HREELS study on the effect of iodine on the bonding of CO on Rh(111)

The adsorption of CO on I-covered Rh(111) surface has been investigated by TDS and HREELS. Adsorbed iodine was produced by decomposition of adsorbed C H3I. The uptake of CO significantly decreased in the presence of I adlayer. At high I coverage (Theta(I)=0.33) the maximum amount of CO adsorbed was o nly one third of that measured for clean Rh(111). Preadsorbed I lowered the stability of adsorbed CO. HREELS measurements revealed that the I adlayer reduced the intensity of the vibration loss for the on-rep bonded CO and ca used a new loss feature at 1700-1800 cm(-1) due to the bridge-bonded CO. At ambient CO pressure, a high frequency CO peak was detected by RAIRS, which was attributed to a short range CO-I interaction. (C) 1999 Elsevier Scienc e B.V. All rights reserved.