CV Data Research Articles

Does the Scopus author ID suffice to track scientific international mobility? A case study based on Leibniz laureates

In this paper I outline how author identifiers enable to track international mobility of scientists. Authorship systems help to distinguish among similar names and provide information on affiliations and thus countries of stay. This study explores the relation between CV data and Scopus data in regard to tracking international mobility of scientists. To test the consistency and applicability of data on mobility episodes, residence countries as provided in CVs of a set of German scientists were compared against country information in the affiliations of their publications. Therefore, the CVs of Leibniz laureates were coded for the period 1996–2015 and their publications were gathered on the basis of Scopus author ID. Results show that the majority of scientists under study have a single author ID (68.4%). However, there are laureates with so-called ‘split identities’ where more than one author ID exists. Most of them have a dominant author ID that covers the majority of their publications and one or more additional IDs with only a few publications causing these split identities. Recall statistic shows that the use of the dominant author ID of each laureate would result in around 97% of their publication output. In contrast, the precision of Scopus author ID proves to be high. A random sample shows that all publications assigned to a specific author ID relate to a single individual, so that the precision statistic would yield 100%. Further results show that the registry systems ORCID and ResearcherID are no alternatives to Scopus author ID, because a minority of laureates make use of these identifier systems and data is often incomplete. Unlike ORCID and ResearcherID that suffer from a selection bias as those scientists who remain in science maintain their author profiles, Scopus author ID exists for every author publishing in sources covered by Scopus. The comparison of mobility data in Scopus versus CV data shows that bibliometric data is suitable to identify a scientist’s international mobility and appears to be a good solution if there are no CVs available or if they are incomplete. Furthermore, the reasons for inconsistencies in mobility data are discussed. These mainly reside in the lack of co-author affiliations, incomplete CV data, and other minor reasons.

A Continuous Semi-Empirical VJFET Capacitance Model from Sub to above Threshold Regime

This paper presents and discusses the depletion mechanisms that dominate in a TSI-VJFET under different bias conditions as expressed by the gate-source (CGS) and gate-drain (CGD) capacitances. It is shown that at pinch off the dominant capacitance is the drift capacitance and that in conduction the drain source voltage plays a significant role in channel’s formation. Furthermore a semi empirical capacitance model is introduced. CGS and CGD are modeled below and above threshold voltage by considering parallel plate capacitors with different plate configuration in te two cases. Then, the derived expressions are unified using a transition function that preserves the continuity of the model. The model was adjusted and fitted adequately to measured CV data from fabricated TSI-VJFET.

The Role of Hydrogen Bonding in Proton-Coupled Electron Transfer. It Does Not Have to be Concerted Pcet: The Case of Phenylenediamines and Pyridines in Acetonitrile

Proton transfer often accompanies electron transfer in organic redox couples due to the large changes in acidity or basicity that result from oxidation or reduction. Classically, the overall reaction is thought to occur in two separate steps, either proton transfer followed by electron transfer, PT-ET, or electron transfer followed by proton transfer, ET-PT. More recently it has become abundantly apparent that a third option is also possible in which the proton and electron move together in a single kinetic step. This is concerted proton-electron transfer, CPET, and is generally believed to occur within a H-bonded intermediate. It is straightforward to show that E° of this step will have a value in between the E° values corresponding to the oxidation of the fully protonated and fully deprotonated forms. Experimental evidence for CPET is typically the observance of a significant deuterium isotope effect for the apparent one electron transfer. However, it is important to note that the electron-proton transfer does not have to be concerted within the H-bond complex. It could also occur step-wise. If slow electron transfer occurred followed by rapid proton transfer within the H-bond complex, no significant deuterium isotope effect would be expected, yet, at the same time, the overall reversibility of the electron-proton transfer would still be aided by providing a mechanistic pathway through the H-bond complex with its intermediate E°. We believe that the second oxidation of a simple phenylenediamine, H2PD, in the presence of pyridines in acetonitrile provides a nice example of the significant role that step-wise electron-proton transfer within a H-bond intermediate can play. Without added base, the second oxidation corresponds to the reversible one electron oxidation of the radical cation, H2PD+, to the quinoidal dication, H2PD2+. CV data in the presence of one equivalent of pyridines of different basicity result in a significant negative shift in the E1/2 of the second CV wave with no loss in reversibility. Continued addition of the pyridine leads to smaller incremental shifts with still no change in reversibility. Analysis of the observed E1/2’s with one equivalent pyridine as a function of pyridine basicity indicates that, even with the weakest base, proton transfer to the pyridine occurs. This interpretation is supported by spectroelectrochemical data. Thus, the overall reaction occurring in the second CV wave is H2PD+ + B = HPD+ + HB+ + e-, where B is the pyridine base and HB+ is its conjugate acid. The shifts in E1/2 upon further additions of pyridine are nicely predicted by the Nernst equation with this as the overall reaction. However, attempts to simulate the CV data with just PT and ET steps fail at the higher concentrations of pyridine. This is because the rate of the ET step becomes exceedingly slow as the base concentration increases and the thermodynamic potential becomes increasingly removed from the E° of the actual ET step. This issue is simply solved by including in the mechanism the possibility of electron transfer occurring through the H-bond intermediate. This simple change leads to good fits to the experimental data, providing solid support for such a H-bonding intermediate being involved. However, a comparison of experiments with 10:1 cyanopyridine: H2PD run in 2% CH3OH to those run in 2% CD3OD show no significant difference in the ΔEp of the second oxidation, providing no evidence for the oxidation involving CPET. Thus, it appears that ET-PT within the H-bond complex still greatly aids the reversibility of the reaction even without CPET.

