Figure 8.

DFT calculations on promoter effects. (a) Adsorption energies for PrO₂ and Na₂O on flat Co(111) and stepped Co(211) cobalt surfaces as a function of the oxide coverage (fractional monolayer (ML)). The top views on the models show the corresponding optimized structures for a 0.11 ML oxide coverage in each case. Color codes: Pr: yellow, Na: orange, O: red, Co: gray and blue. For clarity cobalt step-edges on Co(211) are shown in blue. (b) Relative adsorption energies for H* and CO* on Co(111) and Co(211) cobalt surfaces either as neat or precovered with 0.11 ML PrO₂. (c) Relative adsorption energies for ethylene (C₂H₄*) and CO* on Co(111) and Co(211) cobalt surfaces either as neat or precovered with 0.11 ML PrO₂.