Stability electrochemical

The application of the ormolytes in electrochemical applications depends on their stability window. To evaluate the electrochemical stability window of di-ureasil ormolyte compositions we have typically used a two-electrode cell configuration involving the use of a 25 pm-diameter gold microelectrode surface. Cell assembly was initiated by locating a freshly cleaned [Pg.184]

6 Voltammogram of d-U(2000)i5LiTFSI di-ureasil electrolyte at a 25 im diameter gold microelectrode vs. Li/Li . Initial sweep direction is anodic and sweep rate is 100 mV s. Reproduced from Barbosa [Pg.185]

Hie electrochemical stability range of the lithium-doped di-ureasils was determined by microelectrode cyclic voltammetry over the potential range between -1.5 and 6.5 In the anodic region, all ormolytes are stable [Pg.185]

A key criterion for selection of a solvent for electrochemical studies is the electrochemical stability of the solvent [12]. This is most clearly manifested by the range of voltages over which the solvent is electrochemically inert. This useful electrochemical potential window depends on the oxidative and reductive stability of the solvent. In the case of ionic liquids, the potential window depends primarily on the resistance of the cation to reduction and the resistance of the anion to oxidation. (A notable exception to this is in the acidic chloroaluminate ionic liquids, where the reduction of the heptachloroaluminate species [Al2Cl7] is the limiting cathodic process). In addition, the presence of impurities can play an important role in limiting the potential windows of ionic liquids. [Pg.104]

In the tradition of previous reviews [1-22], this section addresses various aspects of nonaqueous electrolytes, including intrinsic properties, such as local structures caused by ion-ion and ion-solvent interactions and bulk properties, such as ionic conductivity, viscosity, and electrochemical stability (voltage window), and their relationships to intrinsic properties. [Pg.457]

More recently considered candidates are large molecular anions with delocalized anionic charge, which offer low lattice energies, relatively small ion-ion interaction, and hence sufficient solubility and relatively large conductivity. Delocalization of the charge is achieved by electron-with drawing substituents such as -F or - CF3. Furthermore, these anions show a good electrochemical stability to oxidation. In contrast to Lewis acid-based salts they are chemically more stable with various solvents and often also show excellent thermal stability. [Pg.462]

The electrochemical stability range determines the usefulness of nonaqueous electrolytes for electrochemical studies as well as for applications. It indicates the absence of electrochemical oxidation or reduction of solvent or ions, and of faradaic current... [Pg.473]

However, even if electrolytes have sufficiently large voltage windows, their components may not be stable (at least ki-netically) with lithium metal for example, acetonitrile shows very large voltage windows with various salts, but is polymerized at deposited lithium if this reaction is not suppressed by additives, such as S02 which forms a protective ionically conductive layer on the lithium surface. Nonetheless, electrochemical stability ranges from CV experiments may be used to choose useful electrolytes. [Pg.473]

It is worth mentioning that the use of microelectrodes allows the investigation of the electrochemical stability range of solvents without addition of a salt [138J. These studies make it possible to discrimi-... [Pg.474]

The use of liquid salts, based on anodi-cally stable cations such as 1,2-dimethyl-3-propylimidazolium (Dmpi) without added solvent, allows the investigation of the electrochemical stability of anions [75],... [Pg.474]

Tahle 7. Electrochemical stability ranges or anodic stability limits of several nonaqueous electrolytes... [Pg.474]

One of the major drawbacks to many promising copolymers is their unsatisfactory electrochemical stability. Carbonyl groups which feature in many of the back-bone/chain linking groups are likely to cause stability concerns. Likewise, urethane, alcohol, and siloxane functions are sensitive to lithium metal. With this in mind, a recent trend has been to find synthetic routes to amorphous structures with... [Pg.505]

