Effect of NO on D-2 adsorption on the Pt(100)-(hex) surface

The influence of NO on the adsorption of D-2 on the Pt(100)-(hex) surface w as studied by means of temperature-programmed reaction (TPR). Deuterium ads orbs negligibly on Pt(100)-(hex) at T = 270 K, whereas an addition of a sma ll amount of NO to D-2 increases drastically the adsorption capacity of Pt( 100)-(hex) towards deuterium. The same phenomenon was observed on the surfa ce pre-covered with NOads as well. As the NOads pre-coverage increases, the uptake of D-ads first increases, then reaches a maximum at theta(NO) appro ximate to 0.25 ML, and finally falls down to zero for the NOads saturated l ayer. The following explanation is supposed. Upon adsorption on the Pt(100)-(hex) surface, NO lifts the (hex) reconstruction and forms the dense NOads/(1 x 1) islands surrounded by the clean (hex) surface. A limited area of the (he x) phase, which is immediately adjacent to the boundaries of the NOads/(1 x 1) islands, is supposed to be distorted and could be able to adsorb deuter ium. (C) 2000 Elsevier Science B.V. All rights reserved.