Self-templating synthesis of hierarchical porous carbon with multi-heteroatom co-doping from tea waste for high-performance supercapacitor

Exploring porous carbon (PC)-based materials from low-cost, renewable precursors has always been a challenging objective, since they meet the demands of next-generation supercapacitors and electrochemical devices. Herein, hierarchical multi-heteroatoms co-doped PC (MHPC) materials are successfully achieved by the carbonization and activation of tea waste that used as the self-template. The natural structure of the tea leaves combined with the activation strategy favor the formation of special hierarchical MHPC materials, which are constructed by ultrathin MHPC nanosheets. In addition, the heteroatomic doped carbon derived from organic compounds in tea leaves can act as an ideal precursor to fabricate the resultant heteroatomic functionalized carbon nanosheets. Such heteroatoms content of carbon nanosheets are adjustable by altering pyrolysis condition to effectively enhance the electrochemical performance of PC. After activation by KOH, the as-prepared MHPC, especially MHPC-3 (weight ratio of KOH/pre-carbonized tea waste is 3:1) has a superior supercapacitance of up to 170 and 132 F g⁻¹ at current density of 0.5 and 10 A g⁻¹ in KOH electrolyte, and an excellent capacitance retention of ∼94.8% over 14,000 cycles at 3 A g⁻¹. The result reported here provides valuable guidelines of high-performance energy storge devices from natural sources at the industrial scale.