Efficient photoelectrochemical decomposition of ZnSe electrodes has been observed in aqueous (indifferent) electrolytes of various pHs, despite the wide band gap of the semiconductor [119, 120]. On the other hand, ZnSe has been found to exhibit better dark electrochemical stability compared to the GdX compounds. Large dark potential ranges of stability (at least 3 V) were determined for I-doped ZnSe electrodes in aqueous media of pH 0, 6.3, and 14, by Gautron et al. [121], who presented also a detailed discussion of the flat band potential behavior on the basis of the Gartner model. Interestingly, a Nernstian pH dependence was found for... [Pg.235]

The ratio ARH/ARj (monoalkylation/dialkylation) should depend principally on the electrophilic capability of RX. Thus it has been shown that in the case of t-butyl halides (due to the chemical and electrochemical stability of t-butyl free radical) the yield of mono alkylation is often good. Naturally, aryl sulphones may also be employed in the role of RX-type compounds. Indeed, the t-butylation of pyrene can be performed when reduced cathodically in the presence of CgHjSOjBu-t. Other alkylation reactions are also possible with sulphones possessing an ArS02 moiety bound to a tertiary carbon. In contrast, coupling reactions via redox catalysis do not occur in a good yield with primary and secondary sulphones. This is probably due to the disappearance of the mediator anion radical due to proton transfer from the acidic sulphone. [Pg.1019]

Before the measurement of HOR activity, a pretreatment of the alloy electrode was carried out by potential sweeps (10 V s ) of 10 cycles between 0.05 and 1.20 V in N2-purged 0.1 M HCIO4. The cyclic voltammograms (CVs) at all the alloys resembled that of pure Pt. As described below, these alloy electrodes were electrochemically stabilized by the pretreatment. Hydrodynamic voltammograms for the HOR were then recorded in the potential range from 0 to 0.20 V with a sweep rate of 10 mV s in 0.1 M HCIO4 saturated with pure H2 or 100 ppm CO/H2 at room temperature. The kinetically controlled current 4 for the HOR at 0.02 V was determined from Levich-Koutecky plots [Bard and Faulkner, 1994]. [Pg.319]

Each test electrode was transferred to the EC chamber and subjected to electrochemical stabilization. The EC chamber was then evacuated rapidly by two sorption pumps and a cryopump to transfer the electrode to the XPS chamber again. [Pg.323]

Figure 10.4 Area-normalized CL spectra of Pt4/7/2 for the pure Pt (dotted Une), Pt5gCo42 (solid line), and PtgoRu4o (dashed line) alloys with respect to p (a) as-prepared (h) after electrochemical stabilization. The samples were thin film pure Pt or Pt-based alloys (diameter 8 mm and thickness 80 nm) prepared on Au disks by DC sputtering. Electrochemical stabilization of Pt58 C042 was performed by repeated potential cycling between 0.075 and 1.00 V at a sweep rate of 0.10 V s in 0.1 M HCIO4 under ultrapure N2 (99.9999%) until CV showed a steady state. PtgoRu4o was stabilized by several potential cycling between 0.075 and 0.80 V at 0.10 V s in 0.05 M H2SO4 under ultrapure N2. (From Wakisaka et al. [2006], reproduced by permission of the American Chemical Society.)...

It was found that the intensity of Co2ps/2 decreased significantly (by a factor of 2.5), supporting the concept of Co dissolution from the alloy and formation of the Pt skin layer on the electrode surface during electrochemical stabilization. As shown in Fig. 10.4b, a clear CL shift was stUl observed in the Pt4/7/2 spectmm for the stabilized Pt-Co, in spite of the dissolution of Co, although the CL shift after stabilization was slightly smaller (0.15 eV) than in the as-prepared alloy (0.19 eV). Thus, we... [Pg.324]

As described in the previous sections, a stable Pt skin of a few nanometers is formed on the Pt-Fe, Pt-Co, and Pt-Ni alloy surfaces after electrochemical stabilization. Figure 10.12 shows Arrhenius plots of kapp on the alloy electrodes at —0.525 V vs. E° in comparison with that of a pure Pt electrode. In the low temperature region (20-50 °C for Pt54Fe45, 20-60 °C for Pt6gCo32 and Ptg3Ni37), linear relationships between log kapp and 1 / Tare observed at all the electrodes, corresponding to the following Arrhenius equation ... [Pg.334]

