Cathode Thickness Research Articles

Finite Element Modeling of Idealized Infiltrated Composite Solid Oxide Fuel Cell Cathodes

Using a two-dimensional finite element approach, the polarization resistance of idealized, branched, nano-particulate, composite cathodes was determined. Porous CGO, LSGM, or YSZ networks infiltrated with additional ionic conductor and subsequently infiltrated with LSCF or BSCF were modeled. For fixed mixed conductor particle size, dual nano-particle infiltrations (ionic + mixed conductor) resulted in an order of magnitude polarization resistance decrease, compared to single component mixed conductor infiltrations. For most SOFC relevant temperatures (500-900C), geometries, and material combinations, cathode performance was limited by the charge transfer reaction occurring at the mixed conductor interface and therefore scaled with the cathode surface area, as long as the cathode thickness was <~10microns. For cathodes thicker than ~10microns, losses within the ionic conducting network determined performance, resulting in a breakdown of the linear performance dependence on cathode surface area. The boundary between these regimes varied with ionic conducting cathode arm width, column width, and ionic conductivity.

Surface Modification by Compositionally Modulated Multilayered Zn‐Fe Alloy Coatings

AbstractCompositionally modulated multilayered alloy (CMMA) coatings of Zn‐Fe were developed from acid chloride baths by single bath technique. The production and properties of CMMA Zn‐Fe coatings were tailored as a function of switching cathode current densities (SCCD's) and thickness of individual layers. Corrosion rates (CR) were measured by electrochemical methods. Corrosion resistances were found to vary with SCCD's and the number of sub layers in the deposit. SCCD's were optimized for production of Zn‐Fe CMMA electroplates showing peak performance against corrosion. The formation of discrete Zn‐Fe alloy layers having different compositions in the deposits were demonstrated by scanning electron microscopy (SEM). Improvements in the corrosion resistance of multilayered alloys are due to the inherent barrier properties of CMMA coatings as evidenced by electrochemical impedance spectroscopy (EIS). Corrosion resistance afforded by Zn‐Fe CMMA coatings are explained in terms of the n‐type semiconductor films at the interface, supported by Mott‐Schottky's plot. It was observed that the alloy with high w(Fe) on the top showed better corrosion resistance compared to that with the less w(Fe) on top. At optimum SCCD's of 3.0–5.5 A·dm−2, a Zn‐Fe CMMA coatings with 600 sub layers showed ca. 45 times better corrosion resistance than conventional Zn‐Fe alloy of the same thickness. The deposit showed no red rust even up to 1130 h in salt spray test.

Morphology and electrochemical activity of SOFC composite cathodes: II. Mathematical modelling

This paper presents a mathematical model of mass and charge transport and electrochemical reaction in porous composite cathodes for application in solid oxide fuel cells. The model describes a porous composite cathode as a continuum, and characterises charge and mass transfer and electrochemical kinetics using effective parameters (i.e. conductivity, diffusivity, exchange current) related to morphology and material properties by percolation theory. The model accounts for the distribution of morphological properties (i.e. porosity, tortuosity, density of contacts among particles) along cathode thickness, as experimentally observed on scanning electron microscope images of LSM/YSZ cathodes of varying thickness. This feature allows the model to reproduce the dependence of polarisation resistance on thickness, as determined by impedance spectroscopy on LSM/YSZ cathodes of varying thickness. Polarisation resistance in these cathodes is almost constant for thin cathodes (up to 10 µm thickness), it sharply decreases for intermediate thickness, to reach a minimum value for about 50 µm thickness, then it slightly increases in thicker cathodes.

Carbon Catalyst-Support Corrosion in Polymer Electrolyte Fuel Cells: Mechanistic Insights

In this paper we discuss a novel mechanistic model describing the coupling between the PEFC MEA electro-catalysis and the cathode carbon catalyst-support corrosion. On a physical basis, the model describes the feedback between the instantaneous performance and the intrinsic cathode carbon oxidation process. It allows exploring the impact of the operating conditions and the initial electrodes compositions on the PEFC MEA durability. Some numerical simulations show agreement with experimental knowledge already reported in literature: in particular, when the anode chamber is partially exposed to oxygen (induced by PEM crossover or fuel starvation), cathode thickness decrease and cell potential decay are predicted. Furthermore, we found that cathode damage increases as platinum loading increases and as platinum nano-particles size decreases. On the basis of our modeling approach we propose, and experimentally validate, the use of anodic injection as a way to mitigate cathodic carbon corrosion in in-house elaborated model MEA.

