Morphological changes potential-dependent

The application of periodic electric potentials to the electrodes in contact with the electrolytes produces morphological changes that depend on the upper and lower potential limits (Eu and E,), the frequency (/), and the time-symmetry of the program [27-29]. In the case of a noble metal in a strong acid or alkaline solution, the effect is assigned to a pulse plating electrodissolution/deposition on different metal sites [30-32], These methods can produce considerable modifications on electrodeposits such as morphology, adherence, uniformity, etc. 

Provided that morphology does not change. The dependences on component potential and doping have to be discussed analogously. 5 An alternative technique uses guard rings.289... 

By changing the surface morphology which then can influence any one of the four factors enumerated above. This last point is the reason why the electric potential dependence of SERS is included in this section, and the focus of the discussion will be on it. Note that such morphological changes may be associated with irreversible behavior as a function of potential, while one may expect a more reversible dependence for the first three effects. One should keep in mind that it is not always possible to determine which of these above points is operative in a given system. 

It has only recently been discovered that SER spectra can be obtained from systems involving non-aqueous electrolyte solutions [35, 36], The first report was for pyridine in N, iV-dimethylformamide solution at a silver electrode [35]. Variations in the relative intensities of the pyridine bands in the 1000 cm-1 wavenumber region as a function of electrode potential are shown in Fig. 19. These potential-dependent changes are quite different from those recorded for the corresponding aqueous system and have been interpreted in terms of the solvent effect on the surface morphology of the electrode. 

The principle of operation of SECCM was explained in Sect. 1.5.6. Unwin s group demonstrated that the reactivity toward ORR of individual nanoparticles with a size in the order of 100 nm can be resolved using SECCM (Fig. 22b) [100]. Their study showed that subtle variations in the morphology of nanoparticles lead to dramatic changes in (potential-dependent) reactivity, which has important implications for the design and assessment of nanoparticle catalysts. 

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