively, it was shown, based on the spectral similarity of p-ABT and 4,4’-DMAB, that the non-a1-type bands correspond to N=N stretching vibrations of 4,4’-DMAB produced from p-ABT via a catalytic coupling reaction [3]. Recently, the formation of the azo-derivative, observed in the cases of gold and silver surfaces, was not detected on copper surfaces [4] pointing out that the metal could play an important role in the azobenzene derivative formation. In our knowledge no studies have been done with Pt-group metals, which are generally accepted to be weak electromagnetic enhancing metals under conditions of visible wavelength excitation. Consequently, the CT mechanism could play an important role. We report in this work a spectroelectrochemical study with different Pt-group metals, for which a correlation between their voltammetric behaviour and the SERS spectra is established.

Figure. (A) SERS spectra and (B) Cyclic voltammetry of p-ABT on Pt nanoparticles depostited on glassy carbon. Test solution: 0.1 M NaClO4 + 0.001 M p-ABT. Sweep rate: 50 mVs-1

[1] Osawa, M., Matsuda, N., Yoshii, K., Uchida, I., J. Phys. Chem. 98 (1994) 12702

[2] Kim, K., Kim, K.L., Shin, K.S., J. Phys. Chem. C 117 (2013) 5975

[3]Huang, Y.F. Zhu, H.P., Liu, G.K., Wu, D.Y., Ren, B. Tian, Z.Q. J. Am. Chem. Soc. 132 (2010) 9244

[4] Dendisova, M., Havranek, L., Oncak, M. Matejka, P. J. Phys. Chem. C 117 (2013) 21245
Potentiometry in Gas Phase
Authors: Janata Jiri
Published: February 2020

Properties of organic semiconductors (OS) are controlled by the primary and secondary doping1,2. These highly versatile materials have found sensing application in modern potentiometric sensors for ions as well as for potentiometric sensing of gases. Operation of the equilibrium ion sensors is governed by the modulation of the potential at the interface between the solution and the OS, according to the Nikolskij-Eisenman equation. Exchange of ions with the OS can be seen as a form of primary doping of the latter. For the operation of such potentiometric sensors a stable and well-defined external reference electrode is needed2.

When a dry, solid state OS is exposed to a gas or a vapor that can donate or accept electrons, a charge transfer complex is formed between the OS and the gas. Such interaction is called secondary doping, which results in modulation of work function (WF) of the OS. Such interaction can be measured with a Kelvin Probe or with a field-effect transistor. From the sensing point of view the biggest difference and advantage of WF-FET vis-à-vis ion sensors is the fact that no external reference electrode is needed because silicon is used as reference and its WF is stable under normal operating conditions. That fact alone makes the WF-FETs ideally suited for miniaturization, leading to gas-sensing arrays3.

Jiri Janata and Mira Josowicz, J.Solid State Electrochem. 13 (2009) 41-49, “Organic Semiconductors in Potentiometric Gas Sensors”

Jiri Janata, Principles of Chemical Sensors, 2nd Edition, Springer, 2009, New York

Jiri Janata, Coll.Czechoslov..Chem.Commun.  2009, 74, 1623–1634, Potentiometry in gas phase
Selectivity and Electrochemistry of Symmetrical Ion Channels: A Three-Dimensional Nernst-Planck- Poisson Model Preferred Oral Presentation
Authors: Tkacz-Smiech Katarzyna , Bozek Boguslaw , Lewenstam Andrzej Lewenstam , Danielewski Marek
Published: February 2020

Ion channels are of major interest for their important function in living organisms. It has been demonstrated that nanofabricated channels can mimictransport properties of biological ones [1].The fluctuations and rectification effects in conical nano-channels are of interest [2]. Although modeling of ionic transport throughout open channel, known as “selective filter”, presents a difficult task it is of major importance in the understanding of fundamental processes in the cell physiology. The so called voltage-gated ion channels have charged domains that make their structure and behavior sensitive to the variation of the applied field. The ion gating is driven by conformal protein changes, that are due to the variation of the electric field. For a particular range of membrane potentials the proteins adopt a conformation with a central narrow hole permeable for chosen ions. Such open channel pores, known as “selective filters”, present a difficult task of major importance in the understanding of fundamental processes in the cell physiology.

