The zno/aqueous solution interface. I. Capacity of the double layer

Abstract

At the ZnO/aqueous electrolyte solution interface, three processes occur on changing the pH of the medium: (a) adsorption of H ÷ or OH-; (b) dissolution or precipitation of ZnO; (c) a slow process consuming H + or OH-, A technique is described by which these processes can be separated. When due allowance is made for the slow process and when the influence of changes in solubility is eliminated, the capacity due to adsorption of H ÷ or OH-alone can be calculated: it is significantly smaller than that found by titration, and smaller than that of the diffuse double layer. The Stern capacity is comparable to that found at AgI/aqueous electrolyte solution interfaces near the pzc.

Surface charge and coagulation of aqueous ZnO dispersions

“…show the same characteristics as reported by Trimbos et al (5), which had been found by other investigators as well (2, 3). Thus, a fast H ÷ or OH-consumption was followed by a slow process.…”

“…Thus, we must conclude that this slow process is connected with surface carbonate groups rather than with a surface reaction involving ZnOH groups with mobile charge cartiers, as suggested earlier by the kinetics of the process (5). Similarly slow H + or OH-consumption as found for ZnO a.r.…”

“…Surface charge measurements were performed in concentrated suspensions (7.00 g ZnO in 300 ml) by the pH stat method described by Trimbos et al (5). The liquid phase was, before addition of the ZnO, saturated by 15 mg of ZnO; the attainment of solubility equilibrium was followed through the accompanying H + or OH-consumption.…”

“…(1)(2)(3)(4)(5)). One of the interesting aspects of ZnO from a colloid chemical point of view is, that one ~" potential can be found combined with different situations at the ZnO/aqueous solution phase boundary (different amounts of adsorbed ions, or of interstitial Zn).…”

Interfase Óxido/Electrolito: Fenómeno de transferencia de electrones

“…The semiconductor/electrolyte solution interface system (16-18) was studied in order to explain the phenomenon of electron transfer between semiconductor and electrolyte (16,17,20). The semiconductor/electrolyte solution interface has been studied by comparing the P-N junction (18)(19) because of the phenomenological similarities found between semiconductor/electrolyte and P-N junctions (16,19,20,23).…”