Hydrogen interaction with solid surfaces

Christmann K. 1988. Interaction of hydrogen with solid surfaces. Surf Sci Rep 9 1. 

Palladium hydride is not a stoichiometric chemical compound but simply a metal in which hydrogen is dissolved and stored in solid state, in space between Pd atoms of crystal lattice of the host metal. Relatively high solubility and mobility of H in the FCC (face-centered-cubic) Pd lattice made the Pd H system one of the most transparent, and hence most studied from microstructural, thermodynamic, and kinetic points of view. Over the century that followed many metal-hydrogen systems were investigated while those studies were driven mostly by scientific curiosity. Researchers were interested in the interaction of hydrogen molecule with metal surfaces adsorption and diffusion into metals. Many reports on absorption of in Ni, Fe, Ni, Co, Cu, Pd, Pt, Rh, Pd-Pt, Pd-Rh, Mo-Fe, Ag-Cu, Au-Cu, Cu-Ni, Cu-Pt, Cu-Sn, and lack of absorption in Ag, Au, Cd, Pb, Sn, Zn came from Sieverts et al. [30-33]. 

The contact of a lubricating substance with a solid is particularly significant from a tribological point of view. Oxyethylated alcohols are nonionic surfactants, and their interactions with the surface are basically quite specific (hydrogen bonds). The contribution of universal (electrostatic) interactions is considerably smaller, as these are very weak dispersion interactions. In the solution in contact with a solid, one can distinguish the surface phase and the bulk phase. Due to adsorption from solutions, the surface phase is enriched with the component that has a stronger affinity for the surface. It is a characteristic of adsorption from solutions on a solid surface that individual components compete for free sites on the surface. At this point, one should not confuse adsorption with absorption, the latter of which may lead to penetration of the components into the solid. 

K. Christmann, Surf Sci. Rep. 9,1 (1988). Provides a general extensive review on the interaction of hydrogen with solid surfaces. 

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