Oxygen-induced nano-faceting of Ir(210)

Selective Oxidation of Ammonia by Co-adsorbed Oxygen on Iridium Surfaces: Formation of N2O

“…In this work, ammonia oxidation by oxygen was investigated via temperature programmed desorption (TPD) under UHV conditions (\1 9 10 -9 Torr) on clean planar Ir(210) and clean faceted Ir(210) with a focus on structural and size effects in the reaction. Nanoscale three-sided pyramids exposing (110), (311) and (31-1) faces are formed on an initially planar Ir(210) surface upon annealing in O 2 at T C 600 K and the average facet size is controlled by annealing temperature [23,24]. The clean faceted Ir(210) surface can routinely be prepared in situ via heating in H 2 at 400 K to remove surface oxygen without change in facet structure or size, as shown in Fig.…”

Growth of oxygen-induced nanoscale-pyramidal facets on Rh(210) surface

“…1 The thermodynamics of these facets is usually understood in the context of equilibrium crystal shape ͑ECS͒; when facets are formed on planar surface, all the thermally stable facets must be present in the ECS. 31 For a clean metal surface, the anisotropy of the surface free energy is generally so small that a thermally annealed surface with relatively high surface free energy ͓e.g., W͑111͒, 8 Ir͑210͒, 11 and Re͑1231͒ ͑Refs. 12 and 14͔͒ can still retain its original orientation against faceting.…”

“…The planar Ir͑210͒ surface transforms by pyramidal faceting with ͕311͖ and ͑110͒ facets 11 while oxygen interaction induces faceting on Cu͑115͒. In the latter case, the change in the surface-energy anisotropy causes the Cu͑115͒ surface converts to ͑104͒ and ͑014͒ facets that form spontaneously together with stepped facets whose orientation gradually change from ͑115͒ to ͑113͒ as the ͑014͒ facets grow.…”

“…A suitable candidate for faceting studies is an atomically rough metal surface that has higher specific surface free energy than a close-packed surface of the same material and is less stable against the adsorbate-induced faceting. [3][4][5][6][7][8][9][10][11][12][13][14][15] The potential application of these faceted surfaces could be as model systems to study structure sensitivity and size effects in catalytic reactions [16][17][18][19][20] and as templates to grow metallic nanoclusters. 15,21 Many studies have been performed on adsorbate-induced faceting of atomically rough surfaces, e.g., bcc W͑111͒ ͑Refs.…”

“…15͒ surfaces. Recent studies on fcc ͑210͒ surfaces [3][4][5]7,11 indicate that facets can be induced due to the presence of different adsorbates, e.g., oxygen and active nitrogen can induce faceting of Cu͑210͒ ͑Refs. 4 and 7͒ and Ni͑210͒ ͑Refs.…”