Vertically Arrayed Co₄N/MoN Nanosheets for Robust Alkaline Electrocatalytic Hydrogen Evolution at Ampere‐Level Current Density

Abstract Metal nitride electrocatalysts have been extensively developed for efficient alkaline water splitting, but it still remains a huge challenge in improving their stability especially at high current density of over 500 mA cm⁻². Herein the Co₄N/MoN electrocatalyst with hierarchical nanoparticle‐assembled nanosheet arrays is fabricated by a facile electrodeposition‐nitridation method for alkaline hydrogen evolution reaction (HER). Results show that it exhibits an impressively low overpotential of 238 mV and high durability at 1.0 A cm⁻² for over 100 h, which is the best among the reported cobalt‐based nitride electrocatalysts with both excellent HER activity and robust stability at ampere‐level current density. The superior intrinsic HER activity is mainly ascribed to the synergistic effect of Co₄N and MoN, which can effectively reduce the H₂O dissociation energy barrier and accelerate the alkaline HER kinetics. Moreover, benefiting from the vertically arrayed nanosheet structure with a solid framework and excellent mechanical strength, robust water electrolysis even at ampere‐level current density can be achieved. This work provides an alternative way to develop metal nitride electrocatalysts via fabricating hierarchical heterostructure for efficient and stable industrial water splitting.