Practical Application Of Microbial Fuel Cells Research Articles

Enhancing microbial fuel cell performance with free-standing three-dimensional N-doped porous carbon anodes

Microbial fuel cells (MFCs) utilize microorganisms as catalysts to transform the chemical energy to electrical power. However, the practical application of MFCs is currently impeded by low power output, which is caused by insufficient microbial colonization on the anode, slow extracellular electron transfer at the microbe-anode interface, and low oxygen reduction reaction catalytic efficiency at the cathode. Herein, a three-dimensional (3D) hierarchical porous anode of Carbonization-CTS-MF/rGOtempreture (CCMF/rGOT) by pyrolyzing crosslinked composite of melamine formaldehyde resin (MF), chitosan (CTS) and graphene oxide (GO). The macroporous anode provides a biocompatible surface for exoelectrogens and 3D electron transfer pathways. In addition, an appropriate balance of graphitic-N and pyrrolic-N content optimizes both conductivity and the number of active sites, thereby synergistically enhancing extracellular electron transfer (EET) efficiency. Therefore, the power density of CCMF/rGO1000 anode is 11.28 W/m3, which surpasses the CCMF1000 anode without 3D reduced graphene oxide (rGO) conductive network (10.04 W/m3), and traditional carbon cloth anode (4.36 W/m3). Moreover, the anode runs stably for more than 200 days with a maximum operating voltage of 0.69 V, which achieves chemical oxygen demand (COD) removal rate of 95.4 %. This work provides a promising strategy to prepare a free-standing 3D anode with enriched exoelectrogens and enhanced EET to improve the MFCs performance.

Three-dimensional biochar aerogel anode derived from expired yogurt for enhancing power efficiency and electron transfer at the bacteria-anode interface in microbial fuel cells

Microbial fuel cells (MFCs) are a promising and sustainable form of fuel cells that utilize electroactive microorganisms to generate electricity. However, the practical application of MFCs is limited by their low power density, inadequate biocompatibility, and suboptimal electrochemical properties. To overcome these challenges, we developed a three-dimensional high performance biochar aerogel anode (YP) made from a mixture of expired yogurt and polyvinyl alcohol (PVA) and investigated its effect on the performance of the MFC. The incorporation of PVA into the YP anodes resulted in improved electrolyte wettability and hydrophilic surfaces, thereby enhancing biocompatibility and bacterial adhesion, especially with Geobacter, reaching up to 89.6% coverage. The biofilm content reached 68.1 mg, which is 1.7 times that of carbon cloth, which improved the electron transfer efficiency at the bacteria-anode interface. Moreover, the mechanical strength of the YP anodes was increased, improving anode stability and durability. In addition, the aerogel anode exhibited impressive power density and current density values of 15.87 W m−3 and 43.76 A m−3, respectively. These values are 3.16 times and 3.60 times higher than the 5.03 W m−3 and 12.13 A m−3 of carbon cloth. This study makes a significant contribution to improving power generation in MFCs, optimizing electron transfer at the bacteria-anode interface, and paving the way for future practical applications of MFCs.

Cobalt-Intercalated Birnessite-Type Manganese Oxide Catalysts for Low-Cost Cathodes in Microbial Fuel Cells

Microbial fuel cells (MFCs) are a promising technology for solving energy and water pollution problems. However, to promote the practical application of MFC, it is necessary to solve the problems of power output and electrode cost simultaneously. Therefore, transition metal-based catalysts that can improve air cathode functionality without using platinum catalysts, which are commonly used, are attracting attention. In this experiment, a cobalt-intercalated birnessite-type manganese oxide catalyst was used as the cathode of the MFC. In addition, rice husk charcoal from agricultural waste and Sumi ink were used as cathode materials to reduce cost and improve the physical stability of the electrodes. The conductivity of the Sumi ink is expected to compensate for the low conductivity of manganese oxide. The resulting power density was 5.8 times higher with the catalyst than without. It was also confirmed that the fabricated cathode operated for at least 90 days without maintenance.