Hidden Features: Characterizing Carbon Electrodes in Low Ionic Strength Electrolytes for Capacitive Desalination Applications

Capacitive desalination (CDI) is a promising technology for reducing the salinity of brackish water streams. CDI typically employs a nanoporous carbon supercapacitor architecture with the added ability to flow electrolyte through the cell for deionization. Unlike supercapacitors, though, CDI operates with low ionic-strength liquids (e.g., 20 mM NaCl). Characterization in these electrolytes unveils important features in the CV and EIS data that are not commonly observed in supercapacitor studies. Examples of such features are the emergence of a strong “charge-transfer” resistance at mid-to-high frequencies in the EIS spectrum, local minima in the CV curves that are related to a point of zero charge, and potential artifacts due to ion depletion. These features ultimately underlie the system capacitance, device resistance, and effective operational voltage window, which are all strongly related to desalination performance. Here we examine these features in flow-through electrode CDI devices (fteCDI) with activated hierarchical carbon aerogel monoliths (HCAMs) derived from carbonized and activated resorcinol-formaldehyde aerogel. Work at LLNL was performed under the auspices of the US DOE by LLNL under Contract DE-AC52-07NA27344.

Redox-Responsive Dimerization in a Ferrocene-Ureidopyrimidinone Supramolecular Assembly

