Rational engineering of meso-macroporous structured carbon materials for revealing capacitive mechanism

The tailorable meso-macroporous structure of hierarchical porous carbon (HPC) is an essential key to improve ion diffusion dynamics and microporous accessibility for capacitive material. However, few studies focus on the capacitive mechanism of meso-macroporous proportion of HPC. Herein, a regionally selective dissolution and pyrolysis strategies are deployed to tailor the proportion of meso-macropores in facial mask-derived HPC through adjusting the oxalic acid concentration in hydrothermal process in this contribution. The obtained HPC show increasing meso-macroporous volumes of 0.04, 0.12, and 0.40 cm³ g⁻¹, corresponding to the oxalic acid concentrations of 0.2, 0.5, and 1.0 g/50 ml, respectively, while the microporous structures remain similar. Electrochemical results show that with increasing proportion of meso-macropores, the specific capacitances of HPC decrease from 386.9 to 276.5 and 220.3 F g⁻¹ at current density of 1 A g⁻¹, and decrease from 216.7 to 181.1, and 133.1 F g⁻¹ at 50 A g⁻¹. CV fitting results indicate that a small number of meso-macropores can enhance the surface-controlled capacitive contribution, improving the accessibility of micropores and faradaic pseudocapacitive reactions. The optimized HPC-based supercapacitor delivers a high energy density of 11.5 Wh kg⁻¹ at a power density of 125 W kg⁻¹ in KOH electrolyte and a maximum energy density of 49.4 Wh kg⁻¹ at 225 W kg⁻¹ in Na₂SO₄ electrolyte with long cycle stability, suggesting that the rational engineering of meso-macroporous proportion in HPC uncover news insights into developing high performance supercapacitor.