Wafer-Like CoS Architectures and Their Nanocomposites with Polypyrrole for Electrochemical Energy Storage Applications

In this work, we have fabricated wafer-like CoS and their nanocomposite with Polypyrrole (PPy) via hydrothermal and ultra-sonication techniques. The fabrication of the nanocomposite was confirmed by XRD and FT-IR analysis. The morphology and elemental composition of the as-prepared CoS and their nanocomposite with PPy was investigated by FESEM and EDX analysis. The synthesized CoS/PPy nanocomposite (NCs) exhibit higher gravimetric capacitance (564 Fg−1 at 1 Ag−1) and superior cycling durability with 87.6% retention after 1000 charges/discharge cycles compared to CoS wafers, thus exhibiting as a pure pseudocapacitive electrode. The superior capacitive performance of the CoS/PPy NCs is due to wafer-like CoS and highly conductive matrix of PPy. The porous structure of the CoS provides more sites for redox reactions, while the PPy matrix facilitates the transportation of charges via their conductive channels. Hence PPy in NCs plays a double role, one as a pseudocapacitive supplement while second as a highly conductive matrix. The fabricated CoS/PPy NCs exhibits lower electrical resistivity (2.5 × 103 Ω-cm) than that of pristine CoS NWs (3.4 × 107 Ω-cm), due to the presence of highly conductive matrix of PPy. The improved electrical conductivity of the CoS/PPy NCs (2.5 × 103 Ω-cm) than the wafer-like CoS (3.4 × 107 Ω-cm) was confirmed by I−V measurements. Moreover, the lower charge transfer resistance (Rct, 22 Ω) of the CoS/PPy NCs during the EIS test also indicates its superior redox activity. The results of electrical and electrochemical tests show that CoS/PPy NCs can be used as a potential electrode material for higher performance pseudocapacitor applications.