کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5423823 1395803 2009 4 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Structural evolution of sulfur overlayers on Pd(1 1 1)
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
Structural evolution of sulfur overlayers on Pd(1 1 1)
چکیده انگلیسی
Low energy ion scattering spectroscopy (LEISS) has been used to characterize the evolution of ordered structures of S on the Pd(1 1 1) surface during annealing. During exposure of the Pd(1 1 1) surface to 0.7 L H2S at 300 K-conditions that produce the S(√3 × √3)R30 overlayer-the intensity of the Pd LEIS signal decreases and a feature assigned to adsorbed S appears as the adsorbed layer forms. When the surface is held at 300 K after exposure to H2S is stopped, the LEIS Pd intensity partially recovers and the S signal weakens, presumably as surface S atoms assume their equilibrium positions in the S(√3 × √3)R30 overlayer. Subsequent annealing of the S(√3 × √3)R30 structure at 700 K causes it to convert into a S(√7 × √7)R19 overlayer, whose LEIS spectrum is identical to that of clean Pd(1 1 1). The absence of LEIS evidence for S atoms at the exposed surface of the S(√7 × √7)R19 overlayer is at odds with published models of a mixed Pd-S top layer. Despite the similarity of the LEIS spectra of Pd(1 1 1) and Pd(1 1 1)-S(√7 × √7)R19, their activities for dissociative hydrogen adsorption are very different-the former readily adsorbs hydrogen at 100 K, while the latter does not-suggesting that S exerts its influence on surface chemistry from subsurface locations.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Surface Science - Volume 603, Issue 13, 1 July 2009, Pages L82-L85
نویسندگان
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