Membrane And Electrode Assembly Research Articles

Effect of rotating disk electrode conditions on oxygen evolution reaction activity of Ir nanoparticle catalysts and comparison with membrane and electrode assemblies

In this study, we investigated the parameters of the rotating disk electrode (RDE) affecting the activity evaluations for the oxygen evolution reaction (OER). To precisely obtain the activation polarization, the impacts of RDE parameters on the measured OER activity are examined using various iridium catalysts. The potential range, catalyst loading on the disk electrode and anions in the electrolyte have a significant impact on the catalytic activity. The OER activities of the Ir catalysts under the optimized RDE conditions are compared with those determined using a labo-scale electrolyzer test cell and membrane and electrode assembly (MEA). The OER activity of MEA after stabilization is consistent with that of the RDE results. Therefore, the RDE half-cell with proper evaluation condition should be a useful and rapid initial catalyst screening method to estimate the OER activity in the MEA.

In-Situ XAFS Study to Monitor the Degradation of an Fe/N/C Cathode Catalyst in PEMFC

Understanding the degradation mechanism of Fe/N/C cathode catalysts in proton exchange membrane fuel cells (PEMFCs) is extremely important. In this study, an Fe/N/C catalyst prepared from polyimide nano-particles were placed in an in-situ cell for X-ray absorption spectroscopy, and its Fe K-edge adsorption spectra were recorded during a continuous operation of the fuel cell. The Fe/N/C catalyst used in this study was prepared by pyrolyzing Fe-containing polyimide nano-particles, which were synthesized by the precipitation polymerization of Pyromellitic dianhydride and 1,3,5-tris(4-aminophenyl)benzene. The Fe content after the preparation procedure was 0.6 wt%. This catalyst was used to fabricate a membrane and electrode assembly (MEA) with a Pt/C anode and a Nafion 212 membrane. This MEA was installed in a test cell for in-situ X-ray adsorption fine structure (XAFS) measurements, and operated at 0.5 V and 80°C for 8 h monitoring its Fe K-edge adsorption spectra. Fig. 1 shows the changes in the spectra during the fuel cell operation. The valence of the Fe specie at the initial stage was 3+. The spectra gradually changed during the fuel cell operation, suggesting that the dissolution of the Fe species from the active sites. This change could be relevant to the degradation of the cathode catalyst. Acknowledgements This study is financially supported by NEDO. The in-situ XAFS study was carried out at BL36XU in SPring-8 (No. 2016B7907, 2018A7840 and 2018B7907). Figure 1

Durable Oxygen Evolution Catalysts for Alkaline Membrane Water Electrolysis

The utilization of renewable energy has substantially driven more attention into electrolysis technologies. An electrolyzer can utilize “off peak” electricity from solar or wind farms to produce hydrogen or other fuels. These chemicals can then be operated in a fuel cell mode to generate electricity when needed or used for other industrial applications. However, current hydrogen production from electrolysis comprises only a small fraction of the global hydrogen market due to the high costs that results from expensive materials even if “free” electricity from renewable energy can be acquired. Alkaline membrane water electrolysis enables to use non-precious metals (or oxides) as the catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). This is very meaningful as the commercial OER catalyst IrOx for proton exchange membrane (PEM) electrolysis is very expensive; more importantly, the global storage and production of iridium is very scarce, tremendously limiting the mass production and deployment of PEM electrolyzers. However, there have rarely reported active and durable OER and HER catalysts for alkaline membrane water electrolysis, particularly in a membrane and electrode assembly (MEA) level; most previous studies on the OER and HER catalysts were focused on the rotating disk electrodes (RDEs). We have investigated a series of OER catalysts including Co3O4 supported on carbon nanotubes (Co3O4/CNTs), binary transitional metal oxides (nickel cobalt oxide, NiCo2O4), and nanocarbon composites (FeCoNiMn-derived N-doped graphene tube, NC-FeCoNiMn4). These catalysts have first demonstrated remarkable durability in the RDE tests, subject to extensive voltage cycling from 0.0 V to 1.9 V. These catalysts have been integrated with other components including alkaline membrane and ionomer to test their MEA performance. It was discovered that both membrane and ionomers have a significant impact on the MEA performance and durability. The alkaline membrane and ionomer can quickly degrade upon high-voltage operations, leading to rapid MEA performance decay. However, the decayed performance can be restored after the introduction of diluted hydroxide solution (e.g, 0.1 M KOH) to the electrolyzer cell. Therefore, this work can provide insightful guidance on the MEA design for alkaline membrane water electrolysis. Most importantly, the interaction between the catalyst and the ionomer will be investigated. Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-EE0006960.

