Thermal desorption study of Oxygen adsorption on Pt, Ag & Au films deposited on YSZ

Abstract

Abstract. The Thermal Desorption or Temperature Programmed Desorption (TPD) technique hasbeen used for the study of oxygen adsorption on Pt, Ag and Au catalyst films deposited on YSZ. The catalyst film was deposited on the one side of the YSZ specimen while on the other side gold counter and reference electrodes were deposited, constructing a three-electrode electrochemical cell similar to those used in Electrochemical Promotion studies. Oxygen adsorption has been carried out either by exposing the samples to gaseous oxygen (gas phase adsorption) or by the application of a constant current between the catalyst/working electrode and the counter electrode (electrochemical adsorption) or by mixed gas phase and electrochemical adsorption. Oxygen adsorption was carried out at temperatures between 200 and 480 ~ After exposure to gaseous oxygen, normal adsorbed atomic oxygen species have been observed on Pt and Ag surfaces while there was no detectable amount of adsorbed oxygen on Au. Electrochemical O 2-pumping to Pt, Ag and Au catalyst films creates strongly bonded "backspillover" anionic oxygen, along with the more weakly bonded atomic oxygen. Electrochemical 02. pumping to Pt, Ag and Au catalyst films in presence of preadsorbed oxygen creates strongly bonded "backspillover" anionic oxygen, with a concomitant pronounced lowering of the Tp of the more weakly bound preadsorbed atomic oxygen. The two oxygen species co-exist on the surface. The activation energy for oxygen desorption or, equivalently, the binding strength of adsorbed oxygen was found to decrease linearly with increasing catalyst potential, for all three metal electrodes.

The Catalytic Mechanics of Dynamic Surfaces: Stimulating Methods for Promoting Catalytic Resonance

“…When using yttrium-stabilized zirconia (YSZ) as a solid electrolyte support, oxygen ions can back-spillover onto the metal surface and desorb as O 2 . Desorption energy of O 2 from Pt/YSZ was shown to vary as much as 0.6 eV for applied potentials of 0–0.6 V; similar adsorption weakening was observed for other metals such as Ag, Rh, Pd, Ni, IrO 2 , and RuO 2 , with binding energy shifts of oxygen as high as 1.42 eV . Surface modification has been shown to exhibit a significant shift in the work function of the metal catalyst (>0.5 eV) .…”

Oxide desorption process from InSb surface under Sb flux

“…There are no data in the literature on the desorption of oxygen from the surface of InSb or from the surface of indium and antimony oxides. E des.O from the surface of metals (Au, Ag, Pt) varies from 1.19 to 1.68 eV [24,25], which corresponds to chemical adsorption. In our calculation, this E des.O range corresponds to the E form = 1.03−1.52 eV range, at which the calculation describes the experiment.…”

Electrochemical promotion of catalysis: the case of ethylene oxidation

“…8 [85]. In TPD after prolonged electrochemical pumping via positive current or potential application causes significant oxygen spillover from the solid electrolyte YSZ to the catalyst surface and causes oxygen to adsorb in two distinct adsorption states, a strongly bonded "special spillover" ionic oxygen and a weakly bonded atomic oxygen state with a temperature of 50 K lower than that of normally chemisorbed oxygen [86,87]. But then again isotopic O 16 /O 18 exchange experiments with Pt/YSZ conducted by Sobyanin et al demonstrated that an electrochemical polarization of the Pt/YSZ interface does not lead to an enhanced binding strength of oxygen on Pt [88].…”