Iron phthalocyanine supported on amino-functionalized multi-walled carbon nanotube as an alternative cathodic oxygen catalyst in microbial fuel cells

Influence of carbon-based cathodes on biofilm composition and electrochemical performance in soil microbial fuel cells

Increasing energy demands and environmental pollution concerns press for sustainable and environmentally friendly technologies. Soil microbial fuel cell (SMFC) technology has great potential for carbon-neutral bioenergy generation and self-powered electrochemical bioremediation. In this study, an in-depth assessment on the effect of several carbon-based cathode materials on the electrochemical performance of SMFCs is provided for the first time. An innovative carbon nanofibers electrode doped with Fe (CNFFe) is used as cathode material in membrane-less SMFCs, and the performance of the resulting device is compared with SMFCs implementing either Pt-doped carbon cloth (PtC), carbon cloth, or graphite felt (GF) as the cathode. Electrochemical analyses are integrated with microbial analyses to assess the impact on both electrogenesis and microbial composition of the anodic and cathodic biofilm. The results show that CNFFe and PtC generate very stable performances, with a peak power density (with respect to the cathode geometric area) of 25.5 and 30.4 mW m^-2, respectively. The best electrochemical performance was obtained with GF, with a peak power density of 87.3 mW m^-2. Taxonomic profiling of the microbial communities revealed differences between anodic and cathodic communities. The anodes were predominantly enriched with Geobacter and Pseudomonas species, while cathodic communities were dominated by hydrogen-producing and hydrogenotrophic bacteria, indicating H₂ cycling as a possible electron transfer mechanism. The presence of nitrate-reducing bacteria, combined with the results of cyclic voltammograms, suggests microbial nitrate reduction occurred on GF cathodes. The results of this study can contribute to the development of effective SMFC design strategies for field implementation.

Applications of Nanomaterials in Microbial Fuel Cells: A Review

Microbial fuel cells (MFCs) are an environmentally friendly technology and a source of renewable energy. It is used to generate electrical energy from organic waste using bacteria, which is an effective technology in wastewater treatment. The anode and the cathode electrodes and proton exchange membranes (PEM) are important components affecting the performance and operation of MFC. Conventional materials used in the manufacture of electrodes and membranes are insufficient to improve the efficiency of MFC. The use of nanomaterials in the manufacture of the anode had a prominent effect in improving the performance in terms of increasing the surface area, increasing the transfer of electrons from the anode to the cathode, biocompatibility, and biofilm formation and improving the oxidation reactions of organic waste using bacteria. The use of nanomaterials in the manufacture of the cathode also showed the improvement of cathode reactions or oxygen reduction reactions (ORR). The PEM has a prominent role in separating the anode and the cathode in the MFC, transferring protons from the anode chamber to the cathode chamber while preventing the transfer of oxygen. Nanomaterials have been used in the manufacture of membrane components, which led to improving the chemical and physical properties of the membranes and increasing the transfer rates of protons, thus improving the performance and efficiency of MFC in generating electrical energy and improving wastewater treatment.

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.

Carbon supports on preparing iron-nitrogen dual-doped carbon (Fe-N/C) electrocatalysts for microbial fuel cells: mini-review

Microbial fuel cells (MFCs) are devices that treat sewage and generate electricity. Recent researches have demonstrated that the characteristics of carbon precursors can tremendously influence the performance of the MFC cathode. Carbon nanomaterials with good crystallinity as well as high specific surface area (e.x., graphene and carbon nanotube) can not only accelerate charge transport but also afford a good dispersion of catalytic active components, leading to high MFC performance. On these bases, the preparation of highly-active Fe-N/C catalysts using different carbon substrates are mainly discussed in this review. It is pointed out that increasing the surface area and conductivity as well as elevating the density of active sites to reduce the oxygen reduction overpotential is still the emphasis of the current works. At present, although the researchers have made some progress, the output power density is far from meeting the actual application needs.

Multi-walled carbon nanotube and carbide-derived carbon supported metal phthalocyanines as cathode catalysts for microbial fuel cell applications

Metal phthalocyanine (CoPc and FePc) modified MWCNT or CDC materials were explored as superior cathode catalysts for MFC technology.

