Preparation of dye sensitized titanium oxide nanoparticles for solar cell applications

A new method for synthesis of titanium dioxide (TiO₂)-dye nanoparticles is reported. TiO₂ nanocrystals were obtained at 150 and 200 °C by using chemically bonded TiO₂-sensitizer dye as a precursor. Titanium tetraisopropoxide was first modified with a dye molecule and then precipitated by dropping into acidic water. A strongly colored precipitate was obtained. Hydrothermal growth of a colloidal solution was carried out in a Teflon-lined stainless steel autoclave. Dye sensitized solar cell efficiencies obtained were comparable and fill factor values were close to the analogous cells prepared by the use of conventional TiO₂ paste techniques. This method allows the use of different substrates together with nanocrystalline TiO₂ for many technological applications.     

Model study of a fuel cell range extender for a neighborhood electric vehicle (NEV)

Fuel cell systems have the potential to provide high-efficiency, low-cost power for Neighborhood Electric Vehicles (NEVs). Model results are presented examining the utility of placing a hydrogen PEM fuel cell on-board a Miles Electric ZX40ST work truck NEV as an “after-market add-on” range extender to the existing battery electric drive train, thereby creating a NEVx. Through the development and use of the Sandia-Miles-Altergy Range Test (SMART) model, we have examined the potential for a number of PEM fuel cell stack systems (with varying output power), combined with various hydrogen storage and electrical storage system configurations to achieve the desired range extension for a single 8-h work shift. Furthermore, we have evaluated the “well-to-wheels” (WTW) and greenhouse gas (GHG) reductions, and assessed the costs (both capital and O&M) for the different NEVx configurations and operating profiles.     

Development of open-cathode polymer electrolyte fuel cells using printed circuit board flow-field plates: Flow geometry characterisation

Open-cathode air-breathing fuel cells have the advantage of reduced system complexity and simplified operation, as oxygen is taken directly from ambient air without the need for blowers/compressors. In this study, printed circuit boards (PCBs) are used as flow-field plates. The use of PCBs offers the potential for significant cost reduction due to their well-established manufacturing processing and low materials cost. This study investigates the effect of varying the cathode geometry (parallel and circular) and opening ratios (43%, 53% and 63%) on fuel cell performance using polarisation curves, electrochemical impedance spectroscopy (EIS) and thermal imaging. The results obtained indicate that circular openings afford lower Ohmic resistance than parallel flow-field designs, which helps improve contact between the gas diffusion layer and flow-field plate. However, flow-field plates with circular openings suffer from greater mass transport limitation effects. Likewise, greater opening ratios offer better mass transport but increased Ohmic resistance as a result of the reduced area of lands/ribs. The thermal imaging results reveal lower temperature in the middle of the fuel cell due to “bowing” of the printed circuit board flow field plates which reduces the local current density. A trade-off between these factors results in a design with a maximum area specific power density of 250 mW cm⁻².     

Investigation of mass transport and cell performance on μDMFC with different anode flow fields

The study systematically analyzes the performance of micro direct methanol fuel cell (μDMFC) with different flow fields. A two‐phase three‐dimensional model is developed to evaluate the mass transport accurately. The transport of methanol and air, the pressure distribution, the anode saturation, and the methanol crossover are numerically observed, the under‐rib convection is also investigated numerically. The flow fields with an active area of 0.64 cm² are fabricated on silicon wafers by micro electromechanical system technology. Performance of μDMFCs with different flow fields is sorted as: double‐serpentine flow field (DSFF) > single‐serpentine flow field (SSFF) > triple‐serpentine flow field (TSFF), and the dynamic test results indicate the cell with DSFF takes the shortest time to reach a stable power output when compared with other cells. Copyright © 2013 John Wiley & Sons, Ltd.     

