The reduction of oxygen-pretreated Ni(111) by NH3: a study with MIES and UPS data through Monte Carlo simulations

Lescop, Benoît; Jay, J.P.

doi:10.1016/j.susc.2004.07.009

Cited by 1 publication

(1 citation statement)

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“…Due to its higher affinity to oxygen, we find that Fe does not fully reduce by annealing in vacuum or in H 2 pressure below 4 mbar. On the other hand, Fe can be completely reduced by NH 3 , with the subsequent formation of hydroxyl groups and water desorption . For comparison, we probe the catalytic activity of Fe oxide by deliberate oxidation before the hydrocarbon exposure.…”

Section: Resultsmentioning

confidence: 99%

State of Transition Metal Catalysts During Carbon Nanotube Growth

et al. 2009

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We study catalyst-support and catalyst-carbon interactions during the chemical vapor deposition of singlewalled carbon nanotubes by combining environmental transmission microscopy and in situ, time-resolved X-ray photoelectron spectroscopy. We present direct evidence of what constitutes catalyst functionality by comparing the behavior of Ni, Fe, Pd, and Au model catalyst films on SiO 2 during preannealing in O 2 and NH 3 and during C 2 H 2 decomposition. The catalyst metal surface supplies sites to dissociate the hydrocarbon precursor and then guides the formation of a carbon lattice and the liftoff of a carbon cap. The catalysts are sharply distinguished by their reactivity toward activation of the hydrocarbon precursor, following trends known from heterogeneous catalysis. For Fe and Ni, the active state of the catalyst is a crystalline metallic nanoparticle. Graphitic networks do not form on oxidized Fe. Pd forms a silicide on SiO 2 under our reducing conditions. Pd (silicides) and Au nanocrystals are catalytically less efficient in terms of precursor dissociation, while the low adhesion of C on Au surfaces impedes nanotube nucleation.

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Section: Resultsmentioning

confidence: 99%