Halogen adsorption on solid surfaces

Surface-level mechanistic studies of adsorbate–adsorbate interactions in heterogeneous catalysis by metals

“…Campbell and coworkers propose that Cl acts as a site-blocker to favor epoxide formation rather than the more siteintensive combustion on Ag surfaces, and that an electrostatic interaction is not involved [176,177]. In fact, for many coadsorbate systems Cl seems to function primarily as a site blocker [178]. Similarly, Carter and Goddard propose the Cl blocks specific sites that favor adsorption of the nonselective O species [179].…”

“…Selected comparisons between experimental and theoretical studies indicate that the influence of the adsorbed iodine on the resulting surface chemistry is weak [184]. In addition, other studies of adsorption of halogens such as Br and I generally show effects that are similar to Cl but weaker in magnitude due to the lower electron affinity of these elements [178,185,186]. However, the difficulty of preparing many of the relevant surface intermediates via other methods makes assessment of interactions with the adsorbed halogen difficult.…”

Production of negatively charged radioactive ion beams

“…Although halogens are volatile elements, they are reactive elements and prone to strong adsorption and reactions with various structural materials. Data on surface adsorption and desorption properties have been documented for transition metal interfaces such as tantalum and molybdenum [72]. The absolute desorption rates are found in the 1-8 × 10 14 s −1 range and enthalpies in 3.7-5.1 eV ranges for F, Cl, and Br.…”

Electrochemical Sources and Devices

“…The production of pure F 2 by electrochemical means has been partially successful [10], although the high reactivity of fluorine with materials has caused problems. A CaF 2 pellet, held by springy contacts between a Pt plate and a Pt gauze, was employed for electrochemical generation at temperatures of 420-450 K. The gas evolved at the anode was focused onto the sample with a short tube, coated with CaF 2 .…”

“…This discussion concerns the delivery of iodine gas by means of electrochemical generation [8], but others have used similar methods for both chlorine and bromine [7,9,10].…”