Single-chamber Microbial Fuel Cells Research Articles

Engineering the electronic structure of high performance FeCo bimetallic cathode catalysts for microbial fuel cell application in treating wastewater

The development of high-performance, strong-durability and low-cost cathode catalysts toward oxygen reduction reaction (ORR) is of great significance for microbial fuel cells (MFCs). In this study, a series of bimetallic catalysts were synthesized by pyrolyzing a mixture of g-C3N4 and Fe, Co-tannic complex with various Fe/Co atomic ratios. The initial Fe/Co atomic ratio (3.5:0.5, 3:1, 2:2, 1:3) could regulate the electronic state, which effectively promoted the intrinsic electrocatalytic ORR activity. The alloy metal particles and metal-Nx sites presented on the catalyst surface. In addition, N-doped carbon interconnected network consisting of graphene-like and bamboo-like carbon nanotube structure derived from g-C3N4 provided more accessible active sites. The resultant Fe3Co1 catalyst calcined at 700 °C (Fe3Co1-700) exhibited high catalytic performance in neutral electrolyte with a half-wave potential of 0.661 V, exceeding that of the commercial Pt/C (0.6 V). As expected, the single chamber microbial fuel cell (SCMFC) with 1 mg/cm2 loading of Fe3Co1-700 catalyst as the cathode catalyst afforded a maximum power density of 1425 mW/m2, which was 10.5% higher than commercial Pt/C catalyst with the same loading (1290 mW/m2) and comparable to the Pt/C catalyst with 2.5 times higher loading ( 1430 mW/m2). Additionally, the Fe3Co1-700 also displayed better long-term stability over 1100 h than the Pt/C. This work provides an effective strategy for regulating the surface electronic state in the bimetallic electro-catalyst.

ZrP2O7 as a Cathodic Material in Single-Chamber MFC for Bioenergy Production.

The present work is the first investigation of the electrocatalytic performances of ZrP2O7 as a cathode in a single-chamber Microbial Fuel Cell (MFC) for the conversion of chemical energy from wastewater to bioelectricity. This catalyst was prepared by a coprecipitation method, then characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), ultraviolet–visible–near-infrared spectrophotometry (UV–Vis–NIR), and cyclic voltammetry analyses. The acid–basic characteristics of the surface were probed by using 2-butanol decomposition. The conversion of 2-butanol occurs essentially through the dehydrating reaction, indicating the predominantly acidic character of the solid. The electrochemical test shows that the studied cathode material is electroactive. In addition, the ZrP2O7 in the MFC configuration exhibited high performance in terms of bioelectricity generation, giving a maximum output power density of around 449 mW m−2; moreover, it was active for wastewater treatment, reducing the chemical oxygen demand (COD) charge to 50% after three days of reaction.

Enhancing sustainable bioelectricity generation using facile synthesis of nanostructures of bimetallic Co–Ni at the combined support of halloysite nanotubes and reduced graphene oxide as novel oxygen reduction reaction electrocatalyst in single-chambered microbial fuel cells

The present study aims to utilize the high surface area of the nanotube structure of halloysite (HNTs), an aluminosilicate clay, and conductivity of reduced graphene oxide (rGO) as support material for the deposition of nickel (Ni) and cobalt (Co) nanoparticles. With that aim, a novel bimetallic cathode electrocatalyst, Co–Ni @ HNTs-rGO (Catalyst H3), is developed. This catalyst is characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM). Catalyst H3 demonstrates outstanding oxygen reduction reaction (ORR) activity, electrochemical stability, electrocatalytic performance, and lowest resistance in comparison to the other developed catalysts and conventional Pt/C. Catalyst H3 is used in single-chambered MFCs (microbial fuel cells), where the anode is filled with molasses-laden wastewater. The attained maximum power density in MFC (catalyst H3) is 455 ± 9 mW/m2, which is higher than other catalysts. All the results indicate towards its potential use in MFC application.

