Response of anodic biofilm and the performance of microbial fuel cells to different discharging current densities

[Display omitted] •Different discharging current densities were applied to five identical MFCs.•Increasing discharging currents enhanced active biomass and performance of MFCs.•Cell failure occurred when the discharging current density was too high.•A high discharging current induced carbon corrosion and then biofilm detachment. To better understand the responses of anodic biofilm and MFC performance, five identical MFCs started at 100Ω were operated with different discharging current densities (0.3, 1.6, 3.0, 3.6 and 4.8A/m2, denoted as MFC-0.3, MFC-1.6, MFC-3.0, MFC-3.6 and MFC-4.8, respectively). It was demonstrated that the discharging current would significantly influence biofilm development and MFC performance. Compared with the original MFC started at 100Ω, the performance of MFC-0.3 and MFC-1.6 decreased, whereas MFC-3.0 and MFC-3.6 exhibited improved maximum power densities. This was attributed to the reduced charge transfer resistance resulting from the increased active biomass after increasing discharging current. This indicated that the increasing discharging current could enhance active biomass and performance. However, a high discharging current density (4.8A/m2) caused the exfoliation of carbon particles from the carbon cloth and then the detachment of the anode biofilm, resulting in the cell failure of MFC-4.8.