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Sediment microbial fuel cells (SMFC) are bioelectrochemical systems that can use different wastes for energy production. This work studied the implementation of nanoparticles (NPs) of α-FeOOH (goethite, which is well-known as a photoactive catalyst) in the electrodes of an SMFC for its potential use for dye removal. The results obtained demonstrate the feasibility of the NPs activation with the electrical potential generated in the electrodes in the SMFC instead of the activation with light. The NPs of α-FeOOH were synthesized using a hydrothermal process, and the feasibility of a conductive bio-composite (biofilm and NPs) formation was proven by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and electrochemical techniques. The improvement of the power density in the cell was more than twelve times higher with the application of the bio-composite, and it is attributed mostly to the presence of NPs. The results also demonstrate the NPs effect on the increase of the electron transfer, which resulted in 99% of the COD removal. The total electrical energy produced in 30 days in the SMFC was 1.2 kWh based on 1 m2 of the geometric area of the anode. The results confirm that NPs of α-FeOOH can be used to improve organic matter removal. Moreover, the energy produced due to its activation through the potential generated between the electrodes suggests the feasibility of its implementation for dye removal. [ABSTRACT FROM AUTHOR]

A microbial fuel cell (MFC) is a device that converts chemical energy into electrical energy through the catalytic processes of microorganisms. In this study, flexible and porous WO3/CNTs-Graphite-PVC film was fabricated through uniform adding of Zn powder into matrix of carbon nanotubes-graphite- Polyvinyl Chloride) PVC (film followed by selective dissolving of Zn from the film structure in acidic solution and finally electrodeposition of WO3 (Tungsten trioxide) into previously porous CNTs-Graphite-PVC film. Surface morphology studies showed that the flexible film has rough and porous structure and carbon nanotubes are uniformly present as electron conduction channels within the composite film. Studies also showed that porous WO3/MWCNTs-Graphite-PVC film as a bioanode in MFC at resistance of 1000 ohms and current density of 900 mA/m2 has a power density of 324 mW/m2. The method presented in this research can be used as a suitable method for preparing of suitable electrocatalysts based on commercial graphite powder in microbial fuel cells.

A microbial fuel cell (MFC) is a device that converts chemical energy into electrical energy through the catalytic processes of microorganisms. In this study, flexible and porous WO3/CNTs-Graphite-PVC film was fabricated through uniform adding of Zn powder into matrix of carbon nanotubes-graphite-Polyvinyl Chloride) PVC ( film followed by selective dissolving of Zn from the film structure in acidic solution and finally electrodeposition of WO3 (Tungsten trioxide) into previously porous CNTs-Graphite-PVC film. Surface morphology studies showed that the flexible film has rough and porous structure and carbon nanotubes are uniformly present as electron conduction channels within the composite film. Studies also showed that porous WO3/MWCNTs-Graphite-PVC film as a bioanode in MFC at resistance of 1000 ohms and current density of 900 mA/m² has a power density of 324 mW/m². The method presented in this research can be used as a suitable method for preparing of suitable electrocatalysts based on commercial graphite powder in microbial fuel cells. [ABSTRACT FROM AUTHOR]

This study estimated the environmental impacts by life cycle assessment (LCA) of bioanodes fabricated from devilfish bone chars and their application in microbial fuel cells (MFC). Two types of devilfish bone chars were obtained by calcination using nitrogen (BCN) and air (BCA) as purge gases. Two bioanodes were fabricated with BCN and BCA and applied independently in MFC to produce bioenergy from ibuprofen and carbamazepine biodegradation. LCA was performed using the methodology ISO 14,040. 1 kg of fabricated bioanode and 1 kWh of produced bioenergy were the established functional units, integrating a detailed inventory of the materials’ fabrication and application in MFC. The impact assessment was made with SimaPro 9.2 software and the ReCiPe 2016 Midpoint (I) method, considering 18 impact categories. Results showed that the bioanode fabricated with BCN has less environmental impacts (1.09 times) than BCA, finding the highest impact in the categories of human carcinogenic toxicity (1.04 kg 1,4-DCB) and human non-carcinogenic toxicity (13.60 kg 1,4-DCB). The environmental impacts in MFC-Ibuprofen were 3.1 times higher than MFC-Carbamazepine in the same impact categories, with 12.76 kg 1,4-DCB and 168.34 kg 1,4-DCB, respectively. Therefore, it is recommended to use BCN to fabricate the bioanode and to apply it in MFC to produce bioenergy from carbamazepine biodegradation. Although the LCA was performed with data obtained at a laboratory level, the results provide information on the environmental impacts that could be generated if both processes are transferred on a large scale, identifying opportunities for improvement to reduce these impacts. [ABSTRACT FROM AUTHOR]

Background. The possibility of converting organic compounds into electrical energy in microbial fuel cells (MFCs) makes MFCs a promising eco-friendly technology. However, the use of platinum or hexacyanoferrates may increase costs or lead to secondary environmental pollution. The use of microalgae in the cathode chamber is a promising solution to these problems. Objective. We aimed to establish the dependence of electrical energy generation and the efficiency of the appli­cation of a specific type of algae on the type and mode of lighting. Methods. In the study, two-chamber H-type MFC with salt bridge was used. Fermented residue after methanogenesis was used as inoculum in the anode chamber, and microalgae cultures Chlorella vulgaris, Desmodesmus armatus, and Parachlorella kessleri were used as inoculum in the cathode chamber. Results. MFCs with microalgae demonstrate the ability to generate current under different light sources. The maximum voltage for the MFC with an anode biofilm and with microalgae in the cathode chamber is 13–15% lower compared to the MFC with an abiotic cathode (840 ± 42 mV). The maximum current is 2–6% lower than the control (480 ± 24 mA) for the MFC with Chlorella vulgaris and the MFC with Parachlorella kessleri, and 8% higher for the MFC with Desmodesmus armatus compared to the MFC with an abiotic cathode. The MFCs with microalgae are capable of generating electrical energy for an extended period. Conclusions. With a pre-grown anodic biofilm, both the current and voltage maintain relative stability when the light source is changed. The potential use of solar lighting broadens the applicability of the MFCs with microalgae, as it eliminates the need for additional costs associated with artificial light sources.

