Function of Doping Ru Element in the Hydrogen Evolution Reaction in Rare-Earth Transition-Metal Intermetallics.

Transition metal-based intermetallics are promising electrocatalysts for replacing the commercial Pt metal in the hydrogen evolution reaction (HER). In this work, RENi and RERuNi (RE = Pr, Tb, and Er) were synthesized and their electrocatalytic HER activities were explored. Among undoped compounds, PrNi exhibits the best performance and requires an overpotential of 55 mV, while partially replacing Ni with Ru element (PrRuNi) can greatly reduce the overpotential to 20 mV at a current density of 10 mA/cm. Such enhancement was recognized that belongs to their extrinsic property, and their intrinsic HER activities were similar after normalizing the electrocatalytic surface area. Further investigation on ScM and ScRuM (M = Co and Ni) suggests that doping Ru element in ScCo will significantly enhance antibonding character around the Fermi level () and weaken hydrogen adsorption energy. On the other hand, the antibonding population for ScNi and ScRuNi is similar at , which accounts for their close intrinsic HER activities.