Electrode curves

Fig. 10-23. Energy levels and polarization curves for a redox reaction of anodic redox holes at a photoexdted n-type electrode and at a dark p-type electrode of the same semiconductor curve (1) = polarization curve of anodic transfer of photoexdted holes at an n-type electrode curve (2)= polarization curve of anodic transfer of holes at a p-type electrode in the dark (equivalent to a curve representing anodic current as a function of quasi-Fermi level of interfadal holes in a photoexdted n-type electrode) i = anodic transfer current of holes Eredox = equilibriiun potential of redox hole transfer N = anodic polarization at potential n (t) of a photoexdted n-type electrode P = anodic polarization at potential pE(i) of a dark p-type electrode.

Fig. 5.29 ITIES polarogram obtained with a dropping electrolyte electrode. Curve 1 in 0.05 M LiCI + 1 M MgS04 (water) and 0.05 M Bu4NBPh4 (NB) curve 2 in 1 +0.5 mM Me4NCI (water). Dashed curve curve 2 - curve 1. The potential E is referred to the Galvani potential difference between 0.05 M Bu4NCI (water) and 0.05 M Bu4NBPh4 (NB).

Figure 16.4 Cyclic voltammogram of 4.5 mM 2,3-dinitro-2,3-dimethylbutane in N,N-dimethylformamide/0.20 M Bu4NPF6 at a 25-pm-diameter mercury electrode. Curves experimental voltammograms after subtraction of background current. Points digital simulations. Potentials referred to cadmium reference electrode [cadmium amalgam/CdCl2 (sat d) in DMF]. [Reprinted with permission from W.J. Bowyer and D.H. Evans, J. Org. Chem. 53 5234 (1988). Copyright 1988 American Chemical Society.]...

In Fig. 7.7, cyclic voltammetric curves are shown of the oxidation of sodium dithionite at a gold electrode (curves 1,4), at a CoTSPc-modihed gold electrode (curves 2, 5) and at a CoTSPor-modihed gold electrode (curves 3, 6) for two different sodium dithionite concentrations. Several observations indicate electrocatalytic behaviour. First, the voltammetric waves are shifted towards less-positive potentials. This means that less... 

Calibration plot between peak current of the sodium dithionite oxidation reaction and its concentration at a bare gold electrode (curve 1) and at a CoTSPc-modified (curve 2) and CoTSPor-modified (curve 3) gold electrode. T=298.0K. 

Fig. 23. Current-potential (MOE = mercury oxide electrode) curves for hydrogen evolution in 1 M NaOH on an electrolytically prepared NiSx electrode. (1) Initial behaviour (2) After stabilization. After ref. 442, by permission of Pergamon Press.

Fig. 6-6. RDE and HMRDE curves for quinhydrone at platinum. Curve A, RDE traces for cyclic potential scan of 1.00 pM quinhydrone in 0.02 M H2S04 at platinum disk electrode. Curve B, HMRDE traces for the solution in curve A. Curve B, HMRDE residual in 0.02 M H2S04. Conditions QU2 = 60 rpml/2. A 1/2 = 6 rpm1/2. /= 3 Hz, scan rate is 5 mV/s, averaging time constant is 3 s. From [67],...

Figure 3.5 Conventional (bottom), fundamental-harmonic AC, and second-harmonic AC polarograms for a reversible couple at a dropping-mercury electrode. Curves represent the envelope of the upper limits of the current oscillations.

Figure 11.14 Voltammetric oxidation of carbon monoxide at a gold electrode curve a, an inactive electrode curve b, an activated electrode. Scan rate 0.05 Vs 1 supporting electrolyte, 0.01 M NaOH in 0.1 M K2S04 solution saturated with 100% CO ( 1 mM) electrode area 2.42 cm2. 

Fig. 4.5. Photocurrent - potential dependence for J-aggregated Dye III and Dye IV adsorbed onto the surface of nanostructurated W03 electrode (curves 2,4) and incorporated in the W03 film (curves 1, 3). Electrolyte 0.25 M Na2S04. Light intensity 2 mW cm 2.