In this work, a bioanode which was based on carbon felt electrode (CFE) that contained highly boron tolerant bacterium Pseudomonas sp. isolated from a boron mine (Pseudomonas isolate BC4B) and iron‐metal organic framework (Fe‐MOF) was developed. To the best of our knowledge, this is the first study in which a highly boron tolerant bacterium, Pseudomonas isolate BC4B was investigated as a bioanode material. It was observed that Fe‐MOF increased the signal significantly by behaving as a catalyst. During the study, the optimization of Fe‐MOF amount, bacteria amount and substrate concentration were done. Also, the effect of different substrate amounts on the bioanode electrochemical signal was investigated. Consequently, the highest current density value was obtained with 5 mM substrate amount. Meanwhile, in order to investigate the reproducibility of developed bioanode, relative standard deviation value was calculated and found as 1.39 % (n : 3) for 4 mM concentration of H3BO3. [ABSTRACT FROM AUTHOR]

Paper-based biofuel cells have the potential to serve as health monitoring devices for urinary glucose and volume by incorporating the fabricated electrodes into nursing diapers. In this study, we evaluate the output power and stability of a biofuel cell by combining 3D impedance measurement and admittance analysis. The 3D impedance-based analysis method can simultaneously detect changes in the overall electrode structure of the enzyme electrode and in the quantity of active enzymes and mediators on the electrode surface. The biofuel cell electrodes were fabricated via screen-printing, using polydimethylglycidyl (poly-GMA)- modified MgO-templated carbon (GMgOC) or poly-GMA-unmodified MgO-templated carbon (NMgOC). The enzymes used were flavin adenine dinucleotide-dependent glucose dehydrogenase and bilirubin oxidase, with Azure-A serving as the mediator. Admittance analysis was utilized to measure the enzyme activity and estimate the charge transfer resistance by extrapolating the spectra obtained through admittance analysis. The charge transfer resistances of both electrodes exhibited a greater stability for the GMgOC electrode. This can be attributed to the covalent immobilization of the enzyme and mediator on the electrode facilitated by GMgOC, effectively suppressing enzyme and mediator elution. The electric double-layer capacitance values of both electrodes indicated the overall stability of the electrode structure during the measurement. [ABSTRACT FROM AUTHOR]

Background. The formation of an exoelectrogenic biofilm in a microbial fuel cell (MFC) is an important stage, because it affects later on current generation by the system. The fermented residue after methanogenesis as an inoculum contains not only exoelectrogenic microorganisms, but also methanogens, which reduce the productivity of MFC. The use of current allows the formation of a biofilm enriched with exoelectrogenic microorganisms. Objective. The purpose of our study was to establish the parameters of MFC under periodic application of external voltage. Methods. A two-chamber H-type MFC with a salt bridge between the chambers was used for the study. The anolyte was stirred with a magnetic stirrer for 4 h a day and a 3V voltage was simultaneously applied to create selective conditions for exoelectrogenic biofilm growth. Results. The application of external voltage stimulated the increase in the current and voltage of the MFC. With the periodic application of an external voltage, the MFC current increased to 788 ± 40 mA for the MFC with a resistor and without load. After disconnection and discharge, the MFC current dropped to 189 ± 10 mA for the MFC without load and to 154 ± 8 mA for the MFC with a resistor, respectively. Under the conditions of MFC operation without applying external voltage, the current was 960 ± 50 mA for MFC with an open circuit and 672 ± 35 mA for MFC with a closed circuit when a resistor is connected. For all MFC, the current gradually decreased over time. MFC demonstrated capacitive behaviour: after accumulating charge for 4 h, a discharge from 622 ± 30 mV to 462 ± 23 mV was observed. Microscopy showed fouling of the anode. Since the fermented residue after methanogenesis is mixed consortium, the anodic biofilm was also mixed consortium enriched with different species of exoelectrogens. Conclusions. Periodic application of external voltage allowed to increase the current by 17% and double the voltage compared to MFC without external voltage supply. However, after disconnecting the external voltage source, the MFC gradually discharged, that is, the current and voltage decreased. The maximum value of the current of the MFC with an open circuit was 22% more than the MFC with a closed circuit.

In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an electrogenic biofilm on the anode surface. The biofilm community composition determines the function of the system. Both deterministic and stochastic factors affect the community, but the relative importance of different factors is poorly understood. Anode material is a deterministic factor as materials with different properties may select for different microorganisms. Ecological drift is a stochastic factor, which is amplified by dispersal limitation between communities. Here, we compared the effects of three anode materials (graphene, carbon cloth, and nickel) with the effect of dispersal limitation on the function and biofilm community assembly. Twelve MECs were operated for 56 days in four hydraulically connected loops and shotgun metagenomic sequencing was used to analyse the microbial community composition on the anode surfaces at the end of the experiment. The anode material was the most important factor affecting the performance of the MECs, explaining 54–80 % of the variance observed in peak current density, total electric charge generation, and start-up lag time, while dispersal limitation explained 10–16 % of the variance. Carbon cloth anodes had the highest current generation and shortest lag time. However, dispersal limitation was the most important factor affecting microbial community structure, explaining 61–98 % of the variance in community diversity, evenness, and the relative abundance of the most abundant taxa, while anode material explained 0–20 % of the variance. The biofilms contained nine Desulfobacterota metagenome-assembled genomes (MAGs), which made up 64–89 % of the communities and were likely responsible for electricity generation in the MECs. Different MAGs dominated in different MECs. Particularly two different genotypes related to Geobacter benzoatilyticus competed for dominance on the anodes and reached relative abundances up to 83 %. The winning genotype was the same in all MECs that were hydraulically connected irrespective of anode material used.

In this work, Au nanoparticles were synthesized using eco-friendly protocol and then supported on reduced graphene oxide (rGO) nanosheets through in-situ polymerization of indole (In), focusing on their electrochemical efficiency against glucose oxidation in glucose-based biofuel cells (glucose/O2). The bioanode was fabricated by applying ferritin (Frt) and glucose oxidase (GOx) on the glassy carbon electrode (GCE) followed by deposition of Au@rGO/PIn nanocomposite. The physical characterizations such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM), have revealed the successful synthesis of Au@rGO/PIn nanocomposite. In addition, the electrochemical behavior of different modified bioanodes were analyzed using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The modified bioanode Au@rGO/PIn/Frt/GOx attained a maximum current output of 7.2 mA cm−2 at the optimum glucose concentration of 50 mM in phosphate buffer solution (PBS) as an electrolyte. However, the obtained result is not the highest current density as reported in the literature but the materials are cost effective and method is easier and ecofriendly. This suggests that 3D fabricated bioanode could be used in enzymatic biofuel cell (EBFC) applications and allied fields, such as biosensors and bioreactors. [ABSTRACT FROM AUTHOR]

