Enhanced
Activated Carbon Cathode Performance for Microbial Fuel Cell by Blending
Carbon Black
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Abstract
Activated
carbon (AC) is a useful and environmentally sustainable catalyst for
oxygen reduction in air-cathode microbial fuel cells (MFCs), but there
is great interest in improving its performance and longevity. To enhance
the performance of AC cathodes, carbon black (CB) was added into AC
at CB:AC ratios of 0, 2, 5, 10, and 15 wt % to increase electrical
conductivity and facilitate electron transfer. AC cathodes were then
evaluated in both MFCs and electrochemical cells and compared to reactors
with cathodes made with Pt. Maximum power densities of MFCs were increased
by 9–16% with CB compared to the plain AC in the first week.
The optimal CB:AC ratio was 10% based on both MFC polarization tests
and three electrode electrochemical tests. The maximum power density
of the 10% CB cathode was initially 1560 ± 40 mW/m<sup>2</sup> and decreased by only 7% after 5 months of operation compared to
a 61% decrease for the control (Pt catalyst, 570 ± 30 mW/m<sup>2</sup> after 5 months). The catalytic activities of Pt and AC (plain
or with 10% CB) were further examined in rotating disk electrode (RDE)
tests that minimized mass transfer limitations. The RDE tests showed
that the limiting current of the AC with 10% CB was improved by up
to 21% primarily due to a decrease in charge transfer resistance (25%).
These results show that blending CB in AC is a simple and effective
strategy to enhance AC cathode performance in MFCs and that further
improvement in performance could be obtained by reducing mass transfer
limitations