Flower-like nanosheets FeCo₂O₄ for application in supercapacitor and dye-sensitized solar cell

Four different iron cobaltite (FeCo₂O₄) structures namely nanoneedles, nanorods, nanosheets and microcubes have been obtained by varying the duration of hydrothermal reaction. The dependence of electrochemical properties on the FeCo₂O₄ structures has been investigated. The FeCo₂O₄ nanosheet have the highest specific capacitance (C_sp), followed by nanorods, nanoneedles and microcubes. The highest C_sp of FeCo₂O₄ nanosheets is attributed to its highest specific surface area and pore volume. A solid-state asymmetric FeCo₂O₄ nanosheet/polyvinyl alcohol—potassium hydroxide/reduced graphene oxide supercapacitor was fabricated. The supercapacitor exhibits maximum power density of 3202 W kg⁻¹ and maximum energy density of 24.5 Wh kg⁻¹. It demonstrates 70% capacitance retention after 3000 cycles. The poly(vinylidene fluoride-co-hexafluoropropylene)/propylene carbonate/1,2-dimethoxyethane/1-methyl-3-propyl imidazolium iodide/sodium iodide/iodine/4-tert-butylpyridine/guanidine thiocyanate electrolytes were assembled into dye-sensitized solar cells (DSSCs) with FeCo₂O₄ nanosheets or platinum as the counter electrodes. DSSC with FeCo₂O₄ nanosheets counter electrode shows an efficiency of 6.04%.