Search

A biocathode microbial electrolysis cell (MEC) can be considered as an environmentally friendly and self-generative alternative to an abiocathode MEC for the cleaner production of hydrogen in a novel microbial electrolysis system. For the first time, this research focused on the development of the MEC biocathode out of sulphate-reducing bacteria (SRB) for the purpose of hydrogen production based on the previously proposed hypothesis. SRB were initially enriched from a mixed culture source during the ex-situ SRB enrichment stage. Two different MEC bioathodes- namely, the MEC origin (MEC-O) biocathode and the microbial fuel cell-MEC (MFC-MEC) biocathode- were then developed through two different enrichment procedures during the in-situ SRB enrichment stage. Hydrogen gas was the main product of the MEC-O biocathode with a low detection of methane, while methane was detected as the sole product of the MFC-MEC biocathode system. Therefore, the MEC-O biocathode system was selected during the enhancement stage to increase the biocathode MEC performance. It was shown in the study, that in the enhancement stage of the MEC-O biocathode, the concentration of sodium sulphate in the cathodic medium, the hydrogen supply during the enrichment stage and pH of the cathodic medium could significantly affect the MEC performance in terms of the hydrogen production rate, the onset potential for the hydrogen evolution reaction (HER) and the cathodic charge transfer resistance. The hydrogen production was improved significantly by about 6 times from 0.31 to 1.85 m 3 H 2 /(m 3 d) during the enhancement stage, while the methane production was totally hindered. The linear sweep voltammetry analysis displayed a 430-mV (equal to about 1 kWh/m 3 of energy input) reduction of the HER onset potential in the biocathode system compared to that of a non-inoculated graphite felt cathode. Moreover, the electrochemical impedance spectroscopy showed that the cathodic charge transfer resistance of the MEC biocathode reduced by 300 times compared to that of a non-inoculated graphite felt cathode. [ABSTRACT FROM AUTHOR]

SUMMARY Polyaniline (Pani), vanadium oxide (V2O5), and Pani/V2O5 nanocomposite were fabricated and applied as a cathode catalyst in Microbial Fuel Cell (MFC) as an alternative to Pt (Platinum), which is a commonly used expensive cathode catalyst. The cathode catalysts were characterized using Cyclic Voltammetry and Linear Sweep Voltammetry to determine their oxygen reduction activity; furthermore, their structures were observed by X-ray Diffraction, X-ray Photoelectron Spectroscopy, Brunauer-Emmett-Teller, and Field-Emission Scanning Electron Microscopy. The results showed that Pani/V2O5 produced a power density of 79.26 mW/m2, which is higher than V2O5 by 65.31 mW/m2 and Pani by 42.4 mW/m2. Furthermore, the Coulombic Efficiency of the system using Pani/V2O5 (16%) was higher than V2O5 and Pani by 9.2 and 5.5%, respectively. Pani-V2O5 also produced approximately 10% more power than Pt, the best and most common cathode catalyst. It declares that Pani-V2O5 can be a suitable alternative for application in a MFC system. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: In this study, four different catalysts (i.e., carbon black, nickel nanoparticle (Ni)/C, Phthalocyanine/C and copper-phthalocyanine/C), were tested in a two-chamber Microbial Fuel Cell (MFC) and their performances were compared with Pt as the common cathode catalyst in MFC. The characterization of catalysts was done by TEM, XPS and EDX and their electrochemical characteristics were compared by cyclic voltammetry (CV) and Linear Sweep Voltammetry (LSV). The results proved that copper phthalocyanine and nickel nanoparticles are potential alternatives catalyst for Pt. Even copper-phthalocyanine generated power is almost the same as Pt. The CV and LSV results reported high electrochemical activity of these catalysts. The maximum power density and coulombic efficiency was achieved by copper-phthalocyanine/C as 118.2 mW/m2 and 29.3%. [Copyright &y& Elsevier]

