Influence of Cathode Modification by Chitosan and Fe3+ on the Electrochemical Performance of Marine Sediment Microbial Fuel Cell

The electrochemical performances of cathode play a key role in the marine sediment microbial fuel cells(MSMFCs) as a long lasting power source to drive instruments, especially when the dissolved oxygen concentration is very low in seawater. A CTS-Fe3+modified cathode is prepared here by grafting chitosan(CTS) on a carbon fiber surface and then chelating Fe3+through the coordination process. The electrochemical performance in seawater and the output power of the assembled MSMFCs are both studied.The results show that the exchange current densities of CTS and the CTS-Fe3+group are 5.5 and 6.2 times higher than that of the blank group, respectively. The potential of the CTS-Fe3+modified cathode increases by 138 mV. The output power of the fuel cell(613.0 m W m-2) assembled with CTS-Fe3+is 54 times larger than that of the blank group(11.4 m W m-2) and the current output corresponding with the maximum power output also increases by 56 times. Due to the valence conversion between Fe3+and Fe2+on the modified cathode, the kinetic activity of the dissolved oxygen reduction is accelerated and the depolarization capability of the cathode is enhanced, resulting higher cell power. On the basis of this study, the new cathode materials will be encouraged to design with the complex of iron ion in natural seawater as the catalysis for oxygen reduction to improve the cell power in deep sea.