BACKGROUND: A microbial electrolysis cell (MEC) is a bio‐hydrogen production device that uses electrochemically active bacteria on the anode combined with applied voltage to break down organic matter. However, the effects of element content on cathode reduction and cathode catalysts on bioanode activity remain unknown. RESULTS: MEC cathodes with different content of Na2MoO4·2H2O (i.e. 0 g L−1 (Ni), 12.5 g L−1 (Ni–Mo 1), 25 g L−1 (Ni–Mo 2) and 37.5 g L−1 (Ni–Mo 3)) were fabricated by normal pulse voltammetry to evaluate the cathode performance. Nanoparticles of Ni electrode are crystalline NiO on the carbon fiber surface. Compared with the Ni electrode, the catalysts of Ni–Mo electrodes are composed of smaller crystalline NiO and amorphous Mo oxides. The results of electrochemical analysis confirmed that Ni–Mo 1 exhibited low exchange transfer resistance (148.72 Ω), high electrochemically active surface area and strong conductivity, resulting in optimal electrocatalysis performance. The newly fabricated electrodes are applied as cathodes in single‐chamber MEC reactors and inoculated with activated sludge from a municipal wastewater treatment plant. High peak current density determined using cyclic voltammetry of the bioanode indicated the strong electrochemical activity of electroactive bacteria in the bioanode of Ni–Mo 1. This is because the low resistance in the MECs could accelerate electron transfer and boost electrochemical reaction. CONCLUSIONS: The performance of cathodes with different Ni and Mo content in terms of electrochemical activity was evaluated. Consequently, the optimal cathode electrode in MECs was Ni–Mo 1. The obtained results reveal that the cathode affects the bioanode activity in MECs. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

[Display omitted] • Using acetate is not advantageous for improving performance of manure-fed MECs. • Cross-feeding lowers methane production performance during electromethanogenesis. • To produce similar CH 4 from manure as acetate, two times greater sCOD is required. • Model exoelectrogen Geobacter dominated the anodes of all manure-fed MECs. • Hydrogenotrophic Methanoculleus is abundant on the cathodes of manure-fed MECs. This study qualitatively assessed the impacts of different start-up strategies on the performance of methane (CH 4) production from cattle manure (CM) in electromethanogenic reactors. Single chamber MECs were operated with an applied voltage of 0.7 V and the impact of electrode acclimatization with a simple substrate, acetate (ACE) vs a complex waste, CM, was compared. Upon biofilm formation on the sole carbon source (ACE or CM), several MECs (ACE_CM and CM_ACE) were subjected to cross-feeding (switching substrate to CM or ACE) during the test period to evaluate the impact of the primary substrate. Even though there was twice as much peak current density via feeding ACE during biofilm formation, this did not translate into higher CH 4 production during the test period, when reactors were fed with CM. Higher or similar CH 4 production was recorded in CM_CM reactors compared to ACE_CM at various soluble chemical oxygen demand (sCOD) concentrations. Additionally, feeding ACE as primary substrate did not significantly impact either COD removals or coulombic efficiencies. On the other hand, the use of anaerobic digester (AD) seed as an inoculum in CM-fed MECs (CM_CM), relative to no inoculum added MECs (Blank), increased the initial CH 4 production rate by 45% and reduced the start-up time by 20%. In CM-fed MECs, Geobacter dominated bacterial communities of bioanodes and hydrogenotrophic methanogen Methanoculleus dominated archaeal communities of biocathodes. Community cluster analysis revealed the significance of primary substrate in shaping electrode biofilm; thus, it should be carefully selected for successful start-up of electromethanogenic reactors treating wastes. [ABSTRACT FROM AUTHOR]

The search for renewable energy sources has led to the development of plant microbial fuel cells (PMFCs). In this study, Epipremnum aureum plant species was used to generate bioelectricity in a PMFC, demonstrating the synergistic effect of corn cob and carbon road on the power generation and plant growth in PMFC. The maximum voltage output of PMFC with the composite corn cob and carbon rod anode was 465 mV which was 367 mV potential higher than the PMFC with the carbon rod anode only. The maximum power density obtained was 6.75 mW/m2. The results suggest that the use of corn cob has improved the biocompatibility of PMFC. The design of PMFC devices has been developed to increase power output which will be the next step of this research. [ABSTRACT FROM AUTHOR]

In the last years, microbial electrochemical technologies have received increasing attention due to their promising environmental potential. However, the identification of the most suitable materials for further development of these technologies tends to be challenging, especially for operation under realistic wastewater conditions. The objective of the present work is to carry out a systematic comparison of six anode materials (stainless-steel wool, carbon paper, graphite felt, graphite plate, graphite foil, and stainless-steel mesh) for microbial electrolysis cells operated for the treatment of brewery wastewater and determine the best material of these in sight of its electrochemical performance. For this purpose, the medium was semisynthetic brewery wastewater of low buffer capacity and low conductivity. The results suggest, that the degree of fermentation and characteristics of the studied media have only a minor impact on the limiting current density of the bioanodes. Here, the limiting current density of microbial anodes with stainless-steel wool (0.45 ± 0.07 mA·cm−2), a not so extensively studied promising material, outperformed commonly used materials such as graphite felt, without evidence of corrosion.

In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anode, liberating electrons that are used for hydrogen evolution at the cathode. Microbial communities on the anode and cathode surfaces and in the bulk liquid determine the function of the MEC. The communities are complex, and their assembly processes are poorly understood. We investigated MEC performance and community composition in nine MECs with a carbon cloth anode and a cathode of carbon nanoparticles, titanium, or stainless steel. Differences in lag time during the startup of replicate MECs suggested that the initial colonization by electrogenic bacteria was stochastic. A network analysis revealed negative correlations between different putatively electrogenic Deltaproteobacteria on the anode. Proximity to the conductive anode surface is important for electrogens, so the competition for space could explain the observed negative correlations. The cathode communities were dominated by hydrogen-utilizing taxa such as Methanobacterium and had a much lower proportion of negative correlations than the anodes. This could be explained by the diffusion of hydrogen throughout the cathode biofilms, reducing the need to compete for space. [ABSTRACT FROM AUTHOR]

Enzymatic biofuel cells (EBCs) represent a promising technology for biosensors, biodevices, and sustainable green energy applications, thanks to enzymes' high specificity and catalytic efficiency. Nevertheless, drawbacks such as limited output power and short lifetime have to be solved. Nowadays, research is addressed to the use of 3D electrode structures, but the high cost and the industrialization difficulties of such electrodes represent a key issue. The purpose of the paper is thus to describe the use of a low-cost commercial conductive polymer (Sigracell® PV15) as support for the covalent immobilization of glucose oxidase and laccase, for bioanode and biocathode fabrication, respectively. Efficient immobilization protocols were determined for the immobilized enzymes in terms of employed linkers and enzyme concentrations, resulting in significant enzymatic activities for units of area. The analysis focuses specifically on the optimization of the challenging immobilization of laccase and assessing its stability over time. In particular, an optimum activity of 23 mU/cm2 was found by immobilizing 0.18 mg/cm2 of laccase, allowing better performances, as for voltage output and electrochemical stability, and a direct electron transfer mechanism to be revealed for the fabricated biocathode. This study thus poses the basis for the viable development of low-cost functional EBC devices for biomedical applications. [ABSTRACT FROM AUTHOR]

