Wiring microbial biofilms to the electrode by osmium redox polymer for the performance enhancement of microbial fuel cells

• An electron-conducting osmium redox polymer was applied to an MFC anode.
• The redox polymer was found to function as a wire connecting bacteria and the anode.
• A higher current density from acetate oxidation was observed with the redox polymer.
• A great performance enhancement was observed with the modified electrode.

An osmium redox polymer, PAA–PVI–[Os(4,4′-dimethyl-2,2′-bipyridine)2Cl]+/2 + that has been used in enzymatic fuel cells and microbial sensors, was applied for the first time to the anode of single-chamber microbial fuel cells with the mixed culture inoculum aiming at enhancing performance. Functioning as a molecular wire connecting the biofilm to the anode, power density increased from 1479 mW m− 2 without modification to 2355 mW m− 2 after modification of the anode. Evidence from cyclic voltammetry showed that the catalytic activity of an anodic biofilm was greatly enhanced in the presence of an osmium redox polymer, indicating that electrons were more efficiently transferred to the anode via co-immobilized osmium complex tethered to wiring polymer chains at the potential range of − 0.3 V–+0.1 V (vs. SCE). The optimum amount of the redox polymer was determined to be 0.163 mg cm− 2.