Three-Dimensional Walnut-Like, Hierarchically Nanoporous Carbon Microspheres: One-Pot Synthesis, Activation, and Supercapacitive Performance

A one-pot synthesis of three-dimensional walnut-like, hierarchically nanoporous carbon microspheres (HNCMs) via a dual-template method was reported. In our protocol, the organic mesomorphous complexes of hexadecylpyridinium chloride/poly(acrylic acid) (CPC/PAA) were employed as a dynamic soft template; the in situ generated silica during the hydrolysis of tetraethylsiloxane (TEOS) was applied as the hard template and sucrose, as the carbon precursor. When the amount of PAA added was varied, hierarchically nanoporous carbons with other novel morphologies such as having a hexagonal nanoplate, being dumbbell-like, and having a hexagonal microprism were synthesized in a controlled manner. Besides, the pore structure of HNCMs was tailored by tuning the molar ratio of sucrose and TEOS. It was demonstrated that the specific capacitance of the HNCMs was correlated with the orderliness of the mesopores. HNCMs-15 synthesized under the molar ratio of sucrose/TEOS at 15 with well-ordered mesopores exhibited the highest specific capacitance of 232 F g–1 at 1 A g–1. The as-prepared HNCMs-15 was further chemically activated, which resulted in the activated HNCMs-15 (AHNCMs-15) with no obvious morphology change but a high proportion of micropores, large surface area, and superior electrochemical properties (high specific capacitance of 413 F g–1 at 1 A g–1, excellent rate capability). The AHNCMs-15-based symmetric supercapacitor displayed a high energy density of 14.7 Wh kg–1 at a power density of 250 W kg–1 and small capacitance fading (only 1.6%) after 10 000 cycles at 2 A g–1. Our strategy provides a way for the controlled synthesis of hierarchically nanoporous carbon with well-defined morphology and structure and excellent electrochemical properties, which makes them promising electrode materials for high-performance supercapacitors.