Advanced Materials Research Vols. 608-609

Abstract: Microbial fuel cells with microbial brush anode and ferricyanide-cathode which could discharge at current up to 350 mA were constructed, and the effect of anodic pH on the performance of the microbial anode was investigated in the present study. Anodic pH was found to decrease significantly， from 6.23 to 4.35, when the MFC was operated to discharge at high current levels, which in turn reduced the performance of the microbial anode. No obvious pH change was observed during MFC discharge at lower current level (~12 mA), meaning that proton production is mainly related to the electrochemical oxidization of the organic fuels, rather than to the microbial degradation in the anode chamber. Results presented herein indicate that effective approach should be employed to control the anodic pH close to neutral conditions when optimizing the power output of microbial fuel cells, especially at high discharge current.

Abstract: The research history and recent achievements and application of fire resistant fuel in several countries were summarized. The emphases included the background of research, the mechanism of fire resistant, the development of emulsified fuel formulations, and the effects on the performance of engines. The situation of applying at present was also described. It was indicated that the research of fire resistant fuel was very important in the security of military vehicles and civil vehicles.

Abstract: Three kinds of ions (I^-、Fe²⁺and MnO₄^-) were appended into the methanol aqueous solution respectively as an additive and the Cyclic voltammograms of the aqueous solutions were studied. The results showed that Fe²⁺ had obvious promotion effect for electro-oxidation of methanol and could improve the methanol anodic oxidation current by 85 percent. The promotion effect of the thulium Ions were related with the electronic distribution of these elements and their adsorption on the Pt electrode surface. I^- and MnO₄^- could facilitate the electro-oxidation of methanol at different extent.

Abstract: Polymer Electrolyte Membrane fuel cell converts directly electrochemical energy into electricity. Channels in bipolar Plate, a critical component of fuel cell, is designed with Hilbert pattern, which are obtained through offsetting Hilbert curves to both sides according to working size. Polarization curve expresses the same characteristics between Hilbert channel and traditional serpentine and parallel channel. Output current densities of Hilbert channel are equivalent to that of the serpentine channel but larger than that of parallel channel. Simulation demonstrates that fluid flowing states in Hilbert channel are similar to that in serpentine channel and investigates that pressure drop changes with composite Hilbert channel arrangement. Temperature is an important factor influencing fuel cell performance and optimal temperature is close to 333K in this research.

Abstract: In this work, we present the design, fabrication and characterization of increased hydrogen storage capacity of the silicon based Chip Integrated Micro Polymer electrolyte membrane Fuel Cell Systems (CIµ-PFCS), to increase the run time. The increased hydrogen storage capacity is realized from the backside of the silicon wafer and filling (casting process) it with a newly developed advanced hydrogen storage material, palladium - polymer composite. The functionality, current-time measurements, hydrogen charging capacity and charging behaviour of the newly developed hydrogen storage technique in the CIµ-PFCS are investigated and presented in this work. The developed CIµ-PFCS with increased hydrogen storage capacity and advanced hydrogen storage technique shows a factor of 4 increased run time than the state-off-the-art CIµ-PFCS. The power density of the developed CIµ-PFCS was measured to be 2.1 [mW/cm²]. After a number of charging and discharging cycles of CIµ-PFCs with the presented hydrogen storage materials, proved to be long term stable. The advantage of the presented CIµ-PFCS is that there is an increased hydrogen storage volume on board and easy to fabricate with existing microsystem technologies.

Abstract: La_0.7Sr_0.15Ca_0.15Co_1-xFe_xO_3-δ (x=0.1、0.2、0.3、0.4) powders for the applications as the cathode materials in solid oxide fuel cell were synthesized by the citrate method. The results show that the powders calcined at 800°C for 3h were high pure perovskite state and the position of XRD spectra diffraction peak of the cathode materials shifts to the small angle and the grain size of the powders is getting larger with increasing the content of Fe-doped. The open circuit voltage of the single cell made by molding method in the hydrogen/air with La_0.7Sr_0.15Ca_0.15Co_1-xFe_xO_3-δas its cathode got the maximum-value bwteen the the operation temperature from 550°C to 600°C.The maximum power density decreases from 392.85mW/cm2 to 331.99 mW/cm2 with x content increases from 0.1 to 0.4 at the the operation temperature of 650 °C.

Abstract: X-ray diffraction results indicate that pristine alloy has a single LaNi5 phase and the alloys containing Fe0.43B0.57 consist of the matrix LaNi5 phase and the La3Ni13B2 secondary phase. The abundance of La3Ni13B2 phase increases with increasing x value. Maximum discharge capacity of the alloy electrodes monotonically decreases from 336.1 mAh/g (x = 0) to 281.2 mAh/g (x = 0.4). High-rate dischargeability of the alloy electrodes first increases with increasing x from 0 to 0.20, and then decreases when x increases to 0.4. Cycling stability decreases with increasing x from 0 to 0.4.

Abstract: A series of anion exchange membranes (AEMs) based on quaternary poly(ether sulfone)s (QPES) have been successfully prepared through aromatic nucleophilic polymerization, chloromethylation, quaternization and alkalization for alkaline direct methanol fuel cell (ADMFC) applications. The influence of quaternization reagents on properties of the prepared QPES membranes has been discussed in details, including ion exchange capacity (IEC), size change and ionic conductivity. The results indicated that the selection of quaternization reagent is very important. At similar IEC level, the membranes using N,N,N’,N’-tetramethyl-1,3-propanediamine as the quaternization reagent showed relatively high dimensional stability and ionic conductivity.

Abstract: Ni-B-graphene catalysts with high catalytic activity towards the electrochemical oxidation of methanol in alkaline solution have been prepared. Cyclic voltammograms of methanol oxidation shows, the Ni-B-graphene electrode exhibited much higher electrocatalytic activity than the Ni-B/C electrode obtained via direct deposited Ni onto the surface of the graphite. The higher activity could be due to the structural effect of graphene. The graphene can not only make an electroless deposition stable, but also facilitate the formation of more efficient Ni hydroxides and metallic Ni on the electrode surface, which is the key to improving the electrochemical oxidation activity.

Abstract: As the critical component of the system, micro-combustor requires a high and uniform temperature distribution along the wall to meet demands for the band gap of the PV cells. The past experiments have proved that the peak wall temperature of the combustor with porous media increases obviously. This paper will have a research on stratified porous media to enhance the combustion efficiency of the combustor and reduce the emissions.