Datensatz

Zusammenfassung

The interaction of hydrogen with RuO2(110) surfaces was studied by means of thermal desorption and vibration spectroscopies. The stoichiometric surface exposes two types of coordinatively unsaturated atoms: double-bonded O-bridge and five-fold-bonded Ru-cus, while at the O-rich surface the Ru-cus atoms are covered with single-bonded O-cus. On the stoichiometric RuO2(110) surface at 90 K, H-2, either adsorbs molecularly on Ru-cus sites or dissociates and forms with O-bridge an H2O-like surface group. If, in addition, also O-cus is present at the surface, hydrogen interacts exclusively with this species forming H2O-Cus. This demonstrates that hydrogen reacts much more readily with O-cus than with O-bridge as expected from the reduced bond order and smaller binding energy of O-cus. It is furthermore shown that at surface temperatures below 90 K free coordinatively unsaturated Ru-cus sites are needed to activate the incoming H, molecules prior to any reaction with O-cus or O-bridge. Generally, Ru-cus sites play a key role for reactions of a number of molecules at the RuO2(110) surface. These findings are supported by recent DFT-based calculations but are at variance with other reports.