At one extreme, supramolecular polymers can have a high degree of randomness, existing as entangled coils with the mechanical properties of plastics and elastomers. At the other extreme, supramolecular polymers can be formed through directional intermolecular interactions among designed molecular subunits to achieve dynamic behavior as well as high degrees of internal order. The strength of these intermolecular interactions can be altered via external signals such as the absorption of light, temperature, pH, or the voltage of an electrode. Such is one of the important goals in supramolecular chemistry: the development of stimuli-responsive systems where the strength of intermolecular interactions can be perturbed through the use of external signals. Applications of supramolecular chemistry include self-healing polymers and gels, controlled release of entrapped molecules, and smart materials. In this presentation the results of electrochemical studies with a ferrocene-containing ureidopyrimidone (UPy) will be described. The UPy system – introduced by Meijer – can form two self-complementary 4 hydrogen bond arrays (AADD or ADAD) which dimerize in relatively non-polar organic solvents. By attaching an electroactive substituent such as ferrocene, the strength of electrostatic interactions can be perturbed to create a redox-responsive ureidopyrimidinone. Following earlier studies by Graham and co-workers, a ferrocene-functionalized ureidopyrimidinone UPy(Fc) was prepared. Concentration and scan-rate-dependent cyclic voltammetric studies indicate a square scheme type mechanism in dichloromethane. In the starting UPy(Fc) state, the AADD dimer is preferred. Oxidation to UPy(Fc+) results in conversion to another form with a less positive E1/2. Preference for this new form increases at lower concentrations which suggests that UPy(Fc+) exists as a monomeric species. This would indicate that oxidation breaks the dimer apart as desired. Alternatively it is possible that the observed concentration dependence results from rate-limiting dissociation of the dimer, but the monomer then tautomerizes to the ADAD enol form and re-dimerizes. To distinguish between these possibilities the relative diffusion coefficients (D’s) of UPy(Fc+) to UPy(Fc) were measured by steady-state voltammetry at a microdisk electrode. They were then compared to the relative D’s of ferrocenium to ferrocene. If UPy(Fc) is a dimer in both oxidation states, the DUPy(Fc+)/DUPy(Fc) ratio should be similar to that observed for ferrocene (DFc+/DFc), which will be a monomer in both oxidation states. However, if UPy(Fc+) is a monomer, the DUPy(Fc+)/DUPy(Fc) ratio will be larger than DFc+/DFc, since the D of the UPy(Fc+) monomer will be relatively smaller than the D of the UPy(Fc) dimer due to its smaller size. The latter is observed, supporting the conclusion that oxidation breaks apart the UPy(Fc) dimer at mM concentrations in dichloromethane. The results of these studies support the conclusion that UPy(Fc+) is monomeric at milli-molar concentrations in dichloromethane, meaning that oxidation of the UPy(Fc) breaks apart the dimer as hypothesized. Furthermore the process appears to be completely reversible. CV simulations were performed to determine if the square mechanism can quantitatively explain the observed voltammetry. The resulting simulated CV data supported the use of a square scheme mechanism to explain the cyclic voltammetry. However, the mechanism only accounts for the predominant keto AADD tautomer and excludes the enol ADAD tautomer. HNMR studies mimicking experimental conditions in cyclic voltammetry have been performed, revealing the presence of the enol ADAD tautomer in dichloromethane. Further HNMR studies in dichloromethane are underway, along with a comparative study in chloroform which does not appear to contain the enol ADAD tautomer. Cyclic voltammetry of the Upy(Fc) system will also be performed in chloroform. The results of these experiments will determine if the enol ADAD contributes to the redox mechanism of UPy(Fc). In addition, the synthesis of covalently linked UPy(Fc) oligomers is being initiated with the goal of creating a redox-responsive supramolecular polymer.

Heat Capacity of Saturated and Compressed Liquid Dimethyl Ether at Temperatures from (132 to 345) K and at Pressures to 35 MPa

Molar heat capacities at constant volume (Cv) of dimethyl ether have been measured with an adiabatic calorimeter. Temperatures range from the triple point to 345 K, and pressures up to 35 MPa. Measurements were conducted on liquid in equilibrium with its vapor and on compressed liquid samples. The samples are of high purity, as verified by chemical analysis. Calorimetric quantities are reported for the two-phase (Cv(2)), saturated-liquid (Cσ or Cx′), and single-phase (Cv) molar heat capacities. Low temperature Cv(2) data were employed to estimate vapor pressures for values less than 340 kPa by applying a thermodynamic relationship between the two-phase internal energy U(2) and the temperature derivatives of the vapor pressure. Vapor pressures were calculated at temperatures as low as the triple-point temperature. The principal sources of uncertainty are the temperature rise measurement and the change-of-volume work adjustment. The expanded relative uncertainty (with a coverage factor k = 2 and thus a two-...

An electrochemical investigation of the electrodeposition of non-intact tri-nuclear clusters on platinum working electrodes

The goal of this research was to study the electrochemical behavior of tri-nuclear clusters of molybdenum and tungsten - first in the ionic liquid EMIBF4, and then in the polar-aprotic solvent DMSO. Four tri-nuclear cluster compounds were studied: Hexa-μ2-acetatotriaquadi-μ3-oxotrimolybdenum (IV, IV, IV) trifluoromethanesulfonate [Mo₃O₂(O₂CCH₃)₆(H₂O)₃](CF₃SO₃)₂, Hexa-μ2-acetatotriaquadi-μ3-oxodimolybdenum (IV, IV) tungsten (IV) trifluoromethanesulfonate [Mo₂WO₂(O₂CCH₃)₆(H₂O)₃](CF₃SO₃)₂, Hexa-μ2-acetatotriaquadi-μ3-oxomolybdenum (IV) ditungsten (IV, IV) trifluoromethanesulfonate [MoW₂O₂(O₂CCH₃)₆(H₂O)₃](CF₃SO₃)₂, and Hexa-μ2-acetatotriaquadi-μ3-oxotritungsten (IV, IV, IV) trifluoromethanesulfonate [W₃O₂(O₂CCH₃)₆(H₂O)₃](CF₃SO₃)₂. All information gathered from CV data on tri-nuclear clusters will be discussed. The study of the electrodeposition efforts with molybdenum- and tungsten-based tri-nuclear clusters onto Pt electrodes in EMIBF4, and DMSO, will be compared to past investigations by Katovic et al. In addition, the electrochemical properties of these four trinuclear clusters in the DMSO-based solvent system were explored and are novel findings.