Fig. 6.13. Anodic current vs. potential curves for the process of BH4 ions oxidation on the bulk Cu electrode (curve 1 for comparison see curve 2 registered in the same conditions without BH4 ions), on the initial Ti02 electrodes (curve 7 for Ti02 with Nd = 10 19 cm 3 curve 8 for Ti02 with Nd 1018 cm 3) and on the Ti02 electrodes surface modified with different concentration of Cu (curve 3 - 1018 atoms/cm2, curves 4,5 - 1016 atoms/cm2, curve 6 - 1015 atoms/cm2). The values of Nd for Ti02 were 1018 cm 3 (curve 5) and 1019 cm 3 (curves 3,4,6). Curve 9 was obtained with the use of represented electrical circuit modeling the system Ti02 - Cu particles - electrolyte (D - solid-state Schottky diode R - electrical resistor WE, RE and CE - working, reference and counter electrodes, correspondingly). Electrolyte 0.1 M NaBH4 + 0.1 M NaOH. The potential sweep rate is 5 mV/s.

FIGURE 8.32 Typical potential profiles for (a) positive electrode in a conventional asymmetric capacitor built with a non pre-doped Li inter calation carbon for the negative electrode (curve 1), an asymmetric capacitor with a pre-doped Li-ion intercalation carbon material (curve 2), and (b) positive and negative electrodes of an EDLC during the charging process. (From Aida, T., et al., Electrochem. Solid-State Lett., 9, A534, 2006. With permission.)... 

Fig. 2. Typical potential ( ) vs time recording obtained for assay of urease with an ammonia gas sensing electrode. Curve shown is for addition of IS /tl of 6 Af urea to 1 ml of 0.4 nM urease in 0.1 M Tris-HCl-1 mM EDTA, pH 7.5.

Figure 3. The enantioselective bioelectrocatalyzed oxidation of glucose by glucose oxidase at an electrode modified by a chiral electron-transfer mediator. (A) Organization of the chiral ferrocene monolayer-modified Au electrode and its interaction with soluble GOx. EDC = l-(3-dimethylami-nopropyl)-3-ethylcarbodiimide hydrochloride. (B) Cyclic voltammograms of the ferrocene-modified electrode (curves a and b for (i )-Fc (2) and (5)-Fc (3), respectively) in the presence of 1 x 10 M GOx and 50 mM glucose 0.1 M phosphate buffer, pH 7.0 potential scan rate, 5 mV s electrode area, 0.26 cm. ...

Sol-gels containing electroactive species have been used in the development of both amperometric and potentiometric electrodes. Films coated with anionic poly-(dimethyldiallylammonium chloride) (PDMDAAC) and cationic poly(vinylsulfonic acid) were used to concentrate Ru(bpy)3 + and the hexacyanoferrate anion, respectively, for use as amperometric electrodes [208a]. The detection limit by square-wave voltammetry improved by up to 50-fold compared with uncovered electrodes. In Figure 41, curve 1 corresponds to a bare graphite electrode, curve 2 to a sol-gel-covered electrode and curve 3 to a sol-gel-PDMDAAC-modified electrode after 10 min of exposure to Fe(CN)g. ... 

The anodic portion of the potentiodynamic electrode curve shown in Fig. 6 likewise exhibits a special effect, i.e., the development of a current density maximum. This type of curve resembles those of metals that can be passivated. The cause of the current density maximum is examined in greater detail in Sec. 4.5.6. 

In this manner, the assembly of current-potential curves shown in Fig. 10 were produced as a function of the electrolyte temperature of the electrolyte EL II/T. The electrode curves plotted on a semilogarithmic scale yield straight lines from 0 to about — 0.12 V. 

The presence of the 1 1 complex in the electrolyte can be recognized from the shape of the potentiodynamic recorded anodic electrode curve. An El II electrolyte free of 1 1 complex gives rise to the anodic curve (b) exhibited in Fig. 12. After addition of the 1 1 complex, a curve (a) with a current density mtiximum develops. The peak height of this maximum depends on the rotating speed of the anode and increases with rising concentration of the 1 1 complex. The value of the current maximum Ipeak is linearly dependent on l/oT, as well as on the concentration of the 1 1 complex. This concentration dependence can be used to determine the amount of 1 1 complex in the electrolyte [186]. 

Fig. 13. Polarization curves (recorded at 1 mV s ) corresponding to the photoanodic oxidation and the cathodic reduction of hydrogen peroxide at a polycrystalline Ti02-film electrode. Curve a is for an illuminated (X > 335 nm) and curve b for an unilluminated electrode (see text). Measurements performed in a deaerated 0.1 MNaOH/10" M H2O2 solution...

