Performance of vanadium-oxygen redox fuel cell

A promising approach to improving the energy density of the all-vanadium redox flow battery while also saving on raw materials costs, is to eliminate the positive half-cell electrolyte and replace it with an air electrode to produce a hybrid vanadium–oxygen redox fuel cell (VOFC). This concept was initially proposed by Kaneko et al. in 1992 and first evaluated at the University of New South Wales by Menictas and Skyllas-Kazacos in 1997. In this project the performance of the VOFC over a range of temperatures and using different types of membranes and air electrode assemblies was evaluated. Despite early problems with the membrane electrode assemblies that saw separation of the membrane due to swelling and expansion during hydration, with improved fabrication techniques, this problem was minimized and it was possible to operate a 5-cell VOFC system for a total of over 100 h without any deterioration in its performance.     

Evaluation of iodide and titanium halide redox couple combinations for common electrolyte redox flow cell systems

The electrochemical behaviour of a range of halide and titanium halide redox couple combinations has been evaluated for potential application in redox flow cells employing common elements in both half-cells. Cyclic voltammetry and cell cycling measurements were employed to establish the reversibility of the redox couples and the expected cell voltage and performance in a redox flow cell. An all iodine cell was found to be impractical due to the formation of an insoluble iodine deposit in the cell that caused cell blockage. A titanium polyhalide cell that uses a solution of TiCl₄ in HBr/HCl supporting electrolyte in both half-cells was, however, shown to produce an open circuit voltage of 0.9 V and high coulombic efficiencies. Although the voltage efficiency of the cell was low, improvements in cell design may reduce ohmic losses allowing much higher energy efficiencies to be achieved. This cell is equivalent to the vanadium bromide cell that employs a vanadium bromide solution in both half-cells. The lower price of titanium, however, opens the possibility of a significant cost benefit for the titanium polyhalide redox flow cell.     

Dehydrochlorination of propylene chlorohydrin with sodium hydroxide and with catholyte

Dehydrochlorination of an aqueous solution of propylene chlorohydrin with sodium hydroxide (12·5 and 30% by weight), with catholyte (5 or 10% by weight NaOH + 14% by weight NaCl) and with milk of lime (15% by weight) were compared. The use of catholyte (10% by weight NaOH + 14% by weight NaCl) enables propylene oxide to be obtained in a yield of 94·3%, with 100% conversion of chlorohydrin. The concentration of 1,2-propylene glycol in the waste is 0·07% by weight.     

Performance of internal reforming methanol fuel cell under various methanol/water concentrations

Copper-based reforming catalyst was placed adjacent to ADVENT Technologies high-Temperature polymer electrolyte membrane/electrode assembly in a novel internal reforming methanol fuel cell (IRMFC) and tested for their electrochemical properties and chemical stability under various methanol/water anode feedstreams. Polarization measurements and AC impedance spectroscopy combined with measurements of reactor outlet composition were carried out. Methanol is being reformed inside the anode compartment of the fuel cell at 200 °C producing H₂, which is readily oxidized at the anode to produce electricity. The reformer provides enough hydrogen supply for efficient fuel cell operation at 600 mV with 0.2 A cm⁻² and a hydrogen stoichiometric ratio of 1.2 (λ_H2 = H₂ fed/H₂ reacted = 1.2). However, unreacted MeOH (~5 %) in combination with low H₂ content poisons the anode electrode and the cell performance rapidly decreases. Gradual recovery of the initial performance under pure H₂ is observed after switching to pure H₂. A slight improvement of the cell’s design by the introduction of a pre-reforming step significantly improves the electrocatalytic behavior.     

Wet air oxidation of glucose with hydrogen peroxide and metal salts

Wet air oxidation (the patented Zimmermann process) destroys organic matter in sewage sludge by bringing a sludge-air mixture to elevated temperature (260 to 370 °C) and pressure (12.4 MPa) and holding it for a reaction time of 35 to 55 min. These conditions result in 70 to 80% COD removal with carbon dioxide, water, short chain aliphatic acids, and ash as products. Energy recovery provisions enable the process to be self-contained at sludge concentrations of 4.5 to 5% which are difficult to obtain. An additive to the process which would enable successful oxidation to proceed with less concentrated sludge, at lower pressures and shorter times would be useful. Hydrogen peroxide in combination with several metal salts was tested as an additive. Hydrogen peroxide plus dichromate was found to destroy 70% of the COD of a glucose solution (500 mg/1 COD) at 150 °C and 5.2 MPa in 15 min. The ratio of the equivalents of the substances glucose: hydrogen peroxide: dichromate stood as 13 : 6.5 : 1. The amount of COD destroyed exceeded the oxidative equivalents of peroxide and dichromate present; hence it was concluded that molecular oxygen was incorporated in the reaction.     

