https://doi.org/10.1140/epjb/e2010-00112-8
Stereoselectivity in catalytic reactions: CO oxidation on Pd(100) by rotationally aligned O2 molecules
1
Dipartimento di Fisica and IMEM-CNR, via Dodecaneso 33, 16146 Genova, Italy
2
IMEM-CNR, via Dodecaneso 33, 16146 Genova, Italy
3
Dipartimento di Ingegneria Civile ed Ambientale, Università di Perugia, via G. Duranti 93, 06125 Perugia, Italy
4
Dipartimento di Chimica, Università di Perugia, via Elce di Sotto 8, 06123 Perugia, Italy
Corresponding author: rocca@fisica.unige.it
Received:
9
October
2009
Published online:
30
March
2010
We report on stereodynamical effects in heterogeneous catalytic reactions as measured by molecular beam-surface experiments. Specifically for CO oxidation on Pd(100) we find that the rotational alignment of the incoming O2 at low (Θ = 0.04 ML) and at intermediate (ΘCO = 0.17 ML) CO pre-coverage, causes a higher reactivity of molecules in high and in low helicity states, respectively (corresponding to helicoptering and cartwheeling motion of O2). In first approximation, at low CO pre-coverage the difference in reactivity is determined by the different location of the O atoms generated in the dissociation process by the different parent molecules, while at intermediate CO pre-coverage the reactivity is influenced also by the different ability of cartwheeling and helicoptering O2 to penetrate through the CO adlayer. In accord with this the total amount of CO2 produced is always largest for helicopters which generate supersurface O atoms at least in the low CO pre-coverage limit. A deeper inspection of the data indicates, however, that the dynamics is more complex, two different pathways being present for the reaction with O generated by helicopters and one for O generated by cartwheels. Moreover, cartwheels generated oxygen influences the reactivity of subsequently arriving helicopters.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2010