Performance of microbial fuel cells in treating petroleum refinery wastewater

A high level of chemical energy is contained in petroleum refinery wastewater (PRW). In this study, the performance of microbial fuel cell (MFC) treating PRW is investigated in various MFC reactor configurations by studying the removal rate of chemical oxygen demand (COD) from wastewater and the generation of electricity. The effect of different hydraulic retention times (HRTs) with a selected external resistance and the effect of catholyte of different pHs were investigated in batch and continuous mode of operations using single chamber and dual chamber MFCs. The results of continuous modes of operation in dual-chamber MFC indicated that the efficiency of COD removal in treating PRW reached 84.40 %. The bioelectricity generation in terms of voltage and current output of MFC was observed to be higher in continuous mode dual chamber operation with cathodic aeration. The highest obtained cell voltage of 762 mV and the highest volumetric power density of 328.26 mW/m3 were reached in continuously operated dual-chamber MFC at HRT of 16 h. The highest current density obtained was 79.2 mA/m2. This study indicates that the performance of MFC treating PRW is promising and continuous mode can be employed for treating PRW with simultaneous generation of electricity.

Co-Doped Zeolite-GO Nanocomposite as a High-Performance ORR Catalyst for Sustainable Bioelectricity Generation in Air-Cathode Single-Chambered Microbial Fuel Cells.

High-performance cobalt (Co) nanoparticles supported on a zeolite-graphene oxide (1:2) matrix (catalyst Z2) are synthesized through a facile reduction method. In multipoint Brunauer-Emmett-Teller (MBET) surface area analysis, catalyst Z2 demonstrates a higher surface area compared with other synthesized catalysts, indicating the presence of a larger number of catalytic active sites, and supports outstanding ORR performance due to an improved electron-transfer rate and a higher number of redox-active sites. Furthermore, it is observed that catalyst Z2 is an excellent electrocatalytic material due to its low charge-transfer resistance and higher oxygen reduction reaction (ORR) activity. Herein, the electrocatalytic investigation suggests that catalyst Z2 at a potential of 483 mV and a reduction current of -0.382 mA displays a higher electrocatalytic performance and higher stability toward ORR compared with other synthesized catalysts and even the standard Pt/C catalyst. Also, when catalyst Z2 is applied as an air-cathode ORR electrocatalyst for a single-chambered microbial fuel cell (SC-MFC), the SC-MFC coated with catalyst Z2 generates the maximum power density of 416.78 mW/m2, which is 306% higher than that of SC-MFC coated with Pt/C (102.67 mW/m2). In fact, the longer stability and electronic conductivity have contributed to an outstanding ORR activity of the nanocomposite due to its porous surface morphology and the presence of the functional groups in the zeolite-GO support matrix. In brief, Co (cobalt) nanoparticles doped on a zeolite-GO (1:2) support matrix are promising cathode electrocatalysts in the practical application of MFCs and other related devices.

A 1D model for a single chamber microbial fuel cell

A one dimensional (1D) model accounting for the charge and mass transfer, biofilm formation and the electrochemical reactions that occur in a single chamber microbial fuel cell (SCMFC) operated at batch mode was developed. As the authors are aware, this simplified and easy to implement model for this design and operating mode is unique. The assumptions performed on the model development and the set of parameters used in the model predictions were carefully considered and chosen based on the operating and design conditions and following recommendations from literature. Despite the simplifications and assumptions performed, the model predictions are in good agreement with the experimental data, with a maximum power density of 36.7 mW/cm2. The model predictions concerning the effect of the substrate concentration at the biofilm, anode and cathode overpotentials, cell voltage, current density and power density were also studied. The substrate concentration showed a higher impact on the anode overpotential for the medium to high current density values and predicted well the decrease in substrate availability for increasing current densities and higher anodic reaction rates. The model is rapidly implemented using simple numerical tools (like Excel and Matlab) being, therefore, suitable to seek for possibilities of optimizing the performance of a SCMFC by studying the impact of variations on the design parameters (such as membrane thickness, catalyst loading, electrodes type and thicknesses) and operating conditions (such as substrate concentration). This work demonstrated the value of the developed model in understanding the phenomena behind the MFC systems and on developing more efficient systems, towards an increase of their power output.