Engineering extracellular electron transfer to promote simultaneous brewing wastewater treatment and chromium reduction

Microbial fuel cell (MFC) technology has been developed for wastewater treatment in the anodic chamber, and heavy metal reduction in the cathodic chamber. However, the limited extracellular electron transfer (EET) rate of exoelectrogens remained a constraint for practical applications of MFCs. Here, a MFC system that used the electricity derived from anodic wastewater treatment to drive cathodic Cr6+ reduction was developed, which enabled an energy self-sustained approach to efficiently address Cr6+ contamination. This MFC system was achieved by screening exoelectrogens with a superior EET rate, promoting the exoelectrogenic EET rate, and constructing a conductive bio-anode. Firstly, Shewanella algae-L3 was screened from brewing wastewater acclimatized sludge, which generated power density of 566.83 mW m−2. Secondly, to facilitate EET rate, flavin synthesis gene operon ribADEHC was overexpressed in engineered S. algae-L3F to increase flavins biosynthesis, which promoted the power density to 1233.21 mW m−2. Thirdly, to facilitate interface electron transfer, carbon nanotube (CNT) was employed to construct a S. algae-L3F-CNT bio-anode, which further enhanced power density to 3112.98 mW m−2. Lastly, S. algae-L3F-CNT bio-anode was used to harvest electrical energy from brewing wastewater to drive cathodic Cr6+ reduction in MFC, realizing 71.43% anodic COD removal and 98.14% cathodic Cr6+ reduction. This study demonstrated that enhanced exoelectrogenic EET could facilitate cathodic Cr6+ reduction in MFC.

Outline of microbial fuel cells technology and their significant developments, challenges, and prospects of oxygen reduction electrocatalysts

The microbial fuel cells (MFCs) which demonstrates simultaneous production of electricity and wastewater treatment have been considered as one of the potential and greener energy production technology among the available bioelectrochemical systems. The air-cathode MFCs have gained additional benefits due to using air and avoiding any chemical substances as catholyte in the cathode chamber. The sluggish oxygen reduction reaction (ORR) kinetics at the cathode is one of the main obstacles to achieve high microbial fuel cell (MFC) performances. Platinum (Pt) is one of the most widely used efficient ORR electrocatalysts due to its high efficient and more stable in acidic media. Because of the high cost and easily poisoned nature of Pt, several attempts, such as a combination of Pt with other materials, and using non-precious metals and non-metals based electrocatalysts has been demonstrated. However, the efficient practical application of the MFC technology is not yet achieved mainly due to the slow ORR. Therefore, the review which draws attention to develop and choosing the suitable cathode materials should be urgent for the practical applications of the MFCs. In this review article, we present an overview of the present MFC technology, then some significant advancements of ORR electrocatalysts such as precious metals-based catalysts (very briefly), non-precious metals-based, non-metals and carbon-based, and biocatalysts with some significant remarks on the corresponding results for the MFC applications. Lastly, we also discussed the challenges and prospects of ORR electrocatalysts for the practical application of MFCs.

Pave the way for successful treatment of Nylon wastewater by performance enhancement via unit stacking scale up of dual cathodes up-flow microbial fuel cell and C/N adjustment with urea

Integrating filtration membrane cathode and packed granular carbon cathode in an up-flow bio-electrochemical reactor can maintain both higher level treatment capacity and electricity generation in microbial fuel cell (MFC). Further, scale-ups via unit stacking (U-S) or size-enlarged reactor/electrode (SE-RE) were tested treating a Nylon wastewater with inadequate N and high C/N ratio, at suitable hydraulic residence time (HRT). U-S maintained both pollutants removal efficiency and power generation at higher levels than SE-RE, achieving 92.44% NH4+-N, 99.99% NO3--N and 99.66% total inorganic nitrogen removal, and maximum power density 3201 mW/m3 (average 2960 mW/m3). Adjusting influent C/N with urea as additional nitrogen, enhanced COD removal and reduced cathode membrane fouling significantly. The average COD removal reaching 99.28% and 4.23 kg m−3d−1, and average effluent COD concentration and UV254 was 30.37 mg/L and 0.06 cm−1, respectively. The average removals of NH4+-N, NO3--N and total inorganic nitrogen were up to 98.85%, 99.99% and 99.56%, respectively. The EEO (electrical energy at 90% removal) was between 0.48 and 1.40 kWh/m3. U-S scale-up with urea dosage was feasible in practical application of MFC in treating Nylon wastewater.

