Comparison of oxygen and hypochlorite as cathodic electron acceptor in microbial fuel cells

Effect of oxygen and sodium hypochlorite (NaOCl) as cathodic electron acceptors on performance of a clayware microbial fuel cell (MFC) was evaluated in this study. Maximum power density of 6.57 W/m3 was obtained with NaOCl as catholyte, which is about 9 times higher than oxygen being used as an electron acceptor. Voltammetry and Tafel analysis further supported the faster reduction kinetics lead to increase in power output and reduction in internal resistance of MFC operated with NaOCl as an electron acceptor. Using NaOCl as catholyte, higher exchange current density of 10.91 and 11.52 mA/m2 and lower charge transfer resistance of 0.58 and 0.56 kΩ m2 was observed for anode and cathode, respectively. Higher organic matter removal of about 90% with 25% Coulombic efficiency was achieved using NaOCl as catholyte. Higher internal resistance, lower cathode potential and slow reduction kinetics deteriorated performance of MFC using oxygen as cathodic electron acceptor.