Biomass waste-derived mesopore-dominant porous carbon for high-efficiency capacitive energy storage

Mesopore-dominant porous carbon was fabricated from poplar catkin bio-wastes with a facile and mild one-pot strategy. Some fabrication parameters (i.e., H3PO4 dosage and activation temperature) were optimized based on the capacitive behavior of the obtained materials. The optimal carbon (denoted as PCC-3-600), which was prepared under the conditions of H3PO4 solution (15.0 wt%) 3 mL and activation temperature 600 °C, achieved a specific capacitance of 316.5 F g−1 at a current density of 0.5 A g−1 and still kept as 182.0 F g−1 at 20.0 A g−1 in the three-electrode configuration. The PCC-3-600//PCC-3-600 symmetric device provided an appealing energy density (E) of 25.93 Wh kg−1 with the power density (P) of 240 W kg−1, and maintained as high as 15.33 Wh kg−1 with P = 8000 W kg−1. Aside from this, the assembled symmetric configuration delivered excellent cycling stability with a 103.67% retention in capacitance even in the 30,000th cycle at 1.0 A g−1. Compared with many carbon materials in literature, the obtained PCC-3-600 provides superior capacitive energy storage behavior, which is presumably due to its unique mesopore-dominant porous structure with a large surface area of 2011 m2 g−1 as well as the presence of heteroatoms (i.e., N, O and P). Our work paves a facile avenue for the efficient usage of bio-wastes in advanced electric energy storage devices.