EFFECT OF POTASSIUM ON THE SURFACE-POTENTIAL OF TITANIA

The surface potential, chi, of several commercial titania powders has been measured by the vibrating condenser method in the temperature ran ge 100-450-degrees-C in air. The K impurity detected by XPS on some of titanias lowers the chi value of TiO2 considerably. A series of K-dop ed TiO2 anatase samples containing from 1.1 to 11 K atoms nm-2 was pre pared and examined by surface potential and XPS techniques. The surfac e potential of anatase decreases linearly with increasing potassium co ntent up to ca. 2.4 K atoms nm-2 , and then remains constant. The surf ace potential of K-doped samples varies to a smaller extent with tempe rature compared with undoped anatase. On the basis of the surface pote ntial and XPS data obtained, it is suggested that the mode of K deposi tion on the surface of anatase changes at a coverage of about 2 K atom s nm-2.