Thermal degradation and fire performance of wood treated with various inorganic salts

The effects of Na₂WO₄, Na₂SnO₃, and Na₂MoO₄ on the thermal decomposition and fire performance of wood were characterized by thermogravimetric analysis, differential thermogravimetry, differential thermal analysis, and thermogravimetry–mass spectrometry analysis. The kinetics of thermal degradation were analyzed using Doyle's equation and the limiting oxygen index was shown to be enhanced by the addition of Na₂WO₄, Na₂SnO₃, and Na₂MoO₄. The addition of these chemicals caused a decrease in the decomposition temperature, a reduction in weight, and an increase in the amount of char produced. The activation energies of the samples were also decreased after treatment by these flame retardants, during both the charring stage and the calcining stage. The flame retardants were shown to be able to catalyze the dehydration reaction, resulting in the formation of more H₂O, CO₂, and char molecules, but less levoglucosan and levoglucose. Copyright © 2010 John Wiley & Sons, Ltd.     

水循环式热泵干燥装置的性能分析

水循环式热泵干燥装置是指热泵和干燥部分通过水循环耦合而成的热泵干燥系统，是一种中小型热泵干燥装置的结构型式。对水循环式热泵干燥装置的开机过程、调控特性、能源效率进行了分析，相关结论可为推广应用提供参考。     

全钒液流电池充电/放电过程模型

建立全钒液流电池充电/放电过程模型,描述钒离子在离子传导膜中渗透产生的自放电现象对电池过程影响,反映电解液中不同价态钒离子浓度随时间变化规律,以及电池开路电压、端电压的时间依存性。通过与实验结果对比,数值模拟与实验结果保持良好一致性,验证所发展的数学模型的有效性。利用数值模拟再现实验结果,研究了充放电电流与电池容量的关系。结果表明：电池容量随电流的变化存在峰值。所建立的全钒液流电池过程模型,为液流电池储能系统的设计和操作提供依据。     

Reaction of iron and aluminium phosphate ores with sulphuric acid and various salts

A study has been made of the reaction of ore containing high Fe and Al phosphates (crandallite (CaAl₃(PO₄)₂OH₅·H₂O)), millisite (Na, K)CaAl₆(PO₄)₄(OH)₉·3H₂O) and minor minerals) with sulphuric acid. The products are deliquecent, poorly crystalline solids which contain polymeric aluminium phosphate. The deliquecence was greatly reduced by adding enough ammonium, potassium or sodium sulphate to form compounds of the type M(Al, -Fe)(SO₄)₂. Studies of free acid and other properties showed that two products which were still hydroscopic contained considerable amounts of inorganic polymeric phosphate. The content of phosphorus in the optimum products was too low (5.7%) for an economic fertilizer. This phosphorus level can be raised by substituting phosphoric acid for sulphuric acid or, by using ammonium sulphate followed by extraction with water. The results indicate that it may be possible to develop an economic granular fertilizer from this type of ore when competition for high grade phosphate has disappeared. However, the economic extraction of phosphoric acid from the material seem unlikely.     

Stereoregular polymerization of vinyl chloride with the redox system ferrous sulphate/hydrogen peroxide/oxalic acid: 2. Process kinetics

Kinetics relationships of the polymerization of vinyl chloride with the redox system ferrous sulphate/hydrogen peroxide/oxalic acid in the presence of emulsifier have been determined. The investigations have been made at constant monomer, initiator and emulsifier concentrations in the temperature range ?30°C to +15°C. The influence of the polymerization temperature on the rate and the activation energy of the process has been clarified. The process is discussed from the point of view of simultaneous polymerization in solution, emulsion and solid phase and the order of the total reaction with respect to monomer concentration has been determined.     

Reduced graphene oxide with tunable C/O ratio and its activity towards vanadium redox pairs for an all vanadium redox flow battery

Electrochemically reduced graphene oxides (ERGO) are obtained under various reducing potentials in the phosphate buffer solution (PBS). Different characterization methods are used to analyse the changes of structure and surface chemical condition for graphene oxide (GO). The results show that GO could be reduced controllably to certain degree and its electrochemical activity towards VO₂⁺/VO²⁺ and V³⁺/V²⁺ redox couples is also tunable using this environmentally friendly method. The catalytic mechanism of the ERGO is discussed in detail, the CO functional groups other than the C–O functional groups on the surface of ERGO more likely provide reactive sites for those redox couples, leading to a more comprehensive understanding about the catalytic process than previous relevant researches. This controllable modification method and the ERGO as electrode reaction catalyst with enhanced battery performance are supposed to have promising applications in the all vanadium redox flow battery.     

