Hydrogen Evolution Reaction Catalyzed by Transition-Metal Nitrides

Density functional theory (DFT) calculations are used in this study to screen for stable and active catalyst material among transition-metal nitrides (TMNs) for catalyzing the hydrogen evolution reaction (HER). Previously, we have predicted with DFT calculations that some TMNs form ammonia under electrochemical conditions, while others become poisoned or react to give ammonia and its parental metal. The TMNs of Sc, Ti, Y, Hf, Ta, and Mo, however, become fully covered with H adatoms without forming any ammonia. These TMNs are investigated further here, where we focus on the (100) facet of the rocksalt structure. We calculate the H coverage as a function of the applied potential. Activation energies of H-2 formation via the Tafel reaction are also calculated at varying applied potentials. The results nominate a few nitrides (TaN, HfN, MoN, and ScN) capable of catalyzing HER at low overpotentials of -0.09 to -0.34 V vs a reversible hydrogen electrode, with the activation energies of the Tafel reaction being found relatively similar to those reported on Pt(111).