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Advancing the application of bioelectrochemical systems necessitates the comprehensive understanding of electron transfer process in electrode-associated biofilm. While in situ electrical measurement by using the split electrode can illustrate the electron conduction in biofilm, the accuracy and interpretation of the obtained data is still in debate. Here, conductance of Geobacter sulfurreducens biofilm is measured by using the split electrode as substrate concentration is changed. Biofilm conductance decreases with the current production as the consumption of substrate. In addition, the measured conductance increases with the area of drain electrode (13.8 ± 1.8 μS for 0.5 cm2 and 29.4 ± 4.2 μS for 1 cm2). These results suggest the measured conductance of biofilm is influenced by microbial metabolism. This effect will diminish when the measurement is performed by using electrochemical impedance spectroscopy or under non-turnover condition. Our results provide the insight on the electrochemical origin of biofilm conductance determined by the in situ electrical measurement. • Biofilm conductance decreased with current production as consumption of substrate. • Biofilm conductance increased with the area of drain electrode. • The measurement of biofilm conductance was influenced by microbial metabolism. • Biofilm conductance significantly decreased under non-turnover condition. [ABSTRACT FROM AUTHOR]

A structure with ion migration channels and continuous conductive network is crucial for the rate performance of activated carbon. In this work, a phenolic resin and ammonium alginate composite derived carbon is prepared by sol-gel method, carbonization and KOH activation. Compared with pure phenolic resin derived carbon, adding ammonium alginate in carbon preparation process can form interconnected coral-like carbon structure with higher specific surface area and meso-macro pores volume. These advantages of carbon make it provide sufficient access for ions diffusion and continuous skeleton for electron transport. In addition, the morphology of carbon materials can be adjusted by ammonium alginate. A two-electrode system coupled with 6 M KOH as electrolyte is assembled to test the electrochemical properties of these carbon materials. High specific capacitances of 282.8 F g−1 and 232.1 F g−1 at 0.5 A g−1 and 100 A g−1 are obtained, respectively, with a high capacitance retention of 82%. Moreover, high energy density of 9.82 Wh kg−1 at 115 W kg−1 and conspicuous cycling stability with a capacitance retention of 95% after 20,000 cycles are showed for the symmetrical supercapacitor. This work provides reference for preparation of the 3D interconnected hierarchical porous carbon for high performance supercapacitor. [Display omitted] • Coral-like 3D interconnected morphology carbons were prepared. • Ammonium alginate as additive can improve the morphology of carbon. • The Coral-like 3D carbons showed high specific capacitance and cycling stability. • The improved electron/ion transport enhanced the rate performance of supercapacitor. [ABSTRACT FROM AUTHOR]