Figure 4. Electrochemical performance.

(a), Cyclic voltammograms (CVs) for the electrode produced using the bacteria-supported, hierarchical, porous-Co₃O₄ microspheres measured at six different scan rates between 5 and 200 mV s⁻¹ in a 0.6-V potential window. (b), Evolution of the galvanostatic discharge profiles obtained at various current densities. The inset shows enlarged curves measured at current densities of 15 and 20 A g⁻¹. The voltage window is 0.44 V. (c), Corresponding specific capacitance (SC) versus current densities of the electrode produced using the bacteria-supported, hierarchical, porous-Co₃O₄ microspheres. (d), Long-term cycling performance of the 3D-hierarchical, porous-Co₃O₄/bacteria electrode (closed-circle) exhibiting a superior Coulombic efficiency (open-circle, blue line) averaging over ~ 95% at a current density of 2 A g⁻¹, and the inset shows excellent SC retention with a decrease of only ~ 5% after 4,000 consecutive cycling tests. All data were measured in a 3 M KOH aqueous solution at room temperature.