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Inefficient extracellular electron transfer within bioanode leads to low current production by microbial fuel cell (MFC). In this study, magnetite was sprinkled in electroactive biofilm with the aid of magnet field. Magnetite located inside biofilm (interior-doped biofilm) facilitated the electron delivery of electroactive bacteria far away from electrode surface. Electron transfer efficiency was improved by 12% and 37% compared with that of biofilms with magnetite located at the interface of biofilm/electrode (surface-doped biofilm) and that without any magnetite (control biofilm) respectively. The output power density of MFC with interior-doped biofilm (764 ± 32 mW m −2 ) was greatly increased compared with that of MFCs with surface-doped biofilm (604 ± 22 mW m −2 ) and control biofilm (475 ± 12 mW m −2 ). SEM images showed that magnetite evenly distributed inside the interior-doped biofilm and penetrated the electroactive biofilm, which would facilitate extracellular electron transfer across electroactive biofilms and thus improving the bioelectricity production. [ABSTRACT FROM AUTHOR]

The traditional microbial fuel cell (MFC) sensor with bioanode as sensing element delivers limited sensitivity to toxicity monitoring, restricted application to only anaerobic and organic rich water body, and increased potential fault warning to the combined shock of organic matter/toxicity. In this study, the biocathode for oxygen reduction reaction was employed for the first time as the sensing element in MFC sensor for toxicity monitoring. The results shown that the sensitivity of MFC sensor with biocathode sensing element (7.4±2.0 to 67.5±4.0 mA% −1 cm −2 ) was much greater than that showed by bioanode sensing element (3.4±1.5 to 5.5±0.7 mA% −1 cm −2 ). The biocathode sensing element achieved the lowest detection limit reported to date using MFC sensor for formaldehyde detection (0.0005%), while the bioanode was more applicable for higher concentration (>0.0025%). There was a quicker response of biocathode sensing element with the increase of conductivity and dissolved oxygen (DO). The biocathode sensing element made the MFC sensor directly applied to clean water body monitoring, e.g., drinking water and reclaimed water, without the amending of background organic matter, and it also decreased the warning failure when challenged by a combined shock of organic matter/toxicity. [ABSTRACT FROM AUTHOR]

A binder-free, pseudocapacitive anode was fabricated by coating reduced graphene oxide (rGO) and manganese oxide (MnO 2 ) nanoparticles on stainless steel fibre felt (SS). Microbial fuel cell (MFC) equipped with this novel anode yielded a maximum power density of 1045 mW m −2 , 20 times higher than that of a similar MFC with a bare SS anode (46 mW m −2 ). Transient-state regulation (TSR) was implemented to further improve the MFC’s power generation. The optimal TSR duty cycle ranged from 67% to 95%, and the MFC’s power density increased with TSR frequency. A maximum power density output of 1238 mW m −2 was achieved at the TSR duty cycle of 75% and the frequency of 1 Hz, 18.4% greater than that obtained from the steady state operation. The TSR mode delivered better MFC performance especially when the external resistance was small. Long-term operation tests revealed that the current density and power density yielded in the TSR mode were on average 15.0% and 32.7% greater than those in the steady state mode, respectively. The TSR mode was believed to reduce the internal resistance of the MFC while enhance substrate mass transfer and electron transfer within the anode matrix, thereby improving the MFC performance. [ABSTRACT FROM AUTHOR]

A novel anode was developed by coating reduced graphene oxide (rGO) and manganese oxide (MnO 2 ) composite on the carbon felt (CF) surface. With a large surface area and excellent electrical conductivity, this binder-free anode was found to effectively enhance the enrichment and growth of electrochemically active bacteria and facilitate the extracellular electron transfer from the bacteria to the anode. A microbial fuel cell (MFC) equipped with the rGO/MnO 2 /CF anode delivered a maximum power density of 2065 mW m −2 , 154% higher than that with a bare CF anode. The internal resistance of the MFC with this novel anode was 79 Ω, 66% lower than the regular one's (234 Ω). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses affirmed that the rGO/MnO 2 composite significantly increased the anodic reaction rates and facilitated the electron transfer from the bacteria to the anode. The findings from this study suggest that the rGO/MnO 2 /CF anode, fabricated via a simple dip-coating and electro-deposition process, could be a promising anode material for high-performance MFC applications. [ABSTRACT FROM AUTHOR]