Analysis of the Catalyst Layer and the Ionomer for PEFCs of the Different Operating Conditions

1. Introduction In the durability evaluation of the PEFC (Polymer electrolyte fuel cell), the degradation characteristics are different due to the difference of the potential cycle test method. It is inferred that the influence of the PEFC by the potential cycle test is different every the constructional element. In order to improve the cycle characteristics, it is considered that to clarify the correlation between the degradation acceleration part and the test method is one of the important factors.In this study, for the MEA (Membrane and electrode assembly) made by the commercial catalyst and electrolyte materials, two potential cycle tests were carried out. The MEAs was analyzed by EPMA (Electron probe micro analyzer), LC/MS (Liquid chromatography–mass spectrometry), et al., and the degradation part was evaluated. 2. Experimental The electrolyte membrane and the ionomer were composed of Nafion®, and the Pt / C was used as the catalyst powder in both the anode electrode and the cathode electrode. The catalyst ink was applied by the spray method, and the CCMs (Catalyst coated membrane) were created. The durability tests in the two conditions were carried out after the conditioning operation. One of the operating conditions was the Start-Stop cycle test. In that condition, the MEA was operated with the sawtooth-shaped potential cycle of between 1.0 V and 1.5 V (2 s/cycle). With the Load cycle test which is another condition, the MEA was operated with the square-shaped potential cycle of between 0.6V and 1.0V (6 s/cycle). About the CCMs that the durability tests were carried out, the elemental distribution of the cross section was analyzed by EPMA. In addition, the information of the degradation products about the ionomer was obtained by LC/MS. 3. Result and discussion Figure 1 shows the SEM images (upper side) and the line profiles (lower side). From the SEM image of Initial, each thickness of the anode layer, the electrolyte membrane and the cathode layer is about 7 mm, 60 mm and 7 mm, respectively. Each thickness of the anode layer and the electrolyte membrane in Start-Stop cycle is also the same value as Initial. However, the thickness of the cathode layer is thinner than Initial. It is inferred that the change of the layer thickness is due to the influence of the durability test. On the other hand, there is no significant different about each region in Load cycle. In the line profile of the elements by EPMA, the profile shape of Load cycle is almost the same as Initial. The concentration of Pt in the cathode layer of Start-Stop cycle is higher than the other samples. In the cathode layer of Load cycle, because the layer thickness became thin, it is inferred that Pt concentrated.As the result of the other analysis, it was revealed by LC/MS that the degradation product quantity for the ionomer of Load cycle was the largest and the degradation product quantity for the electrolyte of Initial was the smallest.From those results, it is inferred that the influence to the catalyst layer is large on the Start-Stop cycle test and the influence to the ionomer is large on the Load cycle test. Figure 1

돼지 분뇨와 sPAES 막을 이용한 미생물 연료전지의 특성

− Microbial fuel cells (MFC) were operated with pig wastes and PEMFC (Proton Exchange Membrane Fuel Cells) MEA (Membrane and Electrode Assembly). Performance of hydrocarbon membrane was compared with that of perfluoro membrane at MFC condition. Sulfonated-Poly(Arylene Ether Sulfone) was used as hydrocarbon membrane and Gore membrane was used as perfluoro membrane. OCV of sPAES MEA was 50mV higher than that of Gore MEA and power density of sPAES MEA was similar that of Gore MEA. Reinforcement of sPAES membrane stabilized the performance of MEA in MFC. The highest performance was obtained at temperature of 45 C and with culture solution circulation rate of 50 ml/min. The highest power density was 1,100 mW/m at optimum condition in MFC using pig waste.

