Facile construction of highly redox active carbons with regular micropores and rod-like morphology towards high-energy supercapacitors

Abstract

Redox active carbonaceous materials have recently absorbed a wide range of interest in energy-related fields owing to their trade-off superiorities between carbon stability and heteroatom activity. Feasible alkali-calcination of heteroatom-rich precursors is considered as an effective route to obtain large-surface-area carbons in supercapacitors, but preset structure/heteroatomic functionalities generally suffer from a great loss of efficacy due to severe corrosion. In this work, a facile route to construct highly redox active carbons is designed based on one-step potassium bicarbonate-involved calcination of an electroactive benzoquinone/p-phenylenediamine precursor. The resulting high-yield (74.9%) carbon not only presents large specific surface area (1840 m² g⁻¹) with regular micropore diameters predominantly at 0.55 and 0.85 nm, but also retains the high-level heteroatom activity (e.g. N: 11.46 wt%) and rod-like morphology of the synthetic precursor. When applied as a supercapacitor electrode, the representative material delivers a prominent capacitance of 365 F g⁻¹ at 1 A g⁻¹ and energy output of 18.25 W h kg⁻¹ in a hybrid aqueous electrolyte (H₂SO₄ + KBr) at 600 W kg⁻¹ by magnificent support of an extra redox mechanism. Additionally, on account of efficient electrolyte-ion electrosorption by optimized microporous spaces, the as-assembled EMIMBF₄-based ionic liquid cell offers boosted energy density up to 89.5 W h kg⁻¹ under the broadened potential of 3.8 V. Such satisfactory supercapacitive performance of the carbon electrode can be fundamentally assigned to the high-level superiority retention in the preset precursor, which may inspire structure optimization for other functionalized carbons.