Nanoscale design of catalysts has been a promising avenue for development of new materials for industrial problems. Recently, a new class of alloys, called near-surface alloys (NSAs), has been described. Some of these NSAs, materials whose surface compositions vary widely from their bulk composition exhibit some interesting properties for hydrogen dissociation and binding, i.e., easy dissociation of hydrogen gas combined with weak binding of hydrogen atoms on the catalyst surface.[1] In addition to surface hydrogen, the characteristics of subsurface hydrogen may be important in some applications, such as hydrogenation reactions, hydrogen membranes and hydrogen storage.[2] Using state of the art Density Function theory, we have analyzed the diffusion of hydrogen from the surface into the subsurface of certain NSAs and the binding of hydrogen in the subsurface region. We discuss the dynamics of hydrogen diffusion through these NSAs and the stabilization of hydrogen in the subsurface of such alloys. We identify certain alloy combinations that may allow for the ‘trapping' of hydrogen in the subsurface of the alloy. We further examine the change in electronic structure of these alloys in the presence of this subsurface hydrogen and its effect on the catalytic properties of this class of NSAs. Using a novel electrochemical technique,[3] we have synthesized certain NSAs identified as having promising characteristics and tested the adsorption of hydrogen in these alloys.

[1] J. Greeley, M. Mavrikakis, Nature Materials 2004, 3, 810.

[2] J. Greeley, M. Mavrikakis, Journal of Physical Chemistry B 2005, 109, 3460.

[3] S. R. Brankovic, J. X. Wang, R. R. Adzic, Surface Science 2001, 474, L173.