A generalized whole-cell model for wastewater-fed microbial fuel cells

A comprehensive mathematical modeling of wastewater-fed microbial fuel cells (MFC) demands an in-depth process understanding of the main electrical and bioelectrochemical interactions at both electrodes. In this study, a novel holistic simulation approach using a low-parameterized model was applied to predict pollutant transport, conversion, and electrical processes of mixed-culture single-chamber MFCs. The proposed whole-cell model couples the combined bioelectrochemical-electrical model with the well-established Activated Sludge Model No.1 (ASM1) and specific equations from ASM2. The cathodic gas–liquid mass transfer of oxygen and free ammonia nitrogen was described in terms of a diffusion film model, while the diminishing diffusivity due to salt deposits was considered via a fouling decline kinetic model. The predictive capacity of the model was validated using experimental data of three continuous-flow single-chamber MFCs operated with municipal wastewater for 150 days. Electrochemical parameters were estimated in real-time by pulse-width modulated connection of the external electrical load resistance. Following a sensitivity analysis, the most relevant model parameters were optimized through the Monte-Carlo Markov-Chain method using the adaptive Metropolis algorithm. All other parameters were adopted from benchmark simulation studies. The simulated relative contributions of aerobic carbon oxidation, denitrification, electrogenesis, and methanogenesis to the total COD removal rate were 21–22%, 44–45%, 21–25%, and 9–14%. Overall, the presented whole-cell model is able to successfully predict the evolution of electricity generation, methane production, and effluent concentrations (soluble COD and total ammonia nitrogen) under different hydraulic conditions and organic loading rates.

Transformation of harmful algae bloom to helpful renewable energy development with artificial intelligence development

The harmful effects of various algae blooms on human and marine life are well-known globally. It is necessary to invent the utilization of such algae bloom for betterment of society and hence proposed research provided multiple benefits. As a supportive tool, Artificial Intelligence (AI) is becoming the high potential area for the fast analysis and predictions in almost all research areas. Also, a microbial fuel cell (MFC) is a relatively new type of bioreactor for wastewater treatment. As there is a need for invention of new renewable energy sources, we invented Sargassum as a new media for energy generation and therefore this research is the first time using Sargassum samples in a single-chambered MFC. This paper presents the development of new deep learning algorithm SargassoCNN to identify the various types of Sargassum bloom samples which further can be analyzed for selection of sample for best electricity generation medium using deep learning image processing algorithm.

Development of polypyrrole nanotube coated with chitosan and nickel oxide as a biocompatible anode to enhance the power generation in microbial fuel cell

In this work, polypyrrole nanotubes (PPy-NT) are prepared by using a soft template of methyl orange and applied as anode catalyst in single chamber microbial fuel cell (SMFC). The coating of chitosan over PPy-NT (CHI@PPy-NT) provides good biocompatibility, proven by the increase in power density of the CHI@PPy-NT anode based SMFC compared to PPy-NT anode based SMFC. With the objective for further improvement in electrochemical efficiency, PPy-NT are coated with chitosan along with nickel oxide (NiO/CHI@PPy-NT) through hydrothermal method. XRD, FTIR, and XPS studies are used to characterize the structural and functional groups of the prepared nanocomposite. Morphological features reveal that nickel oxide is uniformly dispersed in chitosan coated on the surface of polypyrrole nanotubes. Cyclic voltammetry characterization shows high oxidation peak for CHI@PPy-NT (−0.0282 mA) and NiO/CHI@PPy-NT (−0.0286 mA), in comparison to PPy-NT (0.00860 mA). The coating of stainless steel mesh (SSM) anode with NiO/CHI@PPy-NT generates power density of 755 mW m−2, which is 4.4 times higher than the power density for bare stainless steel anode (170 mW m−2). Additionally, the charge transfer resistance obtained from the bare SSM is 817 Ω, 4.9 times high than the NiO/CHI@PPy-NT (165.3 Ω) modified SSM anode based MFC.

