THE SURFACE-STATE AND CATALYTIC PROPERTIES OF PT BLACK AFTER O2-H2 CYCLES

XPS and UPS of a Pt black catalyst after customary H2-O2 regeneration shows considerable amounts of residual C as well as surface OH/H2O species. Surface C could not be removed even by O2 at 800 K. Oxygenates are stable even after H-2 treatment up to 750 K. Their chemical state has been tentatively identified by comparing XPS and UPS results. Catalytic transformations of n-hexane on Pt black treated analogously is reported and the effect of surface species on catalytic properties discussed. Possible consequences of the presence of stable surface OH/H2O species on H2-O2 titrations are mentioned.