Interfacial electronic coupling in g-C3N4/RGO heterostructure enabled high-performance ammonium-ion storage

The development of sustainable aqueous energy storage systems requires electrode materials capable of fast ion transport, high reversibility, and long-term stability. Herein, we report a metal-free graphitic carbon nitride/reduced graphene oxide (g-C 3 N 4 /RGO) heterostructure for aqueous NH 4 + ion storage and investigate the role of heterointerface formation and nitrogen functionalities in charge-storage. To the best of our knowledge, this is the first report of a g-C 3 N 4 /RGO heterostructure as an electrode material for aqueous NH 4 + -ion storage. The nitrogen-rich g-C 3 N 4 provides abundant nitrogen-containing active sites, while the conductive porous RGO network facilitates electron transport and electrolyte accessibility. A rational stacking of g-C 3 N 4 /RGO (10 wt%) heterostructure exhibits a specific capacitance of 256 F g −1 at 1 A g −1 in aqueous (NH 4 ) 2 SO 4 electrolyte. Electrochemical and kinetic analyses reveal a mixed charge-storage mechanism involving surface-controlled capacitive contributions and pseudocapacitive processes. A symmetric device assembled with the optimized material delivers highly balanced performance, with an energy density of 42 Wh kg −1 and a power density of 1000 W kg −1 along with excellent cycling stability. The findings highlight the importance of heterointerface engineering and nitrogen-rich carbon architectures for the development of sustainable NH 4 + ion energy storage system.