Double pulse method

CS = coulostatic method, CV = cyclic voltamogram, FD = Faradaic distortion method, FR = Faradaic rectification, GD = galvanostatic double pulse method, IP = impedance method, PS = potential step method. See also list of... 

Fig. 5.18 Potentiostatic methods (A) single-pulse method, (B), (C) double-pulse methods (B for an electrocrystallization study and C for the study of products of electrolysis during the first pulse), (D) potential-sweep voltammetry, (E) triangular pulse voltammetry, (F) a series of pulses for electrode preparation, (G) cyclic voltammetry (the last pulse is recorded), (H) d.c. polarography (the electrode potential during the drop-time is considered constant this fact is expressed by the step function of time—actually the potential increases continuously), (I) a.c. polarography and (J) pulse polarography...

If the reaction is too fast for this procedure, a double-pulse method can be used The current pulse is preceded by a short but high pulse which is designed to charge the double layer. The height of the pulse is adjusted in such a way that the transient 77(f) is horizontal at the... 

Double Heck reaction, 42 494 Double layer interface, 30 223-225 Double nucleophilic displacement, capped cyclodextrin, 32 437 Double-pulse method, 38 31 Double recognition models, 32 451 52 Doublet mechanisms, 30 43, 45, 47 Drago parameters, 38 212 Drougard-Decrooq equation, 30 345, 356, 371 Dry evaporation, perovskite preparation, 36 246-247... 

Figure 10 The geminate decay of the radical cation in irradiated neat -dodecane observed by the subpicosecond pulse radiolysis before (a) and after (b) the improvement of the system by mainly using the double-pulse method.

From Eq. (44), to achieve a good S/N ratio measurement, it is necessary and sufficient to lower the fluctuation of /q//. Based on this information, we devised a new method to measure I and /q with a good S/N ratio. We named it the double-pulse method. In the new method, /q is measured by the laser pulse passing just before the laser pulse used to measure 7. Because the frequency of the TirSapphire laser is 81 MHz, the time interval of two laser pulses is 12.3 nsec. The laser pulse for the measurement of 7 passes through the sample 12.3 nsec after the laser pulse for the measurement of 7q. An... 

In the double-pulse method, the first pulse directed on wet cells consumes, by free-radical reactions, all the 02 which is dissolved in the cells. The second pulse... 

According to the above, the electrochemical response in the different differential pulse techniques can be very different, and it is worth analyzing the advantages and disadvantages of each method. Regarding the double pulse methods, in normal mode, DNDPV, this has the inconvenience of presenting asymmetrical peaks that can hinder the experimental determination of the peak current. In addition, the peak... 

Fig. 8.2 Schematic representation of the double-pulse method utilized for the preparation of silver and gold clusters...

Recent investigations on the electrodeposition of silver demonstrated that the double-pulse method is a suitable technique for controlling the nanoparticle preparation, if the pulse parameters are carefully chosen and adjusted to the desired particle structure [29, 30]. Whereas particle density can be controlled via the overpotential and duration time ti of the nucleation pulse 1, the particle size can be enlarged by the growth time 2 (Fig. 8.5, [30]). 

Fig. 8.8 Optical images (at an active zone I) of isolated silver clusters electrodeposited onto ITO by means of the double-pulse method ( i = —1,550 mV 2 = —VOO mV, 25 s) [37] (a) Scanning confocal microscopy image (topography mode), (b) Raman/fluorescence image of the same sample area, (c) SEM image corresponding to (a) and (b)...

Sandmann G, Dietz H, Plieth W (2000) Preparation of silver nanoparticles on TTO surfaces by a double-pulse method. J Electroanal Chem 491 78... 

Fig. 8. Results from the double-pulse method for evaluation of extents of chemisorbed H in the course of the HER. (From Ref. 121.)...

Early work by Gerischer and Mehl (106) employed impedance analysis at Ag and Cu electrodes. However, these metals are not of major interest as H adsorption is weak, and these materials are not attractive as water electrolyzer cathodes. Bockris et al. (121) and Selvaratnam and Devanathan (122) employed the double-pulse method (see Section VI,B,1) for Ag and Ni, but the results did not seem to be very meaningful. 

Using the double-pulse method for the electrodeposition process [2], the kwon SERS signal of adsorbed cyanide ions at 2110 cm showed a splitting into different bands first results were reported in [3]. A tentative explanation was given by the assumption of formation of different sizes of clusters with different SER fiequencies of the adsorbed ions. 

The intercept of the plot allows the determination of l/t o only when this term is appreciable compared to RT/F)ACdN (8). To overcome this limitation for fast electron-transfer reactions, where /q is large, the galvanostatic double-pulse method has been proposed (Section 8.6). 

Figure 8.6.1 Excitation waveform for the galvanostatic double pulse method.

Figure 8.6.2 Block diagram for galvanostatic double-pulse method. A two-electrode cell (i.e., with a common counter/reference electrode) is placed in a bridge circuit for compensation of the cell ohmic resistance, The bridge is adjusted with = Rb so that the...

Figure 8.6.3 a) Overpotential-time traces for galvanostatic double-pulse method for reduction of... 

If separate reduction waves are observed for O2 and CO2 and there is no interference between the two it may be possible to measure the two gases using a double pulse method. This is analogous to the determination of oxygen and nitrous oxide on silver (vide infra). If the pulses are short enough this might be considered to be a simultaneous determination. 

A sensor based on this reaction scheme has been described by Hahn [37]. This is a Clark type sensor which operates using a double pulse method. The first pulse is to a potential at which the reduction of oxygen occurs at its diffusion limited rate. The integrated current is used as a measure of oxygen concentration. The second pulse is to a potential where the superoxide ion is oxidised back to oxygen. In the absence of COj the integrated current should match that of the forward pulse. When CO2 is present the reverse pulse is diminished. The difference between the two pulses is therefore a measure of the amount of carbon dioxide present. The interested reader is referred to the review by Hahn for further details of this system. 

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