Changes in fundamental and catalytic properties of β-molybdenum carbide decorated by a single atom of Fe, Co, Ni and Cu

The interaction of single Fe, Co, Ni, and Cu atoms with polar terminations of orthorhombic Mo2C(0 0 1) surface has been investigated at low surface coverage by using density functional theory. Calculations indicate high stability of all considered adsorbates, regardless the surface termination. The presence of a single foreign atom has a localized impact on the properties of the surface, causing charge redistribution in the adsorbate/surface interface. As the result lowering of the work function is observed for both Mo2C(0 0 1) terminations. Another effect is shifting the position of d-band center further away from the Fermi level for surface Mo atoms of metal-terminated carbide, while no changes are seen for carbon’s near-Fermi level electronic states in the case of C-terminated modified surface. Results demonstrate a short-range effect on the stability of atomic hydrogen caused by the foreign adatom on both terminations. Specifically, the observed adsorption energy weakening would entail an enhancement in the catalytic activity of Mo2C toward hydrogen evolution reaction according to the Sabatier principle. Results evidence that molybdenum carbide modified by cobalt and iron is expected to be more active toward hydrogen evolution reaction than Mo2C modified by nickel and copper or than unmodified carbide.