Here, the stationary behavior is studied of the different symmetrical channels showing complex geometry. The rigid channel wall is assumed to be locally charged. The ion transport is described by the nonequilibrium steady-state solution in cylindrical geometry of the 3DNernst-Planck-Poisson system. The total flux includes drift (convection) and diffusion terms. The solution of the coupled differential drift-diffusion equations is achieved by finite element method. The essential importance of the asymmetry in the potential distribution at the channel ends on the selectivity effect is demonstrated. The model satisfactorily describes the regime of small-to-moderate ionic currents. For various boundary conditions that are key parameters controlling the selectivity of the channel, it allows determining the flow characteristic, calculating the local concentration across the channel showing cylindrical symmetry and potential distribution. The model gives understanding of the mechanism of ion selectivity by channels but it can be also applied to simulate transport in polymer membranes and nanopores which might be useful in designing biosensors and nanodevices.

[1] Z. Siwy, Y. Gu, H. A. Spohr, D. Baur, A. Wolf-Reber, R. Spohr, P. Apel and Y. E. Korchev, Europhys. Lett. 60 (2002) 349.

[2] I. D. Kosiñska, I. Goychuk, M. Kostur, and G. Schmid, Phys. Rev. E 77 (2008) 031131.
Salt Bridges Contained in Nanoporous Glasses or Polymers: Improved Alternatives to Vycor
Authors: Mousavi Maral P. S. , Buhlmann Philippe
Published: February 2020

Nanoporous glass plugs are widely used to contain the electrolyte solution that forms a salt bridge between the sample and the reference electrode. Even though reference electrodes with plugs made of nanoporous glass (such as Vycor or CoralPor glass) are commercially available and are frequently used, the limits of their use were not explored until very recently [1]. It will be shown in this presentation that at ionic strengths lower than 100 mM, the half-cell potentials of reference electrodes with nanoporous glass plugs are not sample independent, as it would be desirable, but they depend on the ionic sample composition. Sample dependent shifts of more than 50 mV in the half cell potential were encountered. Reference potentials were found to be affected in aqueous solutions by HCl, NaCl, KCl, and CaCl2, and in acetonitrile by trifluoroacetic acid and the supporting electrolyte tetrabutylammonium perchlorate. These observations cannot be explained by the liquid junction potential between two mutually miscible electrolyte solutions, as commonly described with the Henderson equation. Instead, they result from the surface charge density on the glass surface and the resulting electrostatic screening of ion transfer into the glass pores when the latter have dimensions comparable to or smaller than the Debye length. Users of reference electrodes with nanoporous plugs at the junction to the sample need to be aware of these limitations to avoid substantial measurement errors.

This presentation will also address how problems at the junction to nanoporous plugs can be avoided using novel plug materials and selecting electrolyte conditions judiciously.

References:

[1] Reference Electrodes with Salt Bridges Contained in Nanoporous Glass: An Underappreciated Source of Error, Mousavi, M. P. S.; Bühlmann, P., Anal. Chem.
2013,
85, 8895–8901.
The Coupled Nernst-Planck-Poisson and Darken Formalisms: Interdiffusion in the Presence of the Electric Field
Authors: Danielewski Marek , Kucza Witold , Lewenstam Andrzej , Szyszkiewicz Krzysztof
Published: February 2020

The coupled Nernst-Planck-Poisson and Darken formalisms are presented. The intrinsic diffusion fluxes are defined in the material (lattice) fixed frame of reference and the Nernst-Planck flux formula is used. The overall fluxes of the components (defined in the laboratory reference frame) are sum of diffusion and drift (convection), that is to say we follow the Darken approach. The resulting set of differential equations has been solved numerically for planar systems by using the method of lines and the Radau solver. The method has been used for predictions of mass and charge transport in polymeric and glassy multicomponent systems. The obtained results are consistent with physical limitations, e.g. allowed to overcome a virtual phenomenon of non-physical values predicted by the NPP model solely in ion-selective electrodes.
Mechanism of Potential Development for Potentiometric Sensors, Based on Modeling of Interaction Between Electrochemically Active Compounds from the Membrane and Analyte
Authors: Stefan-van Staden Raluca Ioana
Published: February 2020

