Bioanode Material Research Articles

Immobilization of Dimethylferrocene-Modified Linear Poly(ethylenimine) on Epoxy-Terminated Supports for in-Situ Confocal Raman Microscopy

Dimethylferrocene-modified linear poly(ethylenimine) (DMFc-LPEI) has been widely studied as a redox-mediating polymer for biosensor and biofuel cell applications. An increasing number of studies have shown the potential for DMFc-LPEI to immobilize oxidoreductase enzymes and to mediate electron transfer at electrode supports, making DMFc-LPEI a promising high current density bioanode material. Herein, we introduce the immobilization of DMFc-LPEI on 3-glycidoxypropyltrimethoxysilane-modified glass substrates. The epoxy-terminated functional groups on the substrate are used to covalently attach the polymer chains to the substrate by a simple nucleophilic substitution reaction, while a crosslinker, ethylene glycol diglycidyl ether, stabilizes a network of polymer chains using the same chemistry. Confocal Raman spectroscopy reveals that the vibrational bands of immobilized linear poly(ethylenimine) (LPEI) broaden compared to those of free solid-phase LPEI, suggesting that immobilized polymer film exists in an amorphous phase. The Raman spectra of DMFc-LPEI showed prominent vibrations corresponding to CH3 wagging mode at 1037 cm-1 and NH || bending mode at 1451 cm-1 of dimethylferrocene (DMFc) and LPEI, respectively. In the future, this chemistry will be extended to in-situ confocal Raman microscopy investigations of DMFc-LPEI on optically-transparent indium tin oxide electrodes to unravel the structural and conformational changes associated with varying the redox state of the DMFc mediator.

3D Porous Sponge/Carbon Nanotube/Polyaniline/Chitosan Capacitive Bioanode Material for Improving the Power Generation and Energy Storage Performance of Microbial Fuel Cells

Anode materials play a crucial role in the performance of microbial fuel cells (MFCs) in terms of power output. In this study, carbon nanotube (CNT)/polyaniline (PANI)/chitosan (CS) composites were prepared on a porous sponge matrix. The high electrical conductivity of CNTs, the capacitive behavior of PANI, and the biocompatibility of CS were leveraged to enhance the electricity generation and energy storage capabilities of MFCs. Experimental results demonstrated that the MFC with the modified anode achieved a maximum power density of 7902.4 mW/m3. Moreover, in the charging–discharging test, the stored electricity of the S/CNT/PANI/CS anode was 16.38 times that of the S/CNT anode when both the charging and discharging times were 30 min. High-throughput sequencing revealed that the modified composite anode exhibited remarkable biocompatibility and selective enrichment of electrogenic bacteria. Overall, this study presents a novel approach for developing composite MFC anode materials with energy storage functionality.

Development of a Highly Boron Tolerant Pseudomonas sp.−Fe‐MOF Bioanode

AbstractIn 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.

A wood pulp sponge cleaning wipe as a high-performance bioanode material in microbial electrochemical systems for its vast biomass carrying capacity, large capacitance, and small charge transfer resistance

