Assessment of voltage reversal effects in the serially connected biocathode-based microbial fuel cells through treatment performance, electrochemical and microbial community analysis
Journal
Chemical Engineering Journal
Journal Volume
397
Date Issued
2020
Author(s)
Abstract
The microbial fuel cell (MFC) is an emerging bioelectrochemical technology, which can harvest energy and purify wastewater simultaneously. Microorganisms not only have been shown critical to oxidize substrates to generate electricity in the anode, but have been used as the catalyst to improve the cathode performance. However, the scaled-up applicability of biocatalyzed cathodes (biocathodes) still needs to be explored. This study evaluated the electrochemical and treatment performance of long-term serial connection of oxygen reducing biocathode-based MFCs. Results showed that biocathode-based MFCs could reach stable wastewater treatment performance without influenced by serial connection. Voltage reversal shock was previously observed in bioanodes during serial connection, but our analysis of cathode potential demonstrated voltage reversal would also occur in biocathodes. Furthermore, our results revealed that the voltage reversal of biocathodes could be self-recoverable after roughly one month of operation, which is much longer than the reported duration in bioanodes. Electrochemical impedance spectroscopy analysis of the biocathode recovered from voltage reversal revealed the substantial increase of polarization resistance due to the capacitance effect. The output voltage of serially connected biocathode-based MFCs could be successfully harvested through charging the capacitor in the power management system. The 16S rRNA gene high throughput sequencing of biocathode samples revealed the presence of abundant nitrifying and denitrifying bacteria and moreover, the unique microbial composition in the biocathode recovered from voltage reversal with Thiothrix highly enriched (40.9%). Overall, these results suggested microbial community of biocathodes could shift to gain biofilm capacitance to overcome the voltage reversal shock during serial connection and warranted the need for further research on the scaled-up of biocathode-based MFCs.
Type
journal article