Modeling of interaction between analyte and electrochemically active compounds represents a new theoretical approach to predict the response and mechanism of potential development for ion-selective membrane electrodes. Therefore, correlations between the parameters (e.g., free energy, HUMO, LUMO, bound lenght) obtained using modeling, and experimental results (e.g., slope, free energy) obtained using ion-selective electrodes will be shown for sensors based on fullerens. The influence of matrix of the ion-selective electrodes on their response and selectivity will be shown.

The very first results of this study (a new mechanism of potential development for ion-selective electrodes) were discussed with Professor Buck during his participation to a conference in Constantza, Romania in 1993. He was the first that recognized the value of this theoretical spects, and his comments were extremely valuable for the work I developed until now in the theoretical field of ion-selective membrane electrodes.

Acknowledgements This work was supported by UEFISCDI PNII Program Ideas 2011-2014, Contract nr. 123/05.10.2011.
Oxygen Reduction and Oxygen Evolution Reactions in Non-Aqueous Electrolyte As Studies By Dems
Authors: Baltruschat Helmut , Abd-El-Latif Abd-El-Aziz Abd-El-Salehin , Molls Christoph , Khodayari Mehdi , Hegemann Philipp , Bondü Christoph
Published: February 2020

Secondary lithium-air batteries are promising candidates for a future energy storage system as they provide in theory high capacity; however, in practice they show bad cyclebility. The key step in discharging these batteries is the reduction of oxygen present in air. So far the oxygen reduction reaction (ORR) has been investigated thoroughly in aqueous media, but little research has been done in non-aqueous solvents.

Organic carbonates are unsuitable for the use in lithium-air batteries because they decompose upon charging [1]. Recently Scrosati [2] showed by XRD that tetraethylene glycol dimethyl ether (tetraglyme) is an appropriate electrolyte for Li-air battery whereas Bruce [3] using XRD and FTIR techniques demonstrated that, tetraglyme is not the best electrolyte because it decomposes in the first few cycles. On the other hand, Li2O2 has been reported as the major discharge product using dimethyl sulfoxide (DMSO) as an electrolyte [4].

Since spectroscopic techniques are superior to diffraction methods in detecting charge/discharge products, mass spectrometry in combination with electrochemistry (DEMS) has been used in this study to determine the electrolyte stability, water content, the amount of O2 reduced and evolved in a variety of aprotic electrolytes such as ethers (tetraglyme) and sulfoxide (DMSO). O2 solubility in aqueous and different non-aqueous electrolyte and its dependence on the flow rate of the electrolyte has been studied.

Crucial is a knowledge of the O2 solubility in these electrolytes. We will present a new method for its determination using differential electrochemical mass spectrometry (DEMS) based on the convection and diffusion behaviour characteristices of the dual thin layer cell used for DEMS. [5]

References:

[1] F. Mizuno, et al., Electrochemitry, 2010, 78, 403. [2] H Jung et al., Nat. Chem., 2012, 4, 579. [3] S. Freunberger, et al., Angew. Chem. Int. Ed., 2011, 50, 8609. [4] Z. Peng, et al., Science, 2012, 337, 563. [5] Fuhrmann, J.; Linke, A.; Langmach, H.; Baltruschat, H., Numerical calculation of the limiting current for a cylindrical thin layer flow cell Electrochimica Acta 2009, 55, 430-438.
Selective Detection of Dopamine against Ascorbic Acid Interference Using 3D Carbon Interdigitated Electrode Arrays
Authors: Kamath Rahul , Madou Marc J
Published: February 2020

