Alkaline Water Oxidation Catalyzed by 3D Self-Supported Cr-Doped Ni₃N Nanosheet Arrays

The development of highly efficient, stable, and low-cost electrocatalysts for oxygen evolution reaction (OER) is crucial for enhancing the efficiency of water splitting, but it still remains a huge challenge. Herein, three-dimensional (3D) self-supported Cr-doped Ni3N (Cr–Ni3N) nanosheet arrays were synthesized successfully on the carbon cloth by the hydrothermal method and subsequent nitridation process. Cr–Ni3N displays a superior alkaline OER performance with a low overpotential of 290 mV at the current density of 50 mA cm–2, a small Tafel slope of 56 mV dec–1, and robust electrochemical stability, which is much better than those of bare Ni3N and commercial RuO2. The calculation of density functional theory reveals that electron-rich Cr atoms transfer electrons to electron-deficient Ni and N atoms, effectively adjust the surface electron configuration of the Cr–Ni3N catalyst, and optimize the H2O adsorption in the 1 M KOH solution during the OER process. Additionally, the partially oxidized Cr6+ during the OER can optimize the electronic structure and enhance the stability of NiOOH active sites by the strong electron withdrawing ability. This work can provide a pathway to rationally design efficient transition metal nitride-based OER electrocatalysts.