Microbial electrochemical systems are a promising green and sustainable technology that can transform waste into electricity. Improving conversion efficiency and lowering system costs, particularly for electrodes, are the primary directions that promote practical application. Cellulose sponges made from wood pulp have been industrially mass-produced in various application scenarios due to their porosity and green sustainability. In this study, the three-dimensional (3D) porous cellulose sponges carbon (CSC) was obtained by directly carbonizing cellulose sponges at different temperatures (600, 700, 800, 900, 1000, and 1100 °C). It has been successfully used as a high-performance anode in microbial fuel cells (MFCs). The carbonization temperature significantly impacted the materials’ specific surface area, conductivity, and capacitance. The greater the anode material's carbonization temperature, the lower the charge transfer resistance and the higher the maximum power density (CSC-1100, 4.1 ± 0.1 W m–2). The CSC-700′s maximum power density (3.62 ± 0.11 W m–2) was the highest power density reported to date among lignocellulose-based anodes with relatively low energy consumption. The pleated multilayer porous surface promotes microbial adhesion and can build thicker biofilms with the highest biomass of 2661 ± 117 μg cm–2 (CSC-1100) and containing 86 % electrogenic bacteria (Geobacter). To investigate the effect of conducting polymers on the material's surface, we introduced polyaniline and polypyrrole. We found that the CSC-1000/PPy bioanodes produced a maximum power density (4.18 ± 0.05 W m–2), slightly higher than of without polypyrrole-modified (CSC-1000, 3.99 ± 0.06 W m–2), indicating that the CSCs anode surface had excellent electron transfer efficiency and could achieve the same amount of energy as the polypyrrole surface. This study introduced a promising method for fabricating high-performance anodes using low-cost, industrialized, and sustainable materials.

Improving Microbial Fuel Cell Performance Using Porous Capacitive Composite Bioanode Materials with Energy Storage Function

Microbial fuel cells (MFCs) have shown promise in solving energy and environmental problems, but their practical application is limited by their low power output. In this study, carbon nanotubes/polypyrrole composite anode materials were prepared on a porous sponge matrix. By combining the porous characteristics of sponge, the good conductive properties of carbon nanotubes, and the energy storage ability of polypyrrole capacitive materials, the prepared anode exhibited a large specific capacity, high porosity, large specific surface area, good electron transport ability, and good biocompatibility. The results showed that the maximum power density of the modified anode MFC reached 7.46 W m−3, which was 2.53 times higher than that of the control anode. The stored energy Qs released by the modified anode was 235.6 C m−2, 6.5 times higher than that of the control electrode. In addition, the transfer impedance Rct of the S/CNT/PPy electrode (5.5 Ω) was much lower than that of the control anode (16.8 Ω). The research presented in this paper demonstrates a new approach to improving the power generation ability and energy storage performance of MFCs.

Silver nanoparticles anchored on zinc oxide synthesized via green route as scaffold for enzymatic biofuel cell application

The present work is based on developing more efficient bioanode nanocomposite materials for enzymatic biofuel cell (EBFCs) applications. The selection of useful electrode materials (EMs) is depended on their long-term stability, high current density, and low open-circuit voltage (OCV). Continuous efforts are being applied by the research communities for developing advanced efficient EMs. In the past few decades, nanomaterials and their composite have become promising materials that have been used as effective EMs in supercapacitors, solar cells (SCs) and BFCs applications. Herein, ternary nanocomposite, composed of silver nanoparticles (Ag NPs) decorated on zinc oxide nanoparticles (ZnO NPs) and graphene oxide sheets (GO), based bioanode was designed by employing Ferritin (Frt) and glucose oxidase (GOx) enzymes on the glassy carbon electrode (GCE). The formation of Ag@ZnO-NPs/GO nanocomposite was confirmed using analytical techniques such as FTIR and XRD. The structural surface morphology and in-depth investigation of Ag@ZnO-NPs/GO nanocomposite were performed using SEM and TEM. Besides these, the electrochemical behavior of as-synthesized Ag@ZnO-NPs/GO nanocomposite and the designed bioanode Ag@ZnO-NPs/GO/Frt/GOx were examined using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The resulting bioanode showed good catalytic activity toward glucose oxidation and splendid stability. In the presence of glucose (optimum concentration = 30 mM), the maximum current density was 7.7 mA cm−2, comparable to the other bioanode EMs. The results of this work reflected the appropriateness of Ag@ZnO-NPs/GO/Frt/GOx bioanode materials as assured EMs for the generation of EBFCs.