2,2'-Bipyridine Equipped with a Disulfide/Dithiol Switch for Coupled Two-Electron and Two-Proton Transfer.

[1,2]Dithiino[4,3-b:5,6-b']dipyridine (1) and its protonated open form 3,3'-dithiol-2,2'-bipyridine (2) were synthesised and their interconversion investigated. The X-ray structure of 2 revealed an anti orientation of the two pyridine units and a zwitterionic form. In depth electrochemical studies in combination with DFT calculations lead to a comprehensive picture of the redox chemistry of 1 in the absence and presence of protons. Initial one-electron reduction at E1 =-1.20 V results in the formation of the radical anion 1red with much elongated S-S bond, which readily undergoes further reduction at E2 =-1.38 V. Water triggers a potential inversion (E≥-1.13 V for the second reduction) as the radical anion 1red is protonated at its basic N atom. DFT studies revealed that S-S bond breaking and twisting of the pyridine units generally occurs after the second reduction step, whereas the potential inversion induced by protonation is a result of charge compensation. The CV data were simulated to derive rate constants for the individual chemical and electrochemical reactions for both scenarios in the absence and presence of protons.

Nitroimidazoles with a halogen-containing side-chain

Syntheses are reported for: nine 2-nitroimidazoles, the abbreviated names all beginning with E, based on derivation from Etanidazole); five 2-methyl-5-nitroimidazoles (M compounds, derived from Metronidazole); and five 2-methyl-4-nitroimidazoles (labelled 2M4N compounds). The nitroimidazoles all have an amide side-chain at the N1 atom of the imidazole, with 17 of them containing one to five halogen atoms. The aim is to study compounds for comparison with EF5 (the number showing the presence of five F-atoms), a previously reported, pentafluoropropylacetamide derivative of 2-nitroimidazole that is currently used as a hypoxia marker drug to detect cancerous tumours. The new compounds are characterized by standard methods, including X-ray structural data for the fluorinated MF5, 2M4NF5, and 2M4NF1(−1) species, with the “–1” indicating two C-atoms in an alkylamide chain rather than the three C-atoms in the propylacetamide of EF5. Intra- and inter-molecular H-bonding is seen in the solid state structures, likely an important property in biological use; another key property of the nitroimidazoles is their reduction potentials, and the measured CV data confirm that 2NO2Im compounds with longer side-chains and more F-atoms (like EF5) are worth investigating for possible activity as hypoxia-selective, bioreductive agents.

W18O49 nanowires assembled on carbon felt for application to supercapacitors

Abstract For supercapacitor applications, W18O49 nanowires have been extensively grown on graphitic carbon felt using a facile solvothermal method. The diameter and length of the nanowires are about 7 and 300 nm, respectively. The nanowires consist of monoclinic W18O49 grown along the [010] direction, as shown by TEM and XRD analyses. The W18O49 nanowires, assembled on carbon felt, exhibit a high capacity of 588.33 F/g at a current density of 1 A/g together with an excellent cycle performance, and a low internal resistance during the electrochemical tests. This outstanding performance may originate from the three-dimensional porous nanostructure of these W18O49 nanowires, which leads to a reduction in the resistance and fast reaction kinetics due to the high specific surface area and electrolyte accessibility. Furthermore, sufficient oxygen deficiencies of the substoichiometric tungsten oxide can also contribute to the electrochemical activity, which can be confirmed by comparison of CV and EIS data with WO3 nanowires.

Electrochemical and Spectrastudies of Some Sulfa Drug Azodyes and Their Metal Complexes in Aqueous Solution

The electrochemical behavior of some azo compounds derived from sulfa drugs derivatives in B.R. buffer solutions of different pH containing 20 (v/v) ethanol was investigated at the mercury electrode using different techniques (DC,DPP,CV and Coulometry) to investigate the effect of medium on the electro reduction process and suggestion the electrode reaction mechanism. The obtained results denoted that these compounds were reduced undergo a single irreversible 4- electron polarographic wave in acid and neutral solutions which represent the cleavage of the N=N center to the amine stage, whereas in alkaline solution, two wave are obtained the second is 2-electron irreversible wave corresponding to the reduction ofCHO group to CH2OH. The DPP and CV data showed a single peak in solutions of pH< 8, whereas three peaks are in alkaline solutions. The dissociation constants of the investigated compounds were determined by using spectrophotometric and potentiometric methods. Also the metal – ligand formation constants were determined potentiometrically and found in the order Cu˃ Co˃ Ni ˃Zn.