Iron/iron carbide coupled with S, N co-doped porous carbon as effective oxygen reduction reaction catalyst for microbial fuel cells

As a novel energy device, microbial fuel cells (MFCs) have attracted much attention for their dual functions of electricity generation and sewage treatment. However, the sluggish oxygen reduction reaction (ORR) kinetic on the cathode have hindered the practical application of MFCs. In this work, metallic organic framework derived carbon framework co-doped by Fe, S, N tri-elements was used as alternative electrocatalyst to the conventional Pt/C cathode catalyst in pH-universal electrolytes. The amount of thiosemicarbazide from 0.3 to 3 g determined the surface chemical property, and therefore the ORR activity of FeSNC catalysts. The sulfur/nitrogen doping and Fe/Fe3C embedded in carbon shell was characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. The synergy of iron salt and thiosemicarbazide contributed to the improvement of nitrogen and sulfur doping. Sulfur atoms were successfully doped into the carbon matrix and formed a certain amount of thiophene- and oxidized-sulfur. The optimal FeSNC-3 catalyst synthesized with 1.5 g of thiosemicarbazide exhibited the highest ORR activity with a positive half wave potential of 0.866 V in alkaline and 0.691 V (vs. Reversible Hydrogen Electrode) in neutral electrolyte, which both outperformed the commercial Pt/C catalyst. However, as the amount of thiosemicarbazide surpassed 1.5 g, the catalytic performance of FeSNC-4 was lowered, and this could be assigned to the decreased defects and low specific surface area. The excellent ORR performance in neutral medium urged FeSNC-3 as good cathode catalyst in single chambered MFC (SCMFC). It showed the highest maximum power density of 2126 ± 100 mW m−2, excellent output stability of 8.14% decline in 550 h, chemical oxygen demand removal of 90.7 ± 1.6% and coulombic efficiency of 12.5 ± 1.1%, all superior to those of benchmark SCMFC-Pt/C (1637 ± 35 mW m−2, 15.4%, 88.9 ± 0.9%, and 10.2 ± 1.1%). These outstanding results were associated to the large specific surface area and synergistic interaction of multiple active sites, like Fe/Fe3C, Fe–N4, pyridinic N, graphite N and thiophene-S.

W2N-MXene composite anode catalyst for efficient microbial fuel cells using domestic wastewater

Microbial fuel cells (MFCs) have enormous potential to treat wastewater and reduce the energy demands of wastewater treatment plants while generating electricity using active microorganisms as biocatalysts. However, the practical application of MFCs is limited by the low power density produced, mainly due to poor anode performance. A tungsten nitride (W2N)-MXene composite catalyst is introduced to modify the anode surface for use in microbial fuel cells during domestic wastewater treatment. The aim is to improve the wettability, electrical conductivity, electron transfer efficiency, and microorganism attachment capability of the anode and ultimately increase the overall performance of the microbial fuel cell to produce electricity during wastewater treatment. In detail, a hydrofluoric acid etching approach is used to synthesize the Ti3C2Tx MXene, the urea glass technique is used to prepare the W2N particles, and an adequate mixing and heat treatment approach is used to produce the W2N-Ti3C2Tx composite catalyst. The W2N-Ti3C2Tx composite on carbon cloth anode provides one of the best performances recorded for MXene in this type of fuel cells and using real domestic wastewater: with a 523 % increase in the power density (548 mW m−2), an 83 % decrease in the chemical oxygen demand (COD), and a 161 % increase in the electron transfer efficiency compared to those of the plain carbon cloth. We demonstrate that this outstanding performance is due to the improvements in hydrophilicity and microorganism attachment, particularly nanowires (or pili) which promote electron transfer. The present work offers an exciting avenue toward the process scale-up and optimization of single-chamber microbial fuel cells.