Ionomer content effects on the electrocatalyst layer with in-situ grown Pt nanowires in PEMFCs

The effects of ionomer contents were investigated in composite electrodes with in-situ grown single crystal Pt nanowires (Pt-NWs) for PEMFCs, including the amount in the carbon matrix and impregnated on the surface of the electrocatalyst layer. The electrocatalyst layer was prepared by growing Pt-NWs directly on the carbon matrix with a simple one-step wet chemical approach at room temperature. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), polarization curve tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were employed to evaluate the ionomer effects. The experimental results showed that the ionomer in the carbon matrix had an influence on the ionic conductivity and aggregation and distribution of the Pt-NWs, and the ionomer impregnated on the surface of the electrocatalyst layer affected the mass transport and ionic conductivity. The performance of the MEA was improved by optimizing the ionomer contents.     

Anodic potential on dual-chambered microbial fuel cell with sulphate reducing bacteria biofilm

Dual chamber microbial fuel cell reactors were inoculated with a mixed culture of sulfate-reducing bacteria with anode potential being the controlling parameter. A negative poised anode potential enhanced the performance of this fuel cell while a positive poised anode potential had adverse effects on cell performance. Negative anodic potential affects the biofilm characteristics, as evidenced by electrochemical analysis. Microbial community was changed accordingly.     

A combined physicochemical and electrocatalytic study of microwave synthesized tungsten mono-carbide nanoparticles on multiwalled carbon nanotubes as a co-catalyst for a proton-exchange membrane fuel cell

Tungsten mono-carbide (WC) nanoparticles supported on multiwalled carbon nanotube (MWCNT) was synthesized by a microwave-assisted solid-state carburization. The prepared samples were used as a co-catalyst to prepare Pt-WC/MWCNT catalyst for a proton-exchange membrane fuel cell. MWCNTs with and without oxidative pretreatments were characterized as the starting precursors. The influence of the carbide formation conditions on the physicochemical characteristics of the final product were extensively investigated. According to the results, surface pretreatment of the MWCNTs can improve the yield of carbide formation. Furthermore, carburization process can improve the catalyst utilization due to increasing the number of surface defects of the MWCNT supporting materials which can be interpreted as structural effect of the carburization process. It is believed that the superior performance of electrodes modified with tungsten carbide is mostly due to the structural effect of the carburization process and synergistic effect between the electrocatalytic activity of WC and Pt.     

电子汽车衡常见故障与预防

本文主要以举例的方式介绍电子汽车衡常见故障及排除方法,再从实际工作出发如何去预防故障的发生。     

New Insights on Plant Cell Elongation: A Role for Acetylcholine

We investigated the effect of auxin and acetylcholine on the expression of the tomato expansin gene LeEXPA2, a specific expansin gene expressed in elongating tomato hypocotyl segments. Since auxin interferes with clathrin-mediated endocytosis, in order to regulate cellular and developmental responses we produced protoplasts from tomato elongating hypocotyls and followed the endocytotic marker, FM4-64, internalization in response to treatments. Tomato protoplasts were observed during auxin and acetylcholine treatments after transient expression of chimerical markers of volume-control related compartments such as vacuoles. Here we describe the contribution of auxin and acetylcholine to LeEXPA2 expression regulation and we support the hypothesis that a possible subcellular target of acetylcholine signal is the vesicular transport, shedding some light on the characterization of this small molecule as local mediator in the plant physiological response.     

Investigation of the electrochemical active thickness of solid oxide fuel cell anode

Determination of the electrochemical active thickness (EAT) is of paramount importance for optimizing the solid oxide fuel cell (SOFC) electrode. However, very different EAT values are reported in the previous literatures. This paper aims to systematically study the EAT of SOFC anode numerically. An SOFC model coupling electrochemical reactions with transport of gas, electron and ion is developed. The microstructure features of the electrode are modeled based on the percolation theory and coordinate number theory. Parametric analysis is performed to examine the effects of various operating conditions and microstructures on EAT. Results indicate that EAT increases with decreasing exchange current density (or decreasing TPB length) and increasing effective ionic conductivity. In addition to the numerical simulations, theoretical analysis is conducted including various losses in the electrode, which clearly shows that the EAT highly depends on the ratio of concentration related activation loss R_act,con to ohmic loss R_ohmic. The theoretical analysis explains very well the different EATs reported in the literature and is different from the common understanding that the EAT is controlled mainly by the ionic conductivity of electrode.