Accurately control the micropore/mesopore ratio to construct a new hierarchical porous carbon with ultrahigh capacitance and rate performance

The synthesis of porous carbon materials with high surface area is an important method to improving their specific capacitances. However, the misfitting distribution of micropore/mesopore leads to serious recession under high current densities. Herein, we report a set of combination methods to accurately control the micropore/mesopore ratio to achieve a hierarchical carbon material with ultra-large capacitance and extra-high rate performance. These methods include adjusting Al/Zn ratios, decarboxylation, zinc volatilization, removal of nano-Al2O3, and KOH–KCl activation. The first four contribute to micropore structure creation to increase the specific capacitance at low current, while the last one contributes to mesoporous structure formation to increase the specific capacitance at high current. It is found that the corrosion of the excess micropores to form new mesopores and transparent graphene greatly enhances ion diffusion kinetic process and rate performance. Based on these findings, the optimized MDAPC provides a superior specific capacitance of 433 F g−1 at 1 A g−1, 324 F g−1 at 200 A g−1, and 217 F g−1 at 750 A g−1, indicating its ultra-large specific capacitance and extra-high rate performance. These findings provide a research foundation for the future development of hierarchical porous carbon materials with outstanding capacitance, rate performance and durability. •Four methods have been applied to obtain high-content microporous carbon material.•KOH–KCl treatment corrodes the excess micropores structure and form new mesopores.•The formed graphene and mesopores enhance the ion diffusion and rate performance.•The optimized sample with a lower micropore ratio and an open mesoporous structure.•It offers an ultrahigh charge rate and superior specific capacitance of 433 F g−1.