In situ observation of CO oxidation on Ag110(2 x 1)-O by scanning tunneling microscopy: structural fluctuation and catalytic activity.
On the added-row reconstructed Ag(110)(nx1)-O surfaces where one-dimensional -Ag-O-Ag-O- chains arrange periodically, the clean-off reaction of O adatoms by CO was investigated using variable temperature scanning tunneling microscopy (VT-STM). Based on the in situ STM observations of the surface structure variation in the course of the reaction at various temperatures, we found that the reaction kinetics are significantly affected by the structural transition of AgO chains from a solid straight line configuration to dynamically fluctuating configurations. Below 230 K where the chains are straight, the reaction takes place only at the end of the chains, so that the reaction progresses in the zero-order kinetics with the reaction front propagating along the chain. The temperature dependence of the reaction rates yields the activation barrier of 41 kJ/mol and the preexponential factor of 1.7 x 10(3) cm(-2) s(-1). At room temperature, the reaction rate is drastically accelerated when almost half of the O adatoms are eliminated and the chains start fluctuating. The dynamic formation of active sites equivalent to the end of chains upon the chain fluctuation results in the nonlinear increase of the reaction rate.
Nakagoe
Osamu
O
Department of Photoscience, School of Advanced Sciences, The Graduate University for Advanced Studies (Sokendai), Hayama, Kanagawa, 240-0193, Japan.
Watanabe
Kazuya
K
Takagi
Noriaki
N
Matsumoto
Yoshiyasu
Y