带有蛇形流场的微生物燃料电池串联堆性能特性

以四个成功启动的带有蛇形流场的单电池构造了微生物燃料电池串联堆(MFCS-S),测试了MFCS-S性能,探讨了其性能提升的限制因素,研究了增加反极电池阴、阳极电解液流量,采取混联的方式运行,移除反极电池和反接反极电池对电堆性能的影响。实验结果表明:MFCS-S在输出电压为2.11 V时获得最大功率密度(2226 mW·m^-2);在一定电流条件下,性能较差的单电池发生电压反极,这是限制MFCS-S性能提高的主要原因;增加反极电池阴、阳极流量虽然不能较大幅度地改善单电池反极,但是却能大幅度提高电堆功率密度;采用混联方式运行不但可以有效避免电池反极,而且可以大幅度提高电堆功率密度;移除反极电池并不能有效地避免电池的反极,反接反极电池反而进一步加剧反极。     

Performance features of Pt/BaO lean NOx trap with hydrogen as reductant

The performance of a model Pt/BaO/Al₂O₃ monolith catalyst was studied using H₂ as the reductant. The dependence of product selectivities on operating parameters is reported, including the durations of regeneration and storage times, feed composition and temperature, and monolith temperature. The data are explained in terms of a phenomenological model factoring in the transport, kinetic, and spatio‐temporal effects. The Pt/BaO catalyst exhibits high cycle‐averaged NOx conversion above 100°C, generating a mixture of N₂ and byproducts NH₃ and N₂O. The cycle‐averaged NOx conversion exhibits a maximum at about 300°C corresponding to the NOx storage maximum. The N₂ selectivity exhibits a maximum at a somewhat higher temperature, at which point the NH₃ selectivity exhibits a minimum. This trend conveys the intermediate role of NH₃ in reacting with stored NOx. Both N₂ and N₂O are also formed during the storage steps from the oxidation of NH_x species produced during the regeneration. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Sulfonated polyimide/chitosan composite membrane for vanadium redox flow battery: Membrane preparation,characterization, and single cell performance

A novel sulfonated polyimide/chitosan (SPI/CS) composite membrane was prepared from self‐made SPI (50% of sulfonation degree) through an immersion and self‐assembly method, which was successfully applied in vanadium redox flow battery (VRB). The proton conductivity of SPI/CS composite membrane is effectively improved compared to the plain SPI membrane. The VO²⁺ permeability coefficient across SPI/CS composite membrane is 1.12 × 10^?7 cm² min^?1, which is only one tenth of that of Nafion® 117 membrane. Meanwhile, the proton selectivity of SPI/CS composite membrane is about eight times higher than that of Nafion® 117 membrane. In addition, the oxidative stability SPI/CS composite membrane is superior to that of pristine SPI membrane. The VRB single cell using SPI/CS composite membrane showed higher energy efficiency (88.6%) than that using Nafion® 117 membrane, indicating that SPI/CS composite membrane is a promising proton conductive membrane for VRB application. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Chemical hydrogen storage and release properties using redox reaction over the Cu-added Fe/Ce/Zr mixed oxide medium

The chemical hydrogen storage (hydrogen reduction) and release (water-splitting oxidation) properties of the Cu-added Fe/Ce/Zr mixed oxide medium were investigated. The media with Cu content ranging from 0 to 5 wt% were prepared by a co-precipitation method using urea as a precipitant. The hydrogen reduction and the water-splitting oxidation on the medium were tested by temperature programmed reduction/oxidation (TPR/TPO) and repeated isothermal redox cycles at 550 °C for reduction and 350 °C for oxidation. The initial reduction rates and oxidation rates of the media increased with increasing the amount of the Cu additive. In addition, the reactivity of the medium for water-splitting oxidation was enhanced as the CeO₂/ZrO₂ ratio increased. Especially, the Fe-based mixed oxide medium with Cu/CeO₂/ZrO₂ contents of 3/30/10 wt% (Cu(3%)-Fe-CeO₂/ZrO₂(3/1)) showed superior performance in chemical hydrogen storage and release. As the results of isothermal redox cycles using the medium, the total amount of hydrogen evolved in water-splitting oxidation was maintained at ca. 8.5 mmol g^?1-medium (ca. 1.8 wt% hydrogen storage amounts on the basis of the total medium) over 15 repeated redox cycles.     

Degree of crosslinking and physical properties of dimethyloldihydroxyethyleneurea/acrylic acid crosslinked cotton fabrics after treatment with various metallic salts

Three metallic salts were used to posttreat dimethyloldihydroxyethyleneurea (DMDHEU)/acrylic acid (AA) crosslinked cotton fabrics, and the results showed that at a given value of the tensile strength retention (TSR), the dry crease recovery angle (DCRA) and wet crease recovery angle (WCRA) of the crosslinked and posttreated fabrics were higher than those of the DMDHEU–AA‐treated fabrics, and those of the crosslinked and posttreated fabrics were in the order of Ag⁺ > Cu⁺² > Al⁺³. The DCRA and TSR values for the crosslinked and posttreated fabrics were higher than those for the DMDHEU–AA‐crosslinked fabrics, and those for the crosslinked and posttreated fabrics were in the order of Ag⁺ > Cu⁺² > Al⁺³; however, WCRA values for the crosslinked and posttreated fabrics were lower than those for the DMDHEU–AA‐crosslinked fabrics, and those for the crosslinked and posttreated fabrics were ranked as Ag⁺ > Cu⁺² > Al⁺³ at a given number of crosslinks per anhydroglucose unit. IR spectra clearly revealed the different interactions and bonding states between the hydroxyl group of the cellulose and the various metallic ions and the strength of the interaction. All crosslinked and posttreated fabric samples showed good odor absorption and antibacterial and washing‐fastness properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 584–594, 2005