Characterization of porous cobalt hexacyanoferrate and activated carbon electrodes under dynamic polarization conditions in a sodium-ion pseudocapacitor

We report here the activated carbon and cobalt hexacyanoferrate composite, which is applied as the electrode materials in symmetric supercapacitors containing a 1.0 M Na2SO4 aqueous electrolyte. This novel material combines high specific surface area and electrochemical stability of activated carbon with the redox properties of cobalt hexacyanoferrate, resulting in maximum specific capacitance of 329 F g(-1) with large voltage working window of 2.0 V. Electrochemical studies indicated that cobalt hexacyanoferrate introduces important pseudocapacitive properties accounting for the overall charge-storage process, especially when I < 0.5 A g(-1). At lower gravimetric currents (e.g., 0.05 A g(-1)) and up to 1.0 V, the presence of cobalt hexacyanoferrate improves the specific energy for more than 300%. In addition, to better understanding the energy storage process we also provided a careful investigation of the electrode materials under dynamic polarization conditions using the in situ Raman spectroscopy and synchrotron light X-ray diffraction techniques. Interesting complementary findings were obtained in these studies. We believe that this novel electrode material is promising for applications regarding the energy-storage process in pseudocapacitors with long lifespan properties. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

This study presents a novel composite material of activated carbon and cobalt hexacyanoferrate for use as electrode materials in symmetric supercapacitors. The material combines the high specific surface area and electrochemical stability of activated carbon with the redox properties of cobalt hexacyanoferrate, showing improved specific capacitance and specific energy compared to traditional materials. Electrochemical studies and in situ characterization techniques reveal the key mechanisms of this composite material in the energy storage process.