One-pot synthesis of monodisperse phenolic resin spheres with high thermal stability and its derived carbon spheres as supercapacitor electrodes

We report a rapid and energy saving one-pot synthesis method to prepare monodisperse phenolic resin spheres (PSs) under high acidic conditions. This method integrates the low-temperature polymerization and solidification processes into one procedure. The PSs have excellently thermal stability, which shown extremely low skeleton shrinkage ratio of 9.2%–15.8% under different carbonization temperature from 600 °C to 1000 °C. The PSs can be directly converted into sulfur-doped hierarchical porous carbon spheres (HPCSs) by carbonization and KOH activation. In these unique HPCSs, the mesopores and macropores contribute to the mass transportation by reducing and smoothing the diffusion pathways, while the rich micropores ensuring the sufficient active sites to effectively charge storage. Combine with the hierarchical porous structure, high specific surface area and suitable S doping content, as a supercapacitor electrodes, the HPCSs-600 exhibit a high specific capacitance of 321 F g−1 at 0.5 A g−1, excellent rate retention of 72.9% from 0.5 to 50 A g−1, and outstanding cycling stability with 97% capacitance retention after 10 000 cycles.