Surface potential sweep methods

An interesting point to consider is the effect of surface roughness on the range of applicability of the linear potential sweep method. The... 

Reductive removal of these oxygen layers is a slow kinetic process, commencing at potentials well below the characteristic potential for the layer formation on each metal. Thus, adsorption results based on the commonly used triangular potential sweep method can depend on the anodic potential excursions, the frequency of potential cycling and the number of cycles, that is, the catalyst surface history. Similarly, kinetic studies of oxygen reduction can be influenced by the dependence of the oxygen layer formation... 

A useful adjunct of linear potential sweep methods is called cyclic voltammetry. Rather than stopping an oxidative voltammogram at, say, + 0.8 V, the potential is reversed and scanned backward, i.e., a triangular wave potential is applied. The oxidation product formed is present at and close to the electrode surface. With fairly rapid potential sweeps (ca. >4 V/min) it is almost completely re-reduced back to the starting material on the reverse potential sweep. Figure 14B shows a typical cyclic voltammogram for a reversible system (solid line). The ratio of forward to reverse peak currents is unity. If, however, some rapid process removes the product(s), litde or no reverse current is obtained (dotted lines of Fig. 14B). This happens if the overall oxidation is totally irreversible, or fast chemical reactions intervene. We will also see later that a peculiar property of very small electrodes can eliminate most of the reverse current in a cyclic voltammogram. 

Kant, R. (2010) General Theory of Arbitrary Potential Sweep Methods on an Arbitrary Topography Electrode and Its Application to Random Surface Roughness. /, Phys. Chem C. Vol.114, No.24, Qune 2010), pp. 10894-10900, ISSN 1932-7447 Lange, R. Doblhofer, K. (1987) The Transient Response of Electrodes Coated with Membrane-Type Polymer Films under Conditions of Diffusion and Migration of the Redox Ions. /, Electroanal. Chem. Vol.237, No.l, (November 1987), pp. 13-26, ISSN 1572-6657... 

Since the 1960s , various electrochemical methods such as linear potential sweep voltammetry, cyclic voltammetry etc. and various surface analysis apparatuses such as infrared spectra, X-ray photoelecfron spectroscopy etc. have been developed to investigate the electrochemical reaction mechanism involved in the flotation of sulphide minerals (Fuerstenau et al., 1968 Woods, 1976 Ahmed, 1978 Stm, 1990 Feng, 1989 Buckley, 1995 Arce and Gonzalez, 2002 Bulut and Atak, 2002 Costa et al., 2002). 

Linear sweep voltammetry, capacitance-voltage and automated admittance measurements have been applied to characterize the n-GaAs/room temperature molten salt interphase. Semiconductor crystal orientation is shown to be an important factor in the manner in which chemical interactions with the electrolyte can influence the surface potentials. For example, the flat-band shift for (100) orientation was (2.3RT/F)V per pCl" unit compared to 2(2.3RT/F)V per pCl" for (111) orientation. The manner in which these interactions may be used to optimize cell performance is discussed. The equivalent parallel conductance method has been used to identify the circuit elements for the non-illum-inated semi conductor/electrolyte interphase. The utility of this... 

The nature and structure of surface intermediates in hydrocarbon adsorption has been investigated using galvanostatic (constant current) and potential sweep techniques (7, 10, 172-174 or radiotracer methods (175. Niedrach s (172, 173 galvanostatic results with C1-C4 alkanes and with ethylene indicate the existence of common, partially oxidized surface species, despite differences in the initially adsorbed hydrocarbons. Methane adsorption is very slow, but higher saturated hydrocarbons adsorb faster and at similar rates. Potentiostatic adsorption followed by an anodic potential sweep gives two peaks [Fig. 14 (174 corresponding to different adsorbed species. The intermediate responsible for the peak at low potentials (0.7-... 

Fig.6. In-situ STM images of gold surfaces with figures machined into the surface by electrochemical methods, (a) Square produced by a sweep of cell potential fi om 0 to -100 mV five times in a diluted MBS (2-(N-moipholino)ethanesulfonic acid) buffer electrolyte. E = 500 mV, El = 546 mV, d = 24 nm, f = 2.5 nA. (b) Cavity in the surface produced by performing 40 copper electrodepositions and sub-sequent dissolutions with potentials between -500 mV and 500 mV.

The advantage of LPSIRS is that repetitive potential sweeps continuously control the electrode surface by means of LSCV. This technique is particularly useful when unstable systems are considered. However, the successive spectral accumulations may require a rather long time (several hours), and the method is therefore restricted to investigations in narrow wavelength ranges. The equipment is the same as for EMIRS and need not be described further. 

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