Copper, hydrogen adsorption

Nishihara C and Nozoye H 1995 influence of underpotentiai deposition of copper with submonolayer coverage on hydrogen adsorption at the stepped surfaces Pt(955), Pt(322) and Pt(544) in sulfuric acid solution J. Electroanal. Chem. 396 139-42... 

The authors then chose to examine hydrogen adsorption at Cu(110). This was a well-chosen example in that hydrogen adsorption is activated, being pressure dependent, and also was already known from LEED studies to exhibit a missing row (1 x 2) structure with every second close packed (110) copper row missing at high hydrogen pressures. What, then, was learnt from STM ... 

Evidence for a marked difference between the surface and bulk compositions of dilute copper-nickel alloys has been reported recently by a number of investigators (82, 87-90). Much of the experimental evidence comes from hydrogen adsorption data (74, 82, 87, 90). The conclusions of van der Plank and Sachtler were based on the premise that nickel chemisorbs hydrogen while copper does not (82, 87). The total adsorption of hydrogen at room temperature was taken as a measure of the amount of nickel in the surface. However, in hydrogen adsorption studies on the catalysts used to obtain the catalytic results in Fig. 6, the amount of adsorption on the copper catalyst, while small compared to the adsorption on nickel, is not negligible (74) However, the amount of strongly adsorbed... 

Hayden B.E., The dynamics of hydrogen adsorption and desorption on copper surfaces, in Dynamics of Gas-Surface Collisions, M.R. Ashfold, C.T. Rettner, eds., Royal Society of Chemistry London, 1992, 137. 

Fig. 12.9. Relative extent of hydrogen adsorption on copper-nickel...

Figure 2.8 Isotherms for total hydrogen adsorption (circles) and weakly adsorbed hydrogen (squares) at room temperature on unsupported nickel and copper catalysts and on a nickel-copper alloy catalyst (6). (Reprinted with permission from Academic Press, Inc.)...

Cadenhead, D.A. and Wagner, N.J. "Low-temperature hydrogen adsorption on copper-nickel alloys."/. Phys. Chem. 72 2775-2781 1968. 

In a typical hydrogen adsorption experiment, ruthenium-copper aggregates are first contacted with flowing hydrogen in the adsorption cell at 400°C to ensure thorough reduction. The cell is then evacuated to a pressure of approximately 10-6 torr and cooled to room temperature for adsorption measurements. Isotherms for total hydrogen adsorption and for weakly adsorbed hydrogen are then determined in the manner described for nickel-copper catalysts in Chapter 2. 

Kazansky V B and Serykh A1 (2004c), Unusual forms of molecular hydrogen adsorption by Cu ions in the copper-modified ZSM-5 zeolite , Catal Lett, 98, 77. 

Ramirez-CuestaA J and Mitchell PC H (2007), Hydrogen adsorption in a copper ZSM5 zeolite an inelastic neutron scattering study , Catal Today, 120, 368. 

Fio. 5. Hydrogen adsorption rates on copper catalysts at 1 atmosphere. 

The electrocatalytic behavior of the thin palladium layers deposited on Au(hkl) surfaces for hydrogen adsorption/absorp-tion [77, 80], oxygen reduction [79], oxide formation/reduction [80], copper UPD [33, 77], electrochemical oxidation of formic acid [84] as well as formaldehyde [80] has been investigated in detail. These electrocatalytic activities depended significantly on the surface structure and thickness of the ultrathin palladium layers [80, 84]. 

The catalytic effect of copper-nickel alloys as a function of composition for the reaction 2H H2 is shown in Fig. 6.17 [53]. Above 60 at.% Cu, the filled d-band is less favorable to hydrogen adsorption hence, favorable collisions of gaseous H with adsorbed H are less probable, and the reaction rate decreases. The similarity to passive behavior of copper-nickel alloys, which also decreases above 60 at.% Cu, can be noted. The parallel conditions affecting passivity and catalytic activity support the viewpoint that the passive films on transition metals and their alloys are chemisorbed. 

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