고분자 전해질 연료전지에서 sPEEK 막을 이용한 전극과 막 합체(MEA)의 열화에 관한 연구

− Recently, there are many efforts focused on development of more economical non-fluorinated membranes for PEMFCs (Proton Exchange Membrane Fuel Cells). In this study, to test the durability of sPEEK MEA (Membrane and Electrode Assembly), ADT (Accelerated Degradation Test) of MEA degradation was done at the condition that membrane and electrode were degraded simultaneously. Before and after degradation, I-V polarization curve, hydrogen crossover, electrochemical surface area, membrane resistance and charge transfer resistance were measured. Although the permeability of hydrogen through sPEEK membrane was low, sPEEK membrane was weaker to radical evolved at low humidity and OCV condition than fluorinated membrane such as Nafion. Performance after MEA degradation for 144 hours and 271 hours were reduced by 15% and 65%, respectively. It was showed that the main cause of rapid decrease of performance after 144 hours was shorting due to Pt/C particles in the pinholes.

직접개미산 연료전지용 전해질막으로서 sPAES 막과 sPEEK 막의 특성

Recently, direct formic acid fuel cells (DFAFC) among direct liquid fuel cells is studied actively. Economical hydrocarbon membranes alternative to fluorinated membranes for DFAFC's membrane are receiving attention. In this study, characteristics of sulfonated poly(ether ether ketone, sPEEK) and sulfonated poly(arylene ether sulfone, PAES) membranes were compared with Nafion membrane at DFAFC operation condition. Formic acid crossover current density of hydrocarbon membranes were lower than that of Nafion 211 fluorinated membrane. I-V performance of sPEEK MEA(Membrane and Electrode Assembly) was similar to that of Nafion 211 MEA due to similar membrane resistance each other. sPEEK MEA with low formic acid crossover showed higher stability compared with Nafion 211 MEA.

가축 분뇨를 이용한 미생물 연료전지의 특성 및 MEA 열화

고분자전해질 연료전지용 MEA(Membrane and Electrode Assembly)와 가축분뇨를 이용해 미생물연료전지(MFC)를 구동하였다. 여러 균을 혼합해 MFC를 구동했을 때 개별적으로 구동했을 때보다 높은 개회로전위(OCV)를 나타냈다. 돼지분뇨, 소분뇨, 닭분뇨, 오리 분뇨 중 돼지 분뇨를 이용했을 때 제일 높은 OCV 540mV를 보였다. 그리고 돼지분뇨에서 최고 <TEX>$963mW/m^2$</TEX>의 전력이 발생하였다. MFC 구동과정에서 MEA의 <TEX>$Na^{2+}$</TEX>, <TEX>$Ca^{2+}$</TEX>, <TEX>$K^+$</TEX> 이온 및 불순물들에 의한 오염이 MFC의 낮은 성능의 한 원인임을 확인하였다. Microbial fuel cells (MFC) were operated with livestock wastes and PEMFC (Proton Exchange Membrane Fuel Cells) MEA (Membrane and Electrode Assembly). OCV of MFC with mixtures of microbial was higher than that of MFC with single microbial. MFC using pig wastes showed highest OCV (540 mV) among cow waste, chicken waste and duck waste. And the power density of MFC using pig waste was <TEX>$963m</TEX><TEX>W/m^2$</TEX>. Contamination of MEA with <TEX>$Na^{2+}$</TEX>, <TEX>$Ca^{2+}$</TEX>, <TEX>$K^+$</TEX> ion and impurities was the one cause for low performance of MFC during operation.

The performance improvement of membrane and electrode assembly in open-cathode proton exchange membrane fuel cell

An investigation was made to explore the effect of the structural combination of the membrane and electrode assembly (MEA) on the performance improvement of the open-cathode proton exchange membrane (PEM) fuel cell. Two typical MEAs of GDE (gas diffusion electrode) and CCM (catalyst coated membrane) were used, and the results show that the CCM-based MEA could maximize the catalyst utilization under room temperature, and the power density was 818mWcm−2. The employment of hydrophilic gas diffusion layers (GDLs) can further improve the performance of the CCM-based MEA at elevated cell temperature in spite of its high contact resistance and low gas permeation. The variation of cell voltage under different air stoichiometry and cell temperatures was also explored, and the results show that CCM-based MEA with hydrophilic GDLs gives good performance and stability even at 60°C.