3D carbon interdigitated electrode arrays (IDEAs) were fabricated using inexpensive conventional UV photolithography of SU8 with modified exposure and post exposure bake settings. SU8 patterns were pyrolyzed in an inert environment to obtain three-dimensional (3D) carbon IDEAs. In SU8 an IDEA with a digit width of 3µm, digit height of 6µm (aspect ratio of 2) and gap spacing of 0.8µm was achieved. The carbon sensor performance was investigated as a function of IDEA digit width/gap ratio and digit height under no flow and flow conditions. We demonstrated a gradual increase in redox amplification with an increase in IDEA digit width/gap ratio in the lower ratio range. At higher width/gap ratios, from 1.5 onwards, the amplification factor showed a much steeper increase. The highest amplification of 37 we obtained for a width/gap ratio of 2.45 for an electrode height of 0.95µm. Redox amplification increases significantly with increase in IDEA height. Redox amplification increased from a factor of 9 at 0.09µm digit height to a factor of 37 at 0.95µm height. The effect of potential sweep rate on redox amplification was also investigated. As the sweep rate was decreased from 50mV/s to 5mV/s, the collection efficiency increased from 0.92 to 0.97 whereas the amplification increased from 7 to 25. Under flow condition, the amplification decreases substantially as the recycling of the redox species is impeded by convection resulting in a drop in collection efficiency. The highest amplification of 37 dropped to 4 for the same electrode for a flow rate of 500nL/s.
Electrochemical Properties of Boron-Doped Diamond Thin Film Synthesized by MPCVD on Titanium Substrate to Use as an Ozone Generator
Authors: Park YeongMin , Kim DaeWook , Kim JeongWan , Cho Hyoung J. , Cho Hyun , Kim JinKon , Kim TaeGyu
Published: February 2020

Boron doped diamond is an excellent electrode material with a large potential window in aqueous solution and low background current. The wider potential window and lower background currents make the BDD material very attractive for electrochemical analysis experiments.

Furthermore, BDD exhibits high chemical and electrochemical stability, which makes the material a suitable electrode material for various applications such as bioelectrochemical applications and water disinfection.

In this paper, we had succeeded to generate ozone by using the BDD electrode with high efficiency compared to traditional lead oxide (PbO2) and other BDD electrods.

Firstly, a Titanium substrate had been seeded by ultra sonic agitation with diamond powder(30nm ~ 40nm) for an hour, which was used as a nucleation of diamond. After that BDD film was deposited on the substrate by microwave plasma chemical vapor deposition.

The morphology of samples was observed by Scanning Electron Microscopy (SEM) and the structural-chemical properties of synthesized diamond layer was investigated by Raman Spectroscopy. Conductivity, carrier concentration and Hall mobility was then determined by a Hall-effect measurement unit, based on the van der Pauw method. The ozone concentration in water, which was measured by Ozone Colorimeter.
Molecules in Circuits: A New Type of Microelectronics?
Authors: McCreery Richard Louis , Bergren Adam , Nagy Sayed , Yan Haijun , Bayat Akhtar , Kondratenko Mykola
Published: February 2020

Molecules may be considered electronic systems, with electrons rapidly moving through orbitals within molecules and also long distances in biological metabolism and photosynthesis. The prospect of incorporating molecules into microelectronic circuits based on silicon and metallic conductors has great potential for enhancing consumer electronics, providing solar energy conversion, and permitting new functions not possible with silicon. In order to combine the electronic properties of molecules with conventional microelectronics, we need to understand how to “connect” to molecules as well as how electrons are transported through molecules. Once the “rules” of charge transport through molecules are understood, it should be possible to “rationally design” new molecular electronic devices for valuable functions not currently possible with silicon. While Molecular Electronics holds great promise, it also presents significant challenges in handling and fabrication of devices with dimensions of only a few nanometers. We use surface chemistry, spectroscopy, and conjugated organic molecules to make “molecular junctions” consisting of a single layer of molecules a few nanometers thick between conducting carbon and copper electrodes, then we study the behavior of molecules as circuit elements. The primary goal is to design and build functional molecular electronic components to greatly enhance the already powerful world of silicon microelectronics.

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.