Polyaniline/mesoporous tungsten trioxide composite as anode electrocatalyst for high-performance microbial fuel cells

Untreated vs. Treated Carbon Felt Anodes: Impacts on Power Generation in Microbial Fuel Cells

This research sought to enhance the efficiency and biocompatibility of anodes in bioelectrochemical systems (BESs) such as microbial fuel cells (MFCs), with an aim toward large-scale, real-world applications. The study focused on the effects of acid-heat treatment and chemical modification of three-dimensional porous pristine carbon felt (CF) on power generation. Different treatments were applied to the pristine CF, including coating with carbon nanofibers (CNFs) dispersed using dodecylbenzene sulfonate (SDBS) surfactant and biopolymer chitosan (CS). These processes were expected to improve the hydrophilicity, reduce the internal resistance, and increase the electrochemically active surface area of CF anodes. A high-resolution scanning electron microscopy (HR-SEM) analysis confirmed successful CNF coating. An electrochemical analysis showed improved conductivity and charge transfer toward [Fe(CN)6]3-/4- redox probe with treated anodes. When used in an air cathode single-chamber MFC system, the untreated CF facilitated quicker electroactive biofilm growth and reached a maximum power output density of 3.4 W m-2, with an open-circuit potential of 550 mV. Despite a reduction in charge transfer resistance (Rct) with the treated CF anodes, the power densities remained unchanged. These results suggest that untreated CF anodes could be most promising for enhancing power output in BESs, offering a cost-effective solution for large-scale MFC applications.

Functional Nanomaterial-Modified Anodes in Microbial Fuel Cells: Advances and Perspectives

Microbial fuel cell (MFC) is a promising approach that could utilize microorganisms to oxidize biodegradable pollutants in wastewater and generate electrical power simultaneously. Introducing advanced anode nanomaterials is generally considered as an effective way to enhance MFC performance by increasing bacterial adhesion and facilitating extracellular electron transfer (EET). This review focuses on the key advances of recent anode modification materials, as well as the current understanding of the microbial EET process occurring at the bacteria-electrode interface. Based on the difference in combination mode of the exoelectrogens and nanomaterials, anode surface modification, hybrid biofilm construction and single-bacterial surface modification strategies are elucidated exhaustively. The inherent mechanisms may help to break through the performance output bottleneck of MFCs by rational design of EET-related nanomaterials, and lead to the widespread application of microbial electrochemical systems.

A light-enhanced α-FeOOH nanowires/polyaniline anode for improved electricity generation performance in microbial fuel cells

Low power density and poor anode performance seriously limit the potential of practical application of microbial fuel cell (MFC). Utilizing solar energy by developing photoanode is one of the effective pathways to improve the performance of MFC. Here solar energy harvesting was integrated into MFC to achieved the comprehensive utilization of multiple energy sources. A hybrid MFC photoanode (α-FeOOH-NWs/PANI anode) was constructed by loading polyaniline (PANI) and α-FeOOH nanowires (α-FeOOH-NWs) on carbon paper through electro-polymerization synthesis method. Compared with clean carbon paper, nanowires and PANI increased the surface roughness of the electrode, which facilitated the biofilm formation. The electrochemical and photoelectric analysis demonstrated that PANI introduced new electroactive groups and reduced the charge transfer resistance, exhibiting excellent electrochemical and photoelectric activites. The MFC with the α-FeOOH-NWs/PANI photoanode had higher voltage output and power density under light illumination, with the power density of 1.95 W/m² under light, which was 1.4 times higher than that without light. The hybrid α-FeOOH-NWs/PANI photoanode enhanced the separation efficiency of photogenerated electron-hole pairs, thereby improving the photoelectric response capability and generating a high photocurrent. Our research provided a new concept for the combination of solar energy harvesting and MFCs, yielding an overall enhancement of electricity eneration performance in MFC.

