Setup potentiostatic

Figure 6.2-2 Simplified circuit of an electrochemical STM setup. In addition to the potentiostat...

In the following, after a brief description of the experimental setup and procedures (Section 13.2), we will first focus on the adsorption and on the coverage and composition of the adlayer resulting from adsorption of the respective Cj molecules at a potential in the Hup range as determined by adsorbate stripping experiments (Section 13.3.1). Section 13.3.2 deals with bulk oxidation of the respective reactants and the contribution of the different reaction products to the total reaction current under continuous electrolyte flow, first in potentiodynamic experiments and then in potentiostatic reaction transients, after stepping the potential from 0.16 to 0.6 V, which was chosen as a typical reaction potential. The results are discussed in terms of a mechanism in which, for methanol and formaldehyde oxidation, the commonly used dual-pathway mechanism is extended by the possibility that reaction intermediates can desorb as incomplete oxidation products and also re-adsorb for further oxidation (for the formic acid oxidation mechanism, see [Samjeske and Osawa, 2005 Chen et al., 2006a, b Miki et al., 2004]). 

The DBMS setup and experimental procedures used in this study were the same as described in more detail elsewhere [Jusys et al., 2001]. Briefly, the DBMS setup consisted of two differentially pumped chambers, a Balzers QMS 112 quadrupole mass spectrometer (MS), a Pine Instruments potentiostat, and a computerized data acquisition system. 

The experimental setup included a three-electrode electrochemical cell with a liquid contact membrane electrode in which the internal Ag/AgCl electrode acted as a working electrode connected to a potentiostat/galvanostat. The instrument was capable of switching rapidly between potentiostatic and galvanostatic modes [51]. 

Figure 6.2-2 Simplified circuit of an electrochemical STM setup. In addition to the potentiostat (see Figure 6.2.1), an STM preamplifier is added, to which the tip is connected. Ul potentiosta-tic setpoint, U2 tunneling voltage, l(t) tunneling current, U3 = -R l(t).

In terms of the earlier material, this technique is nearest to the potentiostatic technique, but because here the potential is made to vary linearly with time (i.e., it is not static), the more appropriate name ispotentiodynaniic. As far as the electrode, cell, etc., are concerned, one has the same setup as with potentiostatic transients the difference is that instead of being fixed at a given value while the ip is observed, the potential is made to change at a constant rate over a chosen potential range. The range of acceptable values for the sweep rate is something to be discussed in detail later, but it may be stated now that a typical value is 10 mV s ... 

Electropolymerization and cyclic voltammetric experiments are performed with an EG G PARC, Model 173 potentiostat equipped with a Model 175 universal programmer and a Model 179 digital coulometer in conjunction with a Kipp and Zonen BD 91 XY/t recorder. All experiments are carried out using a conventional three-electrode cell. Instrumental setup for amperometric measurements ... 

A distinguishing aspect in electrode kinetics is that the heterogeneous rate constants, kred and kox, can be controlled externally by the difference between the inner potential in the metal electrode (V/>M) and in solution (7/>so1) that is, through the interfacial potential difference E = electrode setup (typically, a three-electrode arrangement and a potentiostat), the E-value can be varied in order to distort the electrochemical equilibrium and favor the electro-oxidation or electro-reduction reactions. Thus, the molar electrochemical Gibbs energy of reaction Scheme (l.IV), as derived from the electrochemical potentials of the reactant and product species, can be written as (see Eqs. 1.32 and 1.33 with n = 1)... 

There are two types of potentiostat setups in the laboratory, and each requires a different procedure to perform a potentiostatic polarization. Determine which type of potentiostat (PAR 273 or VersaStat) is at your station and use the appro-... 

Figure 3 The experimental setup window showing the potentiostatic technique option.

Figure 9 Example of screen setup to run potentiostatic holds as in tests 2 and 3.

During the SECV study, the PEVD system and all experimental parameters were similar to those in the steady-state potentiostatic work. The only difference was the external circuit, in which a CAS-100 system (Gamry, Inc.) was used to connect with a PEVD sample. This setup... 

Figure 1 Schematic of EP sample and experimental setup. G-P, galvanostat-potentiostat A-S, analog switch W,C,R, working, counter-, and reference electrodes, respectively.

Figure 1. Typical H-cell for electrolysis using two-electrode setup (reference electrode can be inserted into working compartment for potentiostatic control).

Figure 1. Schematic of the experimental setup for electrochemical promotion studies using the fuel-cell type design (a) and for using x-ray photoelectron spectroscopy (XPS) (b) to investigate the catalyst-electrode surface G-P Galvanostat-Potentiostat WE Working electrode, RE Reference electrode, CE Counter Electrode (adapted from refs. [6], [25]).

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