Facile chemical synthesis of cobalt tungstates nanoparticles as high performance supercapacitor

Cobalt tungstate (CoWO₄) nanoparticles were synthesized by a chemical precipitation reaction in aqueous ambient involving direct addition of cobalt ion solution to the solution of tungstate reagent. Optimization of the synthesis procedure was carried out using Taguchi robust design as statistical method. In order to controllable, simple and fast synthesis of CoWO₄ nanoparticles, effects of some synthesis conditions such as reagents concentrations (i.e., cobalt and tungstate ions), flow rate of cobalt feeding and temperature of the reactor on the particle size of synthesized CoWO₄ were investigated by the aid of an orthogonal array (OA₉). The results of optimization process showed that CoWO₄ nanoparticles could be prepared by controlling the effective parameters and at optimum conditions of synthesis procedure, the size of prepared CoWO₄ particles was about 55 nm. Chemical composition and microstructure of the prepared CoWO₄ nanoparticles were characterized by means of XRD, SEM, TEM, FT-IR spectroscopy, UV–Vis spectroscopy and fluorescence. The supercapacitive behavior of the CoWO₄ electrode has been investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The CoWO₄ electrode indicates high specific capacitance of 378 F g⁻¹ at scan rate of 2 mV s⁻¹ in 2.0 M H₂SO₄ electrolyte. Therefore, the prepared electrode could be potential electrode materials for supercapacitors. Moreover, an excellent rate performance, good capacitance retention (~95.5 %) was also observed during the continuous 4000 cycles.