The Effects of Operating Conditions on the Performance of a Solid Oxide Steam Electrolyser: A Model‐Based Study

To support the development of hydrogen production by high temperature electrolysis using solid oxide electrolysis cells (SOECs), the effects of operating conditions on the performance of the SOECs were investigated using a one‐dimensional model of a cathode‐supported planar SOEC stack. Among all the operating parameters, temperature is the most influential factor on the performance of an SOEC, in terms of both cell voltage and operation mode (i.e. endothermic, thermoneutral and exothermic). Current density is another influential factor, in terms of both cell voltage and operation mode. For the conditions used in this study it is recommended that the SOEC be operated at 1,073 K and with an average current density of 10,000 A m^–2, as this results in the stack operating at almost constant temperature along the cell length. Both the steam molar fraction at the inlet and the steam utilisation factor have little influence on the cell voltage of the SOEC but their influence on the temperature distribution cannot be neglected. Changes in the operating parameters of the SOEC can result in a transition between endothermic and exothermic operation modes, calling for careful temperature control. The introduction of air into the anode stream appears to be a promising approach to ensure small temperature variations along the cell.     

Study of a Single‐Chamber Solid Oxide Fuel Cell Microstack with V‐Shaped Congener‐Electrode‐Facing Configuration

Single‐chamber solid oxide fuel cell (SC‐SOFC) microstacks with V‐Shaped congener‐electrode‐facing configuration were fabricated and operated successfully in a box‐like stainless steel chamber. Two gas channels with small gas inlets were used to transport the fuel and oxygen to the anodes and cathodes, respectively. The temperature of an anode‐facing‐anode two‐cell stack was higher than that of a cathode‐facing‐cathode two‐cell stack during the test procedure. For a three‐cell stack, the cell in the middle region presented the highest power output. The open circuit voltage (OCV) and maximum power output of the three‐cell stack in a gas mixture of 100 sccm N₂, 120 sccm CH₄, and 80 sccm O₂ were 3.0 V and 413 mW, respectively.     

Evaluation of a Non‐sealed Solid Oxide Fuel Cell Stack with Cells Embedded in Plane Configuration

A non‐sealed solid oxide fuel cell stack with cells embedded in plane configuration was fabricated and operated successfully in a box‐like stainless‐steel chamber. For a two‐cell stack, it demonstrated an open circuit voltage (OCV) of 2.13 V and a maximum power output of 569 mW at the flow rate of 67 sccm CH₄ and 33 sccm O₂. A fuel utilization of 4.16% was obtained. The cell performance was dominated by two different mechanisms, the polarization of the cathode at low current and the concentration polarization of the anode at high current. Finally, a scaled‐up stack with six cells in series generated an OCV of 6.4 V and a maximum power output of 8.18 W.     

Design,Fabrication and Preliminary Study of a Mini Power Source with a Planar Six‐cell PEM Unitised Regenerative Fuel Cell Stack

A novel micro planar fuel cell power supplier, in which a six‐cell PEM unitised regenerative fuel cell (URFC) stack is used as the power generator, was designed and fabricated. Six membrane electrode assemblies were prepared and integrated on one piece of membrane by spraying catalyst slurry on both sides of the membrane. Each cell was made by sandwiching a membrane electrode assembly (MEA) between two graphite monopolar plates and six cell units were mechanically fixed in two organic glass endplates. When the stack was operated in an electrolysis mode, hydrogen was generated from the splitting of water and stored using a hydrogen storage alloy; conversely, when the stack was operated in fuel cell mode, hydrogen was supplied by the hydrogen storage alloy and oxygen was supplied from air by self‐breathing of the cathode. At room temperature and standard atmospheric pressure, the open‐circuit voltage (OCV) of the system reached 4.9 V, the system could be discharged at a constant current density of 20 mA cm^–2 for about 40 min, and the work voltage was ∼2.9 V. The system showed good stability for 10 charge–discharge cycles.     

