Enhanced supercapacitor performance of Camellia oleifera shell derived hierarchical porous carbon by carbon quantum dots

Biomass-derived porous carbons have great potential as electrode materials for supercapacitors. However, their amorphous and micropore-dominated structures are unfavorable for the electrochemical kinetics, which will limit their rate capability and cycle stability. In this work, we reported a facile strategy to improve the capacitive behavior of porous carbons derived from Camellia oleifera shell by introducing carbon quantum dots (CQDs) with highly graphitization degree into the skeleton of porous carbons. Benefiting from the unique surface property of CQDs, the obtained CQD/hierarchically porous carbon composites (CQDs/HPC) possessed a well-developed porous structure with high mesopore content and moderate surface heteroatom doping. Furthermore, their charge/ion transfer kinetics were improved due to the formation of the conductive channels in the carbon skeleton as well as optimized pore structure and surface doping. Consequently, the optimized CQDs/HPC-2 presented a high capacitance of 259 F g −1 at 1 A g −1 and a high rate capability in 1 M H 2 SO 4 , which is much better than bare HPC. The assembled symmetric supercapacitors delivered an energy density of 8.61 (17.86) Wh kg −1 at the power density of 477 (954) W kg −1 in 1 M H 2 SO 4 (1 M Na 2 SO 4 ) solution and high long-term stability with 94 % capacitance retention after 20,000 cycles at 5 A g −1 . • CQDs tune the pore structure and heteroatom doping of biomass-derived carbon. • CQDs improve the conductive channels in carbon skeleton. • CQDs accelerate the charge/ion transfer kinetics of biomass-derived carbon. • CQDs promote the rate capability and long-term cycle stability of biomass-derived carbon.