Abstract: Proton exchange membrane fuel cells (PEMFC) comprise a diverse range of fuel cell thought to have future commercial application and transportation. The introduction of nitrogen into carbon nanostructures has created new pathways for the development of non-noble metal electro-catalysts in fuel cells. This review provides insight into the role of nitrogen inclusion into the carbon nanotubes (CNT) and the possible mechanisms involved in oxygen reduction reaction (ORR) activity. The doping effects of nitrogen into CNT on the surface morphology, electronic structures and electrochemical activity are discussed. Catalyst nanoparticles distribution, chemical composition and the incorporation of a binder play crucial roles in the generation of good catalytic activity and high stability in organic electro-catalysts. Synthesize methods for making nitrogen-containing carbon nanostructures and the resultant oxygen reduction reactivity are compared. Finally, stability issues of the N-CNT electrocatalysts are discussed. [Copyright &y& Elsevier]

The cathode reaction is one of the most important limiting factors in bioelectrochemical systems even with precious metal catalysts. Since aerobic bacteria have a much higher affinity for oxygen than any known abiotic cathode catalysts, the performance of a microbial fuel cell can be improved through the use of electrochemically-active oxygen-reducing bacteria acting as the cathode catalyst. These consume electrons available from the electrode to reduce the electron acceptors present, probably conserving energy for growth. Anaerobic bacteria reduce protons to hydrogen in microbial electrolysis cells (MECs). These aerobic and anaerobic bacterial activities resemble those catalyzing microbially-influenced corrosion (MIC). Sulfate-reducing bacteria and homoacetogens have been identified in MEC biocathodes. For sustainable operation, microbes in a biocathode should conserve energy during such electron-consuming reactions probably by similar mechanisms as those occurring in MIC. A novel hypothesis is proposed here which explains how energy can be conserved by microbes in MEC biocathodes. [ABSTRACT FROM AUTHOR]

Abstract: In this investigation, water in a single-cell proton exchange membrane (PEM) fuel cell was managed using saturated hydrogen and dry air. The experiment was conducted at temperatures of 40, 50 and 60 °C and pressures of 1 and 1.5 bar at both the anode and cathode gas inlets. The feed velocities of hydrogen and air were fixed at 3 and 6 L min−1, respectively. After reaching steady-state conditions, the relative humidity along the single serpentine gas channel was measured. From the experimental data, water transport properties were characterized based on a membrane hydration model. The electro-osmotic drag coefficient, water diffusion coefficient, membrane ionic conductivity and water back-diffusion flux were significantly influenced by the water content in the membrane of the PEM fuel cell. The water content depended on the relative humidity profile along the gas channel. In this investigation, a negative value for the water back-diffusion flux was measured; thus, the transport of water from the cathode to the anode did not occur. This phenomenon was due to the large water concentration gradient between the anode and cathode. Therefore, this strategy successfully prevented flooding in the PEM fuel cell. [Copyright &y& Elsevier]

• Catalytic properties of Ni-Fe and GF/Pt were characterized using LSV tests. • Tafel slope was determined based on the data points in the onset potential. • EGF can be used as substrate for hydrogen production. • Ni-Fe shows comparable performance with GF/Pt cathode in BES application. The high cost of Pt-based cathode, and its possibility of being poisoned by the presence of buffer in the electrolyte are two paramount issues in the BES system. The Ni-Fe has become one of the good alternatives because it has excellent catalytic properties, inexpensive, commercially available and low toxicity to microorganisms. In this study, Ni-Fe foam applied as a cathode in dual-chamber BES, while effluent of glucose fermentation as a substrate in the anode side. The characteristic of Ni-Fe surface was analyzed by using field emission scanning electron microscopy. Whereas, the catalytic property of Ni-Fe was evaluated by using linear sweep voltammetry test. The maximum hydrogen production rate and yield obtained were 500 ± 80 m3/m3/d and 470.2 ± 11.2 mL/g COD, respectively. The results show that the Ni-Fe has comparable performance to GF/Pt. Hence it could be used as an alternative cathode in BES application. [ABSTRACT FROM AUTHOR]