PEMFC에서 전극 열화가 전해질 막 열화에 미치는 영향

Until a recent day, degradation of PEMFC MEA (membrane and electrode assembly) has been studied, separated with membrane degradation and electrode degradation, respectively. But membrane and electrode were degraded coincidentally at real PEMFC operation condition. During simultaneous degradation, there was interaction between membrane degradation and electrode degradation. The effect of electrode degradation on membrane degradation was studied in this work. We compared membrane degradation after electrode degradation and membrane degradation without electrode degradation. I-V performance, hydrogen crossover current, fluoride emission rate (FER), impedance and TEM were measured after and before degradation of MEA. Electrode degradation reduced active area of Pt catalyst, and then radical/ evolution rate decreased on Pt. Decrease of radical/ reduced the velocity of membrane degradation.

Stability Evaluation for Polymer Electrolyte Membrane Eletrolyzer

Recently, polymer electrolyte membrane (PEM) electrolyzers consist of the layered structure of membrane and electrode assembly (MEA), titanium flow field plate, gasket, end plate, and others. Among these components, MEA and titanium flow field plate take account for most of the device cost. The cost and time for manufacturing device can be reduced with the gasket-integrated 3-D mesh-applied PEM electrolyzer (Fig. 3), while maintaining the same performance as that of the existing titanium flow field plate devices. The 3-D mesh is found to perform the roles of the existing flow plate which ensures the smooth fluid flow and uniform power supply. The voltage shows 19.3V at current density (0.5 A/cm2), a little lower than 19.6V that is 10 times of 1.96V which is the average cell voltage at the same current density. In addition, hydrogen production and stability for performance are equal to or higher than that of the device for titanium flow field plate.

PEMFC에서 전극과 전해질 막의 열화 가속 시험

최근까지 대부분의 PEMFC MEA (Membrane and Electrode Assembly) 열화 연구는 전극과 전해질막 각각 분리되어 연구되었다. 그런데 실재 PEMFC 운전조건에서는 전극과 막은 동시에 열화된다. 그래서 본 연구에서는 전극과 막열화가 동시에 일어나는 조건에서 열화 가속시험을 하였다. 실험결과 전극과 막 열화가 서로 상호작용함을 보였다. 막열화는 촉매의 활성면적 감소폭을 줄였고, 전극열화는 막의 수소투과 전류와 불소유출속도(FER) 증가폭을 감소시켰다. Until a recent day, degradation of PEMFC MEA (membrane and electrode assembly) has been studied, separated with membrane degradation and electrode degradation, respectively. But membrane and electrode were degraded coincidentally at real PEMFC operation condition. Therefore in this work, AST (Accelerated Stress Test) of MEA degradation was done at the condition that membrane and electrode were degraded simultaneously. There was interaction between membrane degradation and electrode degradation. Membrane degradation reduced the decrease range of catalyst active area by electrode degradation. Electrode degradation reduces increase range of the hydrogen crossover current and FER (Fluoride Emission Rate) by membrane degradation.

이온 오염에 의한 고분자전해질 연료전지의 성능저하

고분자전해질연료전지(PEMFC)에서 음극 공기에 의한 이온오염은 막전극 합체(MEA)의 성능을 심각하게 열화시킨다. 본 연구에서는 산업단지, 길가, 해변의 공기 중 이온 농도를 측정하였다. 이들 지역에서 <TEX>$Na^+$</TEX>, <TEX>$K^+$</TEX>, <TEX>$Ca^{2+}$</TEX>와 <TEX>$Fe^{3+}$</TEX> 이온 농도가 비교적 높았다. 가습수로부터 이들 이온이 cathode에 유입되어 MEA 성능에 미치는 영향에 대해 연구하였다. 수돗물을 가습수로 사용해 170시간 운전한 후 MEA 성능이 초기의 11%로 감소하였다. 이들 오염 이온들이 수소이온보다 전해질 막의 슬폰산기와 친화력이 더 강해 전해질 막에 쉽게 이온 교환된 결과다. MEA 중에서 전극/막 계면에서 이온 오염이 MEA 성능저하에 미치는 영향이 제일 컸다. Contamination of ion from cathode air on the membrane and electrode assembly (MEA) is the serious degradation source in proton exchange membrane fuel cells (PEMFC). In this study, concentration of ions in air at industry region, street and seaside were measured. There were comparably high concentration of <TEX>$Na^+$</TEX>, <TEX>$K^+$</TEX>, <TEX>$Ca^{2+}$</TEX> and <TEX>$Fe^{3+}$</TEX> in this regions. This paper shows the effects of MEA contamination by these ions generated from humidification water. After 170 hours of fuel cell operation using city water as humidification water, the performance of unit cell decrease to 11% of initial performance. The electrolyte membrane easily absorbed foreign contaminant cations due to the stronger affinity of foreign cations with the sulfonic acid group compared to <TEX>$H^+$</TEX>. The contaminant ions existing in the interface between the platinum catalyst and ionomer layer turn out to be the most serious factor to decrease cell performance.