A novel anode is fabricated by electrodepositing manganese dioxide (MnO 2 ) on carbon felt to promote MFC's power production. Compared to the bare carbon felt anode, when the electrodeposition time increases to 60 min, the anode capacitance improves 46 times. The maximum power density of the MFC with the MnO 2 -coated anode reaches 3580 ± 130 mW m −2 , 24.7% higher than that with the bare carbon felt anode (2870 mW m −2 ). MnO 2 is believed to facilitate extracellular electron transfer and accordingly improve the power output. Three anode substrate circulation modes, i.e., flow-through, side-flow, and no-flow, are applied. Electrochemical impedance spectroscopy (EIS) tests reveal that flow-through mode decreases the anode mass transfer resistance by 41.4% compared to the no-flow mode and contributes to the MFC's power production improvement. [ABSTRACT FROM AUTHOR]

Abstract A new photoelectrocatalytic (PEC) and microbial fuel cell (MFC) process was developed and applied to simultaneously remove refractory organic pollutants (i.e., phenol and aniline) from wastewater while recovering energy for in-situ utilization. The current generated by the MFC process was applied to drive the PEC reaction. Compared with single PEC or MFC processes, the PEC-MFC combined process showed higher pollutant and chemical oxygen demand (COD) removal capacities and electricity production. Over 95% of the phenol or aniline was removed by these process, even at high initial concentrations. The COD removal efficiencies for phenol and aniline were ca. 96% (from 700 to 29 mg L−1) and 70% (from 165 to 49 mg L−1), respectively. Although the PEC process showed a limited contribution to phenol and aniline removals (16.5% and 43%, respectively), the utilization of PEC-treated phenol or aniline streams resulted in a MFC with higher voltage output, higher coulombic efficiency, maximal volumetric power density, and lower internal resistance as compared to untreated water. High-performance liquid chromatography coupled with mass spectrometry measurements revealed quinones/hydroquinones and low molecular weight organic acids to be produced as intermediates after the PEC process, which could improve the production of electricity in the MFC. Highlights • A new process composed of photoelectrocatalysis (PEC) and microbial fuel cell (MFC) was developed. • PEC-MFC may simultaneously remove pollutants and recover energy for in-situ utilization. • The (hydro)Quinones and low-molecular-weight organic acid as products from PEC increase electricity production of MFC. • A consecutive, dynamic adsorption and degradation process in MFC supply stable current to drive PEC. [ABSTRACT FROM AUTHOR]

Microbial desalination cells are considered a low-energy-consumption, clean technology to simultaneously purify wastewater and desalinate saline water by utilizing the in situ energy source contained in wastewater. To enhance desalination performance and achieve an optimal membrane stack configuration, an enlarged stacked microbial desalination cell (SMDC) has been developed and tested with 6–14 desalination cells. The cross-membrane area of the enlarged SMDC is 100 cm 2 . The anode and cathode volumes are both 200 mL. To reduce internal resistance, the width of desalination cells is kept as <0.5 mm. The optimal configuration with 10 desalination cells achieves the highest total desalination rate (TDR) of 423 mg/h and the highest charge transfer efficiency (CTE) of 836% when treating the 20 g/L NaCl solution. During this process, the junction potential across membranes increases from 0 to 374 mV, and occupies up to 74% of the total potential loss inside the SMDC. This shows that the SMDC used in this work achieves the highest TDR and CTE among the reported studies, and the junction potential should be effectively controlled to achieve the desired desalination performance in future practical applications. [ABSTRACT FROM AUTHOR]