We report here studies on a polymer fi1m which is formed by the thermal polymerization of a monomeric complex tris(5,5 -bis[(3-acrylvl-l-propoxy)carbonyll-2,2 -bipyridine)ruthenium(11) as its tosylate salt,I (4). Polymer films formed from I (poly-I) are insoluble in all solvents tested and possess extremely good chemical and electrochemical stability. Depending on the formal oxidation state of the ruthenium sites in poly-I the material can either act as a redox conductor or as an electronic (ohmic) conductor having a specific conductivity which is semiconductorlike in magnitude. [Pg.420]

Skotheim et al. [286, 357, 362] have performed in situ electrochemistry and XPS measurements using a solid polymer electrolyte (based on poly (ethylene oxide) (PEO) [363]), which provides a large window of electrochemical stability and overcomes many of the problems associated with UHV electrochemistrty. The use of PEO as an electrolyte has also been investigated by Prosperi et al. [364] who found slow diffusion of the dopant at room temperature as would be expected, and Watanabe et al. have also produced polypyrrole/solid polymer electrolyte composites [365], The electrochemistry of chemically prepared polypyrrole powders has also been investigated using carbon paste electrodes [356, 366] with similar results to those found for electrochemically-prepared material. [Pg.47]

The key role of RuOa for the electrochemical stability of Ru02 based DSA electrodes for Cl2 evolution was also pointed out by Augustynski et al. [45] on the basis of XPS data. After electrolysis in NaCl solution Augustynski found Cl species on the surface of the DSA electrode and a higher Ru oxide species, most probably Ru03. [Pg.102]

Titanium Carbide. Carbides of transition metals are known for their hardness, wear resistance and also for their high electrical conductivity, which makes them attractive as a refractory coating material for cutting tools or bearings. Only little work has been done on the electrochemical stability of transition metal carbides with the exception of TiC, where a corrosion and passivation mechanism was suggested by Hintermann et al. [119,120]. This mechanism was confirmed on amorphous TiC produced by metal-... [Pg.120]

Another important aspect for a material to be used as electrode for supercapacitors is its electrochemical stability. In Figure 2, presenting the specific discharge capacitance versus the cycle number for the optimized a-Mn02-nl FO/CNTs composite in 2 molL 1 KNO3 (pH=6.5), it can be observed that the specific capacitance loss after 200 cycles is about 20%. [Pg.59]

Show possibly broad electrochemical stability window at an interface of carbon electrode ... [Pg.97]

It can be seen that an energy of ca. 150 kJ/kg, comparable to that accumulated in Pb02-Pb or Ni-Cd batteries, can be obtained at voltages of 4V. Somewhat lower energy (100 kJ/kg) is accumulated at a voltage of 3V. Consequently, the searched system carbon/electrolyte should be characterised by (i) specific capacity. > 160 F per gram of activated carbon and (ii) electrochemical stability window at the level of ca. >3V. [Pg.98]

It is essential from the point of view of high power-density to ensure the electrochemical stability of the system at possibly high voltages. Broad electrochemical stability windows are typical if ionic liquids, however, the... [Pg.102]

Table 5. Electrochemical stability window of ionic liquids (IL) at the glassy carbon (potentials [V/ expressed versus Ag/Agf 0.01M in DMSO reference) [26 /.

Table 5 shows cathodic and anodic limits of electrochemical stability windows of a number of ionic liquids. The cathodic limit of the stability window of the ILs based on the EMIm+ and BMIm+ cations, investigated at the glassy carbon electrode, is -2.1 V against the Ag/Ag+ (0.01M in DMSO) reference. The BMPy+ cation is reduced at the glassy carbon at considerably more positive potential, at ca. -1.0 V. [Pg.103]

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