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Kinetics of the sulfur oxidation on palladium: a combined in situ x-ray photoelectron spectroscopy and density-functional study
Authors:Gotterbarm Karin  Luckas Nicola  Höfert Oliver  Lorenz Michael P A  Streber Regine  Papp Christian  Viñes Francesc  Steinrück Hans-Peter  Görling Andreas
Affiliation:Lehrstuhl fu?r Physikalische Chemie II, Universita?t Erlangen-Nu?rnberg, Egerlandstr. 3, 91058 Erlangen, Germany.
Abstract:
We studied the reaction kinetics of sulfur oxidation on the Pd(100) surface by in situ high resolution x-ray photoelectron spectroscopy and ab initio density functional calculations. Isothermal oxidation experiments were performed between 400 and 500 K for small amounts (~0.02 ML) of preadsorbed sulfur, with oxygen in large excess. The main stable reaction intermediate found on the surface is SO(4), with SO(2) and SO(3) being only present in minor amounts. Density-functional calculations depict a reaction energy profile, which explains the sequential formation of SO(2), SO(3), and eventually SO(4), also highlighting that the in-plane formation of SO from S and O adatoms is the rate limiting step. From the experiments we determined the activation energy of the rate limiting step to be 85 ± 6 kJ mol(-1) by Arrhenius analysis, matching the calculated endothermicity of the SO formation.
Keywords:
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