Transition-Metal–Boron Intermetallics with Strong Interatomic d–sp Orbital Hybridization for High-Performance Electrocatalysis

A theoretical and experimental study gives insights into the nature of the metal–boron electronic interaction in boron-bearing intermetallics and its effects on surface hydrogen adsorption and hydrogen-evolving catalytic activity. Strong hybridization between the d orbitals of transition metal (T_M) and the sp orbitals of boron exists in a family of fifteen T_M–boron intermatallics (T_M:B=1:1), and hydrogen atoms adsorb more weakly to the metal-terminated intermetallic surfaces than to the corresponding pure metal surfaces. This modulation of electronic structure makes several intermetallics (e.g., PdB, RuB, ReB) prospective, efficient hydrogen-evolving materials with catalytic activity close to Pt. A general reaction pathway towards the synthesis of such T_MB intermetallics is provided; a class of seven phase-pure T_MB intermetallics, containing V, Nb, Ta, Cr, Mo, W, and Ru, are thus synthesized. RuB is a high-performing, non-platinum electrocatalyst for the hydrogen evolution reaction.