Hydrogen on metallic surfaces

A term used to refer to any chemical process whose rate depends upon saturation of a binding site. Rate saturation is observed in enzyme kinetics, metabolic transport, host-guest reactions, and even heterogenous catalysis such as hydrogenation on metallic surfaces of platinum and nickel. 

Adsorbed hydrogen on metal surfaces is of particular interest from both theoretical and experimental points of view. Vibrational spectroscopy data on hydrogen adsorbed from the gas phase have been obtained from IR reflection-absorption experiments as well as from electron energy loss spectroscopy and inelastic neutron scattering techniques [39-41]. In UHV, absorption bands for the M-H bond have been reported in the mid- and far-infrared regions [41, 42],... 

Surface absorption of hydrogen on metal surfaces is a well-known phenomenon in the electrodes of batteries. It may also be at work for electrodes made of nano-structured carbon and accomplishes nearly the same mass percentage as cryogenic storage for suitable electrolytes, but at ambient temperature. Charging or discharging takes several hours or even days, so the concept is unsuitable for use in cars (Jurewicz et al., 2004). 

It has many applications as a tracer, for example, to study the movement of ground waters, and to study the al sorption of hydrogen by metals and the absorption of hydrogen on metal surfaces. Many deuterated and tritiated compounds have been synthesized and studied. Some of the important physical properties of the isotopes of hydrogen are listed in Table 8-2. 

It is well known that alkynes and diolefins are more strongly chemisorbed during their hydrogenation on metal surfaces than are olefins, although the eflFect can arise from quite small differences in heats of chemisorption (5). The analogy with organometallic complexes is quite close, but the stronger coordination of diolefins compared with monoolefins is almost entirely an entropy effect. 

Heterogeneous Enantioselective Hydrogenation on Metal Surface Modified by Chiral Molecules... 

Metal carbonyls have many derivatives obtained by (formal) substitution of a carbonyl for another ligand, including hydride. The interest in the complexes arose because they were considered as potential models for hydrogen on metal surfaces ( 7.3.1). In general this is valid, in that the frequencies fall in similar ranges to those found on metal surfaces, the detailed interaction with the surface is distinctly different from that in a transition metal cluster and the analogy is imperfect. 

The Temkin and Freundlich adsorption isotherms have been sucessfully applied to treat experimental data not only for adsorption of gases (hydrogen) on metal surfaces and ions on metal electrodes, as well as the adsorption of proteins to functional surfaces. The explicit expression for reaction kinetics in the case of biographic (intrinsic) nonuniform surfaces can be derived only in a few cases, which in fact limits the possibility of wider application of the a priori nonuniform surfaces. 

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