Anhydrous Ethanol Dehydrogenation on Metal–Organic Chemical Vapor Deposition Grown GaN(0001)

Abstract

In this ultrahigh vacuum study, temperature-programmed desorption, Auger electron spectroscopy, and ex-situ atomic force microscopy are used to evaluate the surface chemistry of ethanol on the GaN(0001) surface. Ethanol undergoes dehydration and dehydrogenation reactions on the GaN(0001) surface to a larger extend than on the TiO 2 (110) surface. This enhanced reactivity is attributed to a higher amount of metal-bound ethoxy. In addition, molecular H 2 has been identified as a byproduct of the ethanol dehydrogenation to acetaldehyde. We attribute the reactivity, including the formation of molecular hydrogen, to the combination of wurtzite structure and nitride chemistry, since surface amines are considered to be less stable than surface hydroxyls on other model oxides.

Chemistry of Methanol and Ethanol on Ozone-Prepared α-Fe2O3(0001)

“…Thermal desorption measurements were performed in a line-of-sight geometry between 200 and 800 K. Methanol (Sigma-Aldrich, ≥99.98%) and ethanol (Sigma-Aldrich, ≥99.5%) were cleaned by pump–freeze cycles, until no contaminations were observed with the QMS. The dosage was performed at 200 K; the temperature-programmed desorption data presented are corrected for fragmentation patterns, and the integral amounts further account for ionization cross sections and transmission coefficients to unambiguously quantify the molecular yields. − On the basis of the monitored masses (2, 15, 28, 29, 30, 31, 32, 43, 44, 45, 60), the carbon mass balance can be closed for all experiments. Details of the analysis are presented in the Supporting Information.…”

“…The dosage was performed at 200 K; the temperature-programmed desorption data presented are corrected for fragmentation patterns, and the integral amounts further account for ionization cross sections and transmission coefficients to unambiguously quantify the molecular yields. 30−32 On the basis of the monitored masses (2,15,28,29,30,31,32,43,44,45,60), the carbon mass balance can be closed for all experiments. Details of the analysis are presented in the Supporting Information.…”

Oxidative decomposition of dimethyl methylphosphonate on rutile TiO2(110): the role of oxygen vacancies

“…21,30 The formation of gas phase methanol was observed in the case of hydroxylated TiO 2 anatase. 19 Powdered TiO 2 does not activate the P-CH 3 bond until the temperature is above 800 K. 8,20,24,31,32 Model studies on single crystal rutile TiO 2 (110) under ultrahigh vacuum conditions show that DMMP adsorption occurs via the dative bond between the PQO group and Ti 5c , and that molecular desorption is observed up to 550 K, suggesting a rather low reactivity at room temperature. 26 Decomposition products consisting of methane, methyl and hydrogen evolve at 500 K while phosphorus containing species remain on the surface.…”

Regulating Photochemical Selectivity with Temperature: Isobutanol on TiO2(110)

“…Schematic of isobutanol adsorption and reaction on TiO 2 (110) (top view of surface). A small amount of adsorbed isobutoxy is formed in defects and on regular surface sites. ,, Competing disproportionation to isobutanol and isobutanal and dehydration to isobutene thermally induced above 500 K. The hydroxyl species either remain on the surface or desorb as water. , …”

“…43,45,46 Competing disproportionation to isobutanol and isobutanal and dehydration to isobutene thermally induced above 500 K. The hydroxyl species either remain on the surface or desorb as water. 44,47 Journal of the American Chemical Society lifetime of isobutanal at 240 K is estimated to be ∼420 s compared to a lifetime of ∼0.2 s at 300 K. The surface lifetime under ultrahigh vacuum, t 1/2 , is estimated by assuming firstorder desorption and a prefactor, v d , of 10 13 s −1 , 30…”