Crystal structures, morphology, optical, supercapacitor properties of reduced graphene oxide doped cesium oxide@cobalt oxide bimetallic oxide nanostructures for visible light photocatalysis of Alizarin Red S dye

In the current work, reduced graphene oxide (x = 5, 10, and 15 wt%) decorated over cesium oxide@cobalt oxide nanostructures (NS) was synthesized by a simple chemical precipitation method. The hybrid NS was characterized by XRD (X-ray diffraction), FESEM (field emission scanning electron microscopy), TEM (transmission electron microscopy), TGA (thermogravimetric analysis), XPS (X-ray photoelectron spectroscopy), BET (Brunauer-Emmett-Teller), UV–visible analytical tools. XRD analysis of reduced graphene oxide 15wt% :cesium oxide@cobalt oxide NS revealed orthorhombic/monoclinic crystal structure and average crystallite size decreases with an increase in the concentration of reduced graphene oxide on cesium oxide@cobalt oxide NS. Small flake/plate/petal like morphology of reduced graphene oxide 5wt%-15wt% : cesium oxide@cobalt oxide NS was observed by FESEM images with irregular distribution of the nanoparticles (NPs). The redshift in optical absorption peaks resulted from UV–visible studies with a decrease in optical band gap and an increase in the concentration of reduced graphene oxide on cesium oxide@cobalt oxide NS. Supercapacitor performances of undoped cesium oxide@cobalt oxide NS and reduced graphene oxide 15 wt% : cesium oxide@cobalt oxide NS examined by cyclic voltammetry (CV), galvanostatic charge discharge cycles (GCD), electrochemical impedance studies (EIS) in 3 M KOH aqueous electrolyte . The reduced graphene oxide 15 wt% : cesium oxide@cobalt oxide NS exhibited maximum specific capacitance (SC) of 740 F/g (scan rate of 100 mV/s) with capacitive retention of 95.4 % at current density of 1A/g after 5000 cycles. Photocatalytic dye degradation of Alizarin Red S (ARS) dye under visible light for the reduced graphene oxide 15wt% :cesium oxide@cobalt oxide NS showed a degradation efficiency of 98.3 % with a rate constant of 3.9 × 10 −2 . However, undoped (cesium oxide@cobalt oxide) NS showed degradation efficiency of 77.1 % with a rate constant of 2.4 × 10 −2 . The undoped and reduced graphene oxide 15 wt% : cesium oxide@cobalt oxide NS showed 74.1 % and 95.9 % catalyst reusage after 5 successive cycles. The synthesized reduced graphene oxide x : cesium oxide@cobalt oxide NS is a promising electrode material for supercapacitor and photocatalytic dye degradation. • A novel series of rGO 5, 10, 15 wt.% :Cs 2 O@Co 3 O 4 NS synthesized by chemical precipitation . • Supercapacitive property of rGO 15 wt.% :Cs 2 O@Co 3 O 4 NS showed specific capacitance of 740 F/g, at 1 A/g. • rGO 15 wt.% :Cs 2 O@Co 3 O 4 NS showed capacitive retention of 95.4 % in 3M KOH, after 5000 cycles. • Visible light photocatalysis of rGO 15 wt.% :Cs 2 O@Co 3 O 4 NS Vs ARS dye has 98.3 % efficiency. • Visible light photocatalysis of Cs 2 O@Co 3 O 4 NS Vs ARS dye showed 77.1 % efficiency, k = 2.4 × 10 ˗2 .