The Effects of Wheat and Rice Straw as a Substrate on the Treatment of Reverse Osmosis Reject Wastewater in a Single Chamber Microbial Fuel Cell

AbstractThis work has examined the effect of cellulose based substrates such as rice straw and wheat straw on the treatment of Reverse osmosis (RO) reject wastewater in a single chamber microbial fuel cell (SCMFC). At a substrate concentration of 125 mg/L (125 mg of substrate in 1 L of RO reject wastewater), the two type of MFCs with rice straw and wheat straw as substrates were operated along with the third one as the control without any substrate. MFC with the wheat straw as the substrate outperformed the MFC with rice straw substrate in respect to maximum power density and total dissolved solid (TDS) removal of 127 mW/m2 and 71.88 percent, respectively. Performance of MFC with the three concentrations of 125, 250, and 500 mg/L of the chosen substrate (wheat straw) were compared. Substrate concentration of 125 mg/L was found to be the most effective. In SCMFCs formed for both the substrates, the ohmic losses were predominant, as shown by the polarization curves.

Polyaniline on Stainless Steel Fiber Felt as Anodes for Bioelectrodegradation of Acid Blue 29 in Microbial Fuel Cells

This study investigated the advantages of using low-cost polyaniline-fabricated stainless steel fiber felt anode-based microbial fuel cells (PANI-SSFF-MFCs) for azo dye acid blue 29 (AB29) containing wastewater treatment integrated with an aerobic bioreactor. The findings of electrochemical impedance spectroscopy (EIS) and polarization studies showed that the PANI–SSFF anode considerably decreased the MFC internal resistance. The highest power density of 103 ± 3.6 mW m−2was achieved by PANI-SSFF-MFCs with a decolorization efficiency of 93 ± 3.1% and a start-up time of 13 days. The final chemical oxygen demand (COD) removal efficiencies for integrated PANI–SSFF–MFC–bioreactor and SSFF–MFC–bioreactor set-ups were 92.5 ± 2% and 80 ± 2%, respectively. Based on 16S rRNA gene sequencing, a substantial microbial community change was observed in MFCs. The majority of sequences were from theProteobacteriaphylum, accounting for 72% and 55% in PANI–SSFF–anodic biofilm and suspension, respectively, and 58 and 45% in SSFF–anodic biofilm and suspension, respectively. The relative abundance of the seven most abundant genera (Pseudomonas, Acinetobacter,Stenotrophomonas, Geothrix,Dysgonomonas, Shinella, andRhizobiales) was higher in PANI–SSFF–MFCs (46.1% in biofilm and 55.4% in suspension) as compared to SSFF–MFC (43% in biofilm and 40.8% in suspension) which predominantly contributed to the decolorization of AB29 and/or electron transfer. We demonstrate in this work that microbial consortia acclimated to the MFC environment and PANI-fabricated anodes are capable of high decolorization rates with enhanced electricity production. A combined single-chamber MFC (SMFC)-aerobic bioreactor operation was also performed in this study for the efficient biodegradation of AB29.

