In this research, bismuth oxide (BO) with non-uniform nanorods featuring a monoclinic crystal structure and bismuth manganese oxide (BMO) with irregularly shaped nanosheets exhibiting a cubic crystal structure were synthesized hydrothermally. These materials were designed for applications in supercapacitors and the oxygen evolution reaction (OER). Electrochemical analysis of BO-NF (Nickel Foam) and BMO-NF electrodes in KOH highlights BMO's superior performance for both supercapacitor and water splitting applications. BMO-NF electrode exhibit higher specific capacitance, lower resistance, and exceptional cyclic stability compared to BO-NF electrode. In asymmetric liquid-state supercapacitor devices, BMO-NF electrode outperforms BO-NF electrode, showcasing advanced capabilities. Additionally, for water splitting, BMO-NF electrode demonstrates a lower overpotential, a more favourable Tafel slope, a larger electrochemical active surface area, and greater stability, underscoring its enhanced efficiency and reliability. Overall, this study shows that the BMO is found to be the more promising material for the energy storage and electrocatalytic applications.