Enhancing extracellular electron transfer through selective enrichment of Geobacter with Fe@CN-modified carbon-based anode in microbial fuel cells.

Microbial fuel cells (MFCs) have been demonstrated as a renewable energy strategy to efficiently recover chemical energy stored in wastewater into clean electricity, yet the limited power density limits their practical application. Here, Fe-doped carbon and nitrogen (Fe@CN) nanoparticles were synthesized by a direct pyrolysis process, which was further decorated to fabricate Fe@CN carbon paper anode. The modified Fe@CN anode with a higher electrochemically active surface area was not only benefit for the adhesion of electrochemically active microorganisms (EAMs) and extracellular electron transfer (EET) between the anode and EAMs but also selectively enriched Geobacter, a typical EAMs species. Accordingly, the MFCs with Fe@CN anode successfully achieved a highest voltage output of 792.76mV and a prolonged stable voltage output of 300h based on the mixed culture feeding with acetate. Most importantly, the electroactive biofilms on Fe@CN anode achieved more content ratio of proteins to polysaccharides (1.40) in extracellular polymeric substances for the balance between EET and cell protection under a harsh environment. This work demonstrated the feasibility of development on anode catalysts for the elaboration of the catalytic principle about interface modification, which may contribute to the practical application of MFC in energy generation and wastewater treatment.

MFC based in situ electrocatalytic persulfate activation for degradation of 2,4-dichlorophenol: Process and mechanism

Electrocatalytic persulfate (PS) generation of sulfate radicals has been extensively studied for the removal of organic pollutants, while continuous electricity output causes high energy consumption. Microbial fuel cell (MFC) is an environmentally friendly approach that can catalyze PS for degradation of pollutants through bioelectricity and achieve electricity recovery and utilization at the same time. In this study, a MFC based on electrocatalytic PS activation in cathode (PS-MFC) was constructed to remove 2,4-dichlorophenol (2,4-DCP) with simultaneous electricity recovery. Results showed that 2,4-DCP was successfully removed by PS-MFC with a maximum removal rate of 68.7% after 220 mins of reaction, and the removal process followed pseudo-second-order kinetic. In addition to the wide pH reaction range (pH 3–11), PS-MFC exhibited excellent electrical performance with a higher maximum power density (300.28 mW/m2) than reported studies of the similar type of MFC. Active species for the degradation of 2,4-DCP by PS-MFC system are O2•−, •OH, SO4•−and O21, with O2•− and •OH accounting for major part. The degradation pathway of 2,4-DCP in PS-MFC was proposed by free radical quenching experiments and intermediate product analysis. This work provided a green and sustainable solution for the removal of refractory organic pollutants and promoted research for the further practical application of MFCs.

Engineering Shewanella oneidensis to efficiently harvest electricity power by co-utilizing glucose and lactate in thin stillage of liquor industry

Thin stillage, rich in glucose and lactate, can seriously pollute water resources when directly discharged into the natural environment. Microbial fuel cells (MFC), as a green and sustainable technology, could utilize exoelectrogens to break down organics in wastewater and harvest electricity. Nevertheless, Shewanella oneidensis MR-1, cannot utilize thin stillage for efficient power generation. Here, to enable S. oneidensis to co-utilize glucose and lactate from thin stillage, an engineered S. oneidensis G7∆RSL1 was first created by constructing glucose metabolism pathway, promoting glucose and lactate co-utilization, and enhancing biofilm formation. Then, to enhance biofilm conductivity, we constructed a 3D self-assembled G7∆RSL1-rGO/CNT biohybrid with maximum power density of 560.4 mW m−2 and 373.7 mW m−2 in artificial and actual thin stillage, respectively, the highest among the reported genetically engineered S. oneidensis with thin stillage as carbon source. This study provides a new strategy to facilitate practical applications of MFC in wastewater remediation and efficient power recovery.

