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 (CoS/PC) composite electrode is facilely prepared using the natural eggshell membrane (ESM) as a basal substrate. Under hydrothermal conditions, CoS is grown on the ESM to form CoS/ESM and carbonized to form CoS/PC. The as-synthesized CoS/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 CoS attaching and ion migrating. CoS/PC shows much higher specific capacitance values than the sum of CoS and PC electrodes, indicating a significant synergistic effect. More importantly, the CoS 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 CoS/PC electrode a significant improvement in performance over both the ESM-derived carbon and the original CoS. Besides, the CoS/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.