A systematic DFT investigation of hydrogen sorption properties on 3d, 4d and 5d TM-doped Mg(0001) surfaces

The catalytic effect of all 3d, 4d and 5d transition metals (TMs) as possible dopants of a Mg(0001) surface to enhance its hydrogen sorption properties has been systematically studied with Density Functional Theory (DFT). We discuss on-surface adsorption and first three-layer substitutional preferences of all TMs and compare results with those already available in literature. Our findings show that most of them prefer to substitute in the second layer, apart from Cd and Hg preferring the first layer — and from Co, Zn, Ru, Rh, Lu and Au preferring the third layer instead. We also present a compilation of d-band centre position values for all the TMs of the Periodic Table. Using this descriptor in the context of the Hammer & Norskov model, we find that Fe, Ni and Rh remain the most active catalysts among all TMs, securing low activation barriers for both hydrogen dissociation and diffusion processes.