Preparation of rGO/Bi₂O₃ composites by hydrothermal synthesis for supercapacitor electrode

Reduced graphene oxide/bismuth oxide (rGO/Bi₂O₃) composites were prepared at various weight ratios of raw materials, GO and bismuth nitrate at 1:0.1, 1:0.3, 1:0.6, 1:0.9 and 1:1.2, respectively, by the improved Hummer’s method. During the process, the mixed solutions were prepared, and then rGO was obtained by hydrothermal method. Finally, the complex of rGO/Bi₂O₃ was prepared by calcination after hydrothermal treatment. The results show that the removal of oxygen-containing functional groups in rGO are increased with the increase of graphene agglomeration, and the Raman shifts of G band tending to the lowest wave-number. The electrochemical characteristics of the as-prepared rGO/Bi₂O₃ materials were also examined in 1 M KOH electrolyte. The dominating charge storage mechanisms are attributed to the electric double layer behaviors. As the content of bismuth nitrate increased, the rGO/Bi₂O₃ had a higher capacitance. The rGO/Bi₂O₃ obtained from the weight ratio of GO and bismuth nitrate of 1:1.2 as raw materials exhibit a maximum specific capacitance of 216 Fg⁻¹, revealing that rGO/Bi₂O₃ obtained by hydrothermal synthesis method can be used for the carbon-electrode of a super capacitor.