Facile Preparation of Self-Standing Hierarchical Porous\nNitrogen-Doped Carbon Fibers for Supercapacitors from Plant Protein–Lignin\nElectrospun Fibers

Abstract

This research aims to develop self-standing\nnitrogen-doped carbon\nfiber networks from plant protein–lignin electrospun fibrous\nmats for supercapacitors. The challenge in preparing carbon fiber\nfrom protein is to maintain a fibrous structure during carbonization\nprocess. Thus, lignin was incorporated with protein. At protein-to-lignin\nratio of 50:50 to 20:80, the electrospun fibers maintained their structure\nafter carbonization and formed self-standing carbon fiber mats. Stacked\ngraphene layer structure was developed in the carbon fibers at a relatively\nlow carbonization temperature (<1000 °C) without the use of\ncatalysts, which might be derived from both lignin and protein. Graphene\nlayer structure conferred the carbon fibers with superior conductivity.\nThe optimized carbon fiber networks possessed excellent capacitance\nperformance in 6 M KOH of 410 F/g at 1 A/g and good cyclic stability.\nSuch good electrochemical properties were due to the well-engineered\ncharacteristics of the materials, including a hierarchical porous\ntexture, heteroatoms (nitrogen and oxygen), and the stacked graphene\nlayer structure. This research not only has provided a convenient\nway to develop carbon fibers from plant protein−lignin for\nN-doped supercapacitor electrodes, but also opportunity to add value\nto plant proteins and lignin as by-products of agricultural industry\nprocessing.