Synthesis and Characterization of a New Fluorine‐Containing Polybenzimidazole (PBI) for Proton‐Conducting Membranes in Fuel Cells

A new type of fluorine‐containing polybenzimidazole, namely poly(2,2′‐(2,2′‐bis(trifluoromethyl)‐4,4′‐biphenylene)‐5,5′‐bibenzimidazole) (BTBP‐PBI), was developed as a candidate for proton‐conducting membranes in fuel cells. Polymerization conditions were experimentally investigated to achieve high molecular weight polymers with an inherent viscosity (IV) up to 1.60 dl g^–1. The introduction of the highly twisted 2,2′‐disubstituted biphenyl moiety into the polymer backbone suppressed the polymer chain packing efficiency and improved polymer solubility in certain polar organic solvents. The polymer also exhibited excellent thermal and oxidative stability. Phosphoric acid (PA)‐doped BTBP‐PBI membranes were prepared by the conventional acid imbibing procedure and their corresponding properties such as mechanical properties and proton conductivity were carefully studied. The maximum membrane proton conductivity was approximately 0.02 S cm^–1 at 180 °C with a PA doping level of 7.08 PA/RU. The fuel cell performance of BTBP‐PBI membranes was also evaluated in membrane electrode assemblies (MEA) in single cells at elevated temperatures. The testing results showed reliable performance at 180 °C and confirmed the material as a candidate for high‐temperature polymer electrolyte membrane fuel cell (PEMFC) applications.     

Direct Transesterification/Isomerization/Methoxycarbonylation of Various Plant Oils

A selection of plant oils was catalytically transferred into 1,19-nonadecanedioate by a direct transesterification, isomerization and methoxycarbonylation under mild conditions using Pd/o-C₆H₄(CH₂P ^t Bu₂)₂. Additionally, sulfuric acid was demonstrated as being able to substitute methane sulfonic acid as co-catalyst without any significant loss of activity and selectivity.     

乙二胺-磷酸型退镍液研究

为了减少工件报废率和经济损失,介绍一种新型乙二胺-磷酸型退镍液的配方及其最佳工艺条件,采用静态吊片蚀刻法研究了该退镍液的配方和操作条件对退镍速率的影响.结果表明:在乙二胺为80g/L,磷酸161g/L,间硝基苯磺酸钠为60g/L,DDTC为0.5g/L,pH为10.5,操作温度为80℃时,其退镍速率达到最佳.该新型退镍液具有退速快、成本低和退镍容量大的优点,适用于镀镍不合格品的处理及含镍镀层工件的返修,从而使不合格的镀镍层重新获得良好的镀层质量.     

金属磷化处理剂中的磷酸根离子的测定

本文就金属磷化处理剂的主要成分磷酸二氢根、磷酸一氢根离子,在磷化处理生产过程中的测定进行了分析研究。     

ZG00Cr32Ni31Mo4Cu2Nb钢钝化膜的电子能谱分析

采用ＡＥＳ俄歇电子能谱和ＸＰＳ－Ｘ光电子能谱相结合的方法,对新型ＺＧ００Ｃｒ３２Ｎｉ３１Ｍｏ４Ｃｕ２Ｎｂ钢在９５℃４０％Ｐ２Ｏ５,１％Ｈ２ＳｉＦ６,２％ＨＦ,４％Ｈ２ＳＯ４,０．０５％Ｃｌ＾－１介质中形成的钝化膜进行了分析。试验结果表明,新型钢在该介质中,形成以Ｃｒ２Ｏ３、ＭｎＯ３为主的氧化物膜,而Ｎｉ、Ｃｕ富集在膜的底部,可进一步提高膜的稳定性。     

On the corrosion behaviour of phosphoric irons in simulated concrete pore solution

The corrosion behaviour of three phosphoric irons P₁ (Fe-0.11P-0.028C), P₂ (Fe-0.32P-0.026C) and P₃ (Fe-0.49P-0.022C) has been studied in simulated concrete pore solution (saturated Ca(OH)₂ solution) containing different chloride concentration. This has been compared with that of two commercial concrete reinforcement steels, a low carbon steel TN (Fe-0.148C-0.542Mn-0.128Si) and a microalloyed corrosion resistant steel CS (Fe-0.151C-0.088P-0.197Si-0.149Cr-0.417Cu). The beneficial aspect of phosphoric irons was revealed from potentiodynamic polarization experiments. The pitting potentials and pitting nucleation resistances for phosphoric irons and CS were higher than that for TN. Electrochemical impedance spectroscopy (EIS) studies revealed thickening and growth of passive film as a function of time in case of phosphoric irons and CS in saturated Ca(OH)₂ pore solutions without chloride and in the same solution with 0.05% Cl⁻ and 0.1% Cl⁻. In case of TN, breakdown of passive film resulted in active corrosion in simulated pore solution containing 0.1% Cl⁻. Linear polarization resistance measurements complemented EIS results. Visual observations indicated that phosphoric iron P₃ was immune to corrosion even after 125 days of immersion in saturated Ca(OH)₂ solution containing 5% NaCl. The good corrosion resistance of phosphoric irons in simulated concrete pore solution containing chloride ions has been related to the formation of phosphate, based on ultraviolet spectrophotometric analysis and Pourbaix diagram of phosphorus-water system.     