Treatment of hazardous organic amine wastewater and simultaneous electricity generation using photocatalytic fuel cell based on TiO2/WO3 photoanode and Cu nanowires cathode

Organic amines are regarded as high toxic, refractory chemicals due to the great damage on human body, and ecosystem. The treatment of organic amine wastewater involves the removal of total nitrogen and toxic organics simultaneously, which is one of the biggest difficulties in wastewater treatment. In this study, hazardous organic amine wastewater was purified by a photocatalytic fuel cell (PFC) with efficient nitrogen removal and organic degradation, and its chemical energy was recovered simultaneously based on hydroxyl radical (HO·) and chlorine radical (Cl·) reaction in a novel TiO₂/WO₃ and 3D Cu nanowires modified Cu foam (CuNWs/CF) system. TiO₂/WO₃ heterojunction as photoanode provided rapid charge separation and good stability, and the composite of poly-Si enhanced the light harvest and charge transfer. HO· played critical role in degrading organic amines, while Cl· was responsible for selectively oxidizing amine group or NH₄⁺ to N₂. Besides, trace amount of NO₂^- and NO₃^- formed by over-oxidation was eliminated on CuNWs/CF cathode due to large specific surface area and fast charge transfer. Moderate Cl^- concentration and initial pH had vital influence on strengthening Cl· and HO· generation in the system, and the optimal conditions were 50 mM NaCl and pH = 7. For methylamine, ethylamine and dimethylamine wastewater, the system showed total nitrogen removal efficiency of 94.93%, 91.81%, 93.10% and total organic carbon removal of 58.47%, 53.57%, and 56.71% within 2 h, respectively. Moreover, the corresponding maximum power densities of 2.49, 2.40, 2.27 mW cm^-2 were also generated, respectively. The study proposes an efficient, sustainable method for the treatment of hazardous organic amine wastewater and simultaneous energy recovery.

Nano- and Microscale Optical and Electrical Biointerfaces and Their Relevance to Energy Research

Different research fields in energy sciences, such as photovoltaics for solar energy conversion, supercapacitors for energy storage, electrocatalysis for clean energy conversion technologies, and materials-bacterial hybrid for CO₂ fixation have been under intense investigations over the past decade. In recent years, new platforms for biointerface designs have emerged from the energy conversion and storage principles. This paper reviews recent advances in nano- and microscale materials/devices for optical and electrical biointerfaces. First, a connection is drawn between biointerfaces and energy science, and how these two distinct research fields can be connected is summarized. Then, a brief overview of current available tools for biointerface studies is presented. Third, three representative biointerfaces are reviewed, including neural, cardiac, and bacterial biointerfaces, to show how to apply these tools and principles to biointerface design and research. Finally, two possible future research directions for nano- and microscale biointerfaces are proposed.

Carbon-Based Composites as Anodes for Microbial Fuel Cells: Recent Advances and Challenges

Owing to the low price, chemical stability and good conductivity, carbon-based materials have been extensively applied as the anode in microbial fuel cells (MFCs). In this review, apart from the charge storage mechanism and anode requirements, the major work focuses on five categories of carbon-based anode materials (traditional carbon, porous carbon, nano-carbon, metal/carbon composite and polymer/carbon composite). The relationship is demonstrated in depth between the physicochemical properties of the anode surface/interface/bulk (porosity, surface area, hydrophilicity, partical size, charge, roughness, etc.) and the bioelectrochemical performances (electron transfer, electrolyte diffusion, capacitance, toxicity, start-up time, current, power density, voltage, etc.). An outlook for future work is also proposed.

Outlook on the Role of Microbial Fuel Cells in Remediation of Environmental Pollutants with Electricity Generation

A wide variety of pollutants are discharged into water bodies like lakes, rivers, canal, etc. due to the growing world population, industrial development, depletion of water resources, improper disposal of agricultural and native wastes. Water pollution is becoming a severe problem for the whole world from small villages to big cities. The toxic metals and organic dyes pollutants are considered as significant contaminants that cause severe hazards to human beings and aquatic life. The microbial fuel cell (MFC) is the most promising, eco-friendly, and emerging technique. In this technique, microorganisms play an important role in bioremediation of water pollutants simultaneously generating an electric current. In this review, a new approach based on microbial fuel cells for bioremediation of organic dyes and toxic metals has been summarized. This technique offers an alternative with great potential in the field of wastewater treatment. Finally, their applications are discussed to explore the research gaps for future research direction. From a literature survey of more than 170 recent papers, it is evident that MFCs have demonstrated outstanding removal capabilities for various pollutants.

Tunable Control of the Hydrophilicity and Wettability of Conjugated Polymers by a Postpolymerization Modification Approach

A facile method to prepare hydrophilic polymers by a postpolymerization nucleophillic aromatic substitution reaction of fluoride on an emissive conjugated polymer (CP) backbone is reported. Quantitative functionalization by a series of monofunctionalized ethylene glycol oligomers, from dimer to hexamer, as well as with high molecular weight polyethylene glycol is demonstrated. The length of the ethylene glycol sidechains is shown to have a direct impact on the surface wettability of the polymer, as well as its solubility in polar solvents. However, the energetics and band gap of the CPs remain essentially constant. This method therefore allows an easy way to modulate the wettability and solubility of CP materials for a diverse series of applications.

Application of advanced anodes in microbial fuel cells for power generation: A review

Microbial fuel cells (MFCs) the most extensively described bioelectrochemical systems (BES), have been made remarkable progress in the past few decades. Although the energy and environment benefits of MFCs have been recognized in bioconversion process, there are still several challenges for practical applications on large-scale, particularly for relatively low power output by high ohmic resistance and long period of start-up time. Anodes serving as an attachment carrier of microorganisms plays a vital role on bioelectricity production and extracellular electron transfer (EET) between the electroactive bacteria (EAB) and solid electrode surface in MFCs. Therefore, there has been a surge of interest in developing advanced anodes to enhance electrode electrical properties of MFCs. In this review, different properties of advanced materials for decorating anode have been comprehensively elucidated regarding to the principle of well-designed electrode, power output and electrochemical properties. In particular, the mechanism of these materials to enhance bioelectricity generation and the synergistic action between the EAB and solid electrode were clarified in detail. Furthermore, development of next generation anode materials and the potential modification methods were also prospected.

Vertical alignment of polyaniline nanofibers on electrode surface for high-performance microbial fuel cells

Electrode modifications with conductive and nanostructured polyaniline (PANI) were recognized as efficient approach to improve interaction between electrode surface and electrogenic bacteria for boosting the performance of microbial fuel cell (MFC). However, it still showed undesirable performance because of the challenge to control the orientation (such as vertical alignment) of PANI nanostructure for extracellular electron transfer (EET). In this work, vertically aligned polyaniline (VA-PANI) on carbon cloth electrode surface were prepared by in-situ polymerization method (simply tuning the ratio of tartaric acid (TA) dopant). Impressively, the VA-PANI greatly improved the EET due to the increased opportunity to connect with conductive proteins. Eventually, MFC equipped with the VA-PANI electrodes delivered a power output of 853 mW/m², which greatly outperformed those electrodes modified with un-oriented PANI. This work provided the possibility to control the orientation of PANI for EET and promise to harvest energy from wastewater with MFC.

A 3D porous NCNT sponge anode modified with chitosan and Polyaniline for high-performance microbial fuel cell

A microbial fuel cell (MFC) is a potential bio-electrochemical technology that utilizes microorganisms to convert chemical energy into electrical energy. The low power output of MFCs remain the bottleneck for their practical applications. In this paper, a novel, biocompatible and bioelectrocatalytic composite chitosan-nitrogen doped carbon nanotubes-polyaniline (CS-NCNT-PANI) was prepared in situ on the 3D porous NCNT/sponge and applied to an MFC anode. The PANI was grafted on the CS-NCNT backbone to synthesize the ternary composite. This bioanode not only increased the active surface area and capacity but also facilitated bacterial adhesion and enrichment of microbes. Compared with the NCNT/sponge electrode, the charge transfer impedance of the ternary composite bioanode decreased from 14.07 Ω to 2.25 Ω, and the maximum power density increased from 1.4 W·m^-3 to 4.2 W·m^-3; meanwhile, during the chronoamperometric experiment with a charge-discharge time of 60-60 min, the cumulative charge of the composite bioanode was 18,865.8 C·m^-2, which is much higher than that of the NCNT/S anode (3625.3 C·m^-2). High-throughput sequencing technology revealed that the ternary composite bioanode had good biocompatibility and high diversity. Therefore, this synthesized ternary composite is a promising candidate as a capacitive and biocompatible anode material in MFC.