A novel nano-bio composite polypyrrole (PPy)/kappa-carrageenan(KC) was fabricated and characterized for application as a cathode catalyst in a microbial fuel cell (MFC). High resolution SEM and TEM verified the bud-like shape and uniform distribution of the PPy in the KC matrix. X-ray diffraction (XRD) has approved the amorphous structure of the PPy/KC as well. The PPy/KC nano-bio composites were then studied as an electrode material, due to their oxygen reduction reaction (ORR) ability as the cathode catalyst in the MFC and the results were compared with platinum (Pt) as the most common cathode catalyst. The produced power density of the PPy/KC was 72.1 mW/m 2 while it was 46.8 mW/m 2 and 28.8 mW/m 2 for KC and PPy individually. The efficiency of the PPy/KC electrode system is slightly lower than a Pt electrode (79.9 mW/m 2 ) but due to the high cost of Pt electrodes, the PPy/KC electrode system has potential to be an alternative electrode system for MFCs. [ABSTRACT FROM AUTHOR]

Abstract: Composites consisting of Ag–Y0.25Bi0.75O1.5 (YSB) were investigated as composite cathodes for intermediate-solid oxide fuel cells. A thin film of Ag–YSB composite cathode was fabricated by using slurry painting method. The slurry of Ag–YSB composite cathodes was used to coat anode-bilayered electrolytes (NiO–SDC/SDC/YSB) at room temperature. TGA and DSC results confirmed that all the organic components in the slurry were completely decomposed at temperatures below 600°C. XRD analysis revealed the formation of a pure Ag–YSB composite cathode phase. SEM images showed the grain size increment of the Ag–YSB powder that was ascribed to the consolidation between adjacent grains, which reduced the size of the porosity as the heat treatment temperature was increased. The electrochemical performances (interfacial polarization resistance, R p) were 0.483, 0.469, 0.416, and 0.441Ωcm2 after one, two, three, and four coatings, respectively. [Copyright &y& Elsevier]

Abstract: Microbial fuel cells (MFCs) hold great promise as an alternative for direct biochemical energy extraction from both biomass and wastewater. However, the commercialization and scaling-up of MFCs is not completely feasible, due to the high price of platinum (Pt) as a cathode catalyst. In this paper, we studied the use of a carbon nanotube (CNT) composite catalyst, to reduce the amount of Pt (without decline of efficiency) for moving towards the commercialization of MFCs. CNT/Pt composite electrodes would increase MFC power output by 8.7–32.2%; with respect to the pristine Pt as a catalyst for the cathode at a chemical oxygen demand (COD) substrate of 100mg/l and 2000mg/l, respectively. Moreover, the amount of Pt in the CNT/Pt electrode could be reduced by up to 25% of the amount necessary for a conventional Pt/carbon electrode. [Copyright &y& Elsevier]

Abstract: The cobalt-free perovskite-oxide, Ba0.5Sr0.5Fe0.8Cu0.2O3−δ (BSFC) is a very important cathode material for intermediate-temperature proton-conducting solid oxide fuel cells. Ba0.5Sr0.5Fe0.8Cu0.2O3−δ nanofibers were synthesized for the first time by a sol–gel electrospinning. Process wherein a combination of polyvinylpyrrolidone and acetic acid was used as the spinning aid and barium, strontium, iron and copper nitrates were used as precursors for the synthesis of BSFC nanofibers. X-ray diffraction studies on products prepared at different calcination temperatures revealed a cubic perovskite structure at 900°C. The temperature of calcination has a direct effect on the crystallization and surface morphology of the nanofibers. High porosity, and surface area, in addition to an electrical conductivity of 69.54Scm−1 at 600°C demonstrate the capability of BSFC nanofibers to serve as effective cathode materials for intermediate-temperature solid oxide fuel cells. [Copyright &y& Elsevier]