Structure sensitive hydrogen adsorption: Effect of Ag on Ru/SiO2 catalysts

Savargaonkar, N
Narayan, RL
Pruski, M
Üner, Deniz
King, TS
The dynamics and energetics of hydrogen chemisorption on silica-supported ruthenium and ruthenium-silver bimetallic catalysts were studied by H-1 NMR spectroscopy and microcalorimetry. It was observed that the amount of hydrogen adsorbed on Ru particles having intermediate and low heats of adsorption was significantly reduced with increasing amounts of silver. The desorption and adsorption rate constants, determined from selective excitation NMR experiments, were lower on Ru-Ag catalysts than those on Ru catalysts at the same temperature and hydrogen coverage. The apparent sticking coefficients of hydrogen on a Ru-Ag catalyst with 10 at% Ag were more than 10 times lower than those on a Ru catalyst and were comparable to sticking coefficients reported in the literature for hydrogen adsorbing on Ru single crystal. Thus silver was found to greatly affect both the dynamics and energetics of hydrogen chemisorption on Ru/SiO2. However, ensemble and electronic effects did not play any role in causing these effects. It is postulated here that the influence of silver was due to its tendency to selectively segregate to edge, corner, and other low coordination structures on the Ru particle surface. Hence, hydrogen adsorption on these surfaces was found to be structure sensitive. (C) 1998 Academic Press.


Üner, Deniz; GERSTEIN, BC; KING, TS (Elsevier BV, 1994-04-01)
The interaction of hydrogen on potassium promoted catalysts prepared by both sequential and co-impregnation methods was studied by proton NMR spectroscopy. Potassium addition decreased the amounts of both hydrogen adsorbed on the metal (site blocking) and the support hydroxyl groups. No evidence for a ruthenium-mediated (through-metal) electronic interaction between potassium species and adsorbed hydrogen was found. During catalyst preparation, potassium was incorporated on the support by an exchange with t...
Structure sensitivity of selective CO oxidation over Pt/gamma-Al2O3
Atalik, B.; Üner, Deniz (Elsevier BV, 2006-07-25)
In this study, the effect of particle size on the reaction rate and selectivity of preferential oxidation of CO (PROX) reaction was investigated on 2 wt% Pt/-Al2O3 catalysts prepared by an incipient wetness technique. The particle size of the catalysts was modified by calcination temperature and duration. CO oxidation and preferential CO oxidation reaction were studied on these catalysts at lambda = 2 (P-O2/P-CO) = 1. The CO oxidation reaction activation energy decreased with increasing particle size, consi...
Effect of stabilizer type on the activity and stability of water-dispersible cobalt(0) nanocluster catalysts in hydrogen generation from the hydrolysis of sodium borohydride
Metin, Onder; Koçak, Ebru; ÖZKAR, SAİM (Springer Science and Business Media LLC, 2011-08-01)
Hydrogen phosphate (HPO4 2−) or poly(acrylic acid) (PAA) stabilized cobalt(0) nanoclusters were in situ generated from the reduction of cobalt(II) chloride during the catalytic hydrolysis of sodium borohydride (NaBH4) in the presence of stabilizers, HPO4 2− or PAA. Cobalt(0) nanoclusters stabilized by HPO4 2− or PAA were characterized by using UV–Visible spectroscopy, TEM, XPS and FT-IR techniques. They were employed as catalysts in the hydrolysis of NaBH4 to examine the effect of stabilizer type on their c...
HWANG, SJ; Üner, Deniz; KING, TS; PRUSKI, M; GERSTEIN, BC (American Chemical Society (ACS), 1995-03-16)
Cab-O-Sil HS5, used as the support in silica supported ruthenium (Ru/SiO2) catalysts, was characterized via single and multiple quantum (MQ) H-1 NMR spectroscopy. The samples were studied both in the presence and in the absence of ruthenium. Single quantum spin counting of protons on silica support with and without ruthenium metal indicated that the total number of hydroxyl groups decreased significantly with increasing reduction temperature over the range of 350-530 degrees C. Two different components show...
Üner, Deniz; KING, TS (Elsevier BV, 1995-09-15)
Metal dispersions of silica-supported ruthenium catalysts determined by the standard volumetric chemisorption technique were found to be inaccurate due to irreversible spillover of hydrogen to the support. Direct evidence was obtained via in situ H-1 NMR for an irreversibly bound component of the hydrogen that migrated from the metal to the support on a time scale of tens of minutes or longer at room temperature. It was also shown in this work that hydrogen saturated the surface of the metal particles on a ...
Citation Formats
N. Savargaonkar, R. Narayan, M. Pruski, D. Üner, and T. King, “Structure sensitive hydrogen adsorption: Effect of Ag on Ru/SiO2 catalysts,” JOURNAL OF CATALYSIS, pp. 26–33, 1998, Accessed: 00, 2020. [Online]. Available: