Temperature‐Tuned Nitrogen and Oxygen Self‐Doped Carbonized Polymer Dots for Enhanced Supercapacitor Applications

Abstract A one‐step hydrothermal method is used to synthesize nitrogen and oxygen self‐doped carbonized polymer dots (N, O‐CPDs) from o‐phenylenediamine (o‐PD) as the precursor. Detailed structural analysis shows that the evolution of defects is temperature‐dependent, with the synthesis temperature being crucial in determining the level of carbonization and structural disorder. This process results in a complex carbon structure featuring sp 2 graphitic domains mixed with controlled structural defects, essential for electrochemical activity. The N, O‐CPDs demonstrate remarkable electrochemical performance when tested as electrode materials for supercapacitors. Notably, the sample synthesized at 220 °C achieves a high specific capacitance of 205 Fg −1 at 1 Ag −1 in a three‐electrode setup and 58 Fg −1 in a two‐electrode configuration. Additionally, it shows excellent cycling stability, maintaining 85% of its initial capacitance after 4500 cycles at 4 Ag −1 . This impressive performance is attributed to the synergistic effects of nitrogen and oxygen doping, which create numerous active sites and enhance charge transfer efficiency. The combination of optimized structural disorder and heteroatom doping significantly improves the electrochemical properties of these N, O‐CPDs, highlighting their potential as advanced materials for energy storage applications.