Composition‐Tunable Antiperovskite Cu x In 1− x NNi 3 as Superior Electrocatalysts for the Hydrogen Evolution Reaction

A group of newly reported antiperovskite nitrides Cu x In 1− x NNi 3 (0≤ x ≤1) with tunable composition are employed as electrocatalysts for the hydrogen evolution reaction (HER). Cu 0.4 In 0.6 NNi 3 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 InNNi 3 and CuNNi 3 , revealed by first‐principle calculations. It is found that the partially substituted Cu x In 1− x NNi 3 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.