Combining Battery-like and Pseudocapacitive Charge Storage in 3D MnOx–Carbon Electrode Architectures for Zinc-Ion Cells

The ability of manganese oxides to exhibit charge-storage behavior characteristic of either batteries or electrochemical capacitors (ECs) offers an intriguing opportunity to design electrode materials that innately deliver both high power and high capacity. We previously demonstrated that lamellar birnessite-type MnOx, when expressed in carbon nanofoam–based electrode architectures (MnOx@CNF), amplifies charge storage by pseudocapacitance in aqueous electrolytes (e.g., Na2SO4; Li2SO4). Herein, we extend the functionality of these established electrode materials by varying the ionic composition of the electrolyte in which they are cycled. For example, cycling MnOx/C nanofoam electrodes in aqueous 1 M ZnSO4 yields battery-like voltammetric features reminiscent of those previously reported for “rechargeable Zn-ion batteries.” When cycling in mixed Na2SO4:ZnSO4 electrolytes, we retain Zn2+ redox peaks, but now superimposed on a pseudocapacitive background arising from the presence of Na2SO4. The Zn2+ redox provides high capacity (up to 230 mAh g–1 normalized to MnOx) at low rates (<5 mV s–1), while pseudocapacitance mechanisms take over at high rates to mitigate the effects of slow kinetics for Zn2+ insertion. Fundamental electrochemical properties are established using a three-electrode half-cell configuration. We apply peak-current kinetic analyses (for CV data) and AC impedance to deconvolve the complex mechanisms that give rise to battery-like and pseudocapacitive charge-storage features. On the basis of three-electrode studies, we down-select electrolyte compositions for testing MnOx@CNF, paired against Zn metal, in two-electrode Swagelok cells that are subjected to galvanostatic cycling at challenging C-rates (1C–20C).

Structure/property relationships in branched oligogermanes. Preparation of (Me3Ge)3GePh, (Me2ButGe)3GePh, and (Me2PhGe)3GePh and investigation of their properties by spectroscopic, spectrometric and electrochemical methods

The three branched oligogermanes (Me3Ge)3GePh, (Me2ButGe)3GePh, and (Me2PhGe)3GePh were synthesized via the hydrogermolysis reaction and were characterized by NMR (1H, 13C, and 73Ge) spectroscopy. In addition, these three compounds and (Bun3Ge)3GePh were analyzed using high resolution accurate mass mass spectrometry (HRAM-MS), which represents the first HRAM-MS investigation of branched oligogermanes. The effects of varying the substituent pattern on the peripheral R3Ge- groups on the electronic properties of these oligogermanes were investigated using cyclic and differential pulse voltammetry (CV and DPV), UV/visible spectroscopy, and 73Ge NMR spectroscopy. The CV, DPV, and 73Ge NMR data were compared to several previously reported branched oligogermanes, including (Bun3Ge)3GePh, (Ph3Ge)3GePh, (Ph3Ge)3GeH, and (Me3Ge)4Ge.

Ruthenium(III and II) β-diketonate complexes containing imidazoles

The RuIII complexes, [Ru(acac)2L2] Tf, and the RuII complexes, Ru(hfac)2L2, have been synthesized and characterized; acac=acetylacetonate, hfac=1,1,1,5,5,5-hexafluoroacetonate, Tf=triflate, and L=imidazole (Im) or a substituted imidazole (NMeIm, 2MeIm, 4/5MeIm, 2NO2Im); other nitroimidazoles, named metronidazole, etanidazole, and EF5 (a pentafluorinated derivative of etanidazole) were also used. Cis-isomers of the Ru complexes were usually formed, but some trans-isomers were also isolated. Characterization methods include NMR, UV/Vis, and MS spectroscopies, and CV data; X-ray crystallographic data were obtained for the cis-[Ru(acac)2L2]Tf complexes (L=Im, NMeIm, 2MeIm, and 5MeIm). Interest in these complexes stems from their potential antiproliferatory activity, and use of the nitroimidazole species as radiosensitizers. More incidentally synthesized were cis-[Ru(acac)2L(MeCN)]Tf (L=Im, 2MeIm), cis-Ru(hfac)2Im(MeCN), and [Ru(hfac)(NMeIm)4]PF6.

