Determination of heats of adsorption using metal films

Enthalpies of adsorption of metal atoms on single-crystalline surfaces by microcalorimetry

“…In order to measure heats of adsorption per mole of adsorbed gas, one must measure not only the absolute flux of the gas beam (with a calibrated quartz crystal microbalance), (2). The initial heats start low, and increase up to the bulk heat of sublimation of Cu (337 kJ · mol −1 , (38) shown by the dashed horizontal line) at high coverages.…”

“…This method was initiated in the 1930s by Roberts who determined the enthalpy generated from gas adsorption on annealed metal wires by measuring the temperature increase of the wires. (1) Adsorption energies of simple gases on freshly deposited metal films on the inside walls of glass bulbs were later measured by Beeck et al (2) (see reference 3 and references therein for more details on the development of microcalorimetry). These types of experiments, however, failed to identify and characterize the adsorption sites.…”

Kinetics of Chemical Processes on Well-defined Surfaces

“…On Fe(111) the adsorption energy ofN 2ad is 32 kJ mol-1 giving rise to a maximum in the desorption spectra at about 160 K [22]. Similar adsorption energies were found for polycrystalline Fe surfaces [180,181]. Adsorbed atomic nitrogen, N ad , is formed through dissociation of N 2ad as for example followed by XPS [170].…”

Principles of Chemisorption

“…Until very recently, it has only been possible to undertake such measurements for thin-film systems [1,[14][15][16][17][18][19]. Therefore, for such systems it is more appropriate to resort to a direct calorimetric measurement of the adsorption enthalpy.…”

“…A schematic set-up for a TDS measurement is shown in Fig. If the pumping speed is infinitely high we can ignore readsorption and the change in adsorbate coverage per unit time; then, a measure for the desorption rate (r des ), is given by the Wigner-Polanyi equation [7,35]: (14) where T = T o + βt. The sample is heated resistively and the temperature monitored using a thermocouple.…”