Thermal desorption studies of high-coverage hydrogen overlayers on Ru(001) created with gas-phase atomic hydrogen

Abstract

The adsorption of gas-phase atomic hydrogen on the Ru(001) surface results in a saturation coverage of 1.42 hydrogen adatoms per primitive surface unit cell, which is significantly greater than the saturation coverage of one hydrogen adatom per primitive unit cell in the case of dissociative chemisorption of molecular hydrogen. Thermal desorption spectra of these high-coverage hydrogen overlayers are characterized by a peak temperature of ∼320 K which shifts downward slightly with increasing coverage beyond one monolayer. An isosteric analysis of the thermal desorption spectra yields a desorption energy that decreases from 29.5 kcal/mol at zero coverage to 22 kcal/mol at a coverage of 1.42.