Mass Production of Monodisperse Carbon Microspheres with Size‐Dependent Supercapacitor Performance via Aqueous Self‐Catalyzed Polymerization

A facile, aqueous, self‐catalyzed polymerization method has been developed for the mass production of monodisperse phenolic resin and carbon microspheres. The synthesis is mainly based on the self‐catalyzed reaction between phenol derivatives and the hydrolysis products of hexamethylenetetramine (HMTA). The obtained phenolic resin spheres have a tunable size of 0.8–6.0 μm, depending on the type of phenol and HMTA/phenol ratio. Treating the phenolic resin with steam at an elevated temperature results in monodisperse carbon microspheres with abundant micropores, high surface area, and rich surface functionality. The resultant carbon spheres exhibit a size‐dependent electrical double‐layer capacitor performance; the capacitance increases with decreasing particle size. The nitrogen and oxygen codoped carbon spheres with the smallest size (≈600 nm) deliver a high specific capacitance (282 F g−1 at 0.5 A g−1), excellent rate capability (170 F g−1 at 20 A g−1), and outstanding cycling stability (95.3 % capacitance retention after 10 000 cycles at 5 A g−1). This study provides a new avenue for the mass production of monodisperse carbon microspheres. Size versus capacitance: A facile, aqueous, self‐catalyzed polymerization method has been developed for the mass production of monodisperse carbon microspheres. The resultant carbon spheres exhibit a size‐dependent supercapacitor performance; the capacitance increases with decreasing particle size. Nitrogen and oxygen codoped carbon spheres deliver a high specific capacitance, excellent rate capability, and outstanding cycling stability (see figure).