High-performance supercapacitor electrode based on a layer-by-layer assembled maghemite/magnetite/reduced graphene oxide nanocomposite film

The actual relevance of supercapacitors for powering daily-life electronic devices as well as in future outer-space applications demands for innovative, high-performance and low-cost electrode materials. In this regard, the present contribution reports the electrochemical performance of a new supercapacitor electrode based on a layer-by-layer assembled maghemite/magnetite/reduced graphene oxide (MAG-RGO) nanocomposite film. The MAG-RGO electrode displays specific capacitance as high as 691.29 F g⁻¹ at 5.6 A g⁻¹. Its enhanced charge-storage ability is accomplished by proper adjustment of the electrode porosity with the Fe²⁺ to RGO mass ratio and the number of deposited MAG-RGO bilayers, which work synergistically in a combination of EDLC and pseudocapacitive behaviors. Fitting of the electrochemical impedance of different electrodes with a transmission line based equivalent circuit shows that the appropriate porosity is attained at Fe²⁺/RGO 5:1 and between 7 and 10 bilayers, when the electrode's specific capacitance reaches its maximum and remains practically unaltered (87.5% of retention) over 10,000 charge–discharge cycles. Since the nanocomposite preparation and subsequent film assembly are relatively simple and inexpensive, while providing full control of its electrochemical behavior at the nanometer range, the MAG-RGO nanocomposite film electrode is a promising cost-effective alternative for future supercapacitor development and applications.