Membrane electrode assemblies for high-temperature polymer electrolyte fuel cells based on poly(2,5-benzimidazole) membranes with phosphoric acid impregnation via the catalyst layers

A novel strategy for introducing phosphoric acid as the electrolyte into high-temperature polymer electrolyte fuel cells by using acid impregnated catalyst layers instead of pre-doped membranes is presented in this paper. This experimental approach is used for the development of membrane electrode assemblies based on poly(2,5-benzimidazole) (ABPBI) as the membrane polymer. The acid uptake of free-standing ABPBI used for this work amounts to ABPBI × 3.1 H₃PO₄ which has a specific conductivity of ∼80 mS cm⁻¹ at 140 °C. Rather thick catalyst layers (20% Pt/C, 1 mg Pt cm⁻², 40% PTFE as binder, d = 100-150 μm) are prepared on gas diffusion layers with a dense hydrophobic microlayer. After impregnation of the catalyst layers with phosphoric acid and assembling them with a mechanically robust undoped ABPBI membrane a fast redistribution of the electrolyte occurs during cell start-up. Power densities of about 250 mW cm⁻² are achieved at 160 °C and ambient pressure with hydrogen and air as reactants. Details of membrane properties, preparation and optimization of gas diffusion electrodes and fuel cell characterization are discussed. We consider our novel approach to be especially suitable for an easy and reproducible fabrication of MEAs with large active areas.     

A Soybean Oil-Based Adhesive and Its Application for Birdseed Binding

Current birdseed binders are mainly based on animal protein and fat. However, exporting the seed cakes containing animal products to European countries can be difficult due to their import policies. A plant oil-based adhesive may be capable of binding loose seeds together, enabling it to be used as an alternative to the animal protein-based and fat-based binders used currently and making the exportation possible. A soybean oil-based adhesive was, therefore, synthesized and tested for birdseed binding in this study. The effects of the quantity of saturated fatty acylglycerols (i.e., fully hydrogenated soybean oil, FHSO) introduced into epoxidized soybean oil (ESO) and a phosphoric acid (H₃PO₄) cross-linker on product characteristics were investigated. Increased quantity of FHSO improved the glass transition point (T _g), hardness, and adhesion while further increasing the quantity led to various degrees of phase separation of the product. Increased quantity of H₃PO₄ also improved hardness and adhesion of the binder. A binder-MDAG (a mixture of mono and diacylglycerols at about a 1:1 ratio as a hardening agent) mixture (BMD) having an average hardness and adhesion of 4024 and 1197 g, respectively, was selected for seed binding. Seed cakes bound with 15 wt.% BMD were about twice as hard as gelatin-bound ones. Storage of the BMD itself in open air led to increased hardness, adhesion, and melting point, and storage of the seed cakes bound by BMD in open air led to increased hardness and high temperature tolerance. Seed cakes bound with BMD also presented much better water resistance.     

Cost-effective preparation of metal-free electrocatalysts by phosphoric acid activation of lignocellulosic materials for oxygen reduction reaction

Activated carbons have been prepared by phosphoric acid activation of lignocellulosic precursors, an industrial method, followed by heat treatment in ammonia. Thus, a cost-effective, scalable and metal-free electrocatalyst was developed for use in oxygen reduction reaction (ORR) at fuel cell cathodes. The physicochemical properties of the activated carbons have been analyzed by elemental analysis, X-ray photoelectron spectroscopy, X-ray diffraction, and nitrogen adsorption. The ORR electrocatalytic performances of the activated carbons have been investigated by cyclic voltammetry and linear sweep voltammetry in an alkaline electrolyte. The results showed that phosphorus-containing groups are key to endowing phosphoric-acid-activated carbons with comparable electrocatalytic activity to that of commercial Pt/C. This was because these phosphorus-containing groups facilitated the formation of both nitrogen-containing groups and defects in the microstructure. Besides, heat treatment of phosphoric-acid-activated carbons in ammonia produced a highly developed mesopore structure and thus kinetically facilitated the ORR.     

Mechanism of action of polytetrafluoroethylene binder on the performance and durability of high-temperature polymer electrolyte fuel cells

In this work, new insights into impacts of the polytetrafluoroethylene (PTFE) binder on high temperature polymer electrolyte fuel cells (HT-PEFCs) are provided by means of various characterizations and accelerated stress tests. Cathodes with PTFE contents from 0 wt% to 60 wt% were fabricated and compared using electrochemical measurements. The results indicate that the cell with 10 wt% PTFE in the cathode catalyst layer (CCL) shows the best performance due to having the lowest mass transport resistance and cathode protonic resistance. Moreover, cyclic voltammograms show that Pt (100) edge and corner sites are significantly covered by PTFE and phosphate anions when the PTFE content is higher than 25 wt%. Open-circuit and low load-cycling conditions are applied to accelerate degradation processes of the HT-PEFCs. The PTFE binder shows a network structure in the pores of the catalyst layer, which reduces phosphoric acid leaching during the aging tests. In addition, the high binder HT-PEFCs more easily suffer from a mass transport problem, leading to more severe performance degradation.