As a viable wastewater treatment and energy recovery technology, microbial fuel cell (MFC) requires more research with regard to the simultaneous achievement of high-quality effluent and high power generation. In this study, a novel flow-through carbon-based composite anode configuration is proposed, which combines the carbon cloth of two-dimensional anode with wooden granular activated carbon of three-dimensional anode. The proposed configuration enhances the performance of power production and chemical oxygen demand degradation by promoting the mass transfer, reducing internal resistance and increasing bioburden. Microbial fuel cell with the composite anode exhibited the highest maximum power density (1300 ± 50 mW m−2) and the highest chemical oxygen demand removal rate constant (0.155 ± 0.007 h−1) compared with the microbial fuel cell using the carbon cloth anode (1136 ± 46 mW m−2 and 0.072 ± 0.008 h−1) or the wooden granular activated carbon anode (1045 ± 32 mW m−2 and 0.129 ± 0.009 h−1). Meanwhile, at a lower chemical oxygen demand concentration (about 48 mg L−1), the microbial fuel cell with the composite anode maintained a current density of 2.4 A m−2, which is 18% higher than the wooden granular activated carbon anode (2.04 A m−2) and 400% higher than the carbon cloth anode (0.48 A m−2). The cyclic voltammetry and electrochemical impedance spectroscopy tests confirmed that the composite anodes displayed better electrochemical performance. Improving the flow rate and reducing the external resistance could effectively enhance the power production and chemical oxygen demand removal performance of microbial fuel cells, while the computational fluid dynamics simulation intuitively demonstrated the positive effect of the composite anode on chemical oxygen demand degradation. These results suggest that the flow-through composite anode provides a feasible strategy to simultaneously enhance the power generation and improve the effluent quality. Image 1 • A composite anode was constructed by optimizing 2D and 3D carbon anode materials.. • Flow-through composite anode MFC had higher power generation and COD removal rate. • Flow-through composite anode MFC maintained high power generation at low COD. • Reducing external resistance and improving flow rate enhanced the MFC performance. • Flow-through composite anode MFC was proved better COD removal in CFD simulation. [ABSTRACT FROM AUTHOR]

Cost-effective cobalt oxides were synthesized at mild condition as alternatives to platinum catalyst for oxygen reduction in microbial fuel cells (MFCs). The catalysts were prepared by heating Co(NO 3 ) 2 above its decomposition temperature together with carbon black (CB). At a catalyst loading of 5 mg/cm 2 , cobalt oxide cathodes with a Co(NO 3 ) 2 to CB ratio of 0.732:1 produced a maximum power density of 1220 mW/m 2 , which was slightly lower than that of Pt/C cathodes (1360 mW/m 2 ). Further increase in the loading of cobalt oxides resulted in an increase in performance. The maximum power densities produced by cobalt oxide cathodes increased to 1400 mW/m 2 at a catalyst loading of 20 mg/cm 2 and 1540 mW/m 2 at 30 mg/cm 2 , which outperformed the Pt/C control. The durability of cobalt oxide catalysts was comparable to that of Pt/C in single-chamber MFCs with biological contamination. The costs of cobalt oxide catalysts were much lower than that of Pt/C catalyst, even when the loading of cobalt oxides was several times higher than Pt/C catalyst. These findings show that the facilely synthesized cobalt oxides were cost-effective catalysts for oxygen reduction in air-cathode MFCs. [ABSTRACT FROM AUTHOR]

A microbial fuel cell (MFC), as a cleaner wastewater treatment process, can recover electricity from organic wastes. However, high power production and high quality effluent are difficult to achieve simultaneously. In this study, a novel filtration composite anode (FCA), which combined carbon fiber brush and carbon textile was proposed to enhance COD removal and power generation performance of MFCs. The COD removal rate constant of MFCs with the filtration composite anode (FCA-MFC) was 0.33 h −1 , much higher than that of MFCs with single brush anode (FB-MFC) (0.23 h −1 ) or textile anode (FT-MFC) (0.18 h −1 ) in the recirculation mode, and also exceeded that of CA-MFC in non-recirculation mode (0.12 h −1 ). FCA-MFC delivered a maximum power density of 1140 mW m −2 at a recirculation rate of 2 mL min −1 , which was higher than the FB-MFC (990 mW m −2 ) and the FT-MFC (80 mW m −2 ) and its counterparts in non-recirculation mode (1000 mW m −2 ). Moreover, the FCA-MFC maintained a higher current density (4.0 A m −2 ) than the other two MFCs until the COD decreased to 40 mg L −1 at an external resistance of 100 Ω. CV and EIS tests verified a higher electrochemical performance of the filtration composite anode. These results demonstrated higher COD removals and power generation of the composite anode at ambient temperature, resulting from the filtration effect that facilitated mass transfer, increased microbial colonization, and improved electrochemical activity. Considering the high-quality effluent and high power generation, the filtration composite anode configuration promises a great potential for sustainable wastewater treatment application. [ABSTRACT FROM AUTHOR]