In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anode, liberating electrons that are used for hydrogen evolution at the cathode. Microbial communities on the anode and cathode surfaces and in the bulk liquid determine the function of the MEC. The communities are complex, and their assembly processes are poorly understood. We investigated MEC performance and community composition in nine MECs with a carbon cloth anode and a cathode of carbon nanoparticles, titanium, or stainless steel. Differences in lag time during the startup of replicate MECs suggested that the initial colonization by electrogenic bacteria was stochastic. A network analysis revealed negative correlations between different putatively electrogenic Deltaproteobacteria on the anode. Proximity to the conductive anode surface is important for electrogens, so the competition for space could explain the observed negative correlations. The cathode communities were dominated by hydrogen-utilizing taxa such as Methanobacterium and had a much lower proportion of negative correlations than the anodes. This could be explained by the diffusion of hydrogen throughout the cathode biofilms, reducing the need to compete for space.

Electro-active bacteria (EAB) can form biofilms on an anode (so-called bioanodes), and use the electrode as electron acceptor for oxidation of organics in wastewater. So far, bioanodes have mainly been investigated under a continuous anode potential, but intermittent anode potential has resulted in higher currents and different biofilm morphologies. However, little is known about how intermittent potential influences the electron balance in the anode compartment. In this study, we investigated electron balances of bioanodes at intermittent anode potential regimes. We used a transparent non-capacitive electrode that also allowed for in-situ quantification of the EAB using optical coherence tomography (OCT). We observed comparable current densities between continuous and intermittent bioanodes, and stored charge was similar for all the applied intermittent times (5 mC). Electron balances were further investigated by quantifying Extracellular Polymeric Substances (EPS), by analyzing the elemental composition of biomass, and by quantifying biofilm and planktonic cells. For all tested conditions, a charge balance of the anode compartment showed that more electrons were diverted to planktonic cells than biofilm. Besides, 27–43% of the total charge was detected as soluble EPS in intermittent bioanodes, whereas only 15% was found as soluble EPS in continuous bioanodes. The amount of proteins in the EPS of biofilms was higher for intermittent operated bioanodes (0.21 mg COD proteins mg COD biofilm−1) than for continuous operated bioanodes (0.05 mg COD proteins mg COD biofilm−1). OCT revealed patchy morphologies for biofilms under intermittent anode potential. Overall, this study helped understanding that the use of a non-capacitive electrode and intermittent anode potential deviated electrons to other processes other than electric current at the electrode by identifying electron sinks in the anolyte and quantifying the accumulation of electrons in the form of EPS.

This work aimed to evaluate the devilfish bone char as an alternative material to be used as a bioanode in a microbial fuel cell (MFC) applied in bioenergy production from the pantoprazole biodegradation. The devilfish is an invasive species in Mexico and other countries, so its control and eradication are based on the integral use of its biomass. In addition, the bones are unusable waste and could be used as a raw material to manufacture the bioanode. Two MFCs with an anaerobic anode single chamber of 125 mL were operated independently using the fabricated bioanode and the carbon felt (conventional anode). Both MFCs were fed with 1 g/L of pantoprazole as substrate with a chemical oxygen demand (COD) of 210 ± 1.3 mg/L and 1.2 g of soil as inoculum. The two MFCs were characterized electrochemically, and the COD removal percentage was measured as an indicator of the pantoprazole biodegradation. The results showed that the MFC operated with the bioanode had a better performance than the conventional anode, since it reached a maximum power density of 1.22 mW/m2, being 156% higher than carbon felt. These values were consistent with the COD removal percentages reached in 10 days with values of 47.17 ± 0.23 and 43.34 ± 0.41%, respectively. Therefore, these findings provide a low-cost alternative carbonaceous material for the sustainable construction of MFC applied to produce bioenergy from the biodegradation of pharmaceutical products.

The present study explores the use of carbon dots coated with Iron (II, III) oxide (Fe3O4) for its application as an anode in microbial fuel cells (MFC). Fe3O4@PSA-C was synthesized using a hydrothermal-assisted probe sonication method. Nanoparticles were characterized with XRD, SEM, FTIR, and RAMAN Spectroscopy. Different concentrations of Fe3O4- carbon dots (0.25, 0.5, 0.75, and 1 mg/cm2) were coated onto the graphite sheets (Fe3O4@PSA-C), and their performance in MFC was evaluated. Cyclic voltammetry (CV) of Fe3O4@PSA-C (1 mg/cm2) modified anode indicated oxidation peaks at −0.26 mV and +0.16 mV, respectively, with peak currents of 7.7 mA and 8.1 mA. The fluxes of these anodes were much higher than those of other low-concentration Fe3O4@PSA-C modified anodes and the bare graphite sheet anode. The maximum power density (Pmax) was observed in MFC with a 1 mg/cm2 concentration of Fe3O4@PSA-C was 440.01 mW/m2, 1.54 times higher than MFCs using bare graphite sheet anode (285.01 mW/m2). The elevated interaction area of carbon dots permits pervasive Fe3O4 crystallization providing enhanced cell attachment capability of the anode, boosting the biocompatibility of Fe3O4@PSA-C. This significantly improved the performance of the MFC, making Fe3O4@PSA-C modified graphite sheets a good choice as an anode for its application in MFC. [ABSTRACT FROM AUTHOR]

