Physical chemical interpretation of primary charging behaviour of metal (hydr) oxides

摘要: The primary charging behaviour of metal (hydr)oxides is great practical and theoretical importance. It has been shown in the literature that it possible to describe this with widely different models. This ability experimental observations not contributed a consensus respect physical interpretation. most popular models for interpretation are, essence, all combination description adsorption protons (“site-binding model”) double layer model. classical one- two-pK site-binding assume surface can be treated as chemically homogeneous. Recently, multisite complexation model formulated (MUSIC model) allows priori estimation proton affinity constants various types reactive groups present on (hydr)oxides. Large differences between capacitance (dσo/dpH) well Stern (0.2–4 F m−2 found (hydr)oxides, are discussed. A compact part derived compared AgI. From follows crystallized non-porous expected smaller than or equal around 1.7 m−2. Analysis curves colloids like gibbsite (Al(OH)3), rutile (TiO2) goethite (FeOOH) MUSIC approach leads 1.2±0.4 m−2, agreement proposed structure. Salt dependency value support assumption ion-pair formation. For silica higher which easily interpreted light structure since confined densely packed groups. Goethites specific area less 50 m2 g−1, prepared by rapid neutralization an iron salt, charge significantly better. being due presence other crystal faces and/or porosity.