Cerium Hexacyanoferrate/NPCQD Hybrid Derived from Syzygium cumini Peel for Enhanced Supercapacitor Performance

Recent interest in sustainable electrode materials has surged due to the increasing demand for energy storage systems that
are both highly efficient and environmentally friendly. In this study, a hybrid electrode composed of cerium hexacyanoferrate
(CeHCF) and nitrogen, phosphorus co-doped carbon quantum dots (NPCQDs) derived from Syzygium cumini (jamun)
peel was synthesized through a simple co-precipitation method. The structure and morphology were comprehensively
characterized using XRD, FTIR, SEM, TEM, XPS, and BET analyses. The incorporation of biomass-derived NPCQDs
significantly enhanced the conductivity, surface area, and defect density of CeHCF. As a result, the CeHCF/NPCQD electrode
exhibited a high specific capacitance of 786 F g−
1 at 1 A g−
1 in a three-electrode configuration and retained 91.6% of
its initial capacitance after 10,000 cycles. When assembled into an asymmetric CeHCF/NPCQD‖AC device, it delivered a
specific capacitance of 248 F g−
1, an energy density of 87.8 Wh kg−
1, and a power density of 800 W kg−
1. The remarkable
electrochemical performance arises from the synergistic redox activity of CeHCF and the conductive, defect-rich NPCQDs.
The use of low-cost biomass precursors and green synthesis further ensures scalability and environmental sustainability,
making CeHCF/NPCQD a promising electrode material for next-generation supercapacitors.