Asymmetric Exchange Interaction Induces Highly Efficient Alkaline Hydrogen Evolution in RhFe Bimetallene

An RhFe bimetallene with Fe atoms doped into Rh host for efficient hydrogen evolution reaction (HER), is constructed. When two doped Fe atoms occupy neighboring asymmetric spatial positions, their asymmetric exchange interaction drives electron hopping between the d(xy) orbital of a Fe atom and the d(z)(2) orbital of its neighboring Fe atom to push the d band center closer to the Fermi level as a result of electronic state reconstruction. The designed bimetallene with thickness of 0.77 nm (5 atomic layers), possesses excellent HER performance. The low overpotentials of 24.4 and 34.6 mV are achieved at the 10 and 100 mA cm(-2) current densities in 1 m KOH solution, respectively. An ultra-low Tafel slope of 8.9 mV dec(-1) shows that this kind of RhFe bimetallene is of an ultrafast kinetic process. This work provides a strategy for designing HER catalysts with double metal composites.