Hierarchically designed 3D Cu₃N@Ni₃N porous nanorod arrays: An efficient and robust electrode for high-energy solid-state hybrid supercapacitors

Transition metal nitrides have recently fascinated noteworthy research interest owing to their exclusive electronic structure with high electrical conductivity and their emerging application in energy storage and conversion devices. Herein, we have designed a freestanding Cu₃N@Ni₃N nanorod arrays (NRAs) integrated on copper foam (CF), which serves as an active electrode for hybrid supercapacitors (SCs). The three-dimensional (3D) nano-architecture of Cu₃N@Ni₃N/CF is extremely beneficial for SCs because it possesses improved electrical conductivity, numerous surface active sites, and abundant “superhighways” for charge transportation owing to the self-supported design of material and synergistic effect between each active component. As a consequence, Cu₃N@Ni₃N/CF electrode displays outstanding energy storage performance in terms of specific capacity (390.5 mA h g⁻¹ (2.34 F cm⁻²) at 1 A g⁻¹, cycling stability (94.9% retention over 10 000 cycles), and excellent rate capability. As-fabricated hybrid solid-state SC (HSSC) device with the Cu₃N@Ni₃N NRAs and activated carbon (AC) as positive and negative electrodes, respectively demonstrated a maximum specific energy of 71.8 Wh kg⁻¹ at a specific power of 700 W kg⁻¹ with good cycling stability over 10 000 cycles. Thus, the work signifies a scalable approach for the systematic design of electrode materials and devices for future energy storage applications.