“…In recent years, some energy storage materials that store and release energy through redox reactions have attracted increasing interest as flexible electrode materials, since they have higher specific capacitance than carbon materials [24,25]. Decoration onto graphene of pseudo capacitive materials such as manganese dioxide [26][27][28][29][30], ruthenium dioxide [31,32], titanium dioxide [33,34], cobalt oxide [35,36], nickel and zinc cobaltate (NiCo2O4/ZnCo2O4) [37,38], nickel hydroxide [Ni(OH)2] [39] and cobalt nickel sulfide (CoNi2S4) [40] has led to significant improvements in electrode capacitance. Among the various reported pseudo capacitive materials, MnO2 has attracted much attention due to its low cost, environmental friendliness and high theoretical specific capacitance [27].…”