Experimental results on the direct electrochemical oxidation of methanol in PEM fuel cells

The cell performance of direct methanol fuel cells (DMFC) is 0.5 V at 0.5 A cm^–2 under high pressure oxygen operation (3 bar abs.) at 110 °C. However, high oxygen pressure operation at high temperatures is only useful in special market niches. Therefore, our work has now focused on air operation of a DMFC under low pressure (up to 1.5 bar abs.). At present, a power density of more than 100 mW cm^–2 can be achieved at 0.5 V on air operation at 110 °C. These measurements were carried out in single cells with an electrode area of 3 cm² and the air stoichiometry only amounted to 10. The effects of methanol concentration and temperature on the anode performance were studied by pseudo half cell measurements and the results are presented together with their impact on the cell voltage. A cell design with an electrode area of 550 cm², which is appropriate for assembling a DMFC stack, was tested. A three-celled stack based on this design revealed nearly the same power densities as in the small experimental cells at low air excess pressure and the voltage–current curves for the three cells were almost identical. At 110 °C a power output of 165 W at a stack voltage of 1.5 V can be obtained in the air mode.     

Modeling a Reversible Solid Oxide Fuel Cell as a Storage Device Within AC Power Networks

A reversible solid oxide fuel cell (RSOFC) system, consisting of a RSOFC stack, heat store, and electrical inverters to convert DC to AC power, is shown by computer modeling to have the potential to efficiently store electrical energy. This paper describes the modeling of a single RSOFC, based on a proposed cell geometry, empirical data on the resistivities of the components, and calculation of activation and diffusion polarization resistances from electrochemical theory. Data from ac impedance spectroscopy measurements on symmetrical cells are used to model RSOFC impedance. A RSOFC stack is modeled by electrically linking the individual cells inside a pressurized vessel. A phase change heat store is added to improve energy storage efficiency. The model is implemented in MATLAB®/Simulink®. Two competing inverter control schemes are compared, trading off DC bus ripple against AC power quality. It is found that selection of appropriate DC bus capacitance is important in certain scenarios, with potential system cost implications. It is shown that the system can store electrical energy at an efficiency of 64% over a single discharge–charge cycle, i.e., hydrogen to electricity and heat to hydrogen.     

A Novel Cell‐Array Design for Single Chamber SOFC Microstack

A novel design of single chamber solid oxide fuel cell (SC‐SOFC) microstack with cell‐array arrangement is fabricated and operated successfully in a methane–oxygen–nitrogen mixture. The small stack, consisting of five anode‐supported single cells connected in series, exhibits an open circuit voltage (OCV) of 4.74 V at the furnace temperature of 600 °C and a maximum power output of 420 mW (total active electrode area is 1.4 cm²) at the furnace temperature of 700 °C. A gas mixture of CH₄/O₂ = 1 leads to best performance and stability.     

A validated multi‐scale model of a SOFC stack at elevated pressure

This paper presents a multi‐scale model of a solid oxide fuel cell (SOFC) stack consisting of five anode‐supported cells. A two‐dimensional isothermal elementary kinetic model is used to calculate the performance of single cells. Several of these models are thermally coupled to form the stack model. Simulations can be carried out at steady‐state as well as dynamic operation. The model is validated over a wide range of operating conditions including variation of temperature, gas composition (both on anode and cathode side), and pressure. Validation is carried out using polarization curves and impedance spectra. The model is then used to explain the pressure‐induced performance increase measured at constant fuel utilization of 40%. Results show that activation and concentration overpotentials are reduced with increasing pressure.     

铁基移动床化学链技术进展

在日益增长的能源需求与日益严峻的全球气候变化带来的双重压力下,清洁、高效且经济的能源利用方法显得尤为重要。将化学链概念用于传统化石能源的转化是一种前景广阔的新技术。化学链燃烧利用载氧体间接转化含碳燃料,同时实现二氧化碳的捕集。俄亥俄州立大学研发了采用铁基载氧体和移动床反应器的化学链技术,可实现天然气、煤、生物质等多种燃料向电力、氢、液体燃料等产品的零排放转化。目前,合成气化学链（syngas chemical looping,SCL）和煤直接化学链（coal direct chemical looping,CDCL）技术两套25 kW_th级小试装置已成功运行总计超过850 h,一套250 kW_th级的高压SCL装置即将投入示范运行。     