The effects of the interconnect rib contact resistance on the performance of planar solid oxide fuel cell stack and the rib design optimization

A mathematical model for the performance of the planar solid oxide fuel cell (SOFC) stack is described. The model considered the electric contact resistance between the electrode and interconnect rib, the gas transport in the electrodes, electronic and ionic conductions in the membrane-electrode assembly and the electrochemical reactions at the gas–electrode–electrolyte three phase boundaries. The model is capable of describing in detail the rib effect on the gas transport and the current distribution in the fuel cell. The contact resistance is found to be an important factor in limiting the SOFC performance. Based on the interplay of the concentration and ohmic polarizations, numerical results are provided for the optimal rib widths for different pitch sizes and different area specific contact resistance (ASR contact). The optimal rib width is found to be linear to the pitch width for a given ASR contact and the parameters for the linearity are given. The parameters are little affected by the hydrogen concentration and the thickness, porosity or conductivity of the cathode. The influence of the cathode thickness on the SOFC performance is also examined. Contrary to the common belief on the thin cathode (∼50 μm), thicker cathode layer (100–300 μm) is beneficial to the SOFC stack performance.

Stress field and failure probability analysis for the single cell of planar solid oxide fuel cells

An analytical model is developed to predict the residual thermal stresses in a single cell of solid oxide fuel cells (SOFCs), which consists of a thick porous 8 mol% Y 2O 3 stabilized zirconia/nickel oxide (8YSZ/NiO) anode, a dense 8YSZ electrolyte and a porous lanthanum strontium manganite (LSM) cathode. The simulated stresses in the cell at room temperature, which are resulted from the contraction mismatch of its components, indicate that the major principal stress in the anode is tensile while the electrolyte and cathode are under compressive stresses. The stress in one component decreases with the increase of its thickness when the thicknesses of the other two components are fixed, and the decrease of the tensile stress in the anode will cause the increase of the compressive stresses in both the cathode and the electrolyte, and vice versa. The analysis also reveals that the anode is the part that is most susceptible to fracture since the tensile thermal stress is so high that it reaches to the fracture strength of the anode material. The Weibull statistic is employed to estimate the failure probability of the anode. The simulation results indicate that the anode failure probability decreases with the increase of the anode thickness and the decrease of the electrolyte thickness. To keep the anode failure probability less than 1E−06, the anode thickness should be greater than 0.7 mm for a cell with an electrolyte thickness of 10 μm and a cathode thickness of 20 μm.

Performance of Ni/Y2O3-Stabilized ZrO2 Cermet Cathode Prepared by Mechanical Alloying for High-Temperature Electrolysis of Water Vapor

A Ni/Y2O3-stabilized ZrO2 composite cathode was fabricated by high-energy ball milling of Ni and Y2O3-stabilized ZrO2 powders for high-temperature electrolysis (HTE) of water vapor. The composite powder composition, time and rotation speed of ball milling were optimized by trial and error for suitable performance with the maximum efficiency of the fabricated cathode in high-temperature electrolysis of water vapor (steam) at 800 °C. Thus-synthesized composite powders were characterized using various analytical tools, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis (PSA), and a self-supporting planar unit cell was prepared with a Ni/Y2O3-stabilized ZrO2 composite cathode and a Pt paste anode screen-printed on each side of a Y2O3-stabilized ZrO2 electrolyte disc (30 mm in diameter) and then sintered at 1450 °C for high-temperature electrolysis. XRD and PSA results showed that ball milling parameters, such as ball milling time and rotation speed, affect the crystallinity, average particle size, and particle size distribution of ball-milled Ni/Y2O3-stabilized ZrO2 composites. The effects of cathode and Y2O3-stabilized ZrO2 electrolyte thicknesses on the efficiency of hydrogen production were investigated using a self-supporting planar HTE unit cell operating at 800 °C. The engineering significance of high-energy ball milling (HEBM) is evident: HEBM is approximately equivalent to 60 µm screen printing over the Y2O3-stabilized ZrO2 electrolyte and could obviate a tedious and time-consuming screen-printing process in the fabrication of a cathode.

