Potentiostatically deposited nanostructured α-Co(OH)2: A high performance electrode material for redox-capacitors

A high specific capacitance was obtained for α-Co(OH)2 potentiostatically deposited onto a stainless-steel electrode in 0.1 M Co(NO3)2 electrolyte at −1.0 V vs. Ag/AgCl. The structure and surface morphology of the obtained α-Co(OH)2 were studied by using X-ray diffraction analysis and scanning electron microscopy. A network of nanolayered α-Co(OH)2 sheets was obtained; the average thickness of individual α-Co(OH)2 sheets was 10 nm, and the thickness of the deposit was several micrometers. The capacitive characteristics of the α-Co(OH)2 electrodes were investigated by means of cyclic voltammetry and constant current charge–discharge cycling in 1 M KOH electrolyte. A specific capacitance of 860 F g−1 was obtained for a 0.8 mg cm−2 α-Co(OH)2 deposit. The specific capacitance did not decrease significantly for the active mass loading range of 0.1–0.8 mg cm−2 due its layered structure, which allowed easy penetration of electrolyte and effective utilization of electrode material even at a higher mass. This opens up the possibility of using such materials in supercapacitor applications.