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

Designing efficient metal nitride electrocatalysts with advantageous nanostructures toward 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 HNA architecture can not only 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 the hydrogen evolution reaction (HER) and 50 mA cm-2 for the oxygen evolution reaction (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, higher than many other metal nitride-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.