Composition-Tunable Antiperovskite Cu_x In_1-x NNi₃ as Superior Electrocatalysts for the Hydrogen Evolution Reaction

A group of newly reported antiperovskite nitrides Cu_x In_1-x NNi₃ (0≤x≤1) with tunable composition are employed as electrocatalysts for the hydrogen evolution reaction (HER). Cu_0.4 In_0.6 NNi₃ shows the highest intrinsic performance among all developed catalysts with an overpotential of merely 42 mV at 10 mA cm_geo ^-2 . Stability tests at a high current density of 100 mA cm_geo ^-2 show its super-stable performance with only 7 mV increase in overpotential after more than 60 hours of measurement, surpassing commercial Pt/C (increase of 170 mV). By partial substitution, the derived antiperovskite nitride achieves a smaller kinetic barrier of water dissociation compared to the unsubstituted InNNi₃ and CuNNi₃ , revealed by first-principle calculations. It is found that the partially substituted Cu_x In_1-x NNi₃ possesses a thermal neutral and desirable Gibbs free energy of hydrogen for HER, ascribed to the tailoring of the energy of d-band center arose by the A-site (A=Cu or In) substitution and a resulting optimization of adsorbate interactions.