Ambient pressure phase transitions over Ir(1 1 1): at the onset of CO oxidation

Niclas Johansson, Mie Andersen, Yuji Monya, Jesper N Andersen, Hiroshi Kondoh, Joachim Schnadt, Jan Knudsen

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskriftPeer review


In this study we report on the adsorbate structures on an Ir(1 1 1) surface during the phase transition from the inactive to the active state during CO oxidation. The CO oxidation over Pt(1 1 1) is used as a reference case. Where Pt(1 1 1) either is inactive and CO covered or active and O covered, Ir(1 1 1) exhibits a transition state with co-existing chemisorbed O and CO. The observed structural differences are explained in terms of DFT-calculated adsorption energies. For Pt(1 1 1) the repulsive CO–O interaction makes co-existing chemisorbed CO and O unfavourable, while for Ir(1 1 1) the stronger O and CO adsorption allows for overcoming the repulsive interaction. At the onset of CO oxidation over Ir(1 1 1), a CO structure containing defects forms, which enables O2 to dissociatively adsorb on the Ir(1 1 1) surface, thus enabling the CO oxidation reaction. At the mass transfer limit, the Ir(1 1 1) surface is covered by a chemisorbed O structure with defects; hence, the active surface is predominately chemisorbed O covered at a total pressure of 0.5 mbar and no oxide formation is observed.
TidskriftJournal of Physics: Condensed Matter
StatusPublished - 2017 okt. 5

Ämnesklassifikation (UKÄ)

  • Den kondenserade materiens fysik


Utforska forskningsämnen för ”Ambient pressure phase transitions over Ir(1 1 1): at the onset of CO oxidation”. Tillsammans bildar de ett unikt fingeravtryck.

Citera det här