Electrochemical Characterization of Biomolecular Electron Transfer at Conductive Polymer Interfaces

Bio-electrochemical systems (BESs) are promising for renewable energy generation but remain hindered by inefficient electron transfer at electrode surfaces. As the toolbox of bio-anode materials increases, rigorous electrochemical characterization of emerging materials is needed. Here, we holistically characterize the electrochemical interaction of flavin mononucleotide (FMN), an electron shuttle in biological systems and a cofactor for oxidoreductase enzymes, with the bio-inspired mixed conducting polymer poly{3-[6′-(N-methylimidazolium)hexyl]thiophene} (P3HT-Im+). The behavior of this polymer is compared to the equivalent polymer without the histidine-like imidazolium. We find improved conductivity and charge storage in imidazolium-containing polymers beyond what is explained by differences in the electroactive area. The P3HT-Im+ further shows internal charge storage but with negligible faradaic contribution, indicating that charge storage capacity may translate to improved biocatalysis non-intuitive ways. Finally, one-electron transfer is observed between FMN and glassy carbon, while a bio-similar two-electron transfer is observed for the P3HT-Im+. To our knowledge, this is the first example of a concerted two-electron transfer between FMN and an electrode interface, which we attribute to the bio-inspired, histidine-like imidazolium functional groups in the polymer. These studies demonstrate the importance of bio-relevant materials characterization when such materials are deployed in BESs.

Advancements in Bioelectricity Generation Through Nanomaterial-Modified Anode Electrodes in Microbial Fuel Cells

The use of nanotechnology in bioelectrochemical systems to recover bioelectricity and metals from waste appears to be a potentially appealing alternative to existing established procedures. This trend exactly characterizes the current renewable energy production technology. Hence, this review focuses on the improvement of the anode electrode by using different functional metal oxide-conducting polymer nanocomposites to enhance microbial fuel cell (MFC) performance. Enhancement of interfacial bioelectrocatalysis between electroactive microorganisms and hierarchical porous nanocomposite materials could enhance cost-effective bioanode materials with superior bioelectrocatalytic activity for MFCs. In this review, improvement in efficiency of MFCs by using iron oxide- and manganese oxide-based polypyrrole hybrid composites as model anode modifiers was discussed. The review also extended to discussing and covering the principles, components, power density, current density, and removal efficiencies of biofuel cell systems. In addition, this research review demonstrates the application of MFCs for renewable energy generation, wastewater treatment, and metal recovery. This is due to having their own unique working principle under mild conditions and using renewable biodegradable organic matter as a direct fuel source.

Electrochemical Synthesis of Polyaniline/metal-based Anodes and Their Use in Microbial Fuel Cell

A limited number of metals may be suitable as bioanode material: noble metals, such as gold and platinum, could be the optimum choice being electrochemically inert in the operational potential window of the bio-electrochemical system. However, high costs limit their wide scale application. Even though its antimicrobial nature, copper is being considered as a promising alternative anode material, due to its high conductivity, that allows minimising the electrode material costs. Literature research indicated that high-performing electrochemically active biofilms may be grown on this metal.In the present work, gold and copper substrates have been coated by a conductive polymer (PANI), using a layer – by – layer procedure: surface grafting by reduction of 4-nitrobenzendiazonium salt was followed by reduction of nitro- to amino-groups; PANI was electrodeposited on this under-layer.The synthesized anodes were tested as working electrodes (WE) in a microbial fuel cell fed with anaerobic sludge and acetate; to assess the growth of the biofilm on the WE surface, the trend of the bioelectrocatalytic current of acetate oxidation was monitored over time. Cyclic voltammetries reveal the presence of typical redox couples related to the presence of electroactive microorganisms on the electrode surface. Preliminary data show bioelectrochemical activity on polyaniline-coated metal surfaces.

