Improved electricity generation, coulombic efficiency and microbial community structure of microbial fuel cells using sodium citrate as an effective additive

Cost-effective and easy-to-operate optimization strategies are always crucial for accelerating the practical application of microbial fuel cells (MFCs). In this study, sodium citrate, a widely-used food and industrial additive with the properties of pH adjustment and microbial degradability, is applied as anolyte additive in MFCs to enhance the bioelectricity generation. The maximum power density and coulombic efficiency of MFC with 0.2 g L-1 sodium citrate addition (0.2-Cit MFC) is achieved as 784.05 mW m(-2) and 56.17% respectively, increasing by 58.33% and 64.38% compared with that of the MFC without sodium citrate addition (0-Cit MFC). Electrochemical impedance spectroscopy, cyclic voltammetry and pH tests performed in each MFC cycle show that adding sodium citrate significantly improves the biocatalytic activity of anode, slows down the performance decline tendency and restrains the sharply-dropped pH as the operation cycle increases. Besides, microbial community analysis reveals that the electroactive biofilm in 0.2-Cit MFC has the obviously higher population abundance and diversity than that in 0-Cit MFC. This finding is important in that sodium citrate as the bifunctional and bio-degradable additive can help stimulate the activity of bioanode and regulate the pH in biofilm region simultaneously without causing secondary pollution.