Point of zero potential of single-crystal electrode/inert electrolyte interface

• Published in: Journal of colloid and interface science 2012-03, Vol.370 (1), p.139-143
• Main Authors: Zarzycki, Piotr, Preočanin, Tajana
• Format: Article
• Language: English
• Subjects: Anions; cations; Chemistry; Common intersection point; Electrochemical cells; electrochemistry; Electrodes; electrolytes; Exact sciences and technology; General and physical chemistry; groundwater; Hematite; hysteresis; ionic strength; Mathematical models; oxides; Point of zero potential; Point of zero salt effect; Rutile; Silver bromide; Silver chloride; Silver halides; Single crystals; Single-crystal electrode; soil; solubility; sorption; Surface physical chemistry; Surface potential; titration
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2011.12.068

[Display omitted] ► Electrostatic characteristics of specific crystal faces from non-hysteretic titration. ► Surface reconstruction increases the number of sites with high proton affinity. ► Halide ions preferentially adsorbed on silver halide surfaces. Most of the environmentally important processes occur at the specific hydrated mineral faces. Their rates and mechanisms are in part controlled by the interfacial electrostatics, which can be quantitatively described by the point of zero potential (PZP). Unfortunately, the PZP value of specific crystal face is very difficult to be experimentally determined. Here we show that PZP can be extracted from a single-crystal electrode potentiometric titration, assuming the stable electrochemical cell resistivity and lack of specific electrolyte ions sorption. Our method is based on determining a common intersection point of the electrochemical cell electromotive force at various ionic strengths, and it is illustrated for a few selected surfaces of rutile, hematite, silver chloride, and bromide monocrystals. In the case of metal oxides, we have observed the higher PZP values than those theoretically predicted using the MultiSite Complexation Model (MUSIC), that is, 8.4 for (001) hematite (MUSIC-predicted ∼6), 8.7 for (110) rutile (MUSIC-predicted ∼6), and about 7 for (001) rutile (MUSIC-predicted 6.6). In the case of silver halides, the order of estimated PZP values (6.4 for AgCl