Nitrogen-doped graphene quantum dots modified polymetallic oxyphosphide hollow nanoboxes for boosting supercapacitor...

The regulation of composition and structural design of electrods are pivotal in advancing high-performance supercapacitors. In this study, we prepare a Fe-doped NiCo oxyphosphide (Fe-NiCoOP) nanobox with a hollow structure, which is further modified with nitrogen-doped graphene quantum dots (NGQD). This innovative design integrates multiple high-performance elements, leading to a substantial enhancement in electrochemical properties. The introduction of phosphorus (P) substantially improves the material's conductivity, optimizes its electrochemical active sites, and increases cycle stability. The integration of NGQD forms a distinctive heterostructure with Fe-NiCoOP, which not only refines the charge transport pathways but also markedly accelerates the reaction kinetics of the electrode material. Furthermore, the hollow architecture of the nanocages provides extensive permeation and storage spaces for the electrolyte, while also substantially increasing the redox reaction sites, thereby elevating the overall electrochemical performance. The synergistic combination of these advantages results in the Fe-NiCoOP@NGQD electrode material exhibiting an exceptional specific capacity of 1136.5 F g^-1. When utilized in supercapacitors, this material demonstrates a remarkable energy density of 78.7 Wh kg^-1. Notably, the device retains 81.6% of its initial capacitance after 8000 charge-discharge cycles, underscoring its outstanding cyclic stability.