Abstract
Abstract Aerobic biocathodes provide a low-cost and sustainable substitute for expensive precious metal catalysts at the cathode of Microbial Fuel Cells (MFCs). However, the abiotic formation of peroxide, which is catalyzed by the porous carbon support at certain cathode potentials, may be detrimental to their activity. Two different carbon felt supports, one treated with nitric acid, the other untreated, were characterized electrochemically through a series of chronoamperometry (CA) experiments using a novel 4-electrode electrochemical setup, in order to determine the potential at which peroxide is initially formed. Peroxide was detected at a potential of −0.2 V (all potentials are against Ag/AgCl) for the untreated carbon felt electrode and at a potential of −0.05 V for the nitric acid treated carbon felt. Given these results, two half-cells poised at −0.2 and −0.1 V were setup in order to study biocathode formation. The half-cell poised at −0.2 V did not develop an aerobic biocathode, whereas the half-cell poised at −0.1 V developed an aerobic biocathode. This study shows that to develop aerobic biocathodes on carbon felt, cathode electrode potentials more positive than −0.2 V must be applied.
Highlights
Microbial Fuel Cells (MFCs) are a promising technology that could be used for the production of electricity from wastewater [1e8]
The primary working electrode (PWE) was polarized at a potential at which oxygen reduction occurs, whilst the sensing electrode (SSE) was simultaneously polarized in the same chamber at a potential at which H2O2 is oxidized, detecting H2O2 produced by the PWE
In the CA experiments, the SSE was polarized at þ0.6 V for 15 min, before simultaneous polarization of both the PWE and the SSE, with the PWE polarized at different potentials depending on the experiment
Summary
Microbial Fuel Cells (MFCs) are a promising technology that could be used for the production of electricity from wastewater [1e8]. In MFCs, organic substrates present in wastewater, are oxidized by a biofilm of bacteria which deliver electrons to an anode [1]. These electrons move through an external circuit and go onto reduce oxygen at a cathode. The oxygen reduction reaction (ORR) at the cathode is catalyzed by precious metal catalysts such as Pt. Cheap and sustainable materials are required to make wastewater microbial fuel cells economically viable. Aerobic biocathode biofilms which catalyze the ORR are one alternative, being both cheap and sustainable [12], and have studied extensively in the literature [13e23]
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