Optimization for the improvement of power in equal volume of single chamber microbial fuel cell using dairy wastewater

Microbial fuel cells (MFCs) are a type of sustainable technology that may treat wastewater and generate power at the same time. Therefore, researchers are being challenged to design a technically feasible bio electrochemical system that generates environmentally friendly and renewable electricity from waste water. The current research examined at how MFC may be used to generate electricity while treating real dairy wastewater (RDW) with Pseudomonas aeruginosa-MTCC-7814. The experiments were carried out in fed-batch mode for 15 days in two 300 ml single chamber microbial fuel cells (SCMFCs) that were connected in series. During a fed batch investigation, three process parameters such as inoculum percentage, temperature, and pH were optimized. Inoculum percentage, temperature, and pH were found to be optimal at 5%, 37 °C, and 7.4, respectively and the highest open-circuit voltage was found to be 1025 mV. The COD removal efficiency and columbic efficiency (CE) were found to be 95.84% and 37.13% respectively. The optimized fed batch process yielded the maximum current density and power density of 313 mA/m2 and 105 mW/m2, respectively. Thus, this work successfully demonstrates that connecting single chamber microbial fuel cells (SCMFCs) in series is a viable technique for generating sustainable power utilizing Pseudomonas aeruginosa-MTCC-7814 from dairy wastewater.

Development of miniature self-powered single-chamber microbial fuel cell and its response mechanism to copper ions in high and trace concentration

Copper ions are widely present in water environment and are involved in various biochemical reaction processes, causing irreversible damage to the human body. In this study, we design and establish a self-powered miniature single-chamber microbial fuel cell (SCMFC) reactor using xurography technology. Optimal volume of 188 μL is obtained by controlling the distance between the anode and cathode. Copper ions in two concentration gradients are tested and good linear response curves are obtained. The opposite responses to copper ions in the trace concentration range (0–0.4 mg/L) and high concentration range (1.0–8.0 mg/L) are observed. The results show that at trace concentration range, the inhibitory effect of copper ions on the biofilm activity of micro-SCMFC is dominant; while high concentration copper ions are involved in chemical reactions that produce Cu2O, which may act as a catalyst and promote electron transfer. A good linear response to trace concentration (0–0.4 mg/L) of copper ions with detection limits of 0.05 mg/L is obtained in this study. It could be used in drinking water for trace copper ion detection. The investigation of the mechanisms provides the scientific basis for the design of the efficient detection of copper ions by SCMFC.

Metal-free catalyst for efficient pH-universal oxygen reduction electrocatalysis in microbial fuel cell

• A metal-free and efficient pH-universal ORR catalyst is prepared by simple pyrolysis. • ZIF-8#1000 exhibited ORR electrocatalytic activity, compared with that of 20% Pt/C. • ZIF-8#1000 showed high-performance in air–cathode MFCs. • Three single-chamber MFCs in series can light a light-emitting diode. Developing and utilization of clean and renewable energy is the key to alleviate energy crisis and environmental problems. As a biomass energy utilization, microbial fuel cell (MFC) suffers from low power generation performance caused by the sluggish electronic transfer kinetics of cathodic oxygen reduction reaction (ORR). It is of significance to develop efficient ORR catalysts to get a commercial-scale version in fuel cells. ZIF-8 was usually joined other metal elements (Pt, Fe, Co and etc) to improve ORR catalytic ability. Unfortunately, these catalysts are unstable under acidic conditions. Therefore, it is of great significance to develop an efficient pH-universal ORR catalyst. Herein, a kind of metal-free and efficient pH-universal ORR catalyst are fabricated via a simple method. The catalyst (ZIF-8#1000) exhibits excellent pH-universal ORR electrocatalytic activity and high-performance in single-chamber MFC (distinct output voltage 780 mV and maximum power density 600 mW m −2 ), comparable to those of 20% Pt/C. Interestingly, three single-chamber MFCs in series can light a light-emitting diode. Thus, the as-prepared ZIF-8#1000 has the potential to be alternative of Pt-based ORR catalysts.

