Junfeng Chen

Enhanced performance of microbial fuel cell with in situ preparing dual graphene modified bioelectrode

This study proposed a three-step method to prepare dual graphene modified bioelectrode (D-GM-BE) by in situ microbial-induced reduction of GO and polarity reversion in microbial fuel cell (MFC). Both graphene modified bioanode (GM-BA) and biocathode (GM-BC) were of 3D graphene/biofilm architectures; the viability and thickness of microbial biofilm decreased compared with control bioelectrode (C-BE). The coulombic efficiency (CE) of GM-BA was 2.1 times of the control bioanode (C-BA), which demonstrated higher rate of substrates oxidation; the relationship between peak current and scan rates data meant that GM-BC was of higher efficiency of catalyzing oxygen reduction than the control biocathode (C-BC). The maximum power density obtained in D-GM-BE MFC was 122.4±6.9mWm-2, the interfacial charge transfer resistance of GM-BA and GM-BC were decreased by 79% and 75.7%. The excellent electrochemical performance of D-GM-BE MFC was attributed to the enhanced extracellular electron transfer (EET) process and catalyzing oxygen reduction.

Bacterial community shift and improved performance induced by in situ preparing dual graphene modified bioelectrode in microbial fuel cell

Dual graphene modified bioelectrode (D-GM-BE) was prepared by in situ microbial-induced reduction of graphene oxide (GO) and polarity reversion in microbial fuel cell (MFC). Next Generation Sequencing technology was used to elucidate bacterial community shift in response to improved performance in D-GM-BE MFC. The results indicated an increase in the relative ratio of Proteobacteria, but a decrease of Firmicutes was observed in graphene modified bioanode (GM-BA); increase of Proteobacteria and Firmicutes were observed in graphene modified biocathode (GM-BC). Genus analysis demonstrated that GM-BE was beneficial to enrich electrogens. Typical exoelectrogens were accounted for 13.02% and 8.83% in GM-BA and GM-BC. Morphology showed that both GM-BA and GM-BC formed 3D-like graphene/biofilm architectures and revealed that the biofilm viability and thickness would decrease to some extent when GM-BE was formed. D-GM-BE MFC obtained the maximum power density by 124.58±6.32mWm-2, which was 2.34 times over C-BE MFC.

Bacterial community shift and incurred performance in response to in situ microbial self-assembly graphene and polarity reversion in microbial fuel cell

In this work, bacterial community shift and incurred performance of graphene modified bioelectrode (GM-BE) in microbial fuel cell (MFC) were illustrated by high throughput sequencing technology and electrochemical analysis. The results showed that Firmicutes occupied 48.75% in graphene modified bioanode (GM-BA), while Proteobacteria occupied 62.99% in graphene modified biocathode (GM-BC), both were dominant bacteria in phylum level respectively. Typical exoelectrogens, including Geobacter, Clostridium, Pseudomonas, Geothrix and Hydrogenophaga, were counted 26.66% and 17.53% in GM-BA and GM-BC. GM-BE was tended to decrease the bacterial diversity and enrich the dominant species. Because of the enrichment of exoelectrogens and excellent electrical conductivity of graphene, the maximum power density of MFC with GM-BA and GM-BC increased 33.1% and 21.6% respectively, and the transfer resistance decreased 83.8% and 73.6% compared with blank bioelectrode. This study aimed to enrich the microbial study in MFC and broaden the development and application for bioelectrode.

Positive effects of bio-nano Pd (0) toward direct electron transfer in Pseudomona putida and phenol biodegradation

This study constructed a biological-inorganic hybrid system including Pseudomonas putida (P. putida) and bioreduced Pd (0) nanoparticles (NPs), and inspected the influence of bio-nano Pd (0) on the direct electron transfer and phenol biodegradation. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX) showed that bio-nano Pd (0) (~10 nm) were evenly dispersed on the surface and in the periplasm of P. putida. With the incorporation of bio-nano Pd (0), the redox currents of bacteria in the cyclic voltammetry (CV) became higher and the oxidation current increased as the addition of lactate, while the highest increase rates of two electron transfer system (ETS) rates were 63.97% and 33.79%, respectively. These results indicated that bio-nano Pd (0) could directly promote the electron transfer of P. putida. In phenol biodegradation process, P. putida-Pd (0)- 2 showed the highest k (0.2992 h-1), μm (0.035 h-1) and Ki (714.29 mg/L) and the lowest apparent Ks (76.39 mg/L). The results of kinetic analysis indicated that bio-nano Pd (0) markedly enhanced the biocatalytic efficiency, substrate affinity and the growth of cells compared to native P. putida. The positive effects of bio-nano Pd (0) to the electron transfer of P. putida would promote the biodegradation of phenol.

Biodegradation of oxytetracycline and electricity generation in microbial fuel cell with in situ dual graphene modified bioelectrode

A three-step method to prepare dual graphene modified bioelectrode (D-GM-BE) in microbial fuel cell (MFC) in previous studies. This study explored the biodegradation of oxytetracycline (OTC) and electricity generation in O-D-GM-BE MFC. The OTC removal efficiency of graphene modified biocathode and bioanode (O-GM-BC, O-GM-BA) was 95.0% and 91.8% in eight days. The maximum power density generated by O-D-GM-BE MFC was 86.6 ± 5.1 mW m-2, which was 2.1 times of that in OTC control bioelectrode (O-C-BE) MFC. The Rct of O-GM-BA and O-GM-BC were decreased significantly by 78.3% and 76.3%. OTC was biodegraded to monocyclic benzene compounds by bacteria. O-GM-BA was affected strongly by OTC, and Salmonella and Trabulsiella were accounted for 83.0%, while typical exoelectrogens (Geobacter) were still enriched after the maturity of biofilm. In O-GM-BC, bacteria related with OTC biodegradation (Comamonas, Ensifer, Sphingopyxis, Pseudomonas, Dechloromonas, etc.) were enriched, which contributed to the high removal efficiency of OTC.

Biofilm evolution and viability during in situ preparation of a graphene/exoelectrogen composite biofilm electrode for a high-performance microbial fuel cell

To understand how microbial reduction of graphene oxide (mrGO) influenced the biofilm during the in situ preparation of a graphene/exoelectrogen composite biofilm anode in a microbial fuel cell (MFC), an in situ mrGO-modified anode was fabricated, and the evolution and viability of the anodic biofilm were investigated by sampling the biofilm at different stages of the MFC operation. The total protein, thickness and viability of the anodic biofilm in mrGO-added MFCs were generally lower than that in mrGO-free MFC at the first electricity production cycle (EPC) due to the antibacterial activity of the GO flake. However, the three indicators increased dramatically and were much higher in mrGO-added MFC than in mrGO-free MFC after three EPCs, derived from enhanced bacterial adhesion and accelerated biofilm recovery in the presence of mrGO due to its high specific area for increased biomass attachment and high conductivity for enhanced electron transfer between bacteria and anode. The electricity generation performance of the MFC was found to follow the same trend as biofilm evolution. The power density of the mrGO-modified MFC increased sharply after five electricity production cycles, reaching a maximum value of 1140.63 mW m−2, which is 65.20% higher than the blank control. This study gives an insight into the interaction between the exoelectrogens and their induced GO reduction which contribute to the understanding of the essence of the process for high-performance MFC application.