Multiscale Model of Carbon Corrosion in a PEFC: Coupling with Electrocatalysis and Impact on Performance Degradation

In this paper we propose a mechanistic model describing the coupling between the polymer electrolyte fuel cell (PEFC) membrane electrodes assembly (MEA) electrocatalysis and the cathode carbon catalyst-support corrosion. The electrocatalysis description includes our previously introduced irreversible thermodynamics nanoscale models of the electrochemical reactions (hydrogen oxidation reaction/oxygen reduction reaction) coupled with the catalyst/ionomer interface double layer phenomena. Physically, the model describes the feedback between the instantaneous performance and the intrinsic cathode carbon oxidation process. It allows exploring the impact of the operating conditions (nominal current, reactant gas pressures, temperature, etc.) and the initial electrodes compositions (carbon and platinum loadings) on the PEFC MEA durability. Some numerical simulations show agreement with experimental knowledge already reported in literature, in particular, when the anode chamber is partially exposed to oxygen (induced by polymer electrolyte membrane crossover or fuel starvation), cathode thickness decrease and cell potential decay are predicted. Furthermore, we found that cathode damage increases as platinum loading increases and as platinum nanoparticles size decreases. Moreover, carbon corrosion favors the platinum coarsening; competition between carbon oxidation reaction and electrocatalytic mechanisms is investigated. Simulations also suggest that an “optimal” external load current inducing a “maximal” durability exists. The sensitivities of the electrochemical impedance spectra to the operating conditions and simulated operation time are also provided.

Performance of Ni/YSZ cermet cathode prepared by mechanical alloying for high temperature electrolysis of water vapor (steam): effect of anode and cathode thicknesses on the efficiency of hydrogen production

Abstract Ni/YSZ (Y2O3-stabilized ZrO2) composite cathode is fabricated by high-nergy ball milling of Ni and YSZ powders for high temperature electrolysis of water vapor. Composite powder composition, time and rotation speed of ball milling were optimized by trial and error for suitable performance with maximum efficiency of fabricated cathode in high temperature electrolysis of water vapor (steam) at 800°C. The composite powders thus synthesized were characterized using various analytical tools such as X-ray diffraction, scanning electron microscopy and particle size analysis, and a self-supporting planar type unit cell was prepared with Ni/YSZ composite cathode and Pt paste anode screen-printed on each side of YSZ electrolyte disk (30 mm dia.) and then sintered at 1450°C for high temperature electrolysis. X-ray diffraction and particle size analysis results showed that the Ni/YSZ composite effectively consisted of crystalline Ni and YSZ distributed on a sub-micron scale and evenly distributed without aggregation of particles. To study the effect of anode and cathode thickness on the efficiency of the hydrogen production rate, screen-printing of anode and cathode was carried out on each side of YSZ electrolyte to three different thickness values during the fabrication of a self-supporting planar type unit cell which operated quite satisfactorily during high temperature electrolysis at 800°C: a significantly higher hydrogen production rate of 13 sccm (standard cubic centimeters per minute) was reproducibly observed for triple screen-printing of anode and cathode over each side of the YSZ electrolyte disk compared to 0.5 sccm for the single screen-printed cathode under an applied direct current of 0.7 mA cm−2. Additionally, linear increase in hydrogen production was observed with applied current for triple screen-printed electrodes in contrast to single and double screen-printed electrodes.

