An increase in the PdO surface area by a factor of about 20 was observed af
ter treatment of Pd foils in excess methane at 598 K. The surface area was
increased as the O-2 partial pressure in the activation treatment was decre
ased. The activated foil was probed by the reaction of complete oxidation o
f methane in excess Oz. The rate was proportional to the PdO surface area a
nd thus the turnover rate per unit of PdO area was the same as that for the
untreated foil. Critical for this assessment was the determination of the
PdO surface area measured by exchange of surface oxygen with O-18(2). The P
dO surface area decreased after interaction with water when the sample was
cooled. After treatment of the foil in excess methane, PdO but not Pd was i
dentified by X-ray photoelectron spectroscopy, and carbon deposits from met
hane were identified on the surface and in the bulk by temperature-programm
ed desorption. (C) 2001 Academic Press.