Synergistic Cobalt Sulfide/Eggshell Membrane Carbon Electrode.

The preparation of green, facile, and cost-effective energy storage materials remains a big challenge. In this paper, a cobalt sulfide/porous carbon (Co4S3/PC) composite electrode is facilely prepared using the natural eggshell membrane (ESM) as a basal substrate. Under hydrothermal conditions, Co4S3 is grown on the ESM to form Co4S3/ESM and carbonized to form Co4S3/PC. The as-synthesized Co4S3/PC composite is used as an electrode material. The carbide from the ESM shows a porous structure and high specific surface area, which provides large space for Co4S3 attaching and ion migrating. Co4S3/PC shows much higher specific capacitance values than the sum of Co4S3 and PC electrodes, indicating a significant synergistic effect. More importantly, the Co4S3 is a typical faradic material, which exchanges Faraday charge with an electrolyte and subsequently transmits an electron to the whole electrode due to the high conductivity of the carbonized ESM. Such a synergistic effect offers the as-synthesized Co4S3/PC electrode a significant improvement in performance over both the ESM-derived carbon and the original Co4S3. Besides, the Co4S3/PC electrode shows a wide potential window, low resistance, and high specific capacitance. After 1000 cycles, the electrode retains a high cycling capacity. This study provides a novel insight for high-performance biomass-derived carbon preparation for pseudocapacitors and other electrochemical devices.