Polymer dielectrics with available energy storage performance at high temperatures are critical to meet the demand of the emerging applications such as hybrid electric vehicles (HEVs), wind turbine generators, and...

High internal resistance is a key problem limiting the power output of the microbial fuel cell (MFC). Therefore, more knowledge about the internal resistance is essential to enhance the performance of the MFC. However, different methods are used to determine the internal resistance, which makes the comparison difficult. In this study, three different types of MFCs were constructed to study the composition and distribution of internal resistance. The internal resistance (R(i)) is partitioned into anodic resistance (R(a)), cathodic resistance (R(c)), and ohmic resistance (R(Omega)) according to their origin and the design of the MFCs. These three resistances were then evaluated by the "current interrupt" method and the "steady discharging" method based on the proposed equivalent circuits for MFCs. In MFC-A, MFC-B, and MFC-C, the R(i) values were 3.17, 0.35, and 0.076 Omega m(2), the R(Omega) values were 2.65, 0.085, and 0.008 Omega m(2), the R(a) values were 0.055, 0.115, and 0.034 Omega m(2), and the R(c) values were 0.466, 0.15, and 0.033 Omega m(2), respectively. For MFC-B and MFC-C, the remarkable decrease in R(i) compared with the two-chamber MFC was mainly ascribed to the decline in R(Omega) and R(c). In MFC-C, the membrane electrodes' assembly lowered the ohmic resistance and facilitated the mass transport through the anode and cathode electrodes, resulting in the lowest R(i) among the three types.

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Typical microbial fuel cells (MFCs) rely on precious metals for reduction of oxygen at the cathode, but recently MFCs have been developed that use biocathodes for power generation with alternate electron acceptors. It is shown here that with illumination it is possible to develop a biocathode that uses dissolved carbon dioxide (bicarbonate) as the acceptor. During acclimation, the cathode was set at a potential of 0.242 V (vs. SHE) using a potentiostat. After approximately one month of acclimation, a current of 1 mA was sustained. Bicarbonate was reduced in stoichiometric agreement with current generation, with 0.28 +/- 0.02 moles of bicarbonate reduced per mole of electrons. When this biocathode was used in a two-bottle MFC, a power density of 750 mW m(-2) was produced. These results demonstrate that MFCs can be used to fix carbon dioxide as well as produce electricity