Understanding methane bioelectrosynthesis from carbon dioxide in a two-chamber microbial electrolysis cells (MECs) containing a carbon biocathode
2015
Zhen, Guangyin | Kobayashi, Takuro | Lu, Xueqin | Xu, Kaiqin
To better understand the underlying mechanisms for methane bioelectrosynthesis, a two-chamber MECs containing a carbon biocathode was developed and studied. Methane production substantially increased with increasing cathode potential. Considerable methane yield was achieved at a poised potential of −0.9V (vs. Ag/AgCl), reaching 2.30±0.34mL after 5h of operation with a faradaic efficiency of 24.2±4.7%. Confirmatory tests done at 0.9V by switching the type of flushed substrates (CO2/N2) or the electrical exposure modes (ON/OFF) demonstrated that cathode serving as an electron donor was the vital driving force for methanogenesis occurring at microbe–electrode surface. Fluorescence in situ hybridization reveled Methanobacteriaceae (particularly Methanobacterium) was the predominant methanogens, supporting the mechanisms of direct electron transfer between cell-electrode. Additionally, the analysis of scanning electron microscope confirmed that the multiple pathways of electron transfer, including direct cathode-to-cell, interspecies exchange and semi-conductive conduits all together ensured the successful electromethanogenesis process.
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