An experimental study of furan adsorption and decomposition on vicinal palladium surfaces using scanning tunneling microscopy

摘要

The intact adsorption and decomposition of furan (C4H4O) on vicinal palladium surfaces with (111)-oriented terraces has been studied by scanning tunneling microscopy (STM) over a range of temperatures. STM images at 225K show that furan molecules lie flat and prefer to adsorb at upper step edges. At 225K, furan molecules adsorbed on "narrow" terraces of 20 to 45 angstrom in width appear to diffuse more readily than those adsorbed on "wide" terraces of 160 to 220 angstrom. A distinct population of smaller features appears in STM images on "narrow" terraces at 288 K and on "wide" terraces at 415 K and is identified with the C3H3 decomposition product, agreeing with prior studies which demonstrated that furan dissociates on Pd(111) to yield carbon monoxide (CO) and a C3H3 moiety in the 280 to 320 K range. Based on our direct visualization of this reaction using STM, we propose a spatial mechanism in which adsorption of furan at upper step edges allows catalysis of the dissociation, followed by diffusion of the product to lower step edges. (C) 2017 Elsevier B.V. All rights reserved.