Effects of Fe, Ni, and Fe/Ni metallic nanoparticles on power production and biosurfactant production from used vegetable oil in the anode chamber of a microbial fuel cell

In this study, metallic nanoparticles (Fe, Ni, and Fe/Ni) were used as cathode catalysts to enhance power production and to improve the anode performance of a two-chambered microbial fuel cell (MFC). The metallic nanoparticles were rod-shaped and produced by the precipitation/co-precipitation method. A biosurfactant was produced in the anode chamber of the MFC from used vegetable oil by the bacteria Serratia sp. Overall cell voltage, power density, bacterial growth, and biosurfactant production were studied by applying different types of metallic nanoparticles to the cathode electrode. The influence of various types of nanoparticles on the impedance of the MFC was also investigated by electrochemical impedance spectroscopy (EIS), including analyses of anode impedance, cathode impedance, anode solution resistance, cathode solution resistance, and membrane resistance. The nanoparticles improved MFC performance in the following order: Fe>Ni>Fe/Ni. The addition of 1.5mg/cm² Fe nanoparticles to the cathode surface enhanced power production by over 500% to 66.4mW/m³, promoted bacterial growth and biosurfactant production in the anode solution by 132.5% and 32.0%, respectively, and reduced anode impedance, cathode impedance, and membrane resistance by 26.8%, 81.6%, and 33.8% to 159.00Ω, 7.69Ω, and 261.09Ω, respectively. For the first time, biosurfacant production in the anode chamber of the MFC was promoted by using the metallic nanoparticles as cathode catalysts. By improving the cathode properties, this study showed a new way to manipulated the performance of the anode chamber of the MFC.

Nitrogen-doped porous activated carbon derived from cocoon silk as a highly efficient metal-free electrocatalyst for the oxygen reduction reaction

Nitrogen-doped porous activated carbon (PAC) has been fabricated via a facile heat-treatment and chemical activation of cocoon silk. The prepared PAC exhibits excellent ORR catalytic activity.

Enhanced bioelectricity generation of double-chamber air-cathode catalyst free microbial fuel cells with the addition of non-consumptive vanadium(v)

Improvement of microbial fuel cells (MFCs) via bioelectricity recovery is urgently needed in micro-energy devices nowadays.

A review on protein functionalized carbon nanotubes

Carbon nanotubes (CNTs) have been widely recognized and used for controlled drug delivery and in various other fields due to their unique properties and distinct advantages. Both single-walled carbon nanotubes (SWCNTs) and multiwalled (MWCNTs) carbon nanotubes are used and/or studied for potential applications in medical, energy, textile, composite, and other areas. Since CNTs are chemically inert and are insoluble in water or other organic solvents, they are functionalized or modified to carry payloads or interact with biological molecules. CNTs have been preferably functionalized with proteins because CNTs are predominantly used for medical applications such as delivery of drugs, DNA and genes, and also for biosensing. Extensive studies have been conducted to understand the interactions, cytotoxicity, and potential applications of protein functionalized CNTs but contradicting results have been published on the cytotoxicity of the functionalized CNTs. This paper provides a brief review of CNTs functionalized with proteins, methods used to functionalize the CNTs, and their potential applications.

Embedded cobalt oxide nano particles on carbon could potentially improve oxygen reduction activity of cobalt phthalocyanine and its application in microbial fuel cells

The increasing cost of precious metals, especially platinum, as oxygen reduction catalysts has hindered their widespread use in microbial fuel cells (MFCs).

Solar-assisted dual chamber microbial fuel cell with a CuInS2photocathode

A solar-assisted microbial fuel cell (MFC) was prepared with flower-like CuInS₂(CIS) as the photocathode. CIS with flower flakes and monodispersity could be beneficial to electron transfer under irradiation. The solar MFC achieved a maximum power density of 0.108 mW cm⁻²and a current density of 0.62 mA cm⁻².

Sewage sludge biochar as an efficient catalyst for oxygen reduction reaction in an microbial fuel cell

Sewage sludge (SS) biochars have been prepared under an inert atmosphere at different temperatures. Morphologic and chemical analyses reveal that the surface of the biochar carbonized at 900°C (SS900) has more abundant micropores, and higher nitrogen and iron contents as compared to those carbonized at 500 (SS500) and 700°C (SS700). The electrochemical analyses display that the prepared biochars are active for catalyzing oxygen reduction reaction (ORR). However, more positive peak potential and larger peak current of ORR are found using the SS900 as compared to the SS500 and SS700. In MFCs, the maximum power density of 500±17 mW m(-2) was obtained from the SS900 cathode, which is comparable to the Pt cathode. The proposed cathode exhibited good stability and great tolerance to methanol. Given these results, it is expected that the SS-derived biochar cathode can find application in fuel cell systems.

