Specific Features in Potential-Difference IR Spectra of Electrode-Electrolyte Interfaces

SPECIFIC FEATURES IN POTENTIAL-DIFFERENCE IR SPECTRA OF ELECTRODE-ELECTROLYTE INTERFACES 

According to electrochemical theory, the kinetics of an electrochemical reaction is controlled by the potential drop between the solid and solution phases [133-136]. A dynamic zone extending in both directions from the electrified interface over which this drop exists is called the double layer (DL) of charge. The DL in the solution is made up of adsorbed and solvated ions (molecules) and solvent. Its dense part, which is referred to as the Helmholtz layer (HL), plays the major role in the interfacial processes. At low ion concentration, there is also a diffuse layer Gouy layer) in the solution. The countercharged part of the DL in a metal electrode is comprised of a skin layer with an excess or a deficit of electrons. The DL in a semicondnctor electrode is called the space charge layer. It consists of an accumulation, depletion, or inversion layer with an excess or a deficit of electrons or holes and ionized donor or acceptor states, depending on 

Typically, a potential-difference spectrum of the electrode-electrolyte interface presents negative, positive, and bipolar bands and smooth background absorption, which are due to aU species in the path of IR radiation that are affected by the electrode potential O igs. 3.40, 3.43a, 4.47a, 4.50a, 7.45, and 7.47). In addition to the absorption bands that reflect change in the population in the HL of reagents/products for the reaction under study, these may include the bands due to (1) the electrolyte species in the diffuse layer, (2) the electrolyte species in the HL, (3) the reagent/product species whose absorption (parameters of the elementary oscillators) is modulated by potential and coadsorption of electrolyte species, (4) delocalized and localized charge carries, and (5) optical effects of various nature. Consider these effects in more detail. 

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