Tungsten oxide as electrocatalyst for improved power generation and wastewater treatment in microbial fuel cell

Microbial fuel cell (MFC) is a device that oxidizes the organic matter present in wastewater and simultaneously generates electricity from it. For practical applications, the power production of MFCs needs to be enhanced and the use of novel anode and cathode catalyst can certainly help in this regard. Such a novel catalyst, WO₃, was explored as both anode and cathode catalyst in this study. Performance of MFCs was enhanced when WO₃ was used as an electrocatalyst. The maximum power density of MFC was increased by five times when WO₃ was used as anode catalyst and by four times when it was used as cathode catalyst as compared to control MFC using electrode without any catalyst. Almost six times increment in maximum power production of MFC was observed when WO₃ was used as catalyst on both the electrodes. Electrochemical analysis of WO₃ also proved that it could enhance the current density of the modified electrode owing to its electrochemical catalytic properties. Furthermore, chemical oxygen demand (COD) removal of MFC having WO₃ coated electrodes was also observed to be higher, thus suggesting an overall enhancement in the performance of MFC by the use of WO₃ as an electrocatalyst.

Molybdenum anode: a novel electrode for enhanced power generation in microbial fuel cells, identified via extensive screening of metal electrodes

BACKGROUND

Metals are considered a suitable anode material for microbial fuel cells (MFCs) because of their high electrical conductivity. However, only a few types of metals have been used as anodes, and an extensive screening of metals has not yet been conducted. In this study, to develop a new metal anode for increased electricity generation in MFCs, 14 different metals (Al, Ti, Fe, Ni, Cu, Zn, Zr, Nb, Mo, Ag, In, Sn, Ta, and W) and 31 of their oxidized forms were comprehensively tested. Oxidized-metal anodes were prepared using flame oxidation, heat treatment, and electrochemical oxidation. The selected anodes were further evaluated in detail using air-cathode single-chambered MFCs.

RESULTS

The untreated Mo and electrochemically oxidized Mo anodes showed high averages of maximum power densities in the screening test, followed by flame-oxidized (FO) W, FO-Fe, FO-Mo, and Sn-based anodes. The untreated Mo and FO-W anodes were selected for further evaluation. X-ray analyses revealed that the surface of the Mo anode was naturally oxidized in the presence of air, forming a layer of MoO₃, a known oxidation catalyst. A high maximum power density (1296 mW/m²) was achieved using the Mo anode in the MFCs, which was superior to that obtained using the FO-W anode (1036 mW/m²). The Mo anode, but not the FO-W anode, continued to produce current without detectable corrosion until the end of operation (350 days). Geobacter was abundant in both biofilms on the Mo and FO-W anodes, as analyzed by high-throughput sequencing of the 16S rRNA gene.

CONCLUSIONS

The screening test revealed that Mo, W, Fe, and Sn are useful MFC anode materials. The detailed analyses demonstrated that the Mo anode is a high-performance electrode with structural simplicity and long-term stability in MFCs. The anode can be easily prepared by merely shaping Mo materials to the desired forms. These properties would enable the large-scale preparation of the anode, required for practical MFC applications. This study also implies the potential involvement of Geobacter in the Mo and W cycles on Earth.

The catalytic effect of TiO2 nanosheets on extracellular electron transfer of Shewanella loihica PV-4

Electron transfer kinetics of Shewanella loihica PV-4 at the up-growing TiO₂ nanosheet (TiO₂-NS) modified carbon paper (CP) electrode was investigated. The effect of TiO₂-NSs, which speeds up the interfacial electron transfer of outer membrane c-type cytochromes (OMCs), was revealed for the first time. TiO₂-NSs with a polar surface modified hydrophobic CP into super-hydrophilic TiO₂-NS/CP. The favorable interaction between PV-4 and TiO₂-NSs not only enhanced microbial adhesion, but also altered the redox nature of OMCs. The mid-point potential of OMCs at TiO₂-NS/CP was shifted to a more negative potential, indicating a higher thermodynamic driving force for the protein to release electrons. Moreover, electron transfer from OMCs to TiO₂-NSs was also benefited from the positive shift of flat-band potential V_fb owing to reduced pH at the electrode/microorganism interface, as well as good electrical conductivity of TiO₂-NSs. As a result, the electron transfer rate constant k_et of OMCs at the TiO₂-NS/CP anode was about three times faster than that at the CP anode. The accelerated electron transfer kinetics as well as 15% increase of biomass together accounted for a 97% increase of the maximum output power density in the MFC. The result expanded our knowledge about the role of a designed TiO₂ nanostructure in microbial electron transfer that can be applied in other bio-electrochemical systems.