Viologen-based conjugated ionic polymer for nonvolatile rewritable memory device

A novel soluble viologen-based conjugated ionic copolymer, PTPA-V, was synthesized by using Suzuki coupling reaction in the presence of the tetrakis(triphenylphosphine)palladium(0) as the catalyst. Its HOMO, LUMO, EA, IP and Eg values derived from the CV data are −5.44, −3.10, 3.07, 5.70 and 2.34eV, respectively. The maximum absorption peak observed in the UV/Vis absorption spectrum of the PTPA-V thin film was shifted to the red by about 10nm, suggesting stronger aggregation effect occurred in the thin film. The fluorescence decay profiles of the singlet excited state of PTPA-V in different deaerated organic solvents revealed a mono-exponential decay with a lifetime of 8.9ns (toluene), 6.4ns (THF) and 5.2ns (DMF). The as-prepared electronic device with a configuration of Al/PTPA-V/ITO exhibited two accessible conductivity states, i.e., the high-conductivity (ON) state and the low-conductivity (OFF) state. A typical nonvolatile rewritable memory behavior was observed, with turn-on and turn-off voltages of −1.92 and 2.67V, and a large ON/OFF current ratio of more than 105. Unlike poly(triphenylamine) without any electron paramagnetic resonance (EPR) signal, PTPA-V shows an EPR signal with a g factor of 2.004, suggesting existence of unpaired electrons or free radicals in this polymer due to the charge transfer between the triphenylamine (TPA) moieties and the viologen (V) moieties, which resulted in the formation of TPA+ and V-.

The Controversial Role of Serum Uric Acid in Cardiovascular Diseases

Previous clinical, observation and epidemiologic studies have demonstrated strong association between serum uric acid (SUA) and cardiovascular disease (hypertension, heart failure, asymptomatic atherosclerosis), metabolic states (abdominal obesity, diabetes mellitus, metabolic syndrome, insulin resistance) and kidney disease. There is a large body of evidence regarding the role of SUA as predictor of CV events and CV mortality in general population and individuals with established CV disease and metabolic diseases. However, SUA may exhibit protective effects on endothelium and vasculature as well as attenuate endogenous repair system through mobbing and differentiation of cell precursors. Although SUA lowering drugs are widely used in patients with symptomatic hyperuricemia and gout beyond their etiologies, there is no agreement of SUA below target level 6.0 mg/dL in asymptomatic individuals with kidney injury and CV disease and data of ones are sufficiently limited. The short communication is depicted on the controversial role of SUA as primary cell toxicity agent and secondary cell protector against hypoxia, ischemia and apoptosis.

A generic marginal value function for natural areas

We conduct a CV and a CE experiment using a generic rather than a situation-specific study design in order to obtain a generic marginal value function for different types of natural areas with different characteristics in the Netherlands. We develop a modelling approach in which we use CV and CE choice data in one model. The value function obtained shows that people attach value to the presence of natural areas, and that these values vary due to differences in the magnitude of areas, in distance to areas, and differences in accessibility and fragmentation of natural areas. We discuss how the value function can be used to incorporate potential substitution between natural areas. We also show that for approximately one-fifth of our sample there is no added value having any kind of natural area nearby and that people living in small municipalities tend to be indifferent between accessible and inaccessible areas. Our approach produces a generic marginal value function, which may be used to inform cost–benefit analyses and land use planning decisions that wish to incorporate positive and negative welfare externalities related to changes in the provision of natural areas. However, we also show that applying this value function to the regional or local scale may produce biased value estimates.

Preparation of Pt@Cu Core-Shell Particles Incorporated in Poly-(3,4-ethylenedioxythiophene) for Catalytic Applications