Using viologen‐based redox polymers to wire a variety of different hydrogenases to electrodes and gas diffusion electrodes is the basis to mitigate high potential deactivation of the enzyme, deactivation by molecular O2, as well as for high‐current density H2 oxidation bioanodes. To overcome electron transfer limitations by electron hopping within the viologen‐modified polymer film, a new redox polymer was designed with the highest possible viologen content together with monomers bearing crosslinking units. In combination with an immobilization sequence consisting of oxidative grafting of amino functions, covalent attachment of polymer units to these functionalities, and crosslinking of the polymer layers, an unprecedently fast electron transfer became possible. This enabled a very high current density normalized by the amount of the [NiFe] hydrogenase embedded within a viologen polymer on gas diffusion electrodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The performance of anodic ammonium oxidation at varying potentials was investigated. • Anode potential regulation effectively directed ammonium transformation in bioanodes. • Bioelectrorespiration-driven nitritation for nitrite supply in Anammox was proposed. • Metagenomic sequencing revealed the anode microbiome for nitrogen transformation. • Regulatory mechanisms of anode potential on ammonium metabolism were deciphered. Understanding how potential regulation affects ammonium transformation in bioanodes is crucial for promoting their application. This study explored the performance, electrochemical properties, electromicrobiome of bioanodes across potentials from 0.0 V to 0.4 V vs. standard hydrogen electrode (SHE). Higher anode potentials enhanced the performance of electroactive biofilms and ammonium removal but suppressed nitrite oxidation while favoring dissimilatory nitrate reduction (DNRA), leading to increased nitrite accumulation. A reduction in nitrite-oxidizing bacteria (NOB) and an increase in DNRA-related genes resulted in an optimal nitrite-to-ammonium ratio of 1.32 for the Anammox process. Higher anodic potentials (0.3 and 0.4 V) were less effective for TN removal than lower potentials (0, 0.1, and 0.2 V), likely due to increased NOB and denitrification genes at lower potentials enhancing nitrite oxidation and denitrification. These findings indicate that regulating anodic potential effectively directs ammonium transformation in bioanodes, optimizing its conversion to N 2 or nitrite. [ABSTRACT FROM AUTHOR]

We fabricated a photo-driven bioanode on laser-induced graphene (LIG) using a facile one-step laser-scribed technique. Nb 4 C 3 T x MXene was decorated on the LIG surface to induce a high surface area for immobilizing the photocatalyst. The thylakoid membrane extracted from Spinacia oleracea utilizes its intrinsic photosynthetic and catalytic capability for efficient energy conversion. A platinum-based gas diffusion electrode is used as the cathode material, allowing for charge transfer and oxygen reduction to produce water. The bioelectrochemical activities of the as-fabricated thylakoid-based biofuel cells were investigated. Upon illumination, the assembled biofuel cell exhibited an open circuit voltage of 0.45 V, a maximum photocurrent density of 68.69 µA/cm2, and a power density of 7.24 µW/cm2. The unique features of thylakoid membranes, Nb 4 C 3 T x MXene, and the LIG substrate play a critical role in producing high-performance photo-biofuel cells. Our approach presents a promising strategy for harnessing the biochemical energy of plants to generate bioelectricity. [ABSTRACT FROM AUTHOR]

Xanthine is a metabolite of interest as a medical and food freshness biomarker. We modified a screen‐printed electrode to detect this analyte by co‐entrapping xanthine oxidase (XOD) and an Os‐complex redox polymer over carbon nanotubes. In nature, XOD transfers its electrons to oxygen in solution. We demonstrate that the introduction of the redox polymer allows routing the electrons efficiently to the electrode surface, even under air‐saturated conditions, enabling superior catalytic current and sensing performance. The bioanode was optimized by adjusting the electrode materials and the ratio of enzyme to redox polymer. The impacts of pH and ionic strength of the electrolyte on the sensor performance were also studied. We found that these variables can affect the electrostatic interaction between the enzyme and the redox polymer, and therefore impact the catalytic current extracted from xanthine oxidation. The XOD‐bioanode design was combined with a bi‐enzymatic cathode operating on glucose to demonstrate a biofuel cell (BFC). The resulting device could generate a power output of 16.56 μW cm−2 at 0.25 V and an open‐circuit voltage (OCV) of 0.50 V using 500 μM xanthine as biofuel. The proposed xanthine/glucose BFC showed promising features for application as a self‐powered xanthine biosensor. [ABSTRACT FROM AUTHOR]

Three-dimensional printing could provide flexibility in the design of a new generation of electrodes to be used in microbial electrochemical technologies (MET). In this work, we demonstrate the feasibility of using polylactic acid (PLA)/graphene—a common 3D-printing material—to build custom bioelectrodes. We also show that a suitable activation procedure is crucial to achieve an acceptable electrochemical performance (plain PLA/graphene bioanodes produce negligible amounts of current). Activation with acetone and dimethylformamide resulted in current densities similar to those typically observed in bioanodes built with more conventional materials (about 5 Am−2). In addition, the electrodes thus activated favored the proliferation of electroactive bacteria. [ABSTRACT FROM AUTHOR]

This study investigates the performance of pencil graphite (PG) electrodes to identify the grade of pencil most suitable as bioanode for enzymatic glucose biofuel cell. Pencils of H, 3H, 5H and B grades are selected for this study. The surfaces of different grade PGs are modified with carboxylic acid functionalized multi walled carbon nanotubes (COOH-MW­CNT/PG), followed by immobilization with glucose oxidase (GOx) to fabricate the respect­tive bioanodes (GOx/COOH-MWCNT/PG). Morphological and electrochemical characteri­zations are carried out using scanning electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry and energy dispersive X-ray spectroscopy. All tested PG electrodes exhibited positive results with variable response characteristics towards glucose oxidation reaction. B-grade PG bioanode is found to have the highest coverage of the deposited nanobiocomposite with the fastest electron transfer rate. The half-cell electrode assembly with this grade of PG recorded the highest current density of 4.25 mA cm-2 at physiological glucose conditions (5 mM glucose, pH 7.0). Enzymatic glucose biofuel cell assembled with B-grade PG bioanode and platinum cathode generated an open circuit potential of 149 mV and maximum power density of 0.789 µW cm−2 from 5 mM glucose at ambient conditions (25 ± 3◦C). The results obtained for B-grade PG bioanode are comparable to those of conventional carbon and glassy carbon electrodes, thus demonstrating its applicability to enzymatic glucose biofuel cells.

Enzymatic biofuel cells (EBCs) represent a promising technology for biosensors, biodevices, and sustainable green energy applications, thanks to enzymes’ high specificity and catalytic efficiency. Nevertheless, drawbacks such as limited output power and short lifetime have to be solved. Nowadays, research is addressed to the use of 3D electrode structures, but the high cost and the industrialization difficulties of such electrodes represent a key issue. The purpose of the paper is thus to describe the use of a low-cost commercial conductive polymer (Sigracell® PV15) as support for the covalent immobilization of glucose oxidase and laccase, for bioanode and biocathode fabrication, respectively. Efficient immobilization protocols were determined for the immobilized enzymes in terms of employed linkers and enzyme concentrations, resulting in significant enzymatic activities for units of area. The analysis focuses specifically on the optimization of the challenging immobilization of laccase and assessing its stability over time. In particular, an optimum activity of 23 mU/cm2 was found by immobilizing 0.18 mg/cm2 of laccase, allowing better performances, as for voltage output and electrochemical stability, and a direct electron transfer mechanism to be revealed for the fabricated biocathode. This study thus poses the basis for the viable development of low-cost functional EBC devices for biomedical applications.

