Improved interaction of hydrogen on transition-metal-doped Al(100) stepped surface

Using the density functional theory with generalized gradient approximation, we have studied in detail the enhanced hydrogen interaction with a transition-metal-doped Al(100) stepped surface. Judging from the calculated total energies, the early transition metals prefer to dope at the lower edge sites of a surface step. The Sc, Ti, and V donate electrons, whereas the Cr and Mn gain electrons. The low energy costs for activating both the H₂ splitting and the H atomic diffusion show improved catalytic performances. In the transition states, hydrogen would bond to both transition metal and Al atoms for H₂ splitting on Sc- and Ti-doped surfaces, whereas it would only develop a rather weak interaction with the metals in the other studied materials. The charge transfer results in a 0.8 e charge gain and 0.4 Å increase in bond length of H₂, facilitating H₂ dissociation on Sc- and Ti-doped surfaces. However, in the other studied materials, the presence of hydrogen only induces charge redistribution, resulting in a rather small charge gain of H₂ (<0.1 e). The insights into the catalytic mechanism, on the basis of our detailed analysis on structural and electronic properties, could benefit the experimental investigations in pursuing a moderate hydrogen storage medium.