Benchmarking of Industrial Synthetic Graphite Grades, Carbon Felt, and Carbon Cloth as Cost-Efficient Bioanode Materials for Domestic Wastewater Fed Microbial Electrolysis Cells

Anode material selection is crucial when it comes to building up-scaled microbialelectrolysis cells (MEC), as it has a huge influence on the achievable current density and account for a large part of the MEC total investment cost. Graphite is a material that isperfectly suited to the creation of up-scaled bioanodes as it is conductive, chemically stable, biocompatible, and relatively cheap but there are a very large number of commercially available grades of industrial graphite. In this study, five grades of industrial synthetic graphite (named G1–G5) were bench tested to select the most suitable gradefor future development of 3D bioanode for domestic wastewater (dWW) fed MEC application. The five grades of graphite have been selected with similar physico-chemicaland surface properties (electrical resistivity, surface roughness, and hydrophobicity) theoretically appropriate for EA biofilm development. Nevertheless, significant current density disparities where observed with the five graphite grades, which can certainlybe explained by the fabrication procedures of the respective material grades. With thegraphite grade giving the most efficient anodes (G3), an average steady state currentdensity of 2.3 A/m²was produced, outperforming the other grades by at least 15%.Even though all graphites had very close physico-chemical characteristics, the gradehad a clear significant influence on the current densities produced. G3 graphite was finally compared to carbon felt (CF) and carbon cloth (CC) both in terms of bio-electrochemicalcurrent production and bacterial communities colonizing electrodes. G3 bioanodes outperformed CF and CC bioanodes by 50% in term of steady state current density.Biofilms microbial population analysis showed that theGeobacterspecies was presentat 82% on G3 bioanodes, 39% on CF bioanodes, and 61% on CC bioanodes when it was only present at 0.06% in the activated sludge used as inoculum. This significant difference in bacterial enrichment could come from the huge gap between materials resistivity, as graphite resistivity is 200-fold lower than CF and CC resistivities. The strongly hydrophilic surface of G3 graphite was also certainly beneficial for biofilm development compared tothe hydrophobic surfaces of CF and CC.

Application of the eco-friendly bio-anode for ammonium removal and power generation from wastewater in bio-electrochemical systems

Abstract In this new insight, the potential application of the eco-friendly bioanode material was investigated with the aim of ammonium removal and its recovery, alongside power generation from wastewater in bio-electrochemical systems (BESs). In this procedure, biodegradation of ammonia was directly accrued via bioanode compartment driven by in-situ generated bioelectricity. To this end, this protocol was implemented with the anaerobic microbial as a biocatalyst in an anode chamber, as well as aerobic cathode chamber and a Nafion117 membrane as a separator with attractive results for the BES. The findings of the study suggested that BES, at the optimum operational conditions, can be an effective process for removing the high concentrations of organic materials and ammonium from industrial wastewater. The maximum BES efficiency was obtained 94% for the ammonium removal with a chemical oxygen demand (COD) concentration of 10,000 mg/L and a maximum organic removal rate of 78% with a substrate concentration of 2000 mg/L. The maximum voltage, power and current density of the BES was 481 mV, 62.7 mW/m2, 570 mA/m2, respectively. Further, an increase in NH4Cl concentration improved the maximum current density (808 mA/m2). The results demonstrated that the bio-electrochemical system could be utilized to treat industrial wastewater, containing high amounts of ammonium and organic materials, by adjusting the organic matter to ammonium (COD/NH4+) ratio while simultaneously generating electricity. Generally, the application of this eco-design, and sustainable bioanode material can be a good foundation and new perspective for practical application with regards to green and sustainable chemistry.

