The first-principle DFT calculations were performed using the Vienna ab initio simulation code (VASP) . The Generalized Gradient Approximation (GGA) in the parametrization by Perdew, Burk and Ernzerhof combined with the projector augmented wave (PAW) method was used . Cut-off energy of 600 eV and Gaussian smearing with a width of σ = 0.025 eV for the occupation of the electronic levels were used. A Monkhorst-Pack Γ-centered 14×14×1 k-point mesh was used. We modelled Ni(001) and Ni(111) surfaces using the corresponding p(2×2) cells of given surfaces, with 10 and 9 layers slabs, respectively. Rh was inserted in the surface layer (Rh surf ) or the sub-surface layer (Rh sub ), and the top 6 layers of a given surface were allowed to relax fully. Knowing that on Ni HER proceeds under the conditions of high surface coverage , the surfaces were completely saturated by H ads (1 monolayer of hydrogen, 4 H ads per cell), and the average hydrogen binding energy (E H,b ) was calculated as: