Holey Cobalt-Iron Nitride Nanosheet Arrays as High-Performance Bifunctional Electrocatalysts for Overall Water Splitting.

Designing efficient metal nitrides electrocatalysts with advantageous nanostructures towards overall water splitting is of great significance for energy conversion. In this work, holey cobalt-iron nitride nanosheet arrays grown on Ni foam substrate (CoFeNx HNAs/NF) are prepared via a facile hydrothermal and subsequent thermal nitridation method. This unique HNAs architecture not only can expose abundant active sites but also facilitate the charge/mass transfer. Resulting from these merits, the CoFeNx HNAs/NF exhibits high catalytic performance with overpotentials of 200 and 260 mV at 10 mA cm‒2 for HER and 50 mA cm‒2 for OER, respectively. Furthermore, when using CoFeNx-500 HNAs/NF as both anode and cathode, the alkaline electrolyzer could afford a current density of 10 mA cm‒2 at 1.592 V, superior to many other metal nitrides-based electrocatalysts. This work signifies a simple approach to prepare holey metal nitride nanosheet arrays, which can be applied in various fields of energy conversion and storage.