Heteroatoms-doped porous carbon microspheres derived from cyclotriphosphazene based materials for high performance supercapacitors

Poly-phosphazenes have emerged as a significant category of organic and inorganic composite materials, that can produce efficient co-doped carbons materials for supercapacitors electrode. In this study, the nitrogen and phosphorus rich cyclotriphosphazene-co-1,5-naphthalene diamine microspheres (CTPND-MS) with tailored properties were synthesized by carbonization of carbon precursor. Micro and mesoporous mixed carbon microspheres (CMS) with high specific surface areas were obtained by varying the heating rates during carbonization: 2 °C min⁻¹ (CTPND-MS2), 5 °C min⁻¹ (CTPND-MS5) and 10 °C min⁻¹ (CTPND-MS10). Among these, CTPND-MS2 demonstrated the highest specific surface area of 749.12 m²/g, with approximately 4.64–5.19 % heteroatom content. This high specific surface area and intrinsically N, P dual doped activated carbon microspheres exhibited a specific gravimetric capacitance of 232.0 F g⁻¹ at current density of 0.1 A/g in a 1 M H₂SO₄ electrolyte in symmetric dual electrode capacitor. CTPND-MS2 demonstrated 98 % cycling stability after 10,000th galvanostatic charge–discharge (GCD) cycles at current density of 5 A/g. Additionally, co-doped microspheres achieved energy density of 8.06 Wh kg⁻¹, at a power density of 24.99 Wh kg⁻¹, at 0.1 A/g. The results establish that phosphazene based materials exhibits an excellent potential for the development of high-performance supercapacitors electrode materials.