Impact of light/dark cycle on electrical and electrochemical characteristics of algal cathode sediment microbial fuel cells

In the present study, microalgae strain Chlorella sp. is used in catholyte of sediment microbial fuel cells (SMFCs) to provide oxygen for reduction reaction. Effect of different light/dark cycles on SMFC performance is investigated. Six light (h)/dark (h) cycles of 4/20, 8/16, 12/12, 16/8, 20/4 and 24/0 are applied. SMFC with a light/dark cycle of 12/12 (SMFC-12) produces the highest maximum power density of 19.6 mW m(-2) and open circuit voltage of 442.3 mV, which are remarkably higher than those with other cycles. Individual electrode potentials and electrochemical impedance spectroscopy (EIS) are used to give an in-depth perspective of the observed trends. The anode open circuit potential (OCP) of the cells are approximately the same, whereas the cathode OCPs significantly differ with the most positive value of -23 mV for SMFC-12. Based on EIS analysis total resistance of SMFC-12 is 146.7 Omega that is remarkably lower than those of SMFC-4 (246.4 Omega) and SMFC-24 (214.4 Omega). Findings of this study suggest that the light/dark cycle has a substantial effect on the performance of algal SMFCs and an optimum photoperiod improves the electrical functioning of SMFCs by direct influence on algal growth and sufficient oxygen production at cathode.