Using ferrous-oxidizing bacteria to enhance the performance of a pH neutral all-iron flow battery

Among various redox flow batteries (RFBs), the all-iron RFBs have greater application potential due to high accessibility of electrolytes. However, the potential of microaerobic ferrous-oxidizing bacteria (FeOB) to improve the performance of RFB has been neglected. Here, several experiments were conducted using Fe²⁺-diethylenetriaminepentaacetic acid (DTPA)/Na₃[Fe(CN)₆] as a redox couple for investigating the enhanced performance by FeOB in this RFB. Results showed that the maximum current density of experimental reactors could achieve 22.56 A/m² at 0.1 M, whereas power density could still maintain 3.42 W/m²(16.96 A/m² and 1.58 W/m² for control group); meantime, the polarization impedance of anode increased slower and Fe²⁺-DTPA oxidation peak emerged maximum 494 mV negative shift. With increased electrolyte concentration in chronopotentiometry experiments, the experimental reactor achieved higher discharging specific capacity at 0.3 M, 10 mA/cm². Microbial composition analysis showed maximum 75% is Brucella, indicating Brucella has ferrous-oxidizing electroactivity.