Zeta potential as a tool for functional materials development

Abstract

The importance of the isoelectric point for the preparation and characterization of functional materials to understand their behavior and optimize their performance is highlighted, with especial focus on industrial catalysts. In different liquid-phase steps involved in materials synthesis, the knowledge of the surface charge as a function of the pH of the medium is fundamental, since it is the dynamizing agent of processes such as gelation, peptization, coagulation and agglomeration to form solid particles. Therefore, zeta potential (ζ) measurements, often based on electrophoretic migration techniques, are a powerful source of information. The basic principles are introduced to explain through relevant examples the possibilities for materials design. Regarding materials preparation, the measurement of the zeta potential to control the synthesis and coating of supports is reviewed, with special attention to shaped supports. Aspects as the influence of the binders on the supports properties depending on their mutual interaction are analyzed, with example systems based on TiO2 or Al2O3 and natural silicates such as sepiolite. Also, how the knowledge of ζ as a function of pH allows, by choosing the appropriate pH, the preferential impregnation of noble metals on porous supports, as well as the washcoating of dense ceramic monoliths with porous supports. Special attention has been paid to surfaces characterization based on the use of zeta potential measurements to estimate the formation and relative location of species, the apparent surface coverage, or the adsorption and reactivity, to establish synthesis strategies to achieve specific properties.