A combined temperature-calorimetric study of ion adsorption at the hematite-electrolyte interface: I. Model of a homogeneous oxide surface

The theoretical quantitative analysis of the temperature dependence and ent halpic effects of ion adsorption, developed in our earlier publications, wa s applied here to study the features of hematite/electrolyte interfaces. Th is is the first time that our set of experimental data could be used to car ry out a simultaneous analysis of both the temperature dependence of the ti tration isotherm and directly measured enthalpic effects. To draw possible general conclusions about the features of the hematite/electrolyte interfac es, we considered two sets of experimental data measured in two laboratorie s, using the hematite samples prepared in different ways. The differences i n sample preparations are manifested by substantially different values of t he monitored surface charges and related calorimetric effects. The present quantitative analysis in Part I or this publication was carried out by usin g the model of an energetically homogeneous solid surface, which is still c ommonly accepted. Certain inconsistencies were found in the parameter value s leading to a good fit of titration isotherms and those that are best to f it directly measured enthalpic effects. Thus, the general conclusion was dr awn that this popular model is too crude for a quantitative analysis.