Another reason for the increase in maximum power density might be the decrease in internal resistance as a result of increase in ionic strength [30]. At 50 ppm Cr6+, the internal resistance was 300 V and then decreased to 100 Vas the Cr6+ concentration increased to 500 ppm. You et al. adopted 100 ppm potassium permanganate as the electron acceptor in a dual-chamber MFC. And a maximum power density of 115.6 mW/m2 was generated [27]. Gu et al.
revealed that a maximum power density of 12.4 mW/m2 was generated using 50 ppm chlorophenol as the electron acceptor. In contrast to potassium permanganate and chlorophenol,potassium dichromate was a more favorable electron acceptor,showing a higher power density of MFC.