Performance improvement of microbial fuel cells through assembling anodes modified with nanoscale materials

In microbial fuel cell (MFC), the anode is the carrier of microbial attachment and growth, and its material and surface structure play a vital role in MFC electricity generation. Therefore, anode surface optimization is an effective way to improve MFC performance. Although the power generation of bacteria has been confirmed and studied as early as the beginning of the 20th century, up to now, MFC still has the extremely challenging problem of low current and low power output in practical application. To improve the performance of MFC, several strategies have been applied to enhance the bacterial extracellular electron transfer. One promising technology is the genetic engineering approach, and some outstanding research results have been obtained. Another effective strategy is to design and fabricate a high-performance electrode because anode material is the essential factor affecting MFC performance, which provides surface active sites for microbial adhesion, reproduction and interfacial electron transfer. At present, the MFC anodes mainly include carbon-based electrodes and a variety of metal electrodes, but untreated anodes have always been unable to overcome the obstacle of low power output. Anode modification, a common and effective method, is employed for improving the power output of MFC. For this reason, this review is primarily focused on the applications of various anode materials and its nanoscale modification in the field of MFC, including the influence of different anode materials on the power output of MFC, and analyzes the reasons why anode modification enhances output performance. Furthermore, the influence of anode research on the practical application of MFC in the future is prospected.

A new modification method of metal substrates via candle soot to prepare effective anodes in air‐cathode microbial fuel cells

AbstractBACKGROUNDChoosing applicable anodes can effectively promote the performance of microbial fuel cells (MFCs). This study introduced a novel method to prepare effective metal‐based anodes modified by carbon nanoparticles (CNPs) derived from candle soot. The CNPs can be firmly coated on the metal and the modified metal surfaces show good hydrophilicity.RESULTSThis study used titanium mesh, stainless steel sheet and copper sheet as the anode's substrate, respectively. CNPs could improve the biocompatibility and electrochemical properties of these metals. The power generation performance of MFCs with CNP‐modified anodes has been dramatically enhanced, and the maximum power density is 616 mW m−2 in MFCs with CNP‐modified titanium mesh anode.CONCLUSIONAfter CNP modification, the rough surface and excellent biocompatibility could promote the attachment and growth of microorganisms, which may be the main reasons for the improvement of MFC performance. Besides, this method is suitable to modify different metal substrates. The results showed that the CNP‐coated metal anodes could improve the power output of MFCs compared to pure metal anodes. Therefore, this method has significant advantages in the practical application of MFCs. © 2021 Society of Chemical Industry (SCI).

Enhanced performance of microbial fuel cells using Ag nanoparticles modified Co, N co-doped carbon nanosheets as bifunctional cathode catalyst

The slow kinetics of oxygen reduction reaction (ORR) and the formation of biofilm on cathode severely limited the performance of microbial fuel cells (MFCs). An efficient way to enhance the power-generation capacity and long-term stability of MFCs is to develop bifunctional catalyst by incorporating the efficient ORR catalysts with antibacterial ingredient. In this study, the Ag/Co-N-C nanosheets were designed and synthesized by decorating Ag nanoparticles (NPs) onto Co-N-C nanosheets, which were prepared from Zn/Co bimetallic metal-organic framework (ZIF-67/ZIF-8) precursor. The Zn/Co ratio, Ag doping amount and the calcination temperature of the precursor were systematically investigated. The optimum sample Ag/Co-N-C-30 revealed the excellent ORR performance with a half-wave potential of 0.80 V vs. RHE, which was slightly lower than that of Pt/C (0.82 V vs. RHE). The MFCs equipped with Ag/Co-N-C-30 cathode exhibited maximum power density of 548 ± 12.6 mW m−2 and superior durability even after 1600 h operation. Besides, the selective antimicrobial ability of Ag/Co-N-C-30 was further explored and the aerobic bacteria in cathode biofilm was found to be obviously inhibited by Ag/Co-N-C-30. The results suggested the Ag/Co-N-C nanosheets can serve as a promising cathode catalyst for practical applications of MFCs.

