The insight of self-doped phosphorus on the biocarbon substrate: Co3O4 nanocrystals anchored on porous carbon derived from Manila grass for supercapacitor electrode with long life

•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.