S. Yamamoto et al., USING ATOMIC-FORCE MICROSCOPY TO IMAGE THE SURFACE OF THE POWDERED CATALYST KMN8O16, Journal of catalysis, 159(2), 1996, pp. 401-409
Atomic force microscopy (AFM) was used to determine the atomic configu
ration and topography of the surface of KMn8O16, a powdered form of al
pha-manganese dioxide (alpha-MnO2) containing K ions, By depositing th
e powder on mica, we were able for the first time to use AFM to image
the surface of the powder. We took three types of images: low-resoluti
on, wide-scan (5 x 5 mu m(2) region); high-resolution (500 x 500 nm(2)
region); and atomic-scale (10 x 10 and 2 x 2 nm(2) regions). The low-
resolution imaging showed that the powder has needle-like crystallites
. The high-resolution imaging showed that the surface of the powder ha
s a ''faceted'' structure, The atomic-scale imaging revealed that the
facet plane has a hill-and-valley structure with a height difference o
f 0.2-0.3 nm along the crystal C axis, Furthermore, the surfaces of th
e hills were (110) surfaces, and those of the valleys were surfaces fo
rmed by the removal of O-Mn-O units from these (110) surfaces, Atomic-
scale imaging of a hill shows a periodic structure that corresponds to
the configuration of surface hydroxyl species and bridging oxygen ato
ms of the (110) plane, The close agreement that we found when we super
imposed the atomic-scale images and the bulk structure projection indi
cates that there is no reconstruction on the (110) surface of powdered
KMn8O16. (C) 1996 Academic Press, Inc.