INTERACTION OF GAS-PHASE ATOMIC DEUTERIUM WITH THE RU(001)-P(1X2)-O SURFACE - KINETICS OF HYDROXYL AND WATER FORMATION

摘要

The deuteration of oxygen adatoms on the Ru(001) surface has been investigated by means of temperature programmed desorption and high-resolution electron energy loss spectroscopy. Exposure of gas-phase atomic deuterium to the p(1 X 2) oxygen overlayer with a fractional adatom coverage of oxygen of 0.5 leads to the production of water at a surface temperature as low as 90 K. After exposure to molecular deuterium, no reaction is observed, suggesting that a direct Eley-Rideal (ER) reaction occurs between the impinging deuterium atoms and the preadsorbed oxygen. Only after a very low exposure of deuterium was it possible to isolate chemisorbed OD groups on the surface, implying that OD formation is the rate-limiting step in the formation of water via ER kinetics on Ru(001). Estimates of the ER reaction cross sections were made,and for the deuteration of adsorbed oxygen and hydroxyls, the cross sections were found to be (7.0+/-0.3)X10(-17) cm(2) and (2.2+/-0.1)X10(-15) cm(2), respectively. In addition to the ER mechanism, the chemisorbed OD groups could also react with coadsorbed deuterium adatoms via Langmuir-Hinshelwood (LH) kinetics at surface temperatures near 170 K, suggesting an activation barrier that is less than 9 kcal/mol. This implies that OD formation is also the rate-limiting step in the formation of water via LH kinetics on Ru(001). (C) 1996 American Institute of Physics. [References: 34]