The study of the performance of a microbial fuel cell: a progress towards the improvement of low electrical bioenergy output by using an amplification system.

OBJECTIVE: A microbial fuel cell (MFC) has been conceived and constructed for the treatment of the sheep manure wastes and their conversion into clean sustainable renewable energy. The aim of the present investigation was to examine the performance of this bioelectrochemical device, in breaking down the organic matter (pollutant removal) and simultaneously producing electricity. Furthermore, the objective was to enhance the low electric energy by using an adequate amplification system. RESULTS: So, the chemical oxygen demand (COD) removal was increased by 58.7% with the MFC running for 10 days. However, this technology faces practical barriers as it produces low electrical energy. A power management system was therefore elaborated in this respect. It included the MFC, operational amplifier (OA), solar photovoltaic panel and a boost DC/DC converter. The low voltage output obtained was thus increased substantially using the OA prior to its polarization by the solar photovoltaic module. The amplified voltage was sufficiently enough and in consequence, utilized to feed a light emitting diode. The low output voltage 0.5 V was simply harvested, successfully boosted up to approximately 2 V (i.e. 4 times higher) and finally harnessed as a power supply. CONCLUSIONS: The MFCs association shows the positive stacking effect successfully, when the cells were connected in parallel. This novel application is very interesting to utilize the natural bioenergy contained in wastes to supply small electronic devices.

Platinum nanoparticles embedded into polyaniline on carbon cloth: improvement of oxygen reduction at cathode of microbial fuel cell used for conversion of medicinal plant wastes into bio-energy.

A microbial fuel cell is a biological electrochemical system that extracts electrons stored in organic matter by oxidation using catalytic properties of microorganisms at bioanode. The major problem in such device, is however limited power production due to slow kinetic of oxygen reduction at cathode. It is worthwhile to develop new materials that fulfil these requirements. The polymerization of aniline onto carbon cloth for effective electrodeposition of platinum nanoparticles has been carried out by chronoamperometry and cyclic voltammetry. Three materials were thus elaborated, namely pristine carbon cloth, carbon cloth modified with platinum and carbon cloth modified by polymerization of aniline for immobilization of Pt-nanoparticles. The FTIR spectroscopy analysis revealed characteristic band located in 1720-1650 cm-1, attributed to imine function, main component in skeleton of polymer PANI chain. The modified materials have been utilized as cathode in cell inoculated with medicinal plant wastes for improvement of oxygen reduction. Modified cathode with CC-PANI-Pt proved higher performances in all respects: increase of cell voltage from 338 to 765 mV and power density from 862 to 1510 mW/m2 and abatement of COD of microbial inoculum leachate to 88%. Another feature of cell with modified cathode CC-PANI-Pt, was the enormous electric charge density harvested upon oxidation of 1 mL of acetate 7.62 C/cm2 compared to that of cell with pristine CC cathode 0.54 C/cm2. Nevertheless, coulombic efficiency for conversion of medicinal plant wastes into bioenergy was relatively lower 9%, making in evidence that elaborated electrochemical device was rather efficient and benificial environmentally than energetically.

Scratching and transplanting of electro-active biofilm in fruit peeling leachate by ultrasound: re-inoculation in new microbial fuel cell for enhancement of bio-energy production and organic matter detection.

OBJECTIVE: An electro-active biofilm of Fruit Peeling (FP) leachate was formed onto the Carbon Felt (CF) bio-anode in a Microbial Fuel Cell (MFC), after functioning for a long time. The electro active-biofilm thus formed was then scratched by ultrasound and re-inoculated in a new leachate to be transplanted onto the bio-anode. This procedure allowed the microbial electron charge transfer and therefore the enhancement of the bio-energy production of the fuel cell. RESULTS: By using the repetitive mechanical biofilm removal, re-suspension and electrochemically facilitated biofilm formation, the voltage was substantially increased. In effect, the voltage of the 1st G of biofilm, rose gradually and reached its maximum value of 65 mV after 10 days. Whilst the 2nd generation allowed to obtain the maximum voltage 276 mV and without any lag time. The DCO abatement using the 1st G biofilm was 68% greater than the 3rd G 26%. Besides, the electrochemical impedance spectroscopy characterization and cyclic voltammetry of bio-anode with 2nd G biofilm confirmed the ability of electro-active biofilm formation on a new support. The biofilm transplanted showed thus greater kinetic performance, with reduced lag time demonstrating the interest of the selection that took place during the formation of successive biofilms. CONCLUSIONS: Despite the transplantation of the electro-active biofilm onto the bio-anode, the MFC still produced relatively lower power output. Nevertheless, it has been tested successfully for monitoring and detecting the oxidation of sodium acetate substrate in the very wide concentration range 0.0025-35 g/l.

