<p>Accelerating industrialization introduces polymetallic contamination via industrial wastewater, excessive agrochemicals, and ore processing. These activities result in severe health consequences. Bioabsorption is a green and sustainable method for synthesizing electrode materials, enabling the transformation of biomass into high-value materials and promoting a circular economy. In this study, thermodynamic phase diagram calculations and the “Alloying” material design concept are integrated into this method, facilitating the remediation and recycling of multi-heavy metal composite pollutants in the environment and overcoming the electrochemical performance limitations of single-metal materials. The alloy oxide/carbon composite electrode is successfully fabricated through a synergistic approach combining thermodynamic phase diagram calculations, KOH-assisted high-temperature pyrolysis, and biomass-derived spatial confinement. This study elucidates the positive role of the alloy oxides prepared by this method in enhancing electrochemical performance. Specifically, the composite material exhibits a high specific surface area of 1,644.341 m² g⁻¹ and a high degree of graphitization of <i>I</i>_D/<i>I</i>_G = 1.14, which delivers a specific capacitance of 616 F g⁻¹ at 0.5 A g⁻¹ and a capacity retention rate of 89.76% after 15,000 cycles. Specifically, the composite material exhibits a high specific surface area of 1644.341 m² g⁻¹ and a high degree of graphitization of <i>I</i>_D/<i>I</i>_G = 1.14, which delivers a specific capacitance of 616 F g⁻¹ at 0.5 A g⁻¹ and a capacity retention rate of 89.76% after 15,000 cycles. This work drives energy transformation through innovative material design, contributing a key solution for developing sustainable, high-performance, and recyclable green energy storage systems.</p> Graphical abstract <p></p>