Comparative Study of Different Production Methods of Activated Carbon Cathodic Electrodes in Single Chamber MFC Treating Municipal Landfill Leachate

The treatment of real waste extracts with simultaneous energy production is currently under research. One method of addressing this dual task is using biochemical reactors named microbial fuel cells (MFCs). MFCs consist of a bioanode and a cathode where the oxygen reduction reaction (ORR) occurs. Cathodes are currently under optimization regarding the nature of their support, their catalytic efficiency and their configurations. In this work, we present facile preparation methods for the production of activated carbon ceramic-supported cathodic electrodes produced with three different techniques (wash-coat, brush-coat, and ultrasound-assisted deposition/infiltration). The produced cathodic electrodes were tested in a single-chamber MFC, filled with the concentrated liquid residue, after the reverse osmosis (RO-CLR) treatment of leachate from a municipal waste landfill, in order to exploit their electrochemical potential for simultaneous waste treatment and energy production. The electrode produced utilizing 20 kHz ultrasounds proved to be more effective in terms of energy harvesting (10.7 mW/g·L of leachate) and wastewater treatment (COD removal 85%). Internal resistances of the ultrasound-produced electrodes are lower, as compared to the other two methods, opening new exploitation pathways in the use of ultrasound as a means in producing electrodes for microbial fuel cells.

Fabrication of Single Chamber Microbial Fuel Cell (SMFC) Using Soil as a Substrate

This paper presents a Single-chamber Microbial Fuel Cell (SMFC) design by utilizing soil as a substrate with two sets of electrode combinations, which are graphite-activated carbon and copper-zinc of different sizes. It was found that graphite and activated carbon produced greater power density compared to copper and zinc. Moreover, it was observed that the graphite-activated carbon cloth electrode with a bigger surface area of 51cm2, resulted in a higher power density of 904mW/m2. To further improve the voltage production of this model, four SMFCs were stacked in series and connected to a DC-DC boost converter to increase the voltage to 1.482 V for the copper-zinc electrode and 1.722 V for the graphite-activated carbon electrode, respectively, which was sufficient to light up an LED light.

Polyaniline interweaved iron embedded in urea–formaldehyde resin-based carbon as a cost-effective catalyst for power generation in microbial fuel cell

• Iron-containing urea–formaldehyde (Fe-UF) resins were used as precursors. • Polyaniline (PANI) interweaved Fe-UF was pyrolyzed for the synthesis of PANI@Fe/NC. • Polyaniline interweaving improved the conductivity, charge transfer resistance, and ORR activity over Fe/NC. • Among the catalysts, PANI@Fe/NC achieved the highest power output of 637.53 mW m −2 . Microbial fuel cells (MFCs) have emerged as promising renewable electricity generation devices. However, the technology is challenged by poor durability, sluggish oxygen reduction reaction (ORR) kinetics, and high capital cost. Herein, we developed highly efficient and inexpensive electrocatalysts for commercially viable MFCs. The performance of the fabricated air-cathodes (NC, Fe/NC, and PANI@Fe/NC) was systematically evaluated in single-chamber MFCs with activated sludge as inoculum. Fe containing urea–formaldehyde (UF) resins were interweaved with polyaniline to enhance overall conductivity, charge transfer, and power generation in MFCs. PANI interweaved resins exhibit nanofiber aggregation, which on pyrolysis at 800℃ result in unique coralline-like short rods attributing to the large surface area of PANI@Fe/NC. The electrochemical analysis highlighted the superior performance of PANI@Fe/NC with a peak reduction current of −0.214 mA, charge transfer resistance (Rct) of 132.5 Ω, and improved ORR activity. PANI@Fe/NC achieved the highest power output (637.53 mW m -2 ) achieved by PANI@Fe/NC was 36.25% higher than conventional 10 wt% Pt/C (467.92 mW m -2 ). A high current density of 1943.71 mA m -2 compared to 1665.18 mA m -2 for Pt/C is indicative of the significant improvement in the catalytic ability of PANI@Fe/NC. This could be attributed to diverse Fe and N states in the carbon composites and the large surface area available for high active site density. The outcomes suggest that this novel and cost-effective cathode catalyst could be used for long-term fuel cell and related applications.

