Pw. Kash et al., CHEMICAL DISPLACEMENT OF MOLECULES ADSORBED ON COPPER SURFACES - LOW-TEMPERATURE STUDIES WITH APPLICATIONS TO SURFACE-REACTIONS, JOURNAL OF PHYSICAL CHEMISTRY B, 101(40), 1997, pp. 7908-7918
Previous experiments have demonstrated that displacement of a molecule
adsorbed on a metal surface by an impinging gas-phase molecule can be
quite a facile process. The generality of this process for an enthalp
ic driving force as small as I kcal/mol is demonstrated here using the
displacement of a weakly binding alkene, cyclopentene, by a series of
more strongly binding alkenes on Cu(100). Surface structure sensitivi
ty in the process is also demonstrated by a comparison of benzene and
cyclopentene coadsorption on Cu(100) and Cu(110). This work also shows
the utility of conducting the displacement process below the temperat
ure at which the displaced molecule desorbs from the multilayer so tha
t temperature-programmed desorption can be used to quantify the surfac
e coverage of displaced molecules. It is also shown that one can readi
ly determine the kinetics of adsorbate bond dissociation and bond form
ation reactions by combining these chemical displacement measurements
of surface coverage with an anneal/quench protocol, This approach is d
emonstrated through chemical displacement experiments that determine t
hat the C-Br bond in vinyl bromide adsorbed on Cu(100) dissociates nea
r 157 It and that the formation of toluene from reaction between methy
l iodide and coadsorbed phenyl groups on eu(110) occurs below 160 K. T
he relative importance of enthalpy and entropy in chemical displacemen
t is also discussed.