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The crux to promote the utilization of air-cathode microbial fuel cell (AC-MFC) is to find high-efficiency and low-budget oxygen reduction reaction (ORR) catalysts, which can replace Pt-based catalysts, reduce electrode cost and thus improve the cost-effectiveness of AC-MFC. In this work, a three-dimensional network carbon structure F-MIL-HOF loaded with Fe 2 O 3 material composites have been successfully synthesized by carbonizing by NH 4 F-fluorinated MIL-88B combined with a high nitrogen content hydrogen-bonded organic framework (HOF) to evince excellent catalytic property for ORR in both alkaline and neutral electrolytes. The Fe 2 O 3 obtained after carbonization of MIL-88B portrays efficient ORR catalytic activity, and the combination with the natural pore-rich HOF precisely solves the problems of uncontrolled growth and agglomeration during Fe 2 O 3 synthesis, achieving the high dispersion and full exposure of Fe 2 O 3 nanoparticles as active sites. As-synthesized F-MIL-HOF as cathodic catalyst reaches a limiting current density of 6.40 mA cm−2 in alkaline condition, which exhibits an advantage performance over commercial Pt/C (6.26 mA cm−2). Furthermore, F-MIL-HOF shows approximately four-electron pathway with better methanol resistance and stability than Pt/C, and the performance only decreases by 10.2 % in the stability test, which still had efficient ORR catalytic performance. F-MIL-HOF is an emerging alternative electro-catalyst for AC-MFC. • F-MIL-HOF is an F-modified Fe–N–C material. • MIL-88B pyrolysis produces Fe 2 O 3 active sites to promote mass transfer. • F modification increases the stability and corrosion resistance of F-MIL-HOF. • The synergistic effect of F and N element can reduce the activation barrier. • F-MIL-HOF has outstanding ORR performance in MFC compared with Pt/C. [ABSTRACT FROM AUTHOR]

Microbial community structures and performance of air-cathode microbial fuel cells (MFCs) inoculated with activated sludge from domestic wastewater were investigated to evaluate the effects of three substrate pre-acclimation strategies: 1, serial pre-acclimation with acetate and glucose before supplying domestic wastewater; 2, one step pre-acclimation with acetate before supplying domestic wastewater; and 3, direct supply of domestic wastewater without any pre-acclimation. Strategy 1 showed much higher current generation (1.4 mA) and Coulombic efficiency (33.5%) than strategies 2 (0.7 mA and 9.4%) and 3 (0.9 mA and 10.3%). Pyrosequencing showed that microbial communities were significantly affected by pre-acclimation strategy. Although Proteobacteria was the dominant phylum with all strategies, Actinobacteria was abundant when MFCs were pre-acclimated with glucose after acetate. Not only anode-respiring bacteria (ARB) in the genus Geobacter but also non-ARB belonging to the family Anaerolinaceae seemed to play important roles in air-cathode MFCs to produce electricity from domestic wastewater. [ABSTRACT FROM AUTHOR]

In the study, the effects of electrode material and substrate concentration on the bioelectricity generation and wastewater treatment performances in air-cathode microbial fuel cell coupled with constructed wetland (CW-ACMFC) systems were investigated. Four materials including carbon fiber felt (CFF), stainless steel mesh (SSM), graphite rod (GR), and foamed nickel (FN) were used as air-cathode and anode for each system. The obtained maximum power densities of Systems 1, 2, 3 and 4 were 4.80, 2.30, 3.35, and 5.11 mW m −2 , respectively. In addition, a relative higher NO 3 -N removal efficiency was observed in four reactors, However, average COD removal percentages of Systems 1, 2, 3, and 4 were 42.30%, 37.42%, 48.78%, and 35.73%, respectively. The relative abundance of autotrophic denitrifying bacteria in the FN system was relatively higher. In summary, CFF and FN can be used as the electrode materials in the CW-ACMFCs system for wastewater treatment and bioelectricity generation simultaneously. [ABSTRACT FROM AUTHOR]

The abundance of cellulosic wastes make them attractive source of energy for producing electricity in microbial fuel cells (MFCs). However, electricity production from cellulose requires obligate anaerobes that can degrade cellulose and transfer electrons to the electrode (exoelectrogens), and thus most previous MFC studies have been conducted using two-chamber systems to avoid oxygen contamination of the anode. Single-chamber, air-cathode MFCs typically produce higher power densities than aqueous catholyte MFCs and avoid energy input for the cathodic reaction. To better understand the bacterial communities that evolve in single-chamber air-cathode MFCs fed cellulose, we examined the changes in the bacterial consortium in an MFC fed cellulose over time. The most predominant bacteria shown to be capable electron generation was Firmicutes, with the fermenters decomposing cellulose Bacteroidetes. The main genera developed after extended operation of the cellulose-fed MFC were cellulolytic strains, fermenters and electrogens that included: Parabacteroides, Proteiniphilum, Catonella and Clostridium. These results demonstrate that different communities evolve in air-cathode MFCs fed cellulose than the previous two-chamber reactors.

