Stepped Experiments

FIGURE 1-2 Concentration profiles for different times t after the start of a potential-step experiment. 

Alternately, for potential-step experiments (e.g., chronoamperometry, see Section 3-1), the charging current is die same as that obtained when a potential step is applied to a series RC circuit ... 

The potential-step experiment can also be used to record the charge versus tune dependence. This is accomplished by integrating the current resulting from the... 

Derive the Cottrell equation by combining Fick s first law of diffusion with the tune-dependent change of the concentration gradient during a potential-step experiment. 

As an alternative to potential step experiments, current steps have also been used.163,166,167 Again, small-amplitude experiments are preferable,163 and a migration model should be used for data analysis.167... 

In outline of what follows we will begin by brief reference to previous work on coal liquefaction. The present approach will then be motivated from considerations of coal structure and hydro-gen-donor activity. A theoretical section follows in the form of a pericyclic hypothesis for the coal liquefaction mechanism, with focus on the hydrogen transfer step. Experiments suggested by the theory are then discussed, with presentation of preliminary results for hydrogen transfer among model substrates as well as for the liquefaction of an Illinois No. 6 coal to hexane-, benzene-, and pyridine-solubles by selected hydrogen donors. 

Two types of potential step experiments were carried out in this work those in which the working electrode was electrochemically cycled in acid electrolyte alone (type A) before methanol was admitted with the electrode held at a very low potential, and those in which the electrode was cycled in acid electrolyte in the presence of methanol (type B) before the spectroscopic... 

The initial stages, notably the formation of a monolayer on a foreign substrate at underpotentials, were mainly studied by classical electrochemical techniques, such as cyclic voltammetry [8, 9], potential-step experiments or impedance spectroscopy [10], and by optical spectroscopies, e.g., by differential reflectance [11-13] or electroreflectance [14] spectroscopy, in an attempt to evaluate the optical and electronic properties of thin metal overlayers as function of their thickness. Competently written reviews on the classic approach to metal deposition, which laid the basis of our present understanding and which still is indispensable for a thorough investigation of plating processes, are found in the literature [15-17]. 

Fig. 19. Sampled-current voltammogram constructed from the current-time transients that resulted from a series of potential-step experiments at a stationary Pt electrode in a 35.0 x 10 3 mol L-1 solution of Ni(II) in the 66.7 m/o AlCl3-EtMeImCl melt ( ) total current, ( ) partial current for the electrodeposition of Ni, (O) partial current for the electrodeposition of Al. The total current was sampled at 3 s after the application of each potential pulse. Adapted from Pitner et al. [47] by permission of The Electrochemical Society. 

Cyclic voltammetry (CV) curves were recorded on a Kipp and Zonen BD91 X-Y recorder and the current-time transients resulting from the potential step experiments were recorded digitally. The apparatus used included a PAR Model 173 potentiostat and an IBM XT computer... 

A- Single Step Experiments. Potential step experiments were performed in order to determine the reaction mechanism and the reaction rate. As described above, the platinum surface was initially covered by a monolayer of CO at a controlled potential, Ef = 0.40 V (referred to as the initial potential) and then CO was removed from the bulk of the solution. Next, the electrode potential was suddenly changed to a more positive value, Ef, (referred to as the final potential) where the adsorbed CO was oxidized and the rate of oxidation was followed by recording the resulting current transients. 

Figure 2. Three-dimensional plots of the CO oxidation transients determined in the single potential step experiments on the Pt(100) electrode in 0.10 M HC10., solution. The potential step was applied from E = +0.40 V to Ep displayed on the third axis of the figure.

Figure 6. A plot of the logarithm of the square root of the initial slope of the current time transients determined in the double step experiments against the final potential for the three single crystal surfaces investigated.

Regression of He - 1 vol% CO/He Concentration Step Experiments for the CO Oxidation Over Fully Oxidized Catalyst in the Absence of Oxygen in the Reactor Feed Gas... 

During the potential step experiment, the initial condition (I.C.) and the boundary condition (B.C.) are given as... 

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