Bioelectricity Production through Microbial Fuel Cell: Sustainable Energy Source

Current world is facing the twin crisis of energy security due to depletion of non renewable energy sources and climate change caused by green house effect. This has led the researchers to think for various alternatives for sustainable energy production. Fuel cell technology has emerged as one of the potential options for generating clean and efficient energy. Microbial fuel cell (MFC) is a device for the conversion of chemical energy stored in organic compounds into electrical energy with the help of different microorganisms. For practical application of MFC, the main factors that are considered are efficiency and low costs. Efficiency of MFC is dependent on the effectiveness of the anode and cathode materials used in the fuel cell. In this review paper, various developments in electrode materials for microbial fuel cells (MFC) are discussed. Various modifications of anode and cathode materials for enhancement of power generation and simultaneous waste water treatment are also explored.

Diffusion-layer-free air cathode based on ionic conductive hydrogel for microbial fuel cells

High hydraulic pressure in air-cathode microbial fuel cells (MFCs) can lead to severe cathodic water leakage and power reduction, thereby hindering the practical applications of MFCs. In this study, an alternative air cathode without a diffusion layer was developed using a cross-linked hydrogel, oxidized konjac glucomannan/2-hydroxypropytrimethyl ammonium chloride chitosan (OKH), for ion bridging. The cathode was placed horizontally to avoid hydraulic pressure on its surface. Ion transportation was sustained with a minimal OKH hydrogel loading of 10 mg/cm2. A maximum power density of 1.0 ± 0.04 W/m2 was achieved, which was only slightly lower than the 1.28 ± 0.02 W/m2 of common air cathodes. Moreover, the cost of the OKH hydrogel is only $0.12/m2, which can reduce ~85% of the cathode cost without using the advanced polyvinylidene fluoride diffusion layer. Therefore, the development of this new diffusion-layer-free air cathode using conductive ionic hydrogel provides a low-cost strategy for stable MFC operation, thereby demonstrating great potential for practical applications of MFC technology.

Global regulator engineering enhances bioelectricity generation in Pseudomonas aeruginosa-inoculated MFCs

The electricigens with high-electroactivity is essential for resolving the low electricity power output (EPT) of microbial fuel cells (MFCs). However, the manipulation by single functional genes shows limitation because electroactivity is a complex phenotype controlled by multiple genes. Herein, global regulator engineering (GRE) was developed to optimize the electroactivity of an isolated strain (Pseudomonas aeruginosa P3-A-11) using an exogenous global regulator IrrE (ionizing radiation resistance E linkage group) as an object. The GRE was implemented through in vitro random mutagenesis by error-prone PCR and in vivo high-through screening comprised of cultures color assay, PYO measurement and MFCs operation. Four mutants with higher electroactivity were obtained, among which, the mutant 11/M2-59 not only displayed the maximal power density, but also exhibited stronger salt tolerance, consequently showing good performance of MFCs in the presence of salt. Apart from the reduced internal resistance, the increase in phenazines amounts primarily contributed to EPT improvement, which was realized by enhancing the core biosynthesis pathway and affecting other pathways (such as central metabolism pathway, quorum sensing system, regulatory network). Notably, IrrE exerted its positive effect on electroactivity even without native regulators (such as PmpR and RpoS). In addition, the significant fluctuations in expression levels of stress-responsive genes mediated by GRE were closely associated with the enhanced salt tolerance. This work demonstrated that GRE was an effective approach for simultaneously optimizing multiple phenotypes (such as electroactivity and stress tolerance), and thus would provide more opportunities to create high-efficiency electricigens and further promoted the practical application of MFCs.

