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 (OA(9)). 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 (similar to 95.5 %) was also observed during the continuous 4000 cycles.