An algae bioreactor (ABR) was externally connected to air–cathode microbial fuel cells (MFCs) to increase power generation by supplying a high amount of oxygen to cathode electrode. The MFC with oxygen fed from ABR produced maximum cell voltage and cathode potential at a fixed loading of 459 mV and 10 mV, respectively. During polarization analysis, the MFC displayed a maximum power density of 0.63 W/m 2 (at 2.06 A/m 2 ) using 39.2% O 2 from ABR, which was approximately 30% higher compared with use of atmospheric air (0.44 W/m 2 , 20.8% O 2 ,). The cyclic voltammogram analysis exhibited a higher reduction current of −137 mA with 46.5% O 2 compared to atmospheric air (−115 mA). Oxygen supply by algae bioreactor to air–cathode MFC could also maintain better MFC performance in long term operation by minimizing cathode potential drop over time. [ABSTRACT FROM AUTHOR]

Abstract: Uncharged porous PVDF and sulfonated porous PVDF membranes were prepared as alternative materials to Nafion membrane for application in a microbial fuel cell (MFC). Performances of Nafion, uncharged porous PVDF and sulfonated porous PVDF membranes in an air-cathode MFC were evaluated. Both uncharged and sulfonated porous PVDF membranes performed better than the Nafion membrane during MFC operation. The observed properties of low membrane electrical resistance, high ion exchange capacity, moderate oxygen permeability, and high ion selectivity also indicated that the sulfonated PVDF membrane is the most appropriate membrane for MFC applications. The uncharged porous PVDF membrane exhibited the lowest oxygen permeability resulting in a higher performance than the Nafion membrane. The impedance of the MFC systems was measured and analyzed with an equivalent circuit which accounts for the electrolyte (as media for microorganisms), both electrodes, and a membrane as components. It was found that the high performance of the sulfonated porous PVDF membrane is due to the low impedance of all components in the MFC. The sulfonated porous PVDF membrane, prepared for low resistance proton transport, is successfully applied to the MFC in this study. [Copyright &y& Elsevier]

Microbial fuel cells (MFCs) could achieve the removal of antibiotics and generate power in the meantime, a process in which the bacterial community structure played a key role. Previous work has mainly focused on microbes in the anode, while their role in the cathode was seldomly mentioned. Thus, this study explored the bacterial community of both electrodes in MFCs under sulfadiazine (SDZ) pressure. The results showed that the addition of SDZ had a limited effect on the electrochemical performance, and the maximum output voltage was kept at 0.55 V. As the most abundant phylum, Proteobacteria played an important role in both the anode and cathode. Among them, Geobacter (40.30%) worked for power generation, while Xanthobacter (11.11%), Bradyrhizobium (9.04%), and Achromobacter (7.30%) functioned in SDZ removal. Actinobacteria mainly clustered in the cathode, in which Microbacterium (9.85%) was responsible for SDZ removal. Bacteroidetes, associated with the degradation of SDZ, showed no significant difference between the anode and cathode. Cathodic and part of anodic bacteria could remove SDZ efficiently in MFCs through synergistic interactions and produce metabolites for exoelectrogenic bacteria. The potential hosts of antibiotic resistance genes (ARGs) presented mainly at the anode, while cathodic bacteria might be responsible for ARGs reduction. This work elucidated the role of microorganisms and their synergistic interaction in MFCs and provided a reference to generate power and remove antibiotics using MFCs.

To shorten the time needed for determination of biological oxygen demand (BOD) , this study reports a method that can be used for rapid measurement of BOD in domestic organic wastewater based on air -cathode microbial fuel cell technology. Testing results indicated that when glucose was used as single organic substrate, the relationship between voltage output and glucose concentration followed Monod equation. When glucose concentration (BOD) was less than 100 mg/L, good linear relationship between voltage and glucose concentration was obtained. It's merely needed about 10 h to determine BOD in effluent from aeration grit chamber, primary clarifier and aeration tank in wastewater treatment plant by air-cathode microbial fuel cell, which effectively shortens the measurement time. [ABSTRACT FROM AUTHOR]

Abstract: Sustainable electricity was generated from glucose in up-flow air-cathode microbial fuel cells (MFCs) with carbon cloth cathode and carbon granular anode. Plastic sieves rather than membrane were used to separate the anode and cathode. Based on 1g/l glucose as substrate, a maximum volumetric power density of 25±4W/m3 (89A/m3) was obtained for the MFC with a sieve area of 30cm2 and 49±3W/m3 (215A/m3) for the MFC with a sieve area of 60cm2. The increased power density with larger sieve area was mainly due to the decrease of internal resistance according to the electrochemistry impedance spectroscopy analysis. Increasing the sieve area from 30cm2 to 60cm2 resulted in a decrease of overall internal resistance from 41Ω to 27.5Ω and a decrease of ohmic resistance from 24.3Ω to 14Ω. While increasing operational recirculation ratio (RR) decreased internal resistance and increased power output at low substrate concentration, the effect of RR on cell performance was negligible at higher substrate concentration. [Copyright &y& Elsevier]

SnO 2 :PANI composites were synthesized and used as cathode material to enhance oxygen reduction reaction (ORR) in an air-cathode microbial fuel cell (MFC). The ratios of SnO 2 :PANI composites were varied as 50:50 (5S:5 P), 40:60 (4S:6 P), 30:70 (3S:7 P), SnO 2 (S:0), and PANI (0:P). Analytical techniques were used for physical characterization of composites Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Dynamic light scattering (DLS), and Transmission electron microscopy (TEM). Water uptake and wettability of electrodes were evaluated using contact angle method. It was found that coating improves the hydrophobicity of the electrode. Cyclic voltammetry (CV) showed that the modified electrode had moderate capacitance and Electrochemical impedance spectroscopy (EIS) revealed a reduction in internal resistance due to the modification of the electrode. Tafel analysis showed that the relative kinetic activity of the electrodes having 4S:6 P weight ratio was nearly 102 times more than that of the bare electrode. The highest power density of 65 mW m−2, which is nearly two times that of carbon felt, was obtained by the reactor containing 4S:6 P composite coated cathode. The results revealed that the 4S:6 P composite can be a promising option as a cathode catalyst for enhancing the performance of MFCs. [ABSTRACT FROM AUTHOR]