Studies on synergetic effect of rGO-NiCo2S4 nanocomposite as an effective counter electrode material for DSSC

Nanocomposites of reduced graphene oxide (rGO) and NiCo2S4 with different amount of graphene oxide (GO) are synthesized through a one- step solvothermal method and their catalytic activity towards I-/I-3(-) redox electrolyte for dye-sensitized solar cell (DSSC) application are reported. The growth mechanism of the pristine hierarchical marigold like microspheres of NiCo2S4 that formed without rGO and the nanocomposite of rGO-NiCo2S4 are also proposed. Electrochemical studies confirmed the synergetic effect of nickel and cobalt ions with the high electrical conductive rGO networks that enhance the electrocatalytic activity of NiCo2S4 nanostructures. The synergistic effect between NiCo2S4 and rGO may be attributed to the higher conductivity of rGO and the inverse spinel crystal structure of NiCo2S4 that have more octahedral catalytic active sites of Cos'. The amount of graphene oxide plays the important role of controlling the DSSC performance and the power conversion efficiency. The efficiency achieved for the rGO-NiCo2S4 counter electrode (CE) based DSSC is 8.15%, which is remarkably higher than that of pristine NiCo2S4 (7.36%), and Pt (7.23%) under the same experimental conditions.