Interaction effects in electrodeposited monolayers and the role of the “electrosorption valency” factor

Abstract

Interaction effects in electrodeposited monolayers at electrodes can be evaluated from the half-widths of adsorption pseudo-capacitance ( C) vs. potential ( V) profiles, as treated in earlier papers. It is shown that when the species electrodeposited is an incompletely discharged ion (electrosorption valency number γ<1) half-widths of C vs. V profiles greater than for the zero interaction Langmuir case arise, depending on the value of γ. It is also necessary to take into account a broadening of the C vs. V profile that occurs in any case for γ<1, even in the hypothetical absence of repulsive interaction effects. A scaling factor γ 2 also diminishes C at any given coverage or potential in comparison to its value for a complete surface charge-transfer process. The repulsive effect, characterized by the parameter g, is related to γ through various models of the partially charged ad-layer which behaves as an array of surface dipoles having electrical properties depending on γ and the electronegativity difference between the adsorbate and adsorbent species. Applications to some experimental examples of upd are discussed.