Hydrogel-derived nitrogen-doped porous carbon framework with vanadium nitride decoration for supercapacitors with superior cycling performance

Transition metal nitrides (TMNs) and their composites with carbon materials hold tremendous potential for supercapacitor (SC) electrodes because of their excellent electronic conductivity and electrochemical activity. However, realizing cycling stable TMN/carbon-based supercapacitors with economically viable and environmentally-friendly approaches remains a significant challenge. Significantly, polyacrylamide (PAM) hydrogel, as a water-soluble linear polymer electrolyte, is expected to be a remarkable candidate precursor for preparing N-doped porous carbon (NPC) due to the high contents of carbon and nitrogen elements. In this study, vanadium nitride (VN) embedded in PAM hydrogel-derived NPC was fabricated successfully via an ammonia-free process. The VN/NPC delivers a high specific capacitance of 198.3 F g−1 at a current density of 1 A g−1, with a remarkable cycling stability of 107% after 16,000 cycles. The electrochemical performances of VN/NPC compared to bare VN nanoparticles are strongly improved due to the composite structure. Additionally, the VN/NPC-based solid-state symmetric device delivers an excellent energy density of 21.97 µWh cm−2 at a power density of 0.5 mW cm−2, and an outstanding cycling durability of 90.9% after 18,000 cycles. This work paves the way to design metal nitride/porous carbon materials, which also opens up unique horizons for the recovery of hydrogel electrolyte.