Recent Advances in High Temperature Proton Exchange Membrane Fuel Cell Manufacturing

Not enough attention has been devoted to developing the manufacturing processes required to transition fuel cell science into commercially viable products, despite clear recognition that cost and reliability are two key factors preventing more rapid introduction of the technology. Understandably, there is a natural reluctance of many companies to invest resources in manufacturing processes and systems for a product that is still evolving. Changes in materials, geometries, and even the basic fuel cell architecture can have profound effects on the viability of certain manufacturing processes and equipment. This situation suggests that modular flexible manufacturing processes be adopted to accommodate these uncertainties. Since 1999 researchers in the Center for Automation Technologies and Systems (CATS) at Rensselaer Polytechnic Institute have focused on developing flexible manufacturing processes and systems for the manufacture of high temperature proton exchange membrane (PEM) fuel cell components. One result has been a fully automated membrane and electrode assembly (MEA) pilot manufacturing line developed for BASF Fuel Cell, GmbH, formerly Pemeas, GmbH that has been operating since September of 2002. This pilot line has been designed as a highly flexible modular manufacturing system that is able to respond quickly and cost effectively to changes in product materials, geometries, and architectures. For example, the line has easily accommodated three generations of membrane materials and a broad range of MEA sizes and geometries. Because of this flexibility, short runs of prototype MEAs are feasible, and the pilot line is able to produce a high mix of a broad range of MEA sizes. The CATS research team continues to optimize manufacturing processes to provide increased capacity, consistency, reduced costs, and high product quality. This paper will describe the many challenges and risks associated with the development and implementation of an advanced manufacturing capability for high temperature PEM MEAs, and the continuing collaboration between the BASF Fuel Cell and the CATS. Specific examples of several technical challenges and the adopted solutions are presented, along with ongoing fuel cell manufacturing initiatives.

Treatment of low concentration hydrogen by electrochemical pump or proton exchange membrane fuel cell

Proton exchange membrane fuel cell (PEMFC) can produce electricity through electrochemical reaction of hydrogen with oxygen with the use of a membrane and electrode assembly (MEA). In other words, the hydrogen pressure difference between the anode and cathode can produce electricity via an electrochemical process. Conversely, when we supply electricity to MEA from an external power source, we can pump up or separate hydrogen from the low-pressure anode to the high-pressure cathode, according to the principle of “concentration cell”. By the way, PEMFC cannot use the fuel completely, because a cell potential decreases and electrode material may corrode when most of the fuel is consumed. Therefore the fuel released from PEMFC should be treated safely. The depleted hydrogen from PEMFC can be recovered by the electrochemical hydrogen pump, or further can be used as a fuel for the power generation by PEMFC, even though the cell voltage might be low. In this study we preliminarily measured the voltage–current characteristics of hydrogen pump and PEMFC changing the hydrogen concentration from 99.99% to 1%, as another option to platinum catalytic combustion of low concentration hydrogen. Moreover we could successfully treat the low concentration hydrogen by electrochemical pump or PEMFC, for the widely changing hydrogen concentration and mixture flow rate. The gas chromatography confirmed the hydrogen concentration of the treated gas to be 1000 ppm at most.

