H/D-Isotope Effects in Chemical Wave Propagation on Surfaces: The O-2+H-2 and NO+H-2 Reactions on Rh(110) and Rh(111)
||Catalysis, Hydrogen, Nitrogen oxides, Oxygen, Pattern formation, Photoemission electron microscopy (PEEM), Rhodium, Single crystal surfaces, Surface chemical reaction, Surface diffusion
Institut für Physikalische Chemie und Elektrochemie, Universität Hannover, Callinstrasse 3–3a, 30167 Hannover, Germany
Boreskov Institute of Catalysis, Pr. Lavrentieva 5, Novosibursk 630090, Russia.
H/D-isotope effects in chemical wave propagation in the bistable O2+H2 reaction on Rh(110) and Rh(111) and in the excitable NO+H2 reaction on Rh(110) were investigated using photoemission electron microscopy (PEEM) as spatially resolving method. The systems were studied in the 10−6–10−4 mbar range between 400 K and 700 K. For equivalent partial pressures, i.e., partial pressures which have been corrected for the different impingement rates of H2 and D2, front and pulse propagation with H2 is typically faster than with D2 up to a factor of three. A similar difference exists with respect to the width of the existence range for pattern formation in pH2(D2), which is broader with D2 than with H2. Titration experiments of the oxygen-covered Rh(110) surface demonstrated that at high oxygen coverages, the reactive sticking of D2 is inhibited much more strongly than with H2. From the T-dependence of the front velocities, apparent activation energies were determined for the two isotopes.