Doping and Vacancy Engineering in a Sandwich‐like g‐C₃N₄/NiCo₂O₄ Heterostructure for Robust Oxygen Evolution

Abstract Herein, N doping and O vacancy were simultaneously introduced into a g‐C₃N₄/NiCo₂O₄ heterostructure by a simple reflux and calcination strategy. The constructed g‐C₃N₄ displayed a porous lamellar structure with N‐doped carbon. Furthermore, numerous ultrathin NiCo₂O₄ nanosheets with abundant O vacancies tend to grow vertically on the porous g‐C₃N₄ lamellar, forming a sandwich‐like heterostructure. The prepared sandwich‐like g‐C₃N₄/NiCo₂O₄ heterostructure exhibited excellent oxygen evolution reduction (OER) activity with a low overpotential of 294 mV at 10 mA cm⁻². Meanwhile, the heterostructure presented superior long‐term stability, retaining a current density of 97.9% after a 50 h chronoamperometry test. The outstanding OER performance is ascribed to the synergistic effect of doping and vacancy engineering in the catalyst, the strong coupling interaction between g‐C₃N₄ and NiCo₂O₄, and the porous sandwich‐like structure with abundant active sites. Therefore, the synthetic strategy of g‐C₃N₄/NiCo₂O₄ heterostructure can be extended to fabricate high‐performance noble metal‐free electrocatalysts for water splitting.