Detailed investigation the impact of biofilm formation and cathode limitations on electrochemical performance of biofuel cell

Abstract

• Electrochemical behavior of bacterial colonies was investigated. • Electrochemically was precipitated polyaniline nanorods on the anode surface. • It was shown that the cathode is the limiting factor in the cell performance. • The growth of bacteria on the surface of the bioanode increased the capacitance of the bioanode. • The transient and stable current of the anode improved with the growth of the biofilm. The effect of bacterial colonies on graphite sheet (Gr) and electrochemically modified graphite sheet with polyaniline (PANI-Gr) was carefully investigated in view of the pseudocapacitive and stable current of the bioanode at a microbial fuel cell (MFC). The electrochemical behavior of bioanodes at MFC was studied by chronoamperometry, chronopotentiometry, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The OCP determination of bioanodes showed that the graphite modified with polyaniline starts from a more positive potential and reaches its minimum potential in a shorter time, while the potential of the graphite decreases more slowly, indicating a better growth of the biofilm on the PANI-Gr bioanode. The cyclic voltammetry investigation of the PANI-Gr bioanode on various days proved that with the growth of bacteria and the formation of biofilm over time, the area under the curve of the voltammogram is increased, which can be attributed to the increase in capacitance of the bioanode originating from the pseudocapacitive behavior of polyaniline. EIS studies have shown that the growth of bacteria on the surface of the PANI-Gr bioanode not only significantly decreases charge transfer resistance, but also increases the capacitance of the bioanode compared to the unmodified graphite electrode. The maximum power of the PANI-Gr bioanode of 267 mW/m 2 was obtained at a current density of 1.3 A/m 2 under stable current conditions, while maximum power of the Gr bioanode was 177 mW/m 2 at the same current density. The potential of an 8-cm 2 Pt cathode dropped to −0.6 when a pulse current (2 mA) was applied for 5 s, indicating that the cathode with an area of about 4 times that of the anode was unable to maintain the potential in the desired range for cell performance. A two-chamber microbial fuel cell and mixed bacterial consortium for cell inoculation were used.