Separation and compression characteristics of hydrogen by use of proton exchange membrane

Abstract Fuel cells (FC) can produce electricity through electrochemical reaction of hydrogen with oxygen with the use of a membrane and electrode assembly (MEA). In other words, the hydrogen pressure difference between the anode and cathode can produce electricity via an electrochemical process. Conversely, when we supply electricity to MEA from an external power source, we can pump up or separate hydrogen from the low pressure anode to the high pressure cathode according to the principle of the “concentration cell”. The depleted hydrogen from the FC can be recovered by the hydrogen separation pump proposed herein, or low pressure hydrogen can be pumped to high pressure hydrogen by the hydrogen compression pump proposed herein. In this study we preliminarily tested the hydrogen separation pump and hydrogen compression pump, and demonstrated their good performance. The tested performances were analyzed with the use of our simulation model of a hydrogen pump, which was made by modifying our FC simulation model, and the test results agreed well with the calculated results.

Performance and instabilities of proton exchange membrane fuel cells

Performance of proton exchange fuel cells with different membrane and electrode assembly (MEA) is studied. It is shown that MEA fabricated with catalyst plasma pulverization technology has the maximum performance. Some instabilities in the cell performance, observed with time, are probably due to periodic cathode flooding.

Polymer Electrolyte Dehumidifying Cell and Its Application to Air Conditioners

Large amounts of chlorofluorocarbons (CFCs) have been released into the atmosphere, resulting in the destruction of the ozone layer in the stratosphere. There is thus a need to develop air conditioners that do not use CFCs. As one such air conditioner, we propose a combined system of dehumidifying cells that use proton exchange membranes (PEMs) with a water evaporation air cooler. PEMs are the solid electrolytes for polymer electrolyte fuel cells and can transfer water molecules with protons. The performance of existing dehumidifying cells using PEMs is not well understood. As important factors to determine the dehumidifying performance, in this study we first measured the transmissibility and the electro-osmotic coefficient of water molecules through the membrane and electrode assembly (MEA), water vapor diffusivity through the gas diffusion layer (GDL), and the mass-transfer coefficient between the channel flow and the GDL. These measured factors were then adopted in a performance analysis of our dehumidifying cell. Our simulation code solves simultaneously the conservation equations of mass and energy with an equivalent electric circuit of the cell. The calculated results describe well the experimental dehumidifying performance. By extending this simulation code we predicted the coefficient of performance (COP) of our novel air-conditioning system. The calculated COP for our test cells is small at 0.10 or 0.21, but can be made as large as 4 if of PEM can be increased to 5.

Deposition of platinum nanoparticles on organic functionalized carbon nanotubes grown insitu on carbon paper for fuel cells

Deposition of small Pt nanoparticles of the order of 2–2.5 nm on carbon nanotubes(CNTs) grown directly on carbon paper is demonstrated in this work. Sulfonic acidfunctionalization of CNTs is used as a means to facilitate the uniform deposition of Pt onthe CNT surface. The organic molecules attached covalently to the CNT surfacevia electrochemical reduction of corresponding diazonium salts are treated withconcentrated sulfuric acid and the sulfonic acid sites thus attached are used asmolecular sites for Pt ion adsorption, which are subsequently reduced to yieldthe small Pt nanoparticles. Cyclic voltammograms reveal that, after removal ofthe organic groups during high temperature reduction, these Pt nanoparticlesare in electrical contact with the carbon paper backing. A typical Pt loading of0.09 mg cm−2 isachieved, that shows higher specific surface area of Pt than an E-TEK electrode with Pt loading of0.075 mg cm−2. A membrane and electrode assembly (MEA) is prepared with a Pt/CNT electrode ascathode and an E-TEK electrode as anode, and it offers better performance than aconventional E-TEK MEA.

Materials and processes for small fuel cells

Materials and processes for water management electrode, efficient flow field, low cost ionomer membrane and stack design for proton exchange membrane fuel cell (PEMFC) also with methanol oxidation catalyst, liquid diffusion electrode, low methanol cross-over membrane and efficient monopolar cell pack design for direct methanol fuel cell (DMFC) are discussed. These include the technical achievements of small PEMFC (Membrane and Electrode Assembly (MEA): 400 mW/cm 2 with non-humidified H 2/air, 1 Bar, 30 °C; membrane: 0.1 S/cm; stack: 40 and 200 W with no peripheral) and miniaturized DMFC (MEA: 50 mW/cm 2 with 2 M methanol and 1 Bar air at 30 °C; membrane: hybrid; cell pack: 600 mW). Further studies for the realization of these technologies are also suggested.