Oxygen-Reducing Biocathodes Operating with Passive Oxygen Transfer in Microbial Fuel Cells

Abstract

Oxygen-reducing biocathodes previously developed for microbial fuel cells (MFCs) have required energy-intensive aeration of the catholyte. To avoid the need for aeration, the ability of biocathodes to function with passive oxygen transfer was examined here using air cathode MFCs. Two-chamber, air cathode MFCs with biocathodes produced a maximum power density of 554 ± 0 mW/m(2), which was comparable to that obtained with a Pt cathode (576 ± 16 mW/m(2)), and 38 times higher than that produced without a catalyst (14 ± 3 mW/m(2)). The maximum current density with biocathodes in this air-cathode MFC was 1.0 A/m(2), compared to 0.49 A/m(2) originally produced in a two-chamber MFC with an aqueous cathode (with cathode chamber aeration). Single-chamber, air-cathode MFCs with the same biocathodes initially produced higher voltages than those with Pt cathodes, but after several cycles the catalytic activity of the biocathodes was lost. This change in cathode performance resulted from direct exposure of the cathodes to solutions containing high concentrations of organic matter in the single-chamber configuration. Biocathode performance was not impaired in two-chamber designs where the cathode was kept separated from the anode solution. These results demonstrate that direct-air biocathodes can work very well, but only under conditions that minimize heterotrophic growth of microorganisms on the cathodes.

The Effect of Oxygen Mass Transfer on Aerobic Biocathode Performance, Biofilm Growth and Distribution in Microbial Fuel Cells

“…However, the use of the ORR is attractive for MFCs given its high reduction potential (E 0 = 0.60 V at pH 7.0, pO 2 = 0.2), it is free from the environment, and active aeration can be substituted with passive aeration by using gas diffusion electrodes (GDEs). GDEs for aerobic biocathodes in MFCs show promise , but are difficult to scale‐up due to the increased pressure on the GDE as the reactor size increases, and need to be designed to meet some of the specific requirements of aerobic biocathodes (e.g., biocompatibility).…”

Geobacter sp. SD‐1 with enhanced electrochemical activity in high‐salt concentration solutions

“…Electrochemical impedance spectroscopy was conducted at a set potential equal to the anode operating potential corresponding to the maximum current density obtained in MECs, over a frequency range of 200 kHz to 10 mHz, with a sinusoidal perturbation of 10 mV amplitude. The EIS spectra were fitted into an equivalent circuit containing a solution resistance ( R s ), two charge transfer resistances ( R ct1 and R ct2 ), a diffusion resistance ( R d ) and double layer capacitance ( Q ) (Supporting Information http://onlinelibrary.wiley.com/doi/10.1111/1758-2229.12193/suppinfo) (Xia et al ., ). After all electrochemical tests were finished, electrode potentials were adjusted for the accuracy of the Ag/AgCl electrode.…”

“…The EIS spectra were fitted into an equivalent circuit containing a solution resistance (Rs), two charge transfer resistances (Rct1 and Rct2), a diffusion resistance (Rd) and double layer capacitance (Q) (Supporting Information Fig. S7) (Xia et al, 2013). After all electrochemical tests were finished, electrode potentials were adjusted for the accuracy of the Ag/AgCl electrode.…”

Effective factors on the performance of microbial fuel cells in wastewater treatment – a review

“…[2,5,6] In some cases, biocathodes have been used in order to treat wastewater aerobically. [7] By removing oxygen from the cathodic chamber and applying a small additional voltage to the circuit, hydrogen gas is evolved from the cathode. This kind of biological fuel cell is called Bio-Electrochemically Assisted Microbial Reactor.…”