Carbon nanotube powders as electrode modifier to enhance the activity of anodic biofilm in microbial fuel cells

Carbon nanotube (CNT) is a promising electrode material and has been used as an anode modifier in microbial fuel cells (MFCs). In this study, a new method of simultaneously adding CNT powders and Geobacter sulfurreducens into the anode chamber of a MFC was used, aiming to form a composite biofilm on the anode. The performance of MFCs such as startup time and steady-state power generation was investigated under conditions of different CNT powders dosages. Results showed that both the startup time and the anodic resistance were reduced. The optimal dosage of CNT powders pre-treated by acid was 4 mg/mL for the anode chamber with an effective volume of 25 mL. The anodic resistance and output voltage of the MFC with CNT powders addition were maintained around 180 Ω and 650 mV during 40 days operation, while those of the MFC without CNT powders addition increased from 250 Ω to 540 Ω and decreased from 630 mV to 540 mV, respectively, demonstrating that adding CNT powders helped stabilize the anodic resistance, thus the internal resistance and power generation during long-term operation. Based on cyclic voltammogram, the electrochemical activity of anodic biofilm was enhanced by adding CNT powders, though no significant increase of the biomass in anodic biofilm was detected by phospholipids analysis. There was no remarkable change of ohmic resistance with an addition of CNT powders revealed by current interrupt method, which indicated that the rate of mass transfer might be promoted by the presence of CNT powders.