Synthesis of nanostructured CoOOH film with high electrochemical performance for application in supercapacitor

Nanostructured cobalt oxyhydroxide films were deposited on the indium tin oxide-coated glass substrates at room temperature by a unique chemical bath deposition process. The synthetic procedure included an oxidizing step using ammonium persulfate as oxidant and a deposition step using propylene oxide as precipitation agent. The obtained films were composed of 1.2–3.5 nm CoOOH particles and homogeneously distributed nano-cracks. The small-sized particles provided huge interface for the electrochemical reactions and the nano-cracks facilitated the access of electrolyte to the particles beneath the surface of films. Therefore, high specific capacitance of 520 F g −1 for the as-prepared film was achieved at the scan rate of 5 mV s −1  in 0.5 mol l −1 KOH aqueous solution. The films also presented other high electrochemical performances such as nearly 100 % Coulombic efficiency and high cycle stability of charge and discharge.