Activated Carbon Mixed with Marine Sediment is Suitable as Bioanode Material for Spartina anglica Sediment/Plant Microbial Fuel Cell: Plant Growth, Electricity Generation, and Spatial Microbial Community Diversity

Wetlands cover a significant part of the world’s land surface area. Wetlands are permanently or temporarily inundated with water and rich in nutrients. Therefore, wetlands equipped with Plant-Microbial Fuel Cells (Plant-MFC) can provide a new source of electricity by converting organic matter with the help of electrochemically active bacteria. In addition, sediments provide a source of electron donors to generate electricity from available (organic) matters. Eight lab-wetlands systems in the shape of flat-plate Plant-MFC were constructed. Here, four wetland compositions with activated carbon and/or marine sediment functioning as anodes were investigated for their suitability as a bioanode in a Plant-MFC system. Results show that Spartina anglica grew in all of the plant-MFCs, although the growth was less fertile in the 100% activated carbon (AC100) Plant-MFC. Based on long-term performance (2 weeks) under 1000 ohm external load, the 33% activated carbon (AC33) Plant-MFC outperformed the other plant-MFCs in terms of current density (16.1 mA/m2 plant growth area) and power density (1.04 mW/m2 plant growth area). Results also show a high diversity of microbial communities dominated by Proteobacteria with 42.5–69.7% relative abundance. Principal Coordinates Analysis shows clear different bacterial communities between 100% marine sediment (MS100) Plant-MFC and AC33 Plant-MFC. This result indicates that the bacterial communities were affected by the anode composition. In addition, small worms (Annelida phylum) were found to live around the plant roots within the anode of the wetland with MS100. These findings show that the mixture of activated carbon and marine sediment are suitable material for bioanodes and could be useful for the application of Plant-MFC in a real wetland. Moreover, the usage of activated carbon could provide an additional function like wetland remediation or restoration, and even coastal protection.

The granular capacitive moving bed reactor for the scale up of bioanodes

AbstractBACKGROUNDScaling up bioelectrochemical systems for the treatment of wastewater faces challenges. Material costs, low conductivity of wastewater and clogging are issues that need a novel approach. The granular capacitive moving bed reactor can potentially solve these challenges. In this reactor, capacitive activated carbon granules are used as bioanode material. The charge storage capabilities of these capacitive granules allow for the physical separation of the charging and the discharging process and therefore a separation of the wastewater treatment and energy recovery process.RESULTSThis study investigates the performance of the granular capacitive moving bed reactor. In this reactor, activated granules were transported from the bottom to the top of the reactor using a gas lift and settled on top of the granular bed, which moved downwards through the internal discharge cell. This moving granular bed was applied to increase the contact time with the discharge anode to increase the current density. The capacitive moving bed reactor (total volume 7.7 L) produced a maximum current of 23 A m−2 normalized to membrane area (257 A m−3granules). Without granules, the current was only 1.4 A m−2membrane. The activity of the biofilm on the granules increased over time, from 436 up to 1259 A m−3granules. A second experiment produced similar areal current density and increase in activity over time.CONCLUSIONWhereas the produced current density is promising for further scaling up of bioanodes, the main challenges are to improve the discharge of the charged granules and growth of biofilm on the granules under shear stress. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Functionalized and Enhanced HB Pencil Graphite as Bioanode for Glucose-O2 Biofuel Cell

Herein, a novel, low-cost and readily available HB pencil graphite (PG), as bioanode for enzymatic biofuel cell, is presented. The surface area of the PG is substantially increased by coating carboxylated multiwalled carbon nanotube through the dipping method followed by its covalent immobilization with glucose oxidase enzyme to fabricate the bioanode. The surface morphology of fabricated bioanode is characterized by scanning electron microscopy, and the electrochemical studies are performed through linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy. The results reveal that the fabricated bioanode shows good direct electron transfer characteristics between the dynamic site of the enzyme and the terminal surface of electrode. Approximately, 1.23 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> mol · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> of glucose oxidase is found to anchor on the fabricated bioanode with significant electron transfer rate of 3.2 s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Furthermore, the catalytic activity of fabricated bioanode is enhanced with increase in the glucose concentration, and a hyperbolic Michaelis-Menten kinetics is observed with Km value of 5.5 mM and maximum current density of 4605 μA·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> at 40-mM saturated glucose concentration. Finally, the fabricated bioanode exhibits stability with reasonably good retention of biocatalytic activity, thus establishing HB PG as promising bioanode material for enzymatic biofuel cell.