Ce掺杂La0.7Sr0.3Cr0.5Fe0.5O3-δ材料的制备及其电化学性能

近年来化石燃料大量消耗导致环境污染日益严重,固体氧化物电解池(SOEC)能够高效、环境友好地将CO₂转化为CO等高附加值化学品,因此受到广泛关注。开发高效稳定的SOEC需要采用性能优异的电极材料,La_0.7Sr_0.3Cr_0.5Fe_0.5O_3-δ(Sto-LSCrF)钙钛矿氧化物因其优异的氧化还原稳定性受到了高度重视。为进一步提高Sto-LSCrF燃料电极材料电解CO₂的能力,在Sto-LSCrF的A位掺杂Ce来调控Ce_0.08La_0.62Sr_0.3Cr_0.5Fe_0.5O_3-δ(Ce-LSCrF)中可移动氧空穴含量以便提高其对CO₂的吸附/活化能力,进而改善其电化学性能。同时对材料的相结构、氧空穴含量以及其对CO₂的吸附/脱附能力进行详细的表征和分析。此外,我们还探究了Ce-LSCrF的电化学性能,发现与Sto-LSCrF相比,Ce-LSCrF燃料电极表现出较高的电解性能,也显示出较好的恒压稳定性,电解性能的增强归因于Ce-LSCrF晶格中较多的可移动氧空位可有效吸附/活化CO₂,以上试验结果表明Ce-LSCrF是性能优异的CO₂电解材料。     

Dynamic Modeling of Reversible Solid Oxide Cells

Reversible solid oxide cells (rSOCs) are highly efficient devices, which allow either the generation of electric power or the storage of energy via fuel production. In this paper, the characteristics of the mode switch are investigated by applying a dynamic 3D stack model. The responses of temperature, current density, and species mole fractions regarding a switch from storage (SOEC) to generation mode (SOFC) are examined in detail. Additionally, the impact of using excess air and continuous voltage variations to limit temperature gradients and fluctuations during the mode switch are analyzed.     

金属阳极电解槽改制的可行性分析

普通金属阳极电解槽槽电压高、电耗大。金属阳极改制为扩张阳极降低生产成本，适用于运行时间长的氯碱企业的技术改造。     

Characterization of PTFE-bonded porous carbonelectrodes tested in a 100W phosphoric acid fuel cell(PAFC) stack using XPS and ICP–AES techniques

A 100W PAFC stack with 12 cells was assembled using in-house developed PTFE-bonded gas diffusion porous carbon electrodes, graphite bipolar plates and aluminium external gas manifolds. The stack was operated for 1000h continuously with acid management, using H2 and air at 1bar and at 175°C. After completion of the test the stack was disassembled and the electrodes were characterized using X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma–atomic emission spectroscopy (ICP–AES) techniques. The XPS and ICP–AES results revealed the presence of platinum in the electrolyte matrix layers (SiC+PTFE) and carbon mat layers (carbon+PTFE), which were applied on the cathodes and the anodes, respectively. This clearly indicates that there was a migration of platinum from cathodes to anodes during the stack operation. This may have occurred when operating the stack at it's open circuit voltage (OCV) while taking measurements of stack voltage and curre nt for the I/V curves.     

The effect of hydroxyspiro‐orthocarbonates on the cationic photopolymerization of an epoxy resin and on the mechanical properties of the final polymer

It is well known that bicyclic compounds like spiro‐orthocarbonates (SOCs) have the ability to reduce or eliminate the shrinkage produced during polymerization. In the work reported, four different SOCs were prepared, two of them with one and two hydroxyl groups, respectively, another with two alkoxy groups and one reference compound without substituents. It was found that the SOCs with hydroxyl groups increased the photopolymerization rate and conversion of an epoxycycloaliphatic monomer, while the compound with butoxy groups had an antagonistic effect, reducing both photopolymerization rate and conversion, due to the basic character of the ether groups. The reference compound did not display accelerating effects but it did increase slightly the conversion. Dynamic mechanical analysis revealed that the SOC with two hydroxyl groups increased the values of storage modulus of the obtained polymer in comparison with the polymer from pristine monomer. This may be due to the multifunctionality of this compound that induced a higher level of crosslinking, while the SOC with one hydroxyl group had the opposite effect, decreasing the viscoelastic property values of the polymer due to chain‐transfer reactions originated by the hydroxyl groups. The SOC with two hydroxyl groups was the more efficient of the studied compounds in reducing the shrinkage of the cured polyether. Copyright © 2011 Society of Chemical Industry     

直流电流与电网电压间的函数关系

利用变压器的T形等效电路,以电解槽为归算到变压器高压侧的纯电阻负载,根据电路理论逐步推导出直流电流与网侧电压的函数关系,并成功地将这种函数关系应用于滨化集团股份有限公司离子膜法烧碱配套整流装置的设计中。     

离子膜电解槽的周期性检修

介绍了自贡鸿鹤化工股份有限公司氯碱厂BiTAC-829型复极式电解槽运行7年后,进入周期性检修的情况.通过充分调研使用CEC电解槽较早的部分厂家技术情况以及维修厂家情况,确定检修厂家和检修技术方案.计划性修复后,平均单元槽压由3.373 V降至3.012 V.1年节电价值697 459元,1年即可收回返修技改成本.     