Porous Ni0.1Mn0.9O1.45 microellipsoids as high-performance anode electrocatalyst for microbial fuel cells

A novel bi-component composite of porous self-assembled micro-/nanostructured Ni_0.1Mn_0.9O_1.45 microellipsoids as high-performance anode electrocatalyst for microbial fuel cells (MFCs) is successfully synthesized via a simple coprecipitation reaction in microemulsion and calcination method in air atmosphere. The morphology and structural characterization indicate that the as-fabricated Ni_0.1Mn_0.9O_1.45 product is consist of Mn₂O₃ and NiMn₂O₄ (n(Mn₂O₃₎: n(NiMn₂O₄) = 0.35: 0.1) and has a porous microellipsoidal morphology. The microellipsoids are compose of numerous layered micro-/nanostructured blocks and the special porous microellipsoids structure of Ni_0.1Mn_0.9O_1.45 offers a large specific surface area for bacteria adhesion. The porous Ni_0.1Mn_0.9O_1.45 microellipsoids as anode electrocatalyst for MFCs exhibits excellent electrocatalytic activity to promote the extracellular electron transfer (EET) between the anode and bacteria, hence improves the performance of MFC. The MFC equipped with Ni_0.1Mn_0.9O_1.45/CF anode achieves a maximum power density of 1.39 ± 0.02Wm^-2, is significantly higher than that of commercial carbon felt anode. This work proposes a new method for the synthesis of high-performance and environmentally friendly anode electrocatalyst for MFCs.

Dye removal of AR27 with enhanced degradation and power generation in a microbial fuel cell using bioanode of treated clinoptilolite-modified graphite felt

This work studied the performance of a laboratory-scale microbial fuel cell (MFC) using a bioanode that consisted of treated clinoptilolite fine powder coated onto graphite felt (TC-MGF). The results were compared with another similar MFC that used a bare graphite felt (BGF) bioanode. The anode surfaces provided active sites for the adhesion of the bacterial consortium (NAR-2) and the biodegradation of mono azo dye C.I. Acid Red 27. As a result, bioelectricity was generated in both MFCs. A 98% decolourisation rate was achieved using the TC-MGF bioanode under a fed-batch operation mode. Maximum power densities for BGF and TC-MGF bioanodes were 458.8 ± 5.0 and 940.3 ± 4.2 mW m^-2, respectively. GC-MS analyses showed that the dye was readily degraded in the presence of the TC-MGF bioanode. The MFC using the TC-MGF bioanode showed a stable biofilm with no biomass leached out for more than 300 h operation. In general, MFC performance was substantially improved by the fabricated TC-MGF bioanode. It was also found that the TC-MGF bioanode with the stable biofilm presented the nature of exopolysaccharide (EPS) structure, which is suitable for the biodegradation of the azo dye. In fact, the EPS facilitated the shuttling of electrons to the bioanode for the generation of bioelectricity.

Single chamber microbial fuel cell (SCMFC) with a cathodic microalgal biofilm: A preliminary assessment of the generation of bioelectricity and biodegradation of real dye textile wastewater

