Multi-directional N2 desorption in N2O decomposition on Rh(1 1 0)

Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110)

“…In the presence of adsorbed oxygen, the heat of N 2 O adsorption increases from around 30 to 43 kJ mole −1 on Ru͑0001͒. 61 However, no collimation angle shift has been observed on Rh͑110͒ as a result of the addition of O͑a͒ although the TPD decomposition peak shifted from 70 to 140 K. 13,19 Rather, the intermediate N 2 O may be affected by coadsorbed species, such as N͑a͒ and NO͑a͒. The coverage of N͑a͒ may also be significant in the NO reduction.…”

“…14 Later, we showed that this inclined N 2 desorption is well reproduced in N 2 O decomposition on Pd͑110͒, Rh͑110͒, and Ir͑110͒ as well as in steady-state NO + CO ͑or H 2 ͒ and N 2 O+CO ͑or H 2 ͒ reactions on Pd͑110͒. 13,[15][16][17][18][19][20][21][22] Thus, the intermediate N 2 O͑a͒ formed from the NO͑a͒ +N͑a͒ fast reaction [23][24][25] has been proposed to be oriented along the ͓001͔ direction before dissociation in the course of the catalyzed NO reduction. In the present work, AR-product desorption measurements have been successfully performed at different crystal azimuths for the steady-state NO ͑or N 2 O͒ + CO reaction and the resultant spatial distributions of all products have been constructed in a three-dimensional way.…”

The collimation angle shift of desorbing product N2 in a steady-state N2O+CO reaction on Rh(110)

“…9 This chopper house was evacuated by a 25-K-cooled copper plate yielding a pumping rate of about 7 m 3 / s as well as a tandem-turbomolecular pumping system. The distance from the ionizer to the chopper blade is 377 mm, and the time resolution was set at 20 s. The other apparatus used for N 2 O pressure jump ͑PJ͒ experiments at T S = 60-400 K has a cryoplate in the reaction chamber yielding a pumping rate of about 9 m 3 / s and allows cooling a sample below 50 K. 23 A Rh crystal with ͑110͒ surfaces was rotated to change the desorption angle ͑: polar angle͒ in the plane along the ͓001͔ direction. 2 The crystal was cleaned by repeated cycles of Ar + ion bombardments, oxygen treatments at 850 K, and annealing to 1200 K until a sharp ͑1 ϫ 1͒ LEED structure or the reproducible oxygen temperature-programmed desorption ͑TPD͒ curve was observed.…”

“…24 Before each experiment, the surface was annealed at 1200 K for 5 min to remove the surface oxides. 23 Without further purification, 15 N 2 O ͑the isotope purity: 99%͒ was introduced through a gas doser while 13 CO ͑the isotope purity: 99%͒ was backfilled. The product signals of 15 N 2 and 13 CO 2 were mostly monitored in the AR form.…”

“…8͑b͒ because the incident N 2 O flux decreases with increasing shift from the normal incidence since the angle between the incidence of N 2 O exposure and the detection of desorbing N 2 was fixed at 45°in this apparatus. 23 The N 2 desorption is sharply collimated at around 65°off normal. The intensity was approximated as a cos 10 ͑ −65͒ form except for a small contribution from the cosine component.…”