Platinum high Miller index

Copper high Miller index, 26 12 Copper oxide, 27 184-187, 199 as adsorbent, 21 44 on alumina, 27 80-85 -manganese oxide, 27 91, 92 oxidation of CO over, 24 86 -platinum catalyst, 27 86-88 propylene oxidation, 30 141 Coprecipitation, perovskite preparation, 36 247-250... 

Rainbow scattering has been detected from high Miller Index stepped platinum surfaces. Typical rainbow scattering patterns are shown in Fig. 4.7. The increase in intensity of the surface rainbows, as displayed by this figure, for an increase in the angle of incidence, qualitatively follows the trend predicted from calculations by McClure... 

C. Hydrocarbon Chemisorption on High Miller Index (Stepped) Platinum... 

Platinum crystal surfaces that were prepared in the zones indicated by the arrows at the sides of the triangle are thermally unstable. These surfaces, on heating, will rearrange to yield the two surfaces that appear at the end of the arrows. There is reason to believe that the thermal stability exhibited by various low and high Miller index platinum surfaces is the same for other fee metals. There are, of course, differences expected for surfaces of bcc solids or for surfaces of solids with other crystal structures. 

Fig. 6. A stereographic triangle of a platinum crystal depicting the various high Miller index surfaces of platinum that were studied.

IV. Chemisorption of Hydrocarbons on Low and High Miller Index Surfaces of Platinum, Iridium, and Gold... 

One would therefore expect that vibrational spectra of CO adsorbed on the platinum particle array should resemble spectra of CO on stepped high Miller index platinum single crystals. However, in preparation for UHV experiments, the... 

Blakely DW, Somoijai GA. The dehydrogenation and hydrogenolysis of cyclohexane and cyclohexene on stepped (high miller index) platinum surfaces. J Catal 1976 42 181-196. 

The chemisorption of over 25 hydrocarbons has been studied by LEED on four different stepped-crystal faces of platinum (5), the Pt(S)-[9(l 11) x (100)], Pt(S)-[6(l 11) x (100)], Pt(S)-[7(lll) x (310)], and Pt(S)-[4(l 11 x (100)] structures. These surface structures are shown in Fig. 7. The chemisorption of hydrocarbons produces carbonaceous deposits with characteristics that depend on the substrate structure, the type of hydrocarbon chemisorbed, the rate of adsorption, and the surface temperature. Thus, in contrast with the chemisorption behavior on low Miller index surfaces, breaking of C-H and C-C bonds can readily take place at stepped surfaces of platinum even at 300 K and at low adsorbate pressures (10 9-10-6 Torr). Hydrocarbons on the [9(100) x (100)] and [6(111) x (100)] crystal faces form mostly ordered, partially dehydrogenated carbonaceous deposits, while disordered carbonaceous layers are formed on the [7(111) x (310)] surface, which has a high concentration of kinks in the steps. The distinctly different chemisorption characteristics of these stepped-platinum surfaces can be explained by... 

In summary, a variety of LEED patterns have been observed for oxygen adsorption on the platinum metals. However, their interpretation is complicated by the uncertainty in the oxygen coverage. A second complication is the uncertainty introduced by oxygen-induced surface reconstruction. The stability of 22 high index Miller planes upon exposure to oxygen has recently been investigated by Blakely and Somorjai (160). 

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