Figure 31-UV- visible spectra of catalase in PBS (pH 7)phosphate buffer solution(curve a) and Cat-NiO film on ITO electrode(curve b). Reprinted from Biophysical Chemistry, 125, A.Salimi, E. Sharifi, A. NoorBakhash, S. Soltanian, Direct electrochemistry and electrocatalytic activity of catalase immobilized onto electrodeposited nano-scale islands of nickel-oxide, 542, Copyright( 2007), with permission from Elsevier.

Figure 3.29 In situ SERS spectrum of hem in (Hm) adsorbed on a roughened Ag electrode (curve a, -0.50 V versus SCE) and its reduced counterpart (curve b, 0.1 V) recorded in an aqueous solution pH = 3, Xe%c = 532 nm.

FIGURE 8.18 Long-time chronoamperometric curves recorded for (a) bulky deposit and (b) fine deposit of PTA Y over a glassy carbon electrode. Curve (c) corresponds to the response at zeolite Y-modified electrodes with no attached polymer. 

Figure 16.4.4 SECM approach curves for different values of the heterogeneous rate constant, for the conversion of R to O at the substrate electrode. Curves a-p correspond to og dla) = —1.2,—1.1, —1.0,..., 0.3. [Reprinted with permission from A. J. Bard,...

Under irradiation (curve 2), a photoanodic current, /ph, flows as long as the potential of the electrode is more positive than fb, so that electron/hole pair separation can occur. Thus the onset of the photocurrent is near Ef y (unless surface recombination processes move the onset potential toward more positive values). The photo-oxidation of R to O occurs at less positive applied potentials than those required to carry out this process at an inert metal electrode (curve 3). This is possible because the light energy helps to drive the oxidation process hence such processes are frequently called photoassisted electrode reactions. 

Figure 3.16. Waveforms for pulse and differential-pulse polarography. Curves A and D Excitation signal applied to the working electrode. Curves B and E Instantaneous current observed at a single drop as a function of time. Curves C and F The resulting current-versus-voltage curves. In pulse polarography, square-wave voltage pulses of 40-msec duration are applied to the mercury drop, of drop-life mechanically controlled at 2.5 sec (A) ta,ti,ti,... represent successive drops. The overall rate of increase of the amplitude of the voltage pulses is about...

The cathode was charged from initial GaAs electrode (curve 1) and from GaAs electrode modified by Pt (curve 2). It is clear that the Pt modification significantly improves discharge characteristics. The photopotential of GaAs electrode, Ef has to be -1.15 -1.25 V (relative to the saturated calomel... 

Figure 8. Spectra of cyctochrome c measured in a cell with an optically transparent electrode. Curve 1—cytochrome c reduced at < 0.3 V curve 2— cytochrome c oxidized at Er > 1.2 V curve 3—the initial solution of cytochrome c.

Figure 17. Measurements on the sectional electrode. Curve 1 current versus potential on the completely immersed electrode curve 2 current versus the degree of immersion of the electrode, = +0.15 V, / = distance from the top edge of the electrode to the electrolyte surface.

Recently, much effort has been made on the facilitation of direct electron transfer of the SODs by self-assembled monolayers (SAMs) confined onto Au electrodes. For instance, Ohsaka et al. have formed various kinds of SAMs of alkanethiols onto an Au electrode and studied the electron transfer properties of the SODs [98]. Here, we will use the SAM of cysteine as an example to demonstrate the electron transfer of the SODs promoted by the SAMs of alkanethiols. Figure 6.1 depicts cyclic voltanunograms (CVs) obtained at a cysteine-modified Au electrode (curves a and b) in 25 mM phosphate buffer containing 0.56 mM Cu, Zn-SOD (the concentration used represents that of the Cu or Zn site of Cu, Zn-SOD). For comparison, the CV obtained at a bare Au electrode (curve c) under the same conditions was also given. As shown, the cysteine-modified electrode exhibits one pair of well-defined voltammetric peaks in the SOD-containing phosphate buffer (curve a). These redox peaks were not obtained at the bare Au electrode (curve c). This observation suggests that the direct electron transfer between Cu, Zn-SOD and Au electrode does not occur actually at the bare electrode, but it can be significantly promoted at Au electrode modified with the SAM of cysteine. 

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