Effect of Food Waste Condensate Concentration on the Performance of Microbial Fuel Cells with Different Cathode Assemblies

The aim of this study is to examine the effect of food waste condensate concentration (400–4000 mg COD/L) on the performance of two microbial fuel cells (MFCs). Food waste condensate is produced after condensing the vapors that result from drying and shredding of household food waste (HFW). Two identical single-chamber MFCs were constructed with different cathodic assemblies based on GoreTex cloth (Cell 1) and mullite (Cell 2) materials. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) measurements were carried out to measure the maximum power output and the internal resistances of the cells. High COD removal efficiencies (>86%) were observed in all cases. Both cells performed better at low initial condensate concentrations (400–600 mg COD/L). Cell 1 achieved maximum electricity yield (1.51 mJ/g COD/L) at 500 mg COD/L and maximum coulombic efficiency (6.9%) at 400 mg COD/L. Cell 2 achieved maximum coulombic efficiency (51%) as well as maximum electricity yield (25.9 mJ/g COD/L) at 400 mg COD/L. Maximum power was observed at 600 mg COD/L for Cell 1 (14.2 mW/m2) and Cell 2 (14.4 mW/m2). Impedance measurements revealed that the charge transfer resistance and the solution resistance increased significantly with increasing condensate concentration in both cells.

Tofu gel-derived nitrogen and trace iron co-doped porous carbon as highly efficient air-cathode electrocatalyst for microbial fuel cells

A highly efficient biomass derived nitrogen (N) and trace iron (Fe) co-doped oxygen reduction reaction (ORR) catalyst (NFeC-3) is synthesized through a facile method. Trace Fe doped into carbons plays important roles in physical characteristics of carbons in which the specific surface area (655 m2 g−1), degree of graphitization (ID/IG = 1.023), and content of ORR-related N (N-ORR/C = 2.67%) for NFeC-3 are all higher than that of NC. As expected, NFeC-3 exhibits excellent ORR electrocatalytic performances with more positive ORR peak potential (0.024 V), onset potential (0.157 V) and half-wave potential (−0.026 V) than that of other prepared carbons and even commercial Pt/C catalyst. Also, when NFeC-3 is chosen as air-cathode ORR electrocatalyst for single-chamber air-cathode MFC (AC-MFC), the AC-MFC coated with NFeC-3 runs steadily for ∼ 400 h. The corresponding maximum power density of AC-MFC coated with NFeC-3 (863.40 ± 13.19 mW m−2) is 23.61% and 30.62% higher than that of AC-MFCs coated with NC (698.51 ± 17.89 mW m−2) and Pt/C catalyst (661.02 ± 12.19 mW m−2), respectively. Amazingly, three AC-MFCs in series can drive an LED work properly. Therefore, NFeC-3 is a promising carbon-based ORR electrocatalyst in the practical application of MFCs and related devices.

Microbial fuel cells as an electrical energy source for degradation followed by decolorization of Reactive Black 5 azo dye

The problem of wastewater has long been ubiquitous and has great consequences for the environment and its inhabitants. Microbial fuel cells (MFCs) have enormous potential for the treatment of wastewaters polluted with azo dyes. The amount of energy that can be produced from a single-chamber MFC is sufficient to perform decolorization and degradation of such dyes, which are widely used in the textile industry. This study on the azo dye, reactive black 5 (RB5), provides an alternative method through three parallel-connected MFCs to obtain electricity that directly serves for the dye’s electrochemical degradation. We examined degradation followed by decolorization of RB5 using Fe and Pt electrodes, together with H2O2, to achieve the electro-Fenton process. The amount of voltage produced (295 mV), the current density (276 mA m−3) and the power density (50 mW m−3) were sufficient to degrade 25 mg L-1 RB5 dye with 0.5 mM H2O2 in just 2 h. The dye degradation mechanism was investigated using UV–VIS, FT-IR and HPLC-MS/MS. The ecotoxicity of the degradation products was assessed using a bacterial model, Aliivibrio fischeri. These tests showed that there was successful degradation of the dye to products whose toxicity is less than that of RB5.