A self-template and self-activation co-coupling green strategy to synthesize high surface area ternary-doped hollow...

Development of facile and cost-effective routes to achieve hierarchical porous and heteroatoms-doped carbon architectures is urgently needed for high-performance supercapacitor application. In our study, ternary-doped (nitrogen, phosphorus and oxygen) hollow carbon microspheres (NPO-HCSs) are fabricated by one-step pyrolysis of single poly(cyclotriphosphazene-co-phloroglucinol) (PCPP) microsphere, which is generated through a facile polymerization between hexachlorocyclotriphosphazene and phloroglucinol at mild conditions. The whole preparation process is not used any additional template or activating agent. The obtained NPO-HCS-950 with average diameter of 580 nm and shell thickness of about 80 nm have a high specific surface area (2390 m² g^-1), a large pore volume (1.35 cm³ g^-1), hierarchically interconnected pore texture, and uniform ternary heteroatom doping (O: 3.04 at%; N: 1.33 at% and P: 0.67 at%). As an electrode material for supercapacitors, the specific capacitance of the NPO-HCS-950 reaches 253 F g^-1 of 1 A g^-1 and 176 F g^-1 at 20 A g^-1, revealing superior rate performance. The capacity retention after 10,000 consecutive charge-discharge cycles at 20 A g^-1 is up to 98.9%, demonstrating excellent cycling stability. Moreover, the assembled symmetric supercapacitor using NPO-HCS-950 exhibits a relatively high energy density of 17.6 W h kg^-1 at a power density of 800 W kg^-1. Thus, a promising electrode material for high-performance supercapacitors is obtained through a facile, green and scalable synthesis route.