Dual gas diffusion cathode design for microbial fuel cell (MFC ): optimizing the suitable mode of operation in terms of bioelectrochemical and bioelectro‐kinetic evaluation
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Abstract BACKGROUND Upscaling microbial fuel cells ( MFCs ) to make them energy‐competitive systems requires a systematic understanding of their operating conditions. This study emphasizes the operation of a new MFC design with two gas diffusion cathodes under three different operational modes (batch mode ( MFC‐BM ), semi‐continuous mode ( MFC‐SCM ) and continuous mode ( MFC‐CM )), towards increasing the power density, substrate utilization, bioelectrochemical kinetics and energy conversion efficiencies. RESULTS Higher power density was recorded with MFC‐SCM (20.54 mW m −2 ) followed by MFC‐CM (17.22 mW m −2 ) and MFC‐BM (0.75 mW m −2 ). Such power density magnitudes were obtained with high anode projected surface area 220 cm 2 , which is about 10–100 times larger than frequently used in laboratory‐scale MFCs . On the contrary, susbtrate utilization was higher with MFC‐BM (91–96%) followed by MFC‐SCM (74–84%) and MFC‐CM (53–81%). A higher coulombic efficiency ( CE ) was obtained with the MFC‐CM (7.5–11.2%), followed by MFC‐SCM (5.4–5.6%) and MFC‐BM (0.5–4%). This is of interest due to its dependence on both current generation as well as substrate utilization. Cyclic voltammograms along with derived bioelectro‐kinetic parameters, i.e. redox Tafel's slopes ( β a / β c ) and electron transfer co‐efficients ( α a / α c ), also explained the higher performance of MFC‐CM and MFC‐SCM . CONCLUSION Output from this study demonstrates clearly that the new MFC design can be effectively operated under continuous mode operation with high retention time to enhance wastewater treatment along with good amounts of power output. © 2014 Society of Chemical IndustryKeywords:
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We report a microfabricated microbial fuel cell (MFC) that produces a high power density using a Geobacteraceae-enriched mixed bacterial culture.The MFC features 4.5-L anode/cathode chambers defined by 20-m-thick photo-definable polydimethylsiloxane (PDMS).The short proton diffusion length (20 m) in the anode lowers electrolyte resistance and consequently enhances power generation.A maximum current density of 16.3 mA/cm 3 and power density of 2.3 mW/cm 3 are achieved.The start-up time is only 2 days for maximum current generation.The MFC was operated under semi-continuous flow conditions, and L-cysteine was added in order to chemically scavenge the dissolved oxygen in the anode chamber.
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One area in which computers find use is in the calculation of Corrosion current density and rate calculations. To calculate electrochemical parameters such as anodic and cathodic Tafel slopes, corrosion current density and polarisation resistance, a software has been developed using C++ language. The software would process data obtained either from a galvanostatic experiment or potentiostatic experiment. The potentials are given in milli volts and the current as microamperes as input. The developed software would find: a) Corrosion currents by anodic and cathodic Tafel line extrapolations, b) corrosion rates expressed as mpy, c) Cathodic and Anodic Tafel Slopes, d) Corrosion currents by Stern -Geary method, e) Corrosion currents by Barnatt's method, f) Corrosion currents by Oldham and Mansfeld's method. Details of the Corrocal and its applications to various systems are presented.
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The reactor design is the most significant factor in microbial fuel cell (MFC) which enhances the power production during the treatment of distillery wastewater. The triple chamber MFC was constructed with two anodes and a cathode compartment separated by a proton exchange membrane. The power production in triple chamber MFC was 1.9 times higher as compared to a dual chamber MFC and it achieved power density of 168 mW/m2 normalized to cathode surface area. However, the power density production was not much difference in both MFCs with respect to anode surface area. The power density increased from 168 to 198 mW/m2 with decreasing the interelectrode distance between the anode and cathode. The anolyte and catholyte concentrations were also varied to determine their effect on power production in triple chamber MFC. Higher concentrations of substrate in terms of chemical oxygen demand in the anode chamber exhibited higher power production of 429 mW/m2. The power production was decreased with increasing the concentration of catholyte in triple chamber MFC. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 589–594, 2015
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Oxygen reduction reaction is examined at oxide‐covered Pt electrodes in acid solutions. In the high current density region characterized by the Tafel slope of −120 mV, the reaction is affected by the thickness of the oxide film. As the film thickness increases, current at the same potential decreases. In the low current density region characterized by the Tafel slope of −60 mV, the rate of reduction is unaffected by film thickness. In both current density regions, the potential at a given current decreases 60 mV as pH increases one unit. This leads to the fractional reaction order of with respect to in the high current density region. In the low current density region, the order is 1. Possible mechanisms compatible with the observed kinetic parameters are discussed.
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<p>This study investigates the feasibility of using cathode catalyst (Iron phthalocyanine (FePc) combined multi walled carbon nano tubes (MWCNT) and compares the oxygen reduction rate under different conductivity of catholite solution (50 mM, 100mM) in double chamber Microbial Fuel Cell. Microbial fuel cell (MFC) research is going on for few decades to increase the power density and improve the removal efficiency. Iron phthalocyanine (FePc) combined multi walled carbon nano tubes (MWCNT) cathode catalyst showed the highest power density (9.34 w/m2) in 100 mM PBS than 50 mM (7.58 W/m2). The electrodes are characterized by scanning electron microscopy (SEM) and the electrocatylitic activity of the catalyst coated electrodes were examined by cyclic voltammetry(CV). The high power density indicates a potential alternative to precious platinum metal catalyst in treatment as well as electricity production Microbial Fuel cell.</p>
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Microbial fuel cell (MFC), which can directly generate electricity from biodegradable materials, has been receiving increasing attention. Effects of temperature change on power density, electrode potential, columbic efficiency, chemical oxygen demand removal and internal resistance in two chambers MFCs were examined in this paper. The maximum power density of 7.89 W/m3 was achieved at 37 °C, with 199% higher at 10 °C (2.64 W/m3), 24% higher at 30 °C (6.34 W/m3) and 21% higher at 43 °C, no steady power generation was observed at 55 °C. Low temperature to 10 °C might have a huge effect on anode potential, especially at higher current, but increasing the temperature to 43 °C had a main effect on the cathode performance when the MFCs have been established at 37 °C. The internal resistance of MFC was about 29 Ω at 37 °C, and increased 62% and 303% when MFC switched to 30 °C and 10 °C. Similarly, internal resistance increased 48% at 43 °C. The effect of temperature on MFC performance was expressed by internal resistance, the higher the internal resistance of MFC, the lesser the power density obtained. The Columbic efficiencies were 8.65% at 30 °C, 8.53% at 37 °C, and 13.24% at 43 °C. These results demonstrate that MFCs can effectively be operated over a wide range of temperatures.
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In this study, three single-chamber microbial fuel cells (MFCs), each having Pt-coated carbon cloth as a cathode and four bamboo charcoal (BC) plates as an anode, were run in a fed-batch mode, individually and in series. Simulated potato-processing wastewater was used as a substrate for supporting the growth of a mixed bacterial culture. The maximum power output increased from 0.386 mW with one MFC to 1.047 mW with three MFCs connected in series. The maximum power density, however, decreased from 576 mW/m2 (normalized to the cathode area) with one MFC to 520 mW/m2 with three MFCs in series. The experimental results showed that power can be increased by connecting the MFCs in series; however, choosing low resistance BC is crucial for increasing power density.
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