J. Phys. Colloques 47 (1986) C7-419-C7-424
TEMPERATURE DEPENDENCE OF THE CHEMICAL PROPERTIES OF PT-RH SURFACESR.M. WOLF, M.J. DEES et B.E. NIEUWENHUYS
Gorlaeus Laboratories, P.O. Box 9502, NL-2300 RA Leiden, The Netherlands
Field emission (FEM) has been used to study the behaviour of Pt-Rh surfaces towards adsorption of nitrogen and CO. Adsorption of CO on a Pt-Rh (50%:50%) FEM tip, previously annealed at about 1600 K, shows a Pt-like behaviour of the Pt-Rh tip. On a Pt-Rh(12%:88%) tip, the work function change, caused by nitrogen adsorption, was found to vary with annealing temperature from -0.3 eV following previous annealing at 650K to -0.6 eV after annealing at 1450K. Both the FEM pattern and the work function change point towards a platinum surface enrichment of the Pt-Rh alloy, in particular, following previous annealing at a temperature of 1000K and higher. The most drastic changes in surface composition take place around 1000K on the rough surfaces of the tip.