Ps. Cremer et al., THE FIRST MEASUREMENT OF AN ABSOLUTE SURFACE CONCENTRATION OF REACTION INTERMEDIATES IN ETHYLENE HYDROGENATION, Catalysis letters, 40(3-4), 1996, pp. 143-145
The first measurement of a turnover rate with respect to surface inter
mediate concentration in a high pressure heterogeneous catalytic react
ion is reported. By using infrared-visible sum frequency generation to
study the hydrogenation of ethylene on Pt(111), it was found that the
surface concentration of pi-bonded ethylene, the key reaction interme
diate, represented approximately 4% of a monolayer. Thus the absolute
turnover rate per surface adsorbed ethylene molecule is 25 times faste
r than the rate measured per platinum atom. To explain these results,
we propose a model of weakly adsorbed ethylene intermediates reacting
on atop sites.