Browsing by Author "Niemantsverdriet, J. W."

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Citation - WoS: 13
Citation - Scopus: 13
Application of work function measurements in the study of surface catalyzed reactions on Rh(1 0 0)
(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2018) Başar Ca̧ǧlar; Ali Can Kizilkaya; J. W.Hans Niemantsverdriet; C. J. Weststrate; Weststrate, C. J. (8402915800); Niemantsverdriet, J. W.; Caglar, Basar; Kizilkaya, Ali Can; Weststrated, C. J.
The present article aims to show how work function measurements (WF) can be applied in the study of elementary surface reaction steps on metallic single crystal surfaces. The work function itself can in many cases not be interpreted directly as it lacks direct information on structural and chemical nature of the surface and adsorbates but it can be a powerful tool when used together with other surface science techniques which provide information on the chemical nature of the adsorbed species. We here illustrate the usefulness of work function measurements using Rh(100) as our model catalyst. The examples presented include work function measurements during adsorption surface reaction and desorption of a variety of molecules relevant for heterogeneous catalysis. Surface coverage of adsorbates isosteric heat of adsorption and kinetic parameters for desorption desorption/decomposition temperatures of surface species different reaction regimes were determined by WF with the aid of other surface science techniques. © 2019 Elsevier B.V. All rights reserved.
Citation - WoS: 15
Citation - Scopus: 13
The effect of C-OH functionality on the surface chemistry of biomass-derived molecules: ethanol chemistry on Rh(100)
(ROYAL SOC CHEMISTRY, 2016) B. Caglar; M. Olus Ozbek; J. W. (Hans) Niemantsverdriet; C. J. (Kees-Jan) Weststrate; Ozbek, M. Olus; Weststrate, C. J.; Olus Ozbek, M.; Niemantsverdriet, J. W.; Caglar, B.
The adsorption and decomposition of ethanol on Rh(100) was studied as a model reaction to understand the role of C-OH functionalities in the surface chemistry of biomass-derived molecules. A combination of experimental surface science and computational techniques was used: (i) temperature programmed reaction spectroscopy (TPRS) reflection absorption infrared spectroscopy (RAIRS) work function measurements (Kelvin Probe - KP) and density functional theory (DFT). Ethanol produces ethoxy (CH3CH2O) species via O-H bond breaking upon adsorption at 100 K. Ethoxy decomposition proceeds differently depending on the surface coverage. At low coverage the decomposition of ethoxy species occurs via beta-C-H cleavage which leads to an oxometallacycle (OMC) intermediate. Decomposition of the OMC scissions (at 180-320 K) ultimately produces CO H-2 and surface carbon. At high coverage along with the pathway observed in the low coverage case a second pathway occurs around 140-200 K which produces an acetaldehyde intermediate via alpha-C-H cleavage. Further decomposition of acetaldehyde produces CH4 CO H-2 and surface carbon. However even at high coverage this is a minor pathway and methane selectivity is 10% at saturation coverage. The results suggests that biomass-derived oxygenates which contain an alkyl group react on the Rh(100) surface to produce synthesis gas (CO and H-2) surface carbon and small hydrocarbons due to the high dehydrogenation and C-C bond scission activity of Rh(100).