Surfactant- and Binder-Free Hierarchical Platinum Nanoarrays Directly Grown onto a Carbon Felt Electrode for Efficient Electrocatalysis.

The future of fuel cells that convert chemical energy to electricity relies mostly on the efficiency of oxygen reduction reaction (ORR) due to its sluggish kinetics. By effectively bypassing the use of organic surfactants, the postsynthesis steps for immobilization onto electrodes, catalytic ink preparation using binders, and the common problem of nanoparticles (NPs) detachment from the supports involved in traditional methodologies, we demonstrate a versatile electrodeposition method for growing anisotropic microstructures directly onto a three-dimensional (3D) carbon felt electrode, using platinum NPs as the elementary building blocks. The as-synthesized materials were extensively characterized by integrating methods of physical (thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, inductively coupled plasma, and X-ray photoelectron spectroscopy) and electroanalytical (voltammetry, electrochemical impedance spectrometry) chemistry to examine the intricate relationship of material-to-performance and select the best-performing electrocatalyst to be applied in the model reaction of ORR for its practical integration into a microbial fuel cell (MFC). A tightly optimized procedure enables decorating an electrochemically activated carbon felt electrode by 40-60 nm ultrathin 3D-interconnected platinum nanoarrays leading to a hierarchical framework of ca. 500 nm. Half-cell reactions reveal that the highly rough metallic surface exhibits improved activity and stability toward ORR (Eonset ∼ 1.1 V vs reversible hydrogen electrode, p(HO2-) < 0.1%) and the hydrogen evolution reaction (-10 mA cm-2 for only 75 mV overpotential). Owing to its unique features, the developed material showed distinguished performance as an air-breathing cathode in a garden compost MFC, exhibiting better current and faster power generation than those of its equivalent classical double chamber. The enhanced performance of the material obtained herein is explained by the absence of any organic surfactants on the surface of the nanoarrays, the good metal-support interaction, particular morphology of the nanoarrays, and the reduced aggregation/detachment of particles. It promises a radical improvement in current surface reactions and paves a new way toward electrodes with regulated surface roughness, allowing for their successful application in heterogeneous catalysis.

Alginate/carbon composite beads for laccase and glucose oxidase encapsulation: application in biofuel cell technology.

Alginate-carbon beads were prepared in order to develop a biocompatible matrix for laccase and glucose oxidase immobilization for application in biofuel cell technology. The enzyme loading capacity was high (91%) in pure alginate beads for glucose oxidase. For laccase, the loading capacity was enhanced from 75% to 83% by introducing carbon. Desorption out of the matrix was controlled by the enzymes' diffusion and reached a plateau after 40 h for laccase and 70 h for glucose oxidase. Two-thirds of both enzymes was irreversibly retained inside the alginate beads. This proportion increased to 80% for laccase in combined alginate/carbon beads. Half-life of the adsorbed enzyme was enhanced to 74 days for laccase in carbon/alginate beads and 45 days for glucose oxidase in pure alginate as compared to 38 days and 23 days for free enzymes, respectively.

Nanofibrous poly(acrylonitrile-co-maleic acid) membranes functionalized with gelatin and chitosan for lipase immobilization.

Nanofibrous membranes with an average diameter of 100 and 180 nm were fabricated from poly(acrylonitrile-co-maleic acid) (PANCMA) by the electrospinning process. These nanofibrous membranes contain reactive groups which can be used to covalently immobilize biomacromolecules. Two natural macromolecules, chitosan and gelatin, were tethered on these nanofibrous membranes to fabricate dual-layer biomimetic supports for enzyme immobilization in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxyl succinimide (NHS). Lipase from Candida rugosa was then immobilized on these dual-layer biomimetic supports using glutaraldehyde (GA), and on the nascent PANCMA fibrous membrane using EDC/NHS as coupling agent, respectively. The properties of the immobilized lipases were assayed. It was found that there is an increase of the activity retention of the immobilized lipase on the chitosan-modified nanofibrous membrane (45.6+/-1.8%) and on the gelatin-modified one (49.7+/-1.8%), compared to that on the nascent one (37.6+/-1.8%). The kinetic parameters of the free and immobilized lipases, K(m) and V(max), were also assayed. In comparison with the immobilized lipase on the nascent nanofibrous membrane, there is an increase of the V(max) value for the immobilized lipases on the chitosan- and gelatin-modified nanofibrous membranes. Results also indicate that the pH and thermal stabilities of lipases increase upon immobilization. The residual activities of the immobilized lipases are 55% on the chitosan-modified nanofibrous membrane and 60% on the gelatin-modified one, after 10 uses.