Utilizing waste pomelo peel to develop activated-doped porous biomass carbon as electrode materials: Study of activation mechanism, evaluation of electrochemical properties and assembly of symmetric supercapacitors

To prepare electrode materials with excellent comprehensive properties for supercapacitor applications, and to promote the reuse of waste fruit peels. This work used waste pomelo peel as a carbon source for high-temperature carbonization, and a series of porous biomass carbon materials (YB-K) was prepared using a combination of freeze-drying and activation pore-making. The relationship between the structure of YB-K materials and the amount of activator was investigated by characterization. The results show that the YB-K materials (YB-K5) with the mass ratio of raw materials to activator of 1:5 have the best overall properties, and their specific surface area is as high as 1277.14 m2/g. Notably, the YB-K5 materials can be doped with nitrogen to prepare electrode materials (YB-K5-N) with excellent electrochemical properties. The specific capacitance of YB-K5-N electrode materials reaches 247.26 F/g at 0.5 A/g current density. Importantly, the YB-K5-N symmetric (button type) supercapacitor assembled with YB-K5-N materials showed good cycling stability with 87.58% specific capacitance retention after 3000 cycles. The YB-K5-N electrode materials prepared in this work have potential applications in energy conversion, energy storage and electrochemistry, which provide a new idea for utilizing waste fruit peels.