Electrospun carbon nanofibers from polyacrylonitrile blended with activated or graphitized carbonaceous materials for improving anodic bioelectrocatalysis

The electrospun carbon nanofibers obtained from polyacrylonitrile (PAN) and PAN blends with either activated carbon (PAN-AC) or graphite (PAN-GR) were tested as anodes using Shewanella oneidensis MR-1. Extensive physico-chemical and electrochemical characterization confirmed their formation, their fibrous and porous nature, and their suitability as electrodes. N2 adsorption measurements revealed high specific surface area (229.8, 415.8 and 485.2m(2) g(-1)) and porosity (0.142, 0.202 and 0.239cm(3)g(-1)) for PAN, PAN-AC and PAN-GR, respectively. The chronoamperometric measurements showed a considerable decrease in start-up time and more than a 10-fold increase in the generation of current with these electrodes (115, 139 and 155μAcm(-2) for PAN, PAN-AC and PAN-GR, respectively) compared to the graphite electrode (11.5μAcm(-2)). These results indicate that the bioelectrocatalysis benefits from the blending of PAN with activated or graphitized carbonaceous materials, presumably due to the increased specific surface area, total pore volume and modification of the carbon microstructure.

Metallophthalocyanine/carbon nanotube hybrids: extending applications to microbial fuel cells

Pioneering work by Nyokong and others have highlighted the potential benefits for improved electron transfer processes and catalysis of hybrid configurations of metallophthalocyanines with carbon nanotubes. Here we examine the practical application of such hybrid configurations in an Enterobacter cloacae microbial fuel cell. Electrochemical investigations at glassy carbon electrodes (GCEs) showed that FePc and FePc :multiwalled carbon nanotube (MWCNT) hybrid surface modifications display significant oxygen reduction reaction electrocatalytic properties compared to either MWCNT-modified or bare GCE surfaces throughout acidic- to moderately-alkaline pHs. Significant stabilization of the current response at FePc :MWCNT surfaces are notable throughout the pH range, compared to GCE surfaces modified with FePc alone. Corresponding results were obtained for surface modifications of bare carbon paper (BCP) cathodes in a microbial fuel cell where power density increases were observed in the order: Pt > FePc :MWCNT > FePc > MWCNT > BCP. A synergistic combination of simple treatments such as increased ionic strength (300 mM NaCl ), temperature (35 °C), and agitation of the anode chamber in this MFC configuration increased the power density to 2.5 times greater than that achieved at platinised cathode configurations under non-optimised conditions, achieving peak power densities of 212 mW.m-2. The long-term stability of the MFC was assessed over 55 days. Surprisingly, the majority of signal loss over extended MFC operation was attributed, in this study, to fouling of the Nafion® PEM membrane rather than either leaching/fouling of the catalysts from the electrodes or nutrient depletion in the anode over the time periods examined.

Electrochemical reduction of carbon dioxide in an MFC-MEC system with a layer-by-layer self-assembly carbon nanotube/cobalt phthalocyanine modified electrode

Electrochemical reduction of carbon dioxide (CO(2)) to useful chemical materials is of great significance to the virtuous cycle of CO(2). However, some problems such as high overpotential, high applied voltage, and high energy consumption exist in the course of the conventional electrochemical reduction process. This study presents a new CO(2) reduction technique for targeted production of formic acid in a microbial electrolysis cell (MEC) driven by a microbial fuel cell (MFC). The multiwalled carbon nanotubes (MWCNT) and cobalt tetra-amino phthalocyanine (CoTAPc) composite modified electrode was fabricated by the layer-by-layer (LBL) self-assembly technique. The new electrodes significantly decreased the overpotential of CO(2) reduction, and as cathode successfully reduced CO(2) to formic acid (production rate of up to 21.0 ± 0.2 mg·L(-1)·h(-1)) in an MEC driven by a single MFC. Compared with the electrode modified by CoTAPc alone, the MWCNT/CoTAPc composite modified electrode could increase the current and formic acid production rate by approximately 20% and 100%, respectively. The Faraday efficiency for formic acid production depended on the cathode potential. The MWCNT/CoTAPc composite electrode reached the maximum Faraday efficiency at the cathode potential of ca. -0.5 V vs Ag/AgCl. Increasing the number of electrode modification layers favored the current and formic acid production rate. The production of formic acid was stable in the MFC-MEC system after multiple batches of CO(2) electrolysis, and no significant change was observed on the performances of the modified electrode. The coupling of the catalytic electrode and the bioelectrochemical system realized the targeted reduction of CO(2) in the absence of external energy input, providing a new way for CO(2) capture and conversion.