Potential programs

The measurement of the current for a redox process as a fiinction of an applied potential yields a voltaimnogram characteristic of the analyte of interest. The particular features, such as peak potentials, halfwave potentials, relative peak/wave height of a voltaimnogram give qualitative infonnation about the analyte electrochemistry within the sample being studied, whilst quantitative data can also be detennined. There is a wealth of voltaimnetric teclmiques, which are linked to the fonn of potential program and mode of current measurement adopted. Potential-step and potential-sweep... 

Y. Jiang, I.V. Yentekakis, and C.G. Vayenas, Potential-programmed reduction A new technique for investigating chemisorption on catalysts supported on solid electrolytes, J. Catal. 148, 240-251 (1994). 

The creation of two types of chemisorbed oxygen on Pt and Ag surfaces subject to NEMCA conditions is clearly shown by cyclic voltammetry (Fig. 5.27)319,50,52 or by the similar Potential-Programmed-Reduction (PPR)... 

FIGURE 2.7. Double potential step chronoamperometry for an EC mechanism with an irreversible follow-up reaction, a Potential program with a cyclic voltammogram showing the location of the starting and inversion potentials to avoid interference of the charge transfer kinetics, b Example of chronoamperometric response, c Variation of the normalized anodic-to-cathodic current ratio, R, with the dimensionless kinetic parameter X. 

In the RNPV technique (see Ref. 68 and references therein), which is a derivative of LAPV, the initial potential is set to a value where the electrode reaction of interest occurs, causing an accumulation of the reaction products. Next, an analysis pulse similar to that used in LAPV is applied so as to oxidize or reduce the reaction products as appropriate [68]. The RNPV technique is well suited for studying reactions complicated by adsorption or those producing products that foul the electrode surface, because the potential program can be adjusted so as to elec-... 

Figure 28.13 ECL generation by the step technique. The Ag/AgCl, KC1 (satd.) reference is -0.045 V vs. SCE. (a) Cyclic voltammetric curve (0.593 mAf rubrene in benzo-nitrile with 0.1 M TBAP) (b) working electrode potential program (c) emission intensity versus time.

Fig. 13.7. Crystal impedance spectra acquired during the deposition of a PVF film from CH2Cl2/0.1 mol dm-3 TEAT. Inset shows the potential program. Numbers indicate deposition time. (Reproduced from Ref. (42] with permission.)...

Polarogram — Figure. Potential program and the respective (a) direct current (DC) (staircase ramp), (b) normal pulse (NP) and (c), differential pulse (DP) polarograms of 0.1 mM Cd(NC>3)2. All measurements were in water with 0.1 M KC1, E is versus a SCE, scan rate = 2 mVs-1 and drop time = 2 s. Differential pulse height = 10 mV... 

The promotional index, Pip [Eq. (2)]. After the establishment, via the use of surface spectroscopy (XPS [87,88], UPS [89], TPD [90], PEEM [91], STM [92], work function measurements [93]) but also electrochemistry (cyclic voltammetry [90], potential programmed reduction [94], AC impedance spectroscopy [43,95]), that electrochemical promotion is due to the potential-controlled migration (reverse spillover or backspillover) [13] of promoting ionic species (0 , Na", H, F ) from the solid electrolyte to the gas-exposed catalyst surface, it became clear that electrochemical promotion is functionally very similar to classical promotion and that the promotional index PI, already defined in Eq. (2), can be used interchangeably, both in classical and in electrochemical promotion. 

More recently, the careful work of Benny Johnson has been instrumental in elucidating how best to apply PRISM in the context of the two- and three-center problems. The extraordinary speed of the Electrostatic Potential program in Gaussian 92 is compelling testimony to his successes in this endeavor. 

From the above equation and the integration of the ak(t) values, we can calculate the expressions of the eigenfunctions. We will use the example of the square-wave potential program, since the effects of its crystalline arrangement was clearly demonstrated. First, the vibronic and electronic states of the H+-H20 system perturbed by an ac electric potential are subjected to a pulsating electric field ... 

---