Deep eutectic solvent assisted ionothermal synthesis of cobalt based metal–organic complex as electrode material in supercapacitors

A combination of cobalt and dipicolinic acid-based metal organic complex was synthesized via deep eutectic solvent (DES) based ionothermal synthesis. The DES comprising of choline chloride and urea served as the solvent medium that cater the formation of novel 3-D layered motif as depicted by the crystallographic data of the complex. FESEM, TEM and EDX analysis verified the formation of unique, hollow morphology and homogeneous distribution of metal ions within the cobalt complex synthesized ionothermally. Based on BET surface area analysis, the presence of micro- and mesopores within the structure was verified. The structurally layered cobalt complex was then used as an electrode material for supercapacitor with a specific capacitance of 712 and 556 F g−1 at 1.0 and 5.0 A g−1 respectively. The energy density and power density were calculated to be 5.71 W h kg−1 and 60.09 W kg−1 when tested at the current density of 1 A g−1. The novel material also showed good cycling stability by retaining at 76% of initial value after over 500 cycles. These values demonstrate that ionothermally synthesized transition metal based organic complexes can serve as prospective electrode material in supercapacitors.