Reinforcing bio-electronic networks in microbial cement composites using conductive carbon nanomaterials for structural energy storage

Microbial cement supercapacitors have emerged as a new form of structural energy-storage material, in which electroactive bacteria and their metabolites create bio-electronic pathways within cement matrices. However, the conductivity and connectivity of such biologically derived pathways remain limited in the heterogeneous cement environment, restricting charge transport and energy-storage performance. Here, conductive carbon nanomaterials were introduced to reinforce these pathways and to construct an inorganic–organic bio-electronic network in microbial cement composites. By integrating Shewanella oneidensis MR-1 with multi-walled carbon nanotubes and graphene oxide, we demonstrate that carbon nanomaterials can effectively bridge microbial conductive domains and improve network continuity within cement. The optimized composite (0.3 wt% nanocarbon) achieved a gravimetric capacitance of approximately 213.1 F g −1 and an energy density of about 43.2 Wh kg −1 , representing increases of over 1.2-fold and 0.85-fold, respectively, compared with the control sample. More importantly, the cyclic voltammetry area increased by up to 2.5 times, while the internal resistance decreased to 2.3 kΩ, indicating substantially improved electron transport. The composite also maintained 82% capacitance retention after 10,000 cycles. Microstructural observations confirm that the enhanced performance originates from the formation of a spatially continuous inorganic–organic conductive network composed of carbon nanomaterials and electroactive microorganisms. Cement characterization further shows that this network does not fundamentally alter hydration products and maintains compressive strengths 8–28% lower than the control. These results demonstrate that inorganic–organic bio-electronic network engineering is an effective strategy to improve microbial cement composites for multifunctional structural energy-storage applications.