Metal–organic framework-derived cobalt hydroxide microparticles as supercapacitor electrode materials

In this work, cobalt hexacyanoferrate was synthesized by co-precipitation method. Then, cobalt hexacyanoferrate converted to cobalt hydroxide with a simple method, using a 0.2 M NaOH solution. The obtained composition was detected and analyzed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive x-ray spectroscopy. The results of the identification tests confirmed the successful synthesis of cobalt hexacyanoferrate microparticles as well as cobalt hydroxide microparticles. Electrochemical measurements showed the specific capacitance of 55 F g−1 for cobalt hexacyanoferrate in the current density of 5 A g−1. The specific capacitance of 510.71 F g−1 at the current density of 6 A g−1 was obtained for cobalt hydroxide. The electrode made of cobalt hexacyanoferrate lost 45% of its initial capacitance after 1,000 continuous galvanostatic charge/discharge cycles at the current density of 1 A g−1, whereas cobalt hydroxide was able to reach capacitance of 112.60% of own initial capacitance after 5000 continuous galvanostatic charge/discharge at the current density of 6 A g−1.