An experimental design was performed to study the combined effects of the parameters used for bacteria selective biofilm formation. The parameters were the potential applied, the time of the biofilm formation with electroactive bacteria or the biofilm formation, and the initial substrate concentration in the medium. The performance of the biofilms formed was compared by their kinetic parameter the apparent electron transfer rate constant (Kapp), which was obtained from cyclic voltammetry analysis. The results from the experimental design showed that the highest Kapp of 0.56 s−1 was with the potential applied of −0.45 V for 5 h and 12 mM of the initial substrate concentration in the medium. New values of these parameters were calculated from the statistical analysis of the experimental design results and successfully higher value of Kapp of 0.64 s−1 can be calculated and obtained. The electroactivity and capability of the biofilm for hydrogen production was also proved in a single chamber microbial electrolysis cell, and a hydrogen production yield of 0.24 m3H2/m3d was obtained. The biofilm formed with these last parameters was also identified with molecular techniques as Exiguobacterium which has barely been reported as electroactive bacteria and used for hydrogen production. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) have shown immense potential as a one-stop solution for three major sustainability issues confronting the world today—energy security, global warming and wastewater management. MFCs represent a cross-disciplinary platform for research at the confluence of the natural and engineering sciences. The diversity of variables influencing performance of MFCs has garnered research interest across varied scientific disciplines since the beginning of this century. The increasing number of research publications has made it necessary to keep track of work being carried out by research groups across the globe and consolidate significant findings on a regular basis. Review articles are often the nodal points for beginners who are required to undertake an exploratory survey of literature to identify a suitable research problem. This 'review of reviews' is a ready-reckoner that directs readers to relevant reviews and research articles reporting significant developments in MFC research in the last two decades. The article also highlights the areas needing research attention which when addressed could take this technology a few more steps closer to practical implementation. [ABSTRACT FROM AUTHOR]

Enzymatic biofuel cells (EBFCs) are considered as a promising technology to sustain the requirements of miniaturized portable energy sources. Electrode materials being one of the substantial aspects of EBFCs have stimulated immense interest in research. A new platform made of nanocomposite, involving magnetic particles of iron oxide (Fe 3 O 4), carbon nanotubes (CNT), gold nanoparticles (Au) and a conducting polymer polypyrrole (PPy), was used as the electrode support for the immobilization of glucose oxidase (GOD) which improves the bioelectrocatalysis of the enzyme towards oxidation of glucose. The structural and electrochemical characterization of the modified bioanode GCE/PPy/Au/CNT@Fe 3 O 4 /FRT/GOD was performed using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The performance of the bioanode was evaluated with promising results showing the maximum current density of 6.01 mA cm−2 (0.22 V vs. Ag/AgCl) in 40 mM of glucose concentration at 0.38 V open circuit potential (OCV). The results suggested that PPy/Au/CNT@Fe 3 O 4 nanocomposite significantly improve the surface area of the electrode and served as a suitable environment for enzyme immobilization, and established good electrical communication by facilitating electron transfer between enzymes and electrode surface. The as-synthesized composite has been inferred as a promising platform for improved bioelectrocatalysis owing to the excellent combination of superparamagnetism of Fe 3 O 4 with good electrocatalytic properties of CNT, PPy, and Au nanoparticles. Thus PPy/Au/CNT@Fe 3 O 4 nanocomposite can be considered as a prospective electrode material for developing better electrochemical biosensors and biofuel cell anode. • Use of PPY/Au/CNT@Fe 3 O 4 nanocomposite substrate for enzyme immobilization. • Structural characterization of composite by physical methods. • Use of ferritin as biocompatible redox mediator. • Achieved a current density of 6.01 mA cm−2 in 40 mM of glucose concentration. [ABSTRACT FROM AUTHOR]

Microbial fuel cell (MFC) has novel technological advances in simultaneous power generation and wastewater treatment applications. In this study, low-cost biosynthesized α-MnO2 nanoparticles integration with conducting polyaniline (PANI) matrix to form α-MnO2/PANI hybrid nanocomposite was fabricated by in situ polymerization method. The prepared material was characterized through UV-Vis spectroscopy, XRD, FTIR, TGA-DTA, DSC, SEM, cyclic voltammetry, and impedance spectroscopy. MFC performance study was done by using an external resistance in the range of 100 Ω–100 kΩ. The continuous test on bare pencil graphite electrode (PGE), α-MnO2/PGE, PANI/PGE, and α-MnO2/PANI/PGE were evaluated in glucose-fed-Escherichia coli-based MFC. It was found that α-MnO2/PANI/PGE produces a maximum power and current densities of 426.26±38.89mW m−2 and 2485.51±397.31mA m−2, respectively. This was 6.5 and 5.7-fold higher in power and current densities than unmodified PGE. The maximum chemical oxygen demand produced by hybrid composite modified anode during closed circuit voltage or with external resistance and open circuit voltage (OCV) (circuit without connecting external resistance) measurements were found to be 88.19% and 92.27%, respectively. A maximum of 650.61±10.11mVOCV was obtained by α-MnO2/PANI/PGE while 222.36±8.16mV of OCV was generated by PGE. [ABSTRACT FROM AUTHOR]

3D printing of a living bioanode holds the potential for the rapid and efficient production of bioelectrochemistry systems. However, the ink (such as sodium alginate, SA) that formed the matrix of the 3D-printed bioanode may hinder extracellular electron transfer (EET) between the microorganism and conductive materials. Here, we proposed a biomimetic design of a 3D-printed Shewanella bioanode, wherein riboflavin (RF) was modified on carbon black (CB) to serve as a redox substance for microbial EET. By introducing the medicated EET pathways, the 3D-printed bioanode obtained a maximum power density of 252 ± 12 mW/m 2 , which was 1.7 and 60.5 times higher than those of SA-CB (92 ± 10 mW/m 2 ) and a bare carbon cloth anode (3.8 ± 0.4 mW/m 2 ). Adding RF reduced the charge-transfer resistance of a 3D-printed bioanode by 75% (189.5 ± 18.7 vs 47.3 ± 7.8 Ω), indicating a significant acceleration in the EET efficiency within the bioanode. This work provided a fundamental and instrumental concept for constructing a 3D-printed bioanode.

