Ke Liu,Zhuo Ma,Xinyi Li,Yunfeng Qiu,Danqing Liu,Shaoqin Liu
Microbial fuel cell (MFC) performance is affected by the metabolic activity of bacteria and the extracellular electron transfer (EET) process. The deficiency of nanostructures on macroporous anode obstructs the enrichment of exoelectrogens and the EET. Herein, a N-doped carbon nanowire-modified macroporous carbon foam was prepared and served as an anode in MFCs. The anode has a hierarchical porous structure, which can solve the problem of biofilm blockage, ensure mass transport, favor exoelectrogen enrichment, and enhance the metabolic activity of bacteria. The microscopic morphology, spectroscopy, and electrochemical characterization of the anode confirm that carbon nanowires can penetrate biofilm, decrease charge resistance, and enhance long-distance electron transfer efficiency. In addition, pyrrolic N can effectively reduce the binding energy and electron transfer distance of bacterial outer membrane hemin. With this hierarchical anode, a maximum power density of 5.32 W/m3was obtained, about 2.5-fold that of bare carbon cloth. The one-dimensional nanomaterial-modified macroporous anodes in this study are a promising strategy to improve the exoelectrogen enrichment and EET for MFCs.Keywords:microbial fuel cells;anode;extracellular electron transfer;hierarchical porous structure;exoelectrogen enrichment
Microbial extracellular respiration is an important energy metabolism on earth, which is significant for the elemental biogeochemical cycle. Herein, extracellular Fe(III) and electrode respiration were confirmed in Thermoanaerobacterium thermosaccharolyticum MJ2 . The intra/extracellular electron transfer (IET/EET) mechanism of MJ2 was investigated by comparative genomic analysis for the first time. Morphological characterization and electrochemical properties of anode illustrated that MJ2 generated bio-electricity by forming a biofilm. The respiration chain inhibition and enzyme activity tests showed that hydrogenase with cytochrome c (Cyt- c ) was involved in IET of MJ2 . Noteworthily, the exogenous Cyt- c increased hydrogenase activity to promote bio-electricity generation by 92.84 %. The Cyt- c gene synteny between MJ2 and another well-known exoelectrogen ( Thermincola potens JR ) indicated that Cyt- c bound to the outer membrane mediated the formation of biofilm involved in EET of MJ2 . This study broadened the understanding of microbial extracellular respiration diversity and provided new insights to explore the electron transfer pathways of exoelectrogens.
Xusen Cheng,Bo Liu,Yunfeng Qiu,Ke Liu,Zhuluni Fang,Jinteng Qi,Zhuo Ma,Tiedong Sun,Shaoqin Liu
Commonly used dense arrays of nanomaterials on carbon cloth (CC) are not suitable to accommodate microorganisms in microbial fuel cells (MFCs) due to their unmatched size. To simultaneously enrich exoelectrogens and accelerate the extracellular electron transfer (EET) process, SnS 2 nanosheets were selected as sacrificial templates to prepare binder-free N,S-codoped carbon microflowers (N, [email protected] ) by polymer coating and pyrolysis . N, [email protected] showed a cumulative total charge of 125.70C/m 2 , approximately 2.11 times higher than that of CC, indicating its better electricity storage capacity. Moreover, the interface transfer resistance and diffusion coefficient in bioanodes were 42.68 Ω and 9.27 × 10 -10 cm 2 /s, respectively, superior to CC (141.3 Ω and 1.06 × 10 -11 cm 2 /s). Remarkably, N,S-codoped carbon microflowers excreted more flavin than CC, as confirmed by continuous fluorescence monitoring. Biofilm and 16S rRNA gene sequence analysis revealed that exoelectrogens were enriched, and nanoconduits were generated on the N, [email protected] anode. In particular, flavin excretion was also promoted on our hierarchical electrode, effectively driving the EET process. MFCs equipped with the N, [email protected] anode could deliver a power density of 2.50 W/m 2 , coulombic efficiency of 22.77 %, and chemical oxygen demand (COD) removal amount of 90.72 mg/L/d, higher than that of bare CC. These findings not only demonstrate that our anode is capable of solving the cell enrichment issue, but it may also increase EET rates by bound flavin with outer membrane c-type cytochromes (OMCs) to simultaneously boost the power generation and wastewater treatment performance of MFCs.
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