Ethylene adsorption on Pd( 111 ) studied using infrared reflection–absorption spectroscopy

Abstract

The adsorption of ethylene has been studied on clean and hydrogen-covered Pd(1 1 1) using reflection-absorption infrared spectroscopy and molecular beam methods. Using a correlation diagram, in which vibrational frequencies are plotted versus a rp parameter proposed by Stuve and Madix, shows that ethylene is substantially rehybridized on Pd(1 1 1) having a rp parameter intermediate between those of ethylene on Ni(1 1 1) and Ru(0 0 1). In contrast, when ethylene adsorbs on hydrogen-covered Pd(1 1 1), only p-bonded species are detected. An additional species appears exhibiting a characteristic frequency of 957 cm À1 when Pd(1 1 1) is cooled to $80 K and the system pressurized with $10 À5 Torr of ethylene. This species also appears on a CO-saturated Pd(1 1 1) surface. Molecular beam measurements show that its coverage reaches $1.3 ML indicating that it is due to ethylene adsorbed in the second and subsequent layers. Ó

An infrared spectroscopic and temperature-programmed desorption study of methyl iodide hydrogenation on Pd()

“…Hydrogen background contamination of palladium has been shown to be a problem even under ultrahigh vacuum conditions. Recent experiments, in which great care was taken to completely remove all hydrogen from the sample, have revealed differences with earlier work, even on extensively studied systems such as ethylene on Pd(1 1 1) [13].…”

The kinetics of ethylene hydrogenation catalyzed by metallic palladium

“…More recently, surface science studies in ultrahigh vacuum of ethylene on Pd(111) single crystals [9][10][11][12][13] and palladium nanoparticles supported on planar alumina substrates [14][15][16][17] have yielded additional insights into the chemistry at the surface. Ethylene adsorbs on Pd(111) at low coverages in a di-r-configuration with a heat of adsorption of $79 kJ/mol.…”

Alkene chemistry on the palladium surface: nanoparticles vs single crystals

“…The reactions of ethene with metal surfaces have been investigated on both single crystals and supported catalysts (see reviews of Zaera [6], and Sheppard and De La Cruz [7,8]). As Pd catalysts typically show high activities and selectivities, a considerable research effort has been devoted to studying surface reactions on Pd, employing infrared reflection absorption spectroscopy (IRAS), temperature-programmed desorption (TPD), high-resolution electron (and photoelectron) spectroscopy (HREELS, PES), and ab initio calculations [9][10][11][12][13][14][15][16][17][18][19].…”