Superparamagnetic iron oxide assisted transformation of graphene oxide nanolayers to nanoscrolls for supercapacitor electrode materials: Effect of morphology and electrolyte on supercapacitor performance

Abstract

The study illustrates a facile preparative strategy of graphene oxide (GO) nanoscrolls through surface engineering of GO nanosheets by superparamagnetic iron oxide as the transformative and its application as a supercapacitor electrode. Superparamagnetic iron oxide particles acted like localized magnetic fields, which can establish inter particle attractive force within a GO nanosheet and metamorphose the morphology to nanoscrolls. The morphological transformation effectively restricted the restacking of exfoliated nanomaterials, thereby exterminating one of the major obstructions to acquire the expected electrochemical performances. The mechanism of scrolling process has been unveiled by preparing various combinations of GO:iron oxide and studying the sequential transformation in morphology using TEM, XRD and Raman followed by magnetization study and XPS. The critical ratio of GO:Iron Oxide was optimized at (1:6) and the combination was subjected for detailed electrochemical analysis under a three-electrode system using KOH and Na2S2O3 electrolytes. Cyclic voltammetry, impedance and galvanoscopic charge discharge study suggested an impressive electrode performance with specific capacitance, energy density and power density values of 849 Fg−1, 66.3 Whkg−1 and 416.7 Wkg−1, respectively in Na2S2O3 with an excellent cycle stability by retaining 85 % performance characteristics after 4000 cycles. The surface engineering method has been validated as a reversible strategy since successful unwinding and rewinding process of nanoscrolls made viable followed by the electrochemical performance evaluation. This has been further underlined the critical role of iron oxide for the improved storage/discharge performance via amending the morphology of GO.