The reduction of NO by hydrogen has been studied over Pt0.25 - Rh0.75 (100), (111), (410), Rh(100) and Pt(100) single crystal surfaces in the 10 mbar range. The surfaces were analysed using AES and LEED. Both the activity expressed as conversion after a constant reaction time and selectivity depend strongly on the surface structure and composition. The activity for the (100) surfaces decreases in the order Pt(100) ≥ Pt-Rh(100)〉Rh(100). The activity of pure Rh is drastically enhanced by alloying with 25% Pt. The selectivity towards N2 for the (100) surfaces decreases in the order Rh(100)〉Pt-Rh(100)〉Pt(100) at a temperature of 575K and Rh(100)〉Pt(100)〉Pt-Rh(100) at 520K. The activity for the alloy surfaces decreases in the order Pt-Rh(100)〉Pt-Rh(410)〉Pt-Rh(111), and the selectivity towards N2 formation decreases in the order Pt-Rh(410)〉Pt-Rh(100)〉Pt-Rh(111), at 520K and 575K. The differences in selectivity and activity can be understood on the basis of the relative concentrations of N, NO and H on the various surfaces.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry