Water-induced electrode poisoning and the mitigation strategy for high temperature polymer electrolyte membrane fuel cells

Engineering failure of membrane electrode assembly caused by increasingly fuel poisoning in the high temperature polymer electrolyte membrane fuel cells fed with humidified reformate gases is firstly demonstrated herein this work. Based on the results of the in-situ environmental scanning electron microscope, electrochemical analyses, and limiting current method, a water-induced phosphoric acid invasion model is constructed in the porous electrode to elucidate the failure causations of the hindered hydrogen mass transport and the enhanced carbon monoxide poisoning. To optimize the phosphoric acid distribution under the inevitably humidified circumstance, a facile and effective strategy of constructing acid-proofed electrode is proposed and demonstrates outstanding stability with highly humidified reformate gases as anode fuel. This work discusses a potential defect that was rarely studied previously under practical working circumstance for high temperature polymer electrolyte membrane fuel cells, providing an alternative opinion of electrode design based on the fundamental aspects towards the engineering problems.

SPE Membrane Electrode and Its Application to Chemical Sensor

The structure and proton conducting mechanism of solid polymer electrolyte (SPE) are described. Since the conductivity of electrolyte is important in SPE electrochemical cell research and development, we investigate quantitatively the conductivity of Nafion membrane and its dependence on temperature and relative humidity. Experimental results show that the conductivity of Nafion membrane increases with temperature and relative humidity. We also reports on the preparation and development of SPE membrane electrode with the emphasis on the mixture pressing method and impregnation-reduction process to prepare SPE composite electrode assemblies and their application to electrochemical sensors. We also investigate and fabricate a potentiometric electrochemical sensor of hydrogen and ethylene to measure the hydrogen and ethylene partial pressure.

Performance Investigation of Membrane Electrode Assemblies for High Temperature Proton Exchange Membrane Fuel Cell

Different types of ABPBI (poly(2,5-benzimidazole)) membranes and polymer binders were evaluated to investigate the performance of MEAs for high temperature proton exchange membrane fuel cell (HT-PEMFC). The properties of the prepared MEAs were evaluated and analyzed by polarization curve, electrochemistry impedance spectroscopy (EIS), cyclic voltammetry (CV) and durability test. The results showed that MEA with modified ABPBI membrane (AM) has satisfactory performance and durability for fuel cell application. Compare to conventional PBI or Nafion binders, polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF) are more attractive as binders in the catalyst layer (CL) of gas diffusion electrode (GDE) for HT-PEMFC.

Effects of Freeze/Thaw Cycles and Gas Purging Method on Polymer Electrolyte Membrane Fuel Cells

At subzero temperature, the startup capability and performance of polymer electrolyte membrane fuel cell (PEMFC) deteriorates markedly. The object of this work is to study the degradation mechanism of key components of PEMFC-membrane-electrode assembly (MEA) and seek feasible measures to avoid degradation. The effect of freeze/thaw cycles on the structure of MEA is investigated based on porosity and SEM measurement. The performance of a single cell was also tested before and after repetitious freeze/thaw cycles. The experimental results indicated that the performance of a PEMFC decreased along with the total operating time as well as the pore size distribution shifting and micro configuration changing. However, when the redundant water had been removed by gas purging, the performance of the PEMFC stack was almost resumed when it experienced again the same subzero temperature test. These results show that it is necessary to remove the water in PEMFCs to maintain stable performance under subzero temperature and gas purging is proved to be the effective operation.

Effects of Freeze/Thaw Cycles and Gas Purging Method on Polymer Electrolyte Membrane Fuel Cells

At subzero temperature, the startup capability and performance of polymer electrolyte membrane fuel cell PEMFC deteriorates markedly. The object of this work is to study the degradation mechanism of key compo- nents of PEMFC—membrane-electrode assembly MEA and seek feasible measures to avoid degradation. The ef- fect of freezethaw cycles on the structure of MEA is investigated based on porosity and SEM measurement. The performance of a single cell was also tested before and after repetitious freezethaw cycles. The experimental results indicated that the performance of a PEMFC decreased along with the total operating time as well as the pore size distribution shifting and micro configuration changing. However, when the redundant water had been removed by gas purging, the performance of the PEMFC stack was almost resumed when it experienced again the same subzero temperature test. These results show that it is necessary to remove the water in PEMFCs to maintain stable per- formance under subzero temperature and gas purging is proved to be the effective operation.

Iodide-selective polymeric membrane electrode based on copper(Ⅱ) bis(N-2-bromophenylsalicyldenaminato) complex

A PVC membrane electrode based on copper（II） bis（N-2-bromophenylsalicyldenaminato） as ionophor was prepared. The ion selective electrode was tested by inorganic anions and showed a good selectivity for iodide ion. This sensor exhibited Nernstian behavior with a slope of -57.8 mV per decade at 25℃. The proposed electrode showed a linear range from 1.0 × 10 ^-5 to 1.0 × 10 ^-1 mol/L with a detection limit of 5.0 × 10 ^-6 mol/L. The electrode response was independent of pH in the range of 3.0- 10.0. The proposed sensor was applied to determine the iodide in water and antiseptic samples.

A novel Ce(Ⅳ)ion-selective polyvinyl chloride membrane electrode based on HDEHP and HEH/EHP

A novel Ce（Ⅳ） ion-selective polyvinyl chloride（PVC） membrane electrode based on HDEHP and HEH/EHP as ionophore was successfully prepared. The factors affecting the response of Ce（Ⅳ） ion were investigated, such as membrane composition, internal solution, concentration of SO_4^（2–）, and acidity in test solution. The best performance was obtained using the membrane with PVC：DBP：HDEHP：HEH/EHP：OA mass ratio of 75：175：5：5：5. The proposed electrode exhibited a Nernstian slope of 30.44 mV/decade for Ce（Ⅳ） ion over a linear concentration range of 1×10^（–5）–1×10^（–1） mol/L with the detection limit of 9.0×10^（-6） mol/L. The electrode showed stable response within the SO_4^（2–） concentration range of 0.1–1 mol/L and the acidity range of 0.25–1.2 mol/L H＋. The proposed electrode showed high selectivity for Ce（Ⅳ） over a wide variety of interfering ions and a fast response time. It was used as an indicator in the potentiometric titration of Ce（Ⅳ） solution with H_2O_2 solution, and could also be used for the determination of Ce（Ⅳ） in real Ce（Ⅳ）-containing aqueous samples.

Design of Neutral Carrier for Solvent Polymeric Membrane Iodide Electrode With High Selectivity

Anion-selective electrodes based on dissociated ion-exchangers such as lipophilicquaternary ammonium or phosphonium species always display classical Hofmeister be-havior in the following order: ClO4-】SCN-】I-】Br-】NO2-】Cl-】SO42-.A new sol-vent polymeric membrane electrode based on Schiff base complexes of Co（Ⅱ）[Co（Ⅱ）S]and showing excellent selectivity toward iodide ion is for the first time prepared inour work. The resulting electrodes exhibit fairly low detection limits andpotentiometric anion-selectivity sequences deviated from the Hofmeister pattern.Bis（salicylaldehyde） ethylenediiminecobalt（Ⅱ） [Co（Ⅱ）（salen）], bis（salicylaldehyde）-phenyldiiminecobalt（Ⅱ） [Co（Ⅱ）（salophen）],

Coulometric Response of H-Selective Solid-Contact Ion-Selective Electrodes and Its Application in Flexible Sensors+

The analytical performance of H+-selective solid-contact ion-selective electrodes(SCISEs)based on solid contact polyaniline doped with chloride(PANI(Cl))and poly(3,4-ethylenedioxythiophene)doped with poly(styrene sulfonate)(PEDOT(PSS))was characterized by a developed coulometric signal transduction method.PEDOT(PSS)solid contact is covered by PVC based H+-selective membrane.The obtained coulometric signal demonstrates that the cumulated charge can be amplified by increasing the capacitance of solid contact.SCISEs covered with spin-coated membrane behave faster amperometric response than electrodes with drop-cast mem-brane.In contrast to earlier works,the amperometric response and impedance spectrum demonstrates H+transfer through SCISEs is independent from the thickness of membrane.The exceptional behavior of PANI(Cl)H+-SCISEs shows that the capacitance estimated from impedance spectrum at low frequency 10 mHz and coulometric signal of PANI(Cl)based SCISEs is influenced by the applied po-tentials,whereas PEDOT(PSS)solid contact is independent from the chosen applied potentials.Furthermore,preliminary investiga-tions of coulometric signal transduction on flexible pH sensor implies its potential applications in wearable sensors for sweat ion concentration detection.

A ladder conjugated polymer transducer for solid-contact Cu^(2+)-selective electrodes

In recent years, there has been a pronounced interest in solid-contact ion-selective electrodes （SC-ISEs）, with emphasis on the use of conducting polymers as ion-to-electron transducer. In this work, a ladder conjugated polymer, thieno[3,2-b]thiophene （LCPT）, was investigated in fabricating Cu2＋-selective electrodes for the first time. The resulting electrodes were characterized by electrochemical impedance spectroscopy （EIS）, chronopotentiometry, and the water layer test. Results proved that the active LCPT facilitates the ion-to-electron transduction, and avoids the detrimental aqueous layer formed at the interface of SC-ISEs.

CO_(2)electrolysis:Advances and challenges in electrocatalyst engineering and reactor design

Electrochemical reduction of CO_(2)(CO_(2)RR)coupled with renewable electrical energy is an attractive way of upgrading CO_(2)to value-added chemicals and closing the carbon cycle.However,CO_(2)RR electrocatalysts still suffer from high overpotential,and the complex reaction pathways of CO_(2)RR often lead to mixed products.Early research focuses on tuning the binding of reaction intermediates on electrocatalysts,and recent efforts have revealed that the design of electrolysis reactors is equally important for efficient and selective CO_(2)RR.In this review,we present an overview of recent advances and challenges toward achieving high activity and high selectivity in CO_(2)RR at ambient conditions,with a particular focus on the progress of CO_(2)RR electrocatalyst engineering and reactor design.Our discussion begins with three types of electrocatalysts for CO_(2)RR(noble metalbased,none-noble metal-based,and metal-free electrocatalysts),and then we examine systems-level strategies toward engineering specific components of the electrolyzer,including gas diffusion electrodes,electrolytes,and polymer electrolyte membranes.We close with future perspectives on catalyst development,in-situ/operando characterization,and electrolyzer performance evaluation in CO_(2)RR studies.

四苯硼酸钾衍生物为载体的锂离子选择性电极

合成了3种四苯硼酸钾衍生物，并以此作载体研制了PVC膜锂离子选择性电极。其中四（对－甲氧基苯基）硼酸钾作载体的电极对锂离子响应的线性范围为5．2×10－5～1．0×10－1mol／L；检测下限1．4×10－5mol／L；斜率55．6±0．3mV／pLi（20℃），电极具有较好的稳定性、重视性。研究了这些载体溶剂聚合膜的Li＋离子的传输实验，对含四（对－甲氧基苯基）硼酸钾载体的膜传输离子的次序为Li＋＞Na＋＞K＋，其次序与载体膜响应离子的选择性次序一致。电极用于碳酸锂片剂中锂含量测定，获得满意的结果。

硝酸根离子选择性电极的构建及研究进展

硝酸盐含量的检测对于评价环境中硝酸盐污染和了解生态系统氮循环方面起着非常重要的作用。离子选择性电极因操作简单、选择性好、方便携带、价格低廉等优点被广泛应用于环境样品中硝酸根的测定。本文从离子选择性电极功能材料、电极设计和实际应用三方面阐述了近20年硝酸根离子选择性电极的研究进展,汇总了新合成硝酸根离子载体的选择性性能,从固体接触传导层和离子选择性敏感膜组分角度分析了固体接触式聚合物膜硝酸根离子选择性电极的构建机理,总结了非聚合物膜硝酸根离子选择性电极的发展,并对硝酸根离子选择性电极在环境中的典型应用进行了介绍,以期为水环境和土壤中硝酸根的测定提供技术支持。

溶剂聚合膜pH传感器进展

一、前言由于溶剂聚合膜pH传感器具有容易制备、不易破损、低膜阻抗、易微型化、使用安全、且耐氢氟酸腐蚀等优点,尤其是溶剂聚合膜pH电极在临床医学、生物化学研究领域的应用成功,近年来,它的研究越来越受到重视。我们于1991年综述讨论了中性载体pH电极的一些问题。本文将回顾和总结近年来国内外中性载体溶剂聚合膜pH电极及无载体胺化溶剂聚合膜pH电极研究成果。

基于无序介孔碳的全固态自支撑聚合物膜铅离子选择性微型电极

将无序介孔碳材料填充到尖端直径约150μm的毛细玻璃管内,利用其多孔结构将铅离子选择性敏感膜吸附于电极尖端内部,制备了基于无序介孔碳的全固态自支撑聚合物膜铅离子选择性微型电极(Pb^(2+)-ISμE)。采用循环伏安法(CV)和电化学阻抗法对所制备电极的电化学性质进行表征,并考察了其电位响应性能。结果表明,基于无序介孔碳的微型电极具有微电极所特有的"S"型循环伏安曲线,且由于电极材料的多孔性表现出较大的双电层电容特性,所构建的Pb^(2+)-ISμE测定Pb^(2+)的线性范围为1.0×10^(-7)^1.0×10^(-4)mol/L,响应斜率为(28.9±0.5)mV/dec,检出限为4.0×10^(-8)mol/L。该Pb^(2+)-ISμE表现出良好的选择性、稳定性和重复性,并成功应用于海岸带沉积物加标孔隙水中Pb^(2+)的测定。该文为微型电极的制备提供了一种简单、便捷的方法,并为微环境或微量样品中离子的测定提供了一种有效的检测手段。

新型载体PVC膜水杨酸根离子敏感电极的研制与应用

报导了以三苄基锡辛酸酯为中性载体的一种溶剂聚合膜阴离子敏感电极的研制。该电极对水杨酸根离子的电位响应具有优良的选择性和灵敏度。在ｐＨ５．５的缓冲体系中，电极的线性响应范围为１０－１～５×１０－６ｍｏｌ／Ｌ，斜率为－５７．６ｍＶ／ｄｅｃ．（２２℃）。该电极响应时间短，且具有良好的稳定性和重现性，为药物及生理试样中水杨酸根离子的测定提供了一种新的可靠手段。

聚合物膜钙离子选择性电极检测游离钙和总钙浓度

利用聚合物膜钙离子选择性电极,通过使用不同的内充液,分别实现了游离钙和在络合剂EDTA和腐殖酸存在下总钙浓度的检测。结果表明,采用0.1mol·L^(-1) NaCl+1×10-3 mol·L^(-1) CaCl_2作为内充液的电极,可以实现低至1×10-6 mol·L^(-1)游离钙活度的检测;而采用1×10-3 mol·L^(-1) CaCl_2+5×10^(-2) mol·L^(-1) Na_2EDTA(pH=9.0)作为内充液的电极,在1×10-6~1×10-5 mol·L^(-1) Ca^(2+)浓度范围内有超能斯特现象发生,电位差值为180mV,且在该范围内电位响应与总钙浓度呈线性相关,与游离钙活度无关。该研究为进一步开展形态分析提供了一种简单、有效的技术手段。

Erbium(Ⅲ) PVC membrane sensor based on N-(benzyloxycarbonyloxy)succinimide as a new neutral ionophore

In this study,a new Er^3＋ sensor based on N-（benzyloxycarbonyloxy）succinimide（BCS） as a neutral carrier has been constructed. The sensor exhibits potential linear response with a Nernstian slope of 20.5±0.4 mV/decade in the concentration range of 1.0×10^-6to 1.0×10^-2mol/L of Er^3＋.It has a very short response time（10 s）,detection limit of 6.3×10^-7 mol/L and a good selectivity relative to a wide variety of other metal ions including common alkali,alkaline earth,heavy,and transition metal ions.It can be used in the pH range of 2.5-10.6 without any considerable divergence in potentials.The proposed sensor was successfully applied for the recovery of Er^3＋ ions spiked in tap and river water samples.

Quantitative Analysis of Holmium Ion by a Ho^3＋ Ion-Selective Sensor Based on a Symmetric Thio-Schiff＇s Base

A poly（vinyl chloride） （PVC） membrane sensor for holmium ions was fabricated based on N-[（Z）-l-（2-thienyl）- methylidene]-N-[4-（4-{[（Z）-l-（2-thienyl）methylidene]amino} phenoxy）phenyl] amine （TPA） as a new ion carrier, acetophenon （AP） as plasticizing solvent mediator and sodium tetraphenyl borate （NaTPB） as an anion excluder. The electrode shows a good selectivity towards Ho^3＋ ions respect to other inorganic cations, including alkali, alka- line earth, transition and heavy metal ions. The constructed sensor displays a Nernstian behavior （19.5±0.3 mV/decade） over the concentration range of 1.0× 10^-6 to 1.0 ×10^- 2 mol·L^-1 with the detection limit of the electrode being 4.6）〈 10-7 mol·L^-1 and very short response time （ca. 5 s）. It has a useful working pH range of 3.2-9.8 for at least 8 weeks. The electrode was successfully applied as an indicator electrode for the potentiometric titration of a Ho^3＋ solution with EDTA and holmium determination in some alloys. The proposed sensor accuracy was studied by the determination of Ho^3＋ in mixtures of three different ions.

Application of 2,2'-dithiobis(4-methylthiazole) as sensing material for construction of Lu^(3+) PVC-membrane sensor

In this work a new Lu^（3＋） PVC-membrane sensor based on 2,2＇-dithiobis（4-methylthiazole）（TMT） has been fabricated.The sensor exhibits a Nernstian slope of 19.6±0.4 mV decade（？） in the concentration range of 1.0×10~6-1.0×10~2 mol L^1 and a detection limit of 6.8×10~7 mol L^1.It could work well in the pH range of 2.7-9.6.The selectivity of the sensor against a lot of common alkaline,alkaline earth,transition,heavy metals and specially lanthanide ions was very good.