Electrode material based on reduced graphene oxide (rGO)/transition metal oxide composites for supercapacitor applications: a review

The supercapacitor is a modern electrochemical energy storage technology, exhibiting high specific capacitance, long-term cycle stability, rapid charge rates, high power density, and low cost. Nanostructured materials such nanocarbons, metal oxides, graphene nanosheets, and conducting polymers are used for energy storage applications in recent years. The most fascinating features of 2D reduced graphene oxide-based electrode materials, such as high surface area, superior electrical conductivity, good chemical stability, and excellent mechanical behavior, make them suitable material for supercapacitor devices. Also it attributes the enhancement in specific capacitance, excellent cyclic stability, and high energy density of the composite electrodes that are mainly due to the interconnected conductive network of the composite as well as the synergetic effect of the metal oxide and graphene. This review contains the most significant developments in rGO-TMO-based materials for supercapacitor electrodes, depending on the number of metal oxide composites paired with rGO, i.e., metal oxide, binary metal oxide, and ternary metal oxides. The method of synthesis and supercapacitor performances of rGO and transition metal oxide composites are reviewed. Additionally, a comparison of the rGO composite's synergistic effects on supercapacitor performance in terms of specific capacitance, energy density, power density, rate capability, and cycle stability are tabulated.