Efficient Preparation of Spongy-Like Porous-Activated Carbon from Waste Millfeed Towards High Performance Supercapacitors

Abstract

Biomass-based activated porous carbon (PC) with large porosity and high surface area has been considered as potential electrode material for supercapacitors. The spongy-like porous-activated carbon (SPAC) was prepared from millfeed by one-step carbonization/activation with KOH treatment. It shows three-dimensional (3D) spongy-like structure and high specific surface area (1535[Formula: see text]m2[Formula: see text]g[Formula: see text]). The SPAC electrode exhibits a high specific capacitance (237.9[Formula: see text]F[Formula: see text]g[Formula: see text] at a current density of 0.5[Formula: see text]A[Formula: see text]g[Formula: see text]) and a superior cycle stability (the capacitance retention of 95% after 10[Formula: see text]000 cycles at 2[Formula: see text]A[Formula: see text]g[Formula: see text]) in 2[Formula: see text]M KOH electrolyte, while the SPAC reveals a high specific capacitance of 157[Formula: see text]F[Formula: see text]g[Formula: see text] at 0.5[Formula: see text]A[Formula: see text]g[Formula: see text], good electrochemical stability with 93% capacitance retention after 5000 cycles in ionic liquids. Furthermore, the specific capacitance of SPAC//SPAC supercapacitor reaches 82.1[Formula: see text]F[Formula: see text]g[Formula: see text] at a current density of 0.5[Formula: see text]A[Formula: see text]g[Formula: see text] and achieves a high capacitance retention of 75% when the charging current increases to 10[Formula: see text]A[Formula: see text]g[Formula: see text] in 2[Formula: see text]M KOH electrolyte. The SPAC//SPAC supercapacitor possesses a high specific capacitance of 29.6[Formula: see text]F[Formula: see text]g[Formula: see text] at 0.5[Formula: see text]A[Formula: see text]g[Formula: see text] and a preeminent energy density of 27.8[Formula: see text]Wh[Formula: see text]kg[Formula: see text] (at a power density of 640[Formula: see text]W[Formula: see text]kg[Formula: see text]) in ionic liquids. This paper provides a convenient approach to synthesize low-cost biomass-based carbon material for supercapacitor applications.