Natural Biomass-Derived Hierarchical Porous Carbon Synthesized by an in Situ Hard Template Coupled with NaOH Activation for Ultrahigh Rate Supercapacitors

An in situ hard template strategy coupled with NaOH activation is proposed to prepare hierarchical porous carbons with high surface area from biomass for high-performance supercapacitors. The preparation of the carbon includes the sol–gel process of lotus seed shell and sodium phytate, followed by carbonization and NaOH activation. The soluble sodium phytate is pyrolyzed to nano-Na5P3O10 during carbonization and then reacts with NaOH to convert to nano-Na2CO3 and nano-Na3PO4 particles, which are encapsulated in the carbon matrix as the in situ hard templates and leave large mesopores/macropores after being removed in the subsequent washing treatment. Combined with the micropores created by NaOH activation, the as-prepared carbons possess developed hierarchical pores with a large surface area of 3188 m2 g–1 and a pore volume of 3.2 cm3 g–1. Furthermore, the carbons are rich in the heteroatoms of O, N, and P originated from the biomass precursors and sodium phytate. As a result, the biomass-derived hierarch...