The chemisorption of hydrogen on Rh(111)

Abstract

The chemisorption of H 2 on the (111) surface of Rh has been studied using thermal desorption mass spectrometry and low-energy electron diffraction. No evidence for the formation of an ordered hydrogen overlayer has been detected between 100 and 400 K. Hydrogen adsorbs dissociatively following Langmuir [(1 − θ) 2] adsorption kinetics. Thermal desorption spectra at all coverages suggest that a mobile precursor is involved in the desorption step. In the limit of zero coverage, E( 2) d = 18.6 kcal/mole and v( 2) 0 = 1.2 × 10 −3 cm 2. No differences in H 2 and D 2 desorption kinetics are observed, suggesting that zero-point energy effects do not play a major role in determining desorption rates.