Effect of potassium on the surface potential of titania

Abstract

The surface potential, χ, of several commercial titania powders has been measured by the vibrating condenser method in the temperature range 100–450 °C in air. The K impurity detected by XPS on some of titanias lowers the χ value of TiO₂ considerably. A series of K-doped TiO₂ anatase samples containing from 1.1 to 11 K atoms nm^–2 was prepared and examined by surface potential and XPS techniques. The surface potential of anatase decreases linearly with increasing potassium content up to ca. 2.4 K atoms nm^–2, and then remains constant. The surface potential of K-doped samples varies to a smaller extent with temperature compared with undoped anatase. On the basis of the surface potential and XPS data obtained, it is suggested that the mode of K deposition on the surface of anatase changes at a coverage of about 2 K atoms nm^–2.