Cobalt tailored Bi2O3/MWCNTs as negative electrode for high performance supercapacitors

In this study, a low temperature solution growth was employed to synthesize bismuth(III) oxide (Bi₂O₃) nanostructures (BO), cobalt tailored Bi₂O₃ (BOC) and a composite of cobalt along with multi-walled carbon nanotubes (MWCNTs) incorporated into Bi₂O₃ (BOCM) for high-performance supercapacitor electrode applications. Structural and compositional analyses confirmed the formation of the desired phases, functional groups, vibrational modes, and chemical states. The XRD results revealed an average crystallite size of 25 nm for all the samples along with high crystallinity. SEM and TEM morphological studies indicated flake-like and sheet-like structures, beneficial for ion transport. Electrochemical measurements showed that among the three, the BOCM composite achieved the highest charge storage capability (1402.2 F g⁻¹). Specifically, BOCM demonstrated a 42.4% improvement in capacitance over BOC, indicating enhanced ion diffusion as a complementary action of MWCNTs. Electrochemical impedance testing demonstrated that BOCM featured the minimal solution and charge-transfer resistances, underlining its enhanced electrical conductivity. Moreover, the asymmetric device assembled using BOCM delivered an energy output of 31 Wh kg⁻¹ along with a power delivery rate of 1094 W kg⁻¹, highlighting its potential in advanced energy storage applications.