An air exposed single-chamber microbial fuel cell (SCMFC) using microalgal biocathodes was designed. The reactors were tested for the simultaneous biodegradation of real dye textile wastewater (RTW) and the generation of bioelectricity. The results of digital image processing revealed a maximum coverage area on the biocathodes by microalgal cells of 42%. The atmospheric and diffused CO₂ could enable good algal growth and its immobilized operation on the cathode electrode. The biocathode-SCMFCs outperformed an open circuit voltage (OCV), which was 18%-43% higher than the control. Furthermore, the maximum volumetric power density achieved was 123.2 ± 27.5 mW m^-3. The system was suitable for the treatment of RTW and the removal/decrease of COD, colour and heavy metals. High removal efficiencies were observed in the SCMFCs for Zn (98%) and COD (92-98%), but the removal efficiencies were considerably lower for Cr (54-80%). We observed that this single chamber MFC simplifies a double chamber system. The bioelectrochemical performance was relatively low, but the treatment capacity of the system seems encouraging in contrast to previous studies. A proof-of-concept experiment demonstrated that the microalgal biocathode could operate in air exposed conditions, seems to be a promising alternative to a Pt cathode and is an efficient and cost-effective approach to improve the performance of single chamber MFCs.

Carbon-Based Microbial-Fuel-Cell Electrodes: From Conductive Supports to Active Catalysts

Microbial fuel cells (MFCs) have attracted considerable interest due to their potential in renewable electrical power generation using the broad diversity of biomass and organic substrates. However, the difficulties in achieving high power densities and commercially affordable electrode materials have limited their industrial applications to date. Carbon materials, which can exhibit a wide range of different morphologies and structures, usually possess physiological activity to interact with microorganisms and are therefore fast-emerging electrode materials. As the anode, carbon materials can significantly promote interfacial microbial colonization and accelerate the formation of extracellular biofilms, which eventually promotes the electrical power density by providing a conductive microenvironment for extracellular electron transfer. As the cathode, carbon-based materials can function as catalysts for the oxygen-reduction reaction, showing satisfying activities and efficiencies nowadays even reaching the performance of Pt catalysts. Here, first, recent advancements on the design of carbon materials for anodes in MFCs are summarized, and the influence of structure and surface functionalization of different types of carbon materials on microorganism immobilization and electrochemical performance is elucidated. Then, synthetic strategies and structures of typical carbon-based cathodes in MFCs are briefly presented. Furthermore, future applications of carbon-electrode-based MFC devices in the energy, environmental, and biological fields are discussed, and the emerging challenges in transferring them from laboratory to industrial scale are described.

Engineering of Microbial Electrodes

This chapter provides an overview of the current state-of-the-art in the engineering of microbial electrodes for application in microbial electrosynthesis. First, important functional aspects and requirements of basic materials for microbial electrodes are introduced, including the meaningful benchmarking of electrode performance, a comparison of electrode materials, and methods to improve microbe-electrode interaction. Suitable current collectors and composite materials that combine different functionalities are also discussed. Subsequently, the chapter focuses on the design of macroscopic electrode structures. Aspects such as mass transfer and electrode topology are touched upon, and a comparison of the performance of microbial electrodes relevant for practical application is provided. The chapter closes with an overall conclusion and outlook, highlighting the future prospects and challenges for the engineering of microbial electrodes toward practical application in the field of microbial electrosynthesis. Graphical Abstract.

Preparation of conductive microfiltration membrane and its performance in a coupled configuration of membrane bioreactor with microbial fuel cell

A conductive flat microfiltration membrane with graphene (G-FM) was prepared with polyvinylidene fluoride (PVDF) and reduced graphene oxide (RGO) on stainless steel mesh base by the method of immersion-precipitation phase transformation.

Applications of Graphene-Modified Electrodes in Microbial Fuel Cells

Graphene-modified materials have captured increasing attention for energy applications due to their superior physical and chemical properties, which can significantly enhance the electricity generation performance of microbial fuel cells (MFC). In this review, several typical synthesis methods of graphene-modified electrodes, such as graphite oxide reduction methods, self-assembly methods, and chemical vapor deposition, are summarized. According to the different functions of the graphene-modified materials in the MFC anode and cathode chambers, a series of design concepts for MFC electrodes are assembled, e.g., enhancing the biocompatibility and improving the extracellular electron transfer efficiency for anode electrodes and increasing the active sites and strengthening the reduction pathway for cathode electrodes. In spite of the challenges of MFC electrodes, graphene-modified electrodes are promising for MFC development to address the reduction in efficiency brought about by organic waste by converting it into electrical energy.

A monolithic three-dimensional macroporous graphene anode with low cost for high performance microbial fuel cells

Monolithic 3D-G which is inflexible and has a macroporous structure, crumpled matrix, good conductivity and low cost enhanced the electrogenesis of a MFC.

