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Porous carbons have recently drawn extensive attention in energy conversion and storage devices. Boosting energy densities of carbon family is still a challenge due to their limited surface area and accessible active sites. In this work, porous carbons with hierarchically structures were prepared from natural Juncus effuses (CJE) and homogeneous MnO 2 layer was successfully incorporated on their surfaces without changing their original porous structure. The CJE/MnO 2 composite showed large specific capacitance (283 F/g at 1 A/g), which was on account of high specific surface area (1283 m2/g) and abundant active sites for pseudocapacitance, particularly, resulted from the introduction of MnO 2. Significantly, the assembled symmetric supercapacitor from CJE/MnO 2 in Na 2 SO 4 aqueous electrolyte delivered high energy/power densities (19.13 Wh/kg at 225 W/kg and 13.73 Wh/kg at 8984 W/kg) and good cyclic performance (86.2% capacitance retention over 5000 cycles at 10.0 A/g). These results demonstrate the CJE/MnO 2 composite can be a potential candidate for supercapacitors. • The surfaces of porous carbons from Juncus effuses are functioned. • Oxygen-containing functional groups facilitate the formation of MnO 2 layer. • Prepared CJE/MnO 2 composites show high specific surface area and capacitance. • The supercapacitor from CJE/MnO 2 delivers excellent energy-power output. [ABSTRACT FROM AUTHOR]

• We first explained the interface style of the Co atoms anchored on the carbon substrate derived from biochar systematically. • The self-doped phosphorus inherited from manila grass play an important role of supplying extra capacitance. • The novel hive-like 3D hierarchical carbon skeleton was low cost. • The ASC based on this electrode delivers excellent rate abilities and cycle performance. Hive-like Co 3 O 4 @C composites with well performance were fabricated using Manila grass as a novel carbonous precursor with self-doped phosphorus. [Display omitted] A novel hive-like Co 3 O 4 @C composite is synthesized solvothermally and calcinated using Manila grass as an interesting precursor of porous carbonous skeleton with self-doped phosphorus and oxygen, anchored by Co 3 O 4 nanocryclusters through the sites rich in doped atoms. The capacitance of the as-fabricated materials is 767.6 F·g−1 (1 A·g−1) with long life of 96.2% retention after 12,000 cycles, according with the phosphorus content in composites. Moreover, the supercapacitor is assembled by KC-600 (+) and active-carbon () delivers an energy density of 81.42 Wh·kg 1 at 875 W·kg 1 and satisfactory cycling stabilities (9.17% lost after 24,000 cycles), owing to its unique microstructure and the self-doped phosphorus of Manila grass. Therefore, the porous hive-like Co 3 O 4 @C composite can better achieve as an electrode material through an easy and eco-friendly process based on biocarbon for the energy storage devices in the future. [ABSTRACT FROM AUTHOR]