This work presents the study of different electrical potentials applied to a carbon cloth material to develop biofilms for their application as bioelectrodes in a microbial fuel cell (MFC). The principal aim of this work was to develop bioanodes and biocathodes for their simultaneous operation in a MFC. The potentials applied were 0.1 V, 0.4 V, and –0.42 V vs. Ag/AgCl KCl reference electrode. Also, electrodes were studied, where a positive potential was applied and gold as the catalyst for oxygen reduction reaction (ORR) was used. The bioelectrodes were characterized with the cyclic voltammetry (CV) technique and the results determined the application of the bioelectrodes as bioanode or biocathode in the MFC. The biofilms formed were observed with the scanning electron microscopy (SEM) technique, and also a new type of electroactive bacteria (Sphingomonas paucimobilis) for biocathodes was identified with a molecular technique. The bioelectrodes developed were tested in a MFC and a maximum power density of 0.585 W m−2 was obtained. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems (BES) are growing future sustainable energy and chemical production technologies that combine biological catalytic redox activity with classic abiotic electrochemical reactions and physics. Several aspects of these systems, such as cell configuration, applied voltage, electrode materials, inoculum/substrate, and low-cost electrodes to facilitate scaling, have been studied and reported. This work focuses on the development of inexpensive materials with desirable characteristics for use as electrodes for BES. The two selected carbon-based anode materials were carbon xerogels and bone char; both have different surface morphologies and are carbonaceous materials with precursors that allow control of their porosity. Industrial-grade raw material and cattle bone waste were used to fabricate the anodes. The electrochemical properties of the bone char and carbon xerogel electrodes were characterized by the open circuit voltage (OCV), electrochemical impedance spectroscopy, and cyclic voltammetry. Chronoamperometry was recorded for 25 days to follow the setup bioanodes. When the microbial bioanode process was completed, the bioelectrodes were immersed into fresh inoculum/substrate, and BES were operated for 10 days at the OCV until a relatively constant cell voltage output was achieved. The results show that the carbon xerogel surface area (468 m2/g) is 5 times higher than bone char, but the xerogel surface roughness is lower than that of the char. Similar to the electrochemical properties, the current density of the xerogel (25 mA/cm2) is 4 times less than that of the bone; therefore, the biofilm growth is promoted on the bone char surface. Our findings show that the bone char bioanode has a capacitance feature of 1.65 F/m2, which is even higher than the double layer capacitances of carbon-based materials reported in the literature. Hence, it is possible to use BES for simultaneous production and storage of renewable electricity. [ABSTRACT FROM AUTHOR]

The structure and biocompatibility of anode materials significantly affect the performance of microbial fuel cells (MFCs). A biocompatible polyaniline–sodium alginate (PANI–SA) composite was prepared in situ oxidation polymerization on the 3D porous nitrogen-doped carbon nanotube/sponge (NCNT/S) to construct a high-performance microbial fuel cell in this investigation. The SEM showed that PANI–SA composite anode had a three-dimensional macroporous structure, and nitrogen-doped nanotubes were wound around the sponge skeleton, which had a large specific surface area, provided more places for the attachment and growth of microorganisms. A dual-chamber MFC equipped with a PANI–SA/NCNT/S bioanode to achieve a power density of 4380 mW m−3, which was much greater than the other MFCs. During the charge–discharge time of 60–90 min, the PANI–SA/NCNT/S bioanode had the highest total charge value of 26,617.86 C m−2, which was 3.23 times higher than that of NCNT/S (8231.87 C m−2). High-throughput sequencing results showed that the PANI–SA/NCNT/S bioanode exhibited high community diversity and selective enrichment of electrogenic bacteria. The excellent performance of the MFC equipped with PANI–SA/NCNT/S anode was attributed to the composite materials, which could be attributed to the large-pore network structure, better biocompatibility, large capacitance and high specific surface area. Illustration of the process for the preparation of PANI–SA [ABSTRACT FROM AUTHOR]

[Display omitted] • The hydrothermal method was utilized for the synthesis of nanomaterials. • Zinc oxide nanoparticles were synthesized via an eco-friendly route. • Ternary nanocomposite was used as a scaffold for anchoring the biomolecules. • A bioanode was undergone for electrochemical testing. • Optimal current density (8.1 mA cm−2) was obtained with 50 mM of glucose. The performance of an enzymatic biofuel cell (EBFC) is very much related to the electrode architecture. Thus, designing a new electrode material by employing nanotechnology broadens the horizon in this field. In this study, a new bioanode is constructed using reduced graphene oxide (RGO) and zinc oxide nanoparticles (ZnO NPs) in polyindole (PIN) matrix for the EBFC system to achieve easy shuttling of electrons between enzyme (glucose oxidase, GOx) and the surface of electrode. The prepared ZnO/RGO/PIN nanocomposite (NC) was assessed by analytical techniques including fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and the electrochemical activity of the NC and ZnO/RGO/PIN/FRT/GOx bioanode was evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). The bioanode attained a maximum current density of ca. 8.1 mA cm−2 at 50 mM glucose concentration and 100 mV s−1 scan rate. Moreover, the nanocomposite has a unique combination synthesized by the green route which is one of the eco-friendly and novel methodologies for the preparation along with less production cost from the previous chemical route. Besides, this combination offers enhanced electrical conductivity, improved electron transportation, and provides a large number of active sites due high aspect ratio along with biocompatibility. These advantages make this nanocomposite valuable in designing bioanode for this application. To the best of our knowledge, this bioanode is being proposed for the first time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanoporous gold was successfully fabricated by gold anodization. • Nanoporous gold fabricated in glycolic acid exhibits almost ∼ 20 nm smaller nanostructures. • Nanoporous structures increase the electron transfer rate more than 10-fold. • Bioanode based on nanoporous gold synthesized in glycolic acid exhibits higher stability. • Biofuel cell possesses 0.35 mA cm−2 and 31.8 µW cm−2 current and power densities. The inexpensive, relatively fast and scalable production of nanostructured electrodes may benefit future disposable biosensor technology. In this research, nanoporous gold (NPG) surfaces were successfully fabricated by anodizing the gold in different organic acid, and further used for glucose dehydrogenase (GDH)-based bioanode design. The porosity of NPG layers was manipulated by changing the anodization time, and the dependency of relative electrochemical surface area (rESA) on the bioanode performances was systematically examined. The X-ray photoelectron spectroscopy (XPS) studies of NPG formed in oxalic acid (NPG ox) and their depth profiles of Au 4f and O 1s evidenced the chemical state of pure metallic gold (Au0), whereas NPG formed in glycolic acid (NPG gly) has appreciable content of gold oxide and hydroxides. The NPG gly /4-ATP/GDH bioanodes exhibited direct electron transfer (DET-type) bioelectrocatalytic activity, while the highest current densities of 0.35 mA cm−2 and low onset potential of −0.189 V (vs. Ag/AgCl) were observed. The electrodes showed long-term stability and, up to three weeks, retained 76 % of their initial value. Furthermore, the biofuel cell possessed the maximum power densities of 31.8 µW cm−2 and open-circuit potential (OCP) differences of 0.441 V, thus evidencing that NPG gly layers could be encouraging for developing biosensors and biofuel cells. [ABSTRACT FROM AUTHOR]

Three-dimensional printing could provide flexibility in the design of a new generation of electrodes to be used in microbial electrochemical technologies (MET). In this work, we demonstrate the feasibility of using polylactic acid (PLA)/graphene—a common 3D-printing material—to build custom bioelectrodes. We also show that a suitable activation procedure is crucial to achieve an acceptable electrochemical performance (plain PLA/graphene bioanodes produce negligible amounts of current). Activation with acetone and dimethylformamide resulted in current densities similar to those typically observed in bioanodes built with more conventional materials (about 5 Am−2). In addition, the electrodes thus activated favored the proliferation of electroactive bacteria.

