The influence of particle size on CO adsorption on Pd/alumina model
catalysts
Surf. Sci., (1994)DOI: 10.1016/0039-6028(94)91159-2
Abstract
The adsorption of CO on Pd(111) and small Pd particles deposited on
an alumina support has been studied by means of temperature programmed
desorption (TPD) using a molecular beam doser. The supported Pd particles
with an average size of 27 and 2.5 nm were prepared by electron bombardment
induced thermal evaporation. The CO desorption data were obtained
for the Pd particles as well as for a Pd(111) single crystal. Major
differences in the Pd particle and single crystal data were observed.
On the 2.5 nm Pd particle surface different CO adsorption states
were found. The decay in CO adsorption capacity during repeated adsorption/desorption
cycles caused by simultaneous accumulation of surface carbon from
partial CO dissociation was monitored. It is shown that surface carbon
formation reduces the value of desorption activation energy for the
adsorption state with higher binding energy. The calculated activation
energy of desorption shows that CO desorption kinetics is particle
size dependent.