Effects of the Structure of TiO2 Nanotube Arrays on Its Catalytic Activity for Microbial Fuel Cell.

To enhance the microbial fuel cell (MFC) for wastewater treatment and chemical oxygen demand degradation, TiO2 nanotubes arrays (TNA) are successfully synthesized on Ti foil substrate by the anodization process in HF and NH4F solution, respectively (hereafter, denoted as TNA‐HF and TNA‐NF). The differences between the two kinds of TNA are revealed based on their morphologies and spectroscopic characterizations. It should be highlighted that 3D TNA‐NF with an appropriate dimension can make a positive contribution to the high photocatalytic activity. In comparison with the TNA‐HF, the 3D TNA‐NF sample exhibits a significant enhancement in current generation as the MFC anode. In particular, the TNA‐NF performs nearly 1.23 times higher than the TNA‐HF, and near twofold higher than the carbon felt. It is found that the two kinds of TiO2‐based anodes have different conductivities and corrosion potentials, which are responsible for the difference in their current generation performances. Based on the experimental results, excellent stability, reliability, and low cost, TNA‐NF can be considered a promising and scalable MFC bioanode material.

Stainless Steel-Based Bioanodes for Applications in Bioelectrochemical Systems

The majority of studies focusing on bioelectrochemical systems (BES) report the utilization of carbon-based electrodes. However, in order to overcome the limitations related to the scale-up of Microbial Fuel Cells (MFC) and Microbial Electro Synthesis (MES) cells technologies, the utilization of metal-based electrodes need to be considered due to their conductivity, cost and robustness. Stainless steel fiber felts (SSFF) as bioanode material for BES applications was investigated in this study. The unmodified SSFF was tested alongside with electrodes modified with reduced graphene oxide (rGO), magnetite nanoparticles (Fe3O4), manganese oxide (MnO2) and flame-oxidation (FO). The performance of the metal-based electrodes as bioanodes were investigated in half-cells in terms of stability and current densities. In addition, the impact of the capacitance of the abiotic electrode materials on the performance of the bioanodes and MFCs was evaluated (Fig. a), especially to assess how these materials can increase the energy harvested compared to non-capacitive bioanodes. The results showed that the stainless steel- based electrodes studied are competitive alternatives to the carbon-based electrodes. Current densities recorded in half-cells were 1.96, 1.95 and 2.26 mA/cm2 for FO-MnO2-SS, rGO-SS and carbon cloth, respectively. In addition, charge/discharge experiments carried out with the bioanodes developed (Fig. c) showed that the modified SSFF electrodes allow the storage of electrical charge from the biofilm to the capacitive layers of the electrodes when cells are left at open circuit potential (OCP). These results demonstrate the potential of these materials for energy generation and storage applications from waste in BES. Figure 1

Electricity generation from wetlands with activated carbon bioanode

Paddy fields are potential non-tidal wetlands to apply Plant Microbial Fuel Cell (PMFC) technology. World widely they cover about 160 million ha of which 13.3 million ha is located in Indonesia. With the PMFC, in-situ electricity is generated by a bioanode with electrochemically active bacteria which use primary the organic matter supplied by the plant (e.g. as rhizodeposits and plant residues). One of limitations when installing a PMFC in a non-tidal wetland is the usage of “expensive” large amounts of electrodes to overcome the poor conductivity of wet soils. However, in a cultivated wetland such as rice paddy field, it is possible to alter soil composition. Adding a conductive carbon material such as activated carbon is believed to improve soil conductivity with minimum impact on plant vitality. The objective of this research was to study the effect of activated carbon as an alternative bioanode material on the electricity output and plants vitality. Lab result shows that activated carbon can be a potential alternative for bioanode material. It can continuously deliver current on average 1.54 A/m3 anode (0.26 A/m2 PGA or 66 mW/m2 PGA) for 98 days. Based on this result the next step is to do a test of this technology in the real paddy fields.