Characterising and control of ammonia emission in microbial fuel cells

The serious ammonia (NH3) emission of air-cathode microbial fuel cells (MFCs) was reported but how to control and mitigate the emission hasn’t been well studied. Considering the importance of the issue for the application of MFCs in wastewater treatment, this study focused on understanding the NH3 emission process in MFCs and investigating mitigation approaches. The study found that when feeding with dairy wastewater the typical flat-cathode MFCs can emit NH3 of more than 0.82 mg-N/L. The NH3 emission reduced with the grown of cathode biofilm and the decrease of ammonium concentration in the influent. Combined experimental and theoretical results showed that the current density rather than the total current was the determined factor for ammonia emission. The novel Cu-blended 3D cathode developed in this study significantly decreased the NH3 emission to 0.037 mg-N/L (or 0.068% of the total removed ammonium), which was 6.3% of that in the activated sludge wastewater treatment plants (WWTP). In addition, the good power performance and high pollutants removal (14.4 W/m3, 88.1%-COD and 92.8%-TN removal) were also obtained by the Cu-blended 3D cathodes. This study unveiled the ammonia emission process and proposed effective mitigation methods, which will promote the practical application of MFCs for ammonium-rich wastewater treatment.

Enhancing oxygen reduction reaction by using metal-free nitrogen-doped carbon black as cathode catalysts in microbial fuel cells treating wastewater

Microbial fuel cells (MFCs) is promising to combat environmental pollution by converting organic waste to electricity. One critical problem for practical application of MFCs treating wastewater is sluggish oxygen reduction reaction (ORR) on cathode. This study focused on developing novel metal-free cost-effective cathodic catalysts to enhance power generation of MFCs. Specifically, carbon powder (Vulcan XC-72R) was modified with acid treatment and pyrazinamide (as nitrogen precursor), and subsequently pyrolyzed at different temperatures. For CN-X (X=700-1000°C) materials, chemical compositions (the doping contents of nitrogen species, oxygen-containing groups, and sulfur-containing groups) were altered with pyrolysis temperature. Linear sweep voltammetry showed that CN-800 exhibited the highest ORR activity, with an onset potential of 0.215V and a half-wave potential of -0.096V (vs. Ag/AgCl). Electrochemical measurements clearly presented an enhancement of ORR activity by treating carbon powder with sulfuric acid and nitrogen doping, which was well correlated with voltage output in single chamber MFCs (SCMFCs). On the other hand, for the nitrogen-doped cathode catalysts, the best performance in SCMFCs was directly related with the amount of pyridinic nitrogen species and total nitrogen amount. The MFC operated with CN-800 exhibited a maximum power density of 371±3mW/m2 with the chemical oxygen demand (COD) removal of 77.2±1.5% and coulombic efficiency (CE) of 8.6±0.3%. Furthermore, the MFC with CN-800 exhibited an excellent stability over longer than 580h of operation with 1.5% voltage reduction. CN-800 possessed comparable COD removal efficiency to conventional costly Pt/C, and exhibited distinct cost-effectiveness for MFC practical applications in wastewater treatment.

Accelerating the startup of microbial fuel cells by facile microbial acclimation

Rapid startup of microbial fuel cells (MFCs) is critical for the practical application of MFCs, while it is still challenging to quickly initiate newly fabricated MFCs. Herein, we show that a simple yet handy strategy for acclimating the inoculum, by modulating brightness, anoxic environment and the presence of carbon powder, can accelerate the startup of MFCs. Using acclimated inoculums, the startup time of MFCs can be reduced to 43 h which is shortened by 63.2% than that of MFCs using unacclimated inoculums, while maximum power densities are well maintained (649–724 and 669 mW m−2 by using acclimated and unacclimated inoculums, respectively). Further studies show that the acclimation can induce the generation of conductive bacterial nanowires and increase the Rhizobiales population. Accordingly, we reason that conductive bacterial nanowires and the metabolically versatile Rhizobiales can synergistically facilitate the irreversible attachment of bacteria and subsequent biofilm formation, and therefore accelerate the startup.