Salt template tuning morphology and porosity of biomass-derived N-doped porous carbon with high redox-activation for efficient energy storage

Abstract

In this work, N-doped porous carbon with effective Faraday reaction activation is fabricated by pyrolysis of egg white in air at high temperature using a mixed KCl and NaCl salt sealing strategy. The mechanism of the morphology and pores affecting the redox reaction are discussed in depth and the morphology and porosity of the carbon product are regulated by adding different amounts of saturated NaCl salt solution to egg white before cooking in a water bath. The increasing amounts of saturated NaCl salt solution added to egg white can enable more salt particles to penetrate into carbon framework at high temperature due to the interaction between water molecules and salt particles, leading to the achievement of N-doped porous carbon with thin sheet and mesopore structure. The sheets and mesopores can accelerate the reaction kinetics involved with fast Faraday reaction and diffusion-controlled process by providing more electron and ion transfer expressways, producing the effective Faraday effects of carbon electrodes. Therefore, explored the supercapacitor applications, as-synthesized N-doped porous carbon is exhibited a superb three-electrode specific capacitance of 304 F g−1 at 1 A g −1. The symmetrical surpercapacitors are also displayed a high specific capacitance of 248 F g−1 at 1 A g −1 and a good cycling stability with 98.7% of initial capacitance retention rate undergoing 15 000 cycles at 2.5 A g−1. This work has fundamental merits for the use of the sustainable abandoned eggs and concentrated protein solution feedstocks to prepare carbon electrode materials and further expands the application field of the salt sealing technique.