Dual-functional modification of magnesium cobaltite via nitrogen doping and nickel boride heterostructuring: Toward enhanced charge storage kinetics and stability

Magnesium cobaltite (MgCo 2 O 4 ) is a promising supercapacitor (SC) electrode material, yet its practical implementation is constrained by low specific capacitance and poor conductivity. To address these challenges, we developed a dual-modification approach through nitrogen doping and heterostructure engineering. Here, we demonstrate the in situ growth of nitrogen-doped MgCo 2 O 4 (N-MgCo 2 O 4 ) nanoparticles wrapped by Ni 2 B nanosheets with crystalline/amorphous interfaces on a flexible carbon cloth (CC) substrate for SC applications. Nitrogen doping leads to the formation of a MgCo 2 O 4 /Co 2 N composite with enhanced electrical conductivity. Simultaneously, the designed N-MgCo 2 O 4 /Ni 2 B core-shell nanoarchitecture increases the density of electroactive sites and reinforces the structural stability. Density functional theory (DFT) studies demonstrate that the formation of N-MgCo 2 O 4 /Ni 2 B heterostructure induces efficient charge redistribution across the N-MgCo 2 O 4 /Ni 2 B heterointerfaces and enhances hydroxide ion adsorption capacity, leading to accelerated charge transport dynamics. The N-MgCo 2 O 4 /Ni 2 B electrode delivers a specific capacitance of 2037.7 F g -1 at 1 A g -1 with a 82.0% capacitance retention at 20 A g -1 , surpassing the performance of pristine MgCo 2 O 4 , N-MgCo 2 O 4 , and Ni 2 B. Furthermore, the fabricated N-MgCo 2 O 4 /Ni 2 B//porous carbon asymmetric supercapacitor (ASC) device illustrates an energy density of 80.7 Wh kg -1 at 795.0 W kg -1 and exceptional cycling stability with 94.7% capacitance retention after 20,000 cycles. • N-doped MgCo 2 O 4 /Ni 2 B heterostructure was rationally fabricated. • DFT calculations confirm improved conductivity and OH − adsorption capability. • The synergy of N-MgCo 2 O 4 and Ni 2 B enhances the charge storage kinetics and structural integrity. • The asymmetric supercapacitor achieves a peak energy density of 80.7 Wh kg -1 .