Conductive Alginate–Carbon-Black Bioanode for Immediate Microbial Electrolysis Cell Operation

This study investigated alginate-immobilized planktonic electroactive bacteria directly coated onto a carbon-felt anode as an alternative bioanode configuration without prolonged biofilm development. Carbon-black (CB) nanoparticles were incorporated into the alginate matrix to enhance conductivity and facilitate extracellular electron transfer (EET). The electrochemical performance of alginate-immobilized Shewanella oneidensis and Pseudomonas aeruginosa was systematically evaluated by examining the effects of bacterial density and CB-nanoparticle loading. For both bacterial systems, the optimal bacterial density was OD600 0.5. At this bacterial density, S. oneidensis and P. aeruginosa achieved current densities of 4.08 ± 0.18 and 1.93 ± 0.18 A/m2, respectively. The incorporation of CB-nanoparticles significantly enhanced electrochemical performance with an optimal loading of 3 mg. Under these conditions, the current densities increased to 5.24 ± 0.31 A/m2 for S. oneidensis and 3.34 ± 0.25 A/m2 for P. aeruginosa, accompanied by a reduction in charge transfer resistance. SEM analysis confirmed the successful incorporation of bacterial cells and CB-nanoparticles within the alginate matrix. The enhanced electrochemical performance was attributed to conductive pathways formed by CB-nanoparticles, which facilitated electron transfer between the immobilized bacterial cells and the anode. Overall, these findings demonstrated the potential of conductive alginate+carbon-black anodes to provide effective strategies for improving EET.