Hybrid materials offer the possibility to combine advantageous properties of the individual components. In the macroscopic world adobe or reinforced concrete are well known examples. The same principle can also be applied to electrodes for electro-catalytic reactions. The usually precious metal catalyst like Pt for fuel cells (or Au for sensors) is reduced in size (and thus in costs) to smaller and smaller particles which are bonded to supporting surfaces. An interesting approach is to prepare a porous matrix in which these catalytic particles can be homogeneously incorporated. Promising candidates are conducting polymers like poly-(3,4-ethylenedioxythiophene) (PEDOT) whose structure can be tuned by the used electrolyte and/or the supporting electrolyte. To homogeneously incorporate the particles they should be prepared in situ with the polymer which is possible by cyclic voltammetry or (reversed) pulse methods. As Pt2+ has the possibility to oxidize EDOT directly we deposited Cu as an intermediate with the polymer by cyclic voltammetry. In a second step a chemical exchange reaction was performed using a Pt4+containing solution. This approach can yield Pt@Cu core shell particles embedded in a polymer matrix. A positive effect of this is also that the electronic structure of the Pt layer is modified by the underlying Cu core which can lead to enhanced catalytic activities. The cyclic voltammograms of the preparation of PEDOT/Cu films show a superposition of PEDOT and Cu features. At potentials more positive than ca. 0.9 V vs. Ag/AgCl sat. KCl polymerization of EDOT occurs while at more negative potentials the capacitive behaviour of the PEDOT film dominates next to the Cu redox waves at ca. 50 mV. SEM/EDX analyses showed that thus prepared films contain 10 to 17 wt% Cu depending on the switch-off potential. If the preparation stopped before Cu oxidation Cu crystallites could be observed on the PEDOT surface and the Cu content was higher. In the case of well oxidized films no distinct Cu centres could be found (see figure 1). The chemical exchange reaction with Pt was monitored by a quartz crystal microbalance (QCM). According to QCM data the deposited mass of Pt corresponds to ca. 60 monolayers on the geometric area. This contribution will discuss the preparation of the PEDOT/Pt@Cu hybrid films as well as the electrochemical and mechanical characterization of these films. This will include CV and impedance (EIS) data as well as QCM data. Fig. 1. SEM images of a PEDOT/Cu film with the preparation stopped at potentials negative to the Cu redox potential. (left) top view of the surface and (right) FIB cross section. Figure 1

Dual-salts of LiTFSI and LiODFB for high voltage cathode LiNi0.5Mn1.5O4

The LiNi0.5Mn1.5O4 has been investigated as promising because of its high operating voltage (4.7 V vs. Li+/Li) and decent specific capacity. Despite these advantages, however, the market penetration of this material was significantly hindered by the lack of proper electrolytes that can work stably up to 5 V. To achieve better cycling stability, mixed salts of lithium bis (trifluoromethanesulfonylimide) (LiTFSI) and lithium difluoro (oxalate) borate (LiODFB) are used in LiNi0.5Mn1.5O4-based batteries to replace the lithium hexafluoride phosphate (LiPF6) salt in non-aqueous electrolytes. The SEM and CV data indicate that the corrosion to Al current collector caused by LiTFSI-based electrolytes under high voltage (similar to 5 V vs. Li+/Li) can be largely reduced by adding LiODFB into LiTFSI-based electrolytes. And a boron-based passivation layer from the oxidative decomposition of LiODFB to suppress the corrosion based on the XPS tests results. In addition, the LiTFSI0.5-LiODFB0.5-based electrolyte has better cycling stability and rate capability for LiNi0.5Mn1.5O4-based cells than LiPF6-based electrolyte.

양분선택형 조건부가치측정(CV) 자료의 추정방법에 따른 지불의사금액의 변동성 연구

ABSTRACT : This study investigated the variability of WTP estimates(i.e. mean or median) with ad hoc assumptions of specific parametric probability distributions(i.e. normal, logistic, lognormal, and exponential distribution) to estimate WTP function using dichotomous choice CV data on mortality risk reduction. From the perspective of policy decision, the variability of these WTP estimates are intolerable in comparison with those of Turnbull nonparametric estimation method which is free from ad hoc distribution assumptions. The Turnbull nonparametric estimation can avoid a kind of misspecification bias due to ad hoc assumption of specific parametric distributions. Furthermore, the WTP estimates by Turnbull nonparametric estimation are robust because the similar estimates are elicited from a dichotomous choice or double dichotomous choice CV data, and the statistically significant WTP estimates can be obtained even though it is not possible by parametric estimation methods. If there are considerable variability among those WTP estimates by parametric estimation methods in condition with no criteria of model adequacy, the mean WTPs from Turnbull nonparametric estimation can be the robust estimates without ad hoc assumptions, which can avoid controversial issues in the perspective of policy decisions. Keywords : Dichotomous choice contingent valuation, Estimation method, Parametric distribution, Turnbull nonparametric distribution, Robustness