An Experimental Study of Furan Adsorption and Decomposition on Vicinal Palladium Surfaces Using Scanning Tunneling Microscopy

Abstract The intact adsorption and decomposition of furan (C 4 H 4 O) on vicinal palladium surfaces with (111)-oriented terraces has been studied by scanning tunneling microscopy (STM) over a range of temperatures. STM images at 225 K show that furan molecules lie flat and prefer to adsorb at upper step edges. At 225 K, furan molecules adsorbed on “narrow” terraces of 20 to 45 A in width appear to diffuse more readily than those adsorbed on “wide” terraces of 160 to 220 A. 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 C 3 H 3 decomposition product, agreeing with prior studies which demonstrated that furan dissociates on Pd(111) to yield carbon monoxide (CO) and a C 3 H 3 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.