Microbial electrochemical technologies (METs) require the establishment of anode biofilms to generate electrical current. The factors driving bioanode formation and their variability during startup remain unclear, leading to a lack of effective strategies to initiate larger-scale systems. Accordingly, our objective was to characterize the electrochemical properties and microbial community structure of a large set of replicate bioanodes during their first cycle of current generation. To do this, we operated eight bioanode replicates at each of two fixed electrode potentials [−0.15 V and +0.15 V vs. standard hydrogen electrode (SHE)] for one fed-batch cycle. We found that startup time decreased and maximum current generation increased at +0.15 V compared to −0.15 V, but at both potentials the bioanode replicates clustered into three distinct activity levels based on when they initiated current. Despite a large variation in current generation across the eight +0.15 V bioanodes, bioanode resistance and abundance of Geobacter species remained quite similar, differing by only 10 and 12%, respectively. At −0.15 V, current production strongly followed Geobacter species abundance and bioanode resistance, wherein the largest abundance of Geobacter was associated with the lowest charge transfer resistance. Our findings show that startup variability occurs at both applied potentials, but the underlying electrochemical and microbial factors driving variability are dependent on the applied potential.

As a renewable energy technology, microbial fuel cell (MFC) has been attracting increasing attention in recent decades. However, practical applications of MFCs has been hampered by the unsatisfactory electrode performance, in particular, at the cathode. Herein, Fe/N/S‐doped carbon hollow tubes were prepared by a facile two‐stage procedure involving hydrothermal treatment and pyrolysis at controlled temperatures. Electrochemical studies showed that the obtained samples exhibited an apparent electrocatalytic activity towards oxygen reduction reaction in both alkaline and acidic media, a performance comparable to that of commercial Pt/C, and the sample prepared at 800 °C stood out as the best among the series with a half‐wave potential of +0.81 V vs. RHE and an electron transfer number of 3.98 at +0.6 V vs. RHE. The Fe/N/S‐doped carbon tubes also exhibited a remarkable performance as an MFC anode by facilitating bacterial growth and electron transfer between the biofilm and electrode. In fact, an MFC based on the carbon tubes as both cathode and anode showed a markedly higher performance (maximum power density 479 W m−3) than the control MFC based on a graphene aerogel anode and Pt/C cathode (359 W m−3). These results suggest that Fe/N/S‐doped carbon composites can be used for the fabrication of high‐efficiency MFC electrodes. [ABSTRACT FROM AUTHOR]

Bioanode stability with glucose oxidase was enhanced significantly by covalent crosslinking without substantial enzymatic activity and affinity loss. Initially, glucose oxidase was immobilized by aldehyde groups on the electrode that was developed using ferrocenecarboxaldehyde, polyethyleneimine, multiwall carbon nanotubes, and carbon cloth for biofuel cell applications. The glucose oxidase half-life was extended by more than 4 times, from 27.2 to 124.7 h, after the electrode was crosslinked. Enzymatic kinetic parameters were determined for the crosslinked enzyme and they were compared to the noncrosslinked immobilized enzyme parameters on the electrode. The apparent substrate affinity of the crosslinked enzyme electrode was decreased (i.e. kM was increased) by 16%, while the maximum reaction rate was decreased by only 3%, by the crosslinking process. Moreover, effects of the electrolyte type (i.e. buffer type) and concentration on the performance of the crosslinked enzyme electrode were evaluated and appropriate conditions were determined. [ABSTRACT FROM AUTHOR]

A bioelectrochemical system (BES) is a technology with potential for accelerating the degradation of recalcitrant compounds, the components and configurations of which are important for treatment performance. In the present work, a membraneless sleeve-type BES (termed BioE) was designed for the treatment of synthetic coal gasification wastewater (CGW, phenol as a model pollutant) and real CGW. Compared with the biological control (termed Bio), the phenol removal rate and COD removal efficiency increased by 2.6 and 2.1 fold in the BioE, respectively. However, the coulombic efficiency of this system was relatively low, ranging from 0.42% to 2.6%. This combination of results indicated that anode respiration was not the main process in the BioE. The increased CH 4 production and higher levels of methanogens obtained from the BioE confirmed that the methanogenic process proceeded, possibly facilitated by the diffusion of H 2 from the cathode to the anode. This study provides new insight into biocathode function for COD oxidation removal in BESs. Moreover, this study indicates that pursuing a high coulombic efficiency may not be necessary for wastewater treatment, as it consumes less energy at the lower value. Unlabelled Image • A membrane-less sleeve type BES (BioE) was designed for treatment of CGW • The removal of phenol/COD was enhanced while the CE was relatively low (0.42% ~2.6%) • Enhanced methanogenic process and higher biomass promoted the phenol/COD removal • H 2 produced from the cathode may accelerate phenol transformation and COD removal [ABSTRACT FROM AUTHOR]

Glucose oxidase was covalently immobilized to a porous electrode, which was developed by using ferrocene functionalized polyethyleneimine, multiwall carbon nanotubes, and carbon cloth for biofuel cell applications in our recent studies. The kinetics parameters (i.e. kM, Vmax) and other parameters required for the modeling study were determined experimentally. Fuel cell flow channel geometry was analyzed by a computational fluid dynamics modeling approach. Substrate flow rate and mass transfer for each proposed channel type were considered in the simulations. The results showed that serpentine type flow channels are advantageous over pin type or parallel flow channels to acquire sufficient performance from the immobilized enzyme electrode at lower substrate flow rates. On the other hand, a disadvantage of using serpentine type channels was observed as higher pressure drops. However, such pressure drops were accepted as reasonable for the considered flow rates for suitable biofuel cell performance. [ABSTRACT FROM AUTHOR]