Bifunctional Manganese Ferrite/Polyaniline Hybrid as Electrode Material for Enhanced Energy Recovery in Microbial Fuel Cell

Microbial fuel cells (MFCs) are emerging as a sustainable technology for waste to energy conversion where electrode materials play a vital role on its performance. Platinum (Pt) is the most common material used as cathode catalyst in the MFCs. However, the high cost and low earth abundance associated with Pt prompt the researcher to explore inexpensive catalysts. The present study demonstrates a noble metal-free MFC using a manganese ferrite (MnFe2O4)/polyaniline (PANI)-based electrode material. The MnFe2O4 nanoparticles (NPs) and MnFe2O4 NPs/PANI hybrid composite not only exhibited superior oxygen reduction reaction (ORR) activity for the air cathode but also enhanced anode half-cell potential upon modifying carbon cloth anode in the single-chambered MFC. This is attributed to the improved extracellular electron transfer of exoelectrogens due to Fe(3+) in MnFe2O4 and its capacitive nature. The present work demonstrates for the first time the dual property of MnFe2O4 NPs/PANI, i.e., as cathode catalyst and an anode modifier, thereby promising cost-effective MFCs for practical applications.

Enhancement of power production with tartaric acid doped polyaniline nanowire network modified anode in microbial fuel cells

The feasibility to use tartaric acid doped PANI for MFC anode modification was determined. Uniform PANI nanowires doped with tartaric acid were synthesized and formed mesoporous networks on the carbon cloth surface. By using this tartaric acid doped PANI modified carbon cloth (PANI-TA) as the anode, the voltage output (435 ± 15 mV) and power output (490 ± 12 mW/m(2)) of MFC were enhanced by 1.6 times and 4.1 times compared to that of MFC with plain carbon cloth anode, respectively. Strikingly, the performance of PANI-TA MFC was superior to that of the MFCs with inorganic acids doped PNAI modified anode. These results substantiated that tartaric acid is a promising PANI dopant for MFC anode modification, and provided new opportunity for MFC performance improvement.

All ecosystems potentially host electrogenic bacteria

Instead of requiring metal catalysts, MFCs utilize bacteria that oxidize organic matter and either transfer electrons to the anode or take electrons from the cathode. These devices are thus based on a wide microbial diversity that can convert a large array of organic matter components into sustainable and renewable energy. A wide variety of explored environments were found to host electrogenic bacteria, including extreme environments. In the present review, we describe how different ecosystems host electrogenic bacteria, as well as the physicochemical, electrochemical and biological parameters that control the currents from MFCs. We also report how using new molecular techniques allowed characterization of electrochemical biofilms and identification of potentially new electrogenic species. Finally we discuss these findings in the context of future research directions.

Holey tungsten oxynitride nanowires: novel anodes efficiently integrate microbial chemical energy conversion and electrochemical energy storage

Holey tungsten oxynitride nanowires with superior conductivity, good biocompatibility, and good stability achieve excellent performance as anodes for both asymmetric supercapacitors and microbial fuel cells. Moreover, an innovative system is devised based on these as-prepared tungsten oxynitride anodes, which can simultaneously realize both energy conversion from chemical to electric energy and its storage.

A Systematic Study of the Catalytic Behavior at Enzyme–Metal-Oxide Nanointerfaces

Metal-oxide nanoparticles with high surface area, controllable functionality and thermal and mechanical stability provide high affinity for enzymes when the next generation of biosensor applications are being considered. We report on the synthesis of metal-oxide-based nanoparticles (with different physical and chemical properties) using hydrothermal processing, photo-deposition and silane functionalization. Physical and chemical properties of the user-synthesized nanoparticles were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Raman scattering, respectively. Thus, characterized metal-oxide-based nanoparticles served as nanosupports for the immobilization of soybean peroxidase enzyme (a model enzyme) through physical binding. The enzyme–nanosupport interface was evaluated to assess the optimum nanosupport characteristics that preserve enzyme functionality and its catalytic behavior. Our results showed that both the nanosupport geometry and its charge influence the functionality and catalytic behavior of the bio-metal-oxide hybrid system.