High toughness well conducting contact layers for solid oxide cell stacks by reactive oxidative bonding

The increasing demand for large scale electrochemical conversion technologies, suppose a scale-up of the solid oxide cell (SOC) technologies. SOCs offer high conversion efficiency compared to competing technologies, but the brittleness of the ceramic components makes up-scaling a challenge, as these challenges grows with the size of the stack. Here, we present a new type of contact layer to be used between the oxygen electrode and the interconnect, which can be applied by a scalable, low-cost processing routes. The microstructural and compositional development of the contact layers was studied by X-ray diffraction and electron microscopy and the performance was evaluated by measuring the fracture toughness and area specific resistance. Five times higher toughness compared to conventional contact layers is achieved by reactive oxidative bonding at moderate temperatures. In this process metal particles (Cu, Co, Mn) are in-situ oxidized to well conductive spinels with low area specific resistance (<23 mΩcm², 750 °C).     

20 V stack of aqueous supercapacitors with carbon (−), titanium bipolar plates and CNT‐polypyrrole composite (+)

A 20 V stack of 19 supercapacitors was fabricated from titanium bipolar plates (150 × 150 × 0.1 mm³) coated on each side with carbon nanotubes and polypyrrole composite (+) and pigment carbon black (?), and microporous polymeric separators containing aqueous KCl. Internal sealing of each cell in the stack was achieved by placing a silicone rubber washer between neighboring bipolar plates. The stack was tested by high voltage cyclic voltammetry, galvanostatic charging and discharging, and electrochemical impedance spectroscopy. It approached 25 kW/kg in maximum specific power and 3.64 Wh/kg in specific energy. Performance of the stack through intermittent charging‐discharging tests in a storage period of 10 months (still ongoing) remained fairly stable. For example, it exhibited almost zero decay in capacitance after 1000 continuous galvanostatic charging‐discharging cycles in the first month of storage (10 V), and less than 6% loss in the seventh month (19 V). © 2011 American Institute of Chemical Engineers AIChE J, 2012     

甲烷辅助高温电解制氢气和合成气

基于固体氧化物电解池(SOEC)的高温电解技术具有能量转换效率高、模块化易组装、应用灵活等优点,是一种极具应用前景的能量转化和存储技术。新型甲烷辅助高温电解模式将SOEC系统与甲烷部分氧化(POM)反应耦合,在有效降低电解能耗的同时制备高品位合成气。这种新型SOEC模式打通了电、热、气等不同能源网络,能够高效、灵活地实现不同能量之间的转化,实现能量和资源的最优利用。本文简述了甲烷辅助SOEC模式的研究进展,详细分析和阐述了该种新型SOEC模式下电解池的热力学参数、Nernst电势、电化学性能、产物组成和能量结构及效率,同时,总结了适用于甲烷辅助SOEC模式的电极体系的研究现状,最后对甲烷辅助SOEC模式的应用前景进行了展望。     

A Factorial Study to Investigate the Purging Effect on the Performance of a Dead‐End Anode PEM Fuel Cell Stack

This paper presents an experimental investigation of the effect of hydrogen purging time period and duration on the performance of a proton exchange membrane (PEM) fuel cell stack with a dead‐end anode. The objective is to develop a better understanding of the interactions between the purging parameters and the cathode air‐stoichiometry. It employs a full factorial approach for three factors (purging period, purging duration and air‐stoichiometry) with two levels and three replications. The study is performed on a 300 cm², 24‐cell PEM fuel cell stack with the rated power of 1.5 kW. The stack was operated with water cooling, fully humidified air and dry hydrogen at the ambient pressure. The results showed that the stack performance is significantly influenced by the interactions of the purging parameters and the cathode air‐stoichiometry. The least square model was utilized to determine the optimum values of these parameters with regard to the stack performance and hydrogen utilization. For the present stack, the optimum values of parameters were: purging period of 3 min, purging duration of 4 s and the cathode air‐stoichiometry of 200%.