Mass Spectrometric Knudsen Cell Measurements of the Vapor Pressure of Palladium and the Partial Pressure of Palladium Oxide

Abstract

1373 droxy-2-propyl radical in agreement with the proposed mechanism. Adams, Baxendale, and Boag24 have demonstrated by pulse radiolysis that the ketyl radical ion, (C6H6)2C-0-, is the primary product from the addition of eaq-to benzophenone in alkaline solutions.In neutral solutions, the rapid neutralization of the ketyl ion produces the neutral radical, (C6H6)20-OH.

Kinetic energy dependence of the reactions of Ru+, Rh+, Pd+, and Ag+ with O2

“…where IE͑M͒ is the ionization energy of M and D 0 ͑M-O͒ is the neutral BDE at 0 K, 16 agrees much better with the literature IE value than the value derived from D 0 ͑PdO͒ estimated by Pedley and Marshall. 12 This helps substantiate the former value.…”

“…For AgO, this is taken from work of Smoes et al 13 For RuO and RhO, these values are taken from work of Norman et al 14,15 These authors also have the only experimental determination of ⌬ f H 298 ‫ؠ‬ ͑PdO͒, 3.63Ϯ0.13 eV. 16 PM discounted this value because they believed that it was too high, and instead estimated a value of 2.55Ϯ0.87 eV. Comparison with theoretical calculations of Siegbahn, 17 however, suggests that the experimental value is likely to be fairly accurate and it has been adopted by Lias et al 11 The only available IE͑MO͒ values are electron impact values that come from the high temperature mass spectrometry studies.…”

Relating adatom emission to improved durability of Pt–Pd diesel oxidation catalysts

“…Using the results of Alcock and Hooper [11], we find that DH for formation of PtO 2 vapor as estimated from vapor pressure measurements to be 39.3 kcal/mol which is 1.7 eV. The calculated value of emission energy for PdO is also in reasonable agreement with the DH 298K for formation of PdO of 83.4 kcal/mol which is 3.6 eV [21].…”

“…While Pt is known to form a volatile oxide, we have already shown in Fig. 2 that Pd forms a stable oxide (PdO) in air, and it is known that PdO has negligible vapor pressure ($3 orders of magnitude less than that of Pd metal) [21]. Therefore, the total disappearance of the smallest particles in the bimetallic Pt-Pd sample (Fig.…”

“…But Pd on the other hand forms a stable oxide (PdO) in air that has negligible vapor pressure ($3 orders of magnitude less than that of Pd metal) [21]. If PtO 2 were the only mobile species, we would expect that Pt-Pd nanoparticles would slowly lose Pt, leaving behind the Pd and causing phase segregation of the catalyst.…”