Electrospun polyaniline/polyvinyl alcohol/multiwalled carbon nanotubes nanofibers as promising bioanode material for biofuel cells

The polyaniline/polyvinyl alcohol/multiwalled carbon nanotubes (PANI/PVA/MWCNTs) composite nanofibers were synthesized using electrospinning technique. Nanofibres morphology was characterized by using scanning electron microscopy (SEM). The electrospun PANI/PVA/MWCNTs nanofibres with average diameter of about 60–100nm exhibited smooth surface at higher magnifications of ×25000. The PANI/PVA/MWCNTs nanofibres modified electrode showed good electron transfer behavior because of the excellent properties of carbon nanotubes and the three dimensional and porous structures of electrospun nanofibres. The enzyme glucose oxidase (GOx) covalently immobilized with PANI/PVA/MWCNTs nanofibres exhibited good electrocatalytic activity towards oxidation of glucose through redox active as well as biocompatible mediator ferritin (FRT). The maximum current density using this nanostructured bioanode was 7.5mAcm−2 at 100mVs−1 vs Ag/AgCl in a 20mM glucose solution. The heterogeneous electron transfer rate constant (Ks) was found to be 3.09s−1. The results indicated that these electrospun PANI/PVA/MWCNTs nanofibres have potential to be used in BFC device as anode.

Nitrogen-enriched pseudographitic anode derived from silk cocoon with tunable flexibility for microbial fuel cells

Microbial fuel cells (MFCs), promising for converting biomass energy into electricity, have attracted much research enthusiasm. However, high performance anode materials for MFC, particularly with tunable flexibility for diverse cell configurations, are still limited. In this study, through a simple one-step carbonization of a versatile protein precursor, silk cocoon, both freestanding and flexible bioanode materials, with enriched nitrogen contents and hierarchical pores, can be easily fabricated. Importantly, the carbonized silk cocoon, as a freestanding MFC anode, and flexible carbon fiber, as a flexible MFC anode, exhibit high performance in electricity generation, yielding about 2.5-fold and 3.1-fold maximum gravimetric power density than that of MFCs with carbon cloth anode, respectively. We attribute the improved anode performance of these flexibility tunable carbon materials to their good biocompatibility, reduced electron transfer resistance and high capacitance. This study will not only offer great opportunities for the fabrication of high-performance MFC anode with varied designs and 3-dimensional architectures, but also shed light on the future development of MFC and proper utilization of the abundant “green” natural resources.

Ferrocene-Modified Linear Poly(ethylenimine) for Enzymatic Immobilization and Electron Mediation.

Enzymatic glucose biosensors and biofuel cells make use of the electrochemical transduction between an oxidoreductase enzyme, such as glucose oxidase (GOx), and an electrode to either quantify the amount of glucose in a solution or generate electrical energy. However, many enzymes including GOx are not able to electrochemically interact with an electrode surface directly, but require an external electrochemical relay to shuttle electrons to the electrode. Ferrocene-modified linear poly(ethylenimine) (Fc-LPEI) redox polymers have been designed to simultaneously immobilize glucose oxidase (GOx) at an electrode and mediate electron transfer from their flavin adenine dinucleotide (FAD) active site to the electrode surface. Cross-linked films of Fc-LPEI create hydrogel networks that allow for rapid transport of glucose, while the covalently bound ferrocene moieties are able to facilitate rapid electron transfer due to the ability of ferrocene to exchange electrons between adjacent ferrocene residues. For these reasons, Fc-LPEI films have been widely used in the development of high current density bioanode materials. This chapter describes the synthesis of a commonly used dimethylferrocene-modified linear poly(ethylenimine), as well as the subsequent preparation and electrochemical characterization of a GOx bioanode film utilizing the synthesized polymer.