Electrical Performance of Calcium doped Lanthanum Ferrite for use in Single-Step Co-fired Solid Oxide Fuel Cells (SOFCs)

AbstractIn the single-step SOFC co-firing process YSZ electrolytes with sintering aid densify at a temperature of ˜1300°C. Electrodes employed in the single-step co-fired SOFC must therefore sinter with the right microstructure at ˜1300°C. Calcium-doped lanthanum ferrite, La0.8Ca0.2FeO3±&amp;#948; (LCF-20) was identified in earlier studies as a possible stable cathode material for the single-step co-fired SOFC. LCF-20 is also expected to be a more stable cathode material than LSCF (strontium and cobalt doped lanthanum ferrite). Four-probe conductivity tests yielded ˜93 S/cm at 800°C and showed an increase in conductivity as pO2 increases, characteristic of p-type conduction. LCF has a higher electrical conductivity compared to LSCF and LCM+YSZ cathode materials. Oxygen ion conductivity of LCF-20 obtained from permeability measurements is higher than that of YSZ and LSF-20. Therefore LCF has excellent mixed conducting properties to serve as a catalytically active cathode material for co-fired solid oxide fuel cells operating at intermediate temperatures. Electrochemical Impedance Spectroscopy (EIS) measurements were made on symmetrical cells fabricated with YSZ electrolyte and the electrode materials. A gadolium doped ceria (GDC) barrier layer was employed to prevent LCF/YSZ reaction. Comparison of LCF/GDC/YSZ/GDC/LCF EIS data to LCM+YSZ/YSZ/LCM+YSZ EIS data gathered using identical test conditions and electrode microstructures shows that LCF has a measured polarization resistance (Rp) of approximately half that seen in LCM+YSZ. Variations in cathode thickness and porosity show the best performance with a cathode of a critical thickness and finer porosity. Slight stoichiometric deviations in LCF result in the formation of a Ca-Fe-O liquid phase during electrode sintering at around 1220 C. The liquid phase migrates into and through the GDC layer. EDX line scans show the second phase to be rich in Ca and Fe. Thicker GDC layers seem to prevent the liquid phase from reaching the electrolyte/GDC interface. Structural analysis with TEM will be performed. The properties and the effect of the Ca-Fe-O phase on the cathodic performance of the cell are being investigated; however, preliminary results indicate that minor amounts of the Ca-Fe-O phase will not interfere with the electrochemical performance of the LCF cathode. The high temperature instability in LCF has been observed in other studies, but has not been studied specifically in the literature.

Effect of radical polymer cathode thickness on the electrochemical performance of organic radical battery

The influence of cathode thickness on the electrochemical performance of an organic radical battery (ORB) with the radical polymer poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) as the cathode active material is presented. The ORB consists of lithium metal anode and PTMA cathode with an active material content of 40 wt.%. An increase in cathode thickness results in a decrease in specific capacity and discharge voltage of the cell and an increase in electrode/electrolyte interfacial resistance. The best performance is achieved with a thin cathode of 17 μm that shows nearly 100% utilization of the active material (∼ 111 mAh/g) at current densities up to 1.0 mA/cm 2. The cell exhibits excellent high-rate capability and cycle characteristics with a stable impedance behavior and an intact cathode structure on cycling. The results demonstrate that high performance can be achieved from the non-conductive PTMA cathode with higher active material content by using a thin and properly prepared cathode consisting of a uniform, nanometer range coating of the polymer layer on the conductive carbon particles.

Chromium Poisoning of the Porous Composite Cathode: Effect of Cathode Thickness and Current Density

Electrochemical behavior of the (LSM)/porous functional layer(FL)/ -stabilized (8YSZ) electrolyte half cell in the presence of a Cr source was studied by dc method and impedance spectroscopy. The porous FL was made of a LSM and 8YSZ powder mixture. The degradation rate of the cell was found to depend strongly on the FL thickness. The increase in the thickness of the FL up to leads to a significant reduction of the Cr poisoning of the cathode. The effect of high current density (up to ) on the long-term performance of half cells in the presence of chromium source was investigated. A few processes occur near the LSM/8YSZ/gas contact under current load in the presence of a chromium source: chemical transformations of this contact accompanied by the formation of chromium oxide under a relatively high current load, destruction of the electrolyte and penetration of chromium into the electrolyte along the grain boundaries. The chemical nature and rate of the transformations taking place near the LSM/8YSZ/gas contact under current load, most probably, determine the electrochemical performance of the cell for the initial operation period whereas the two other processes could contribute to the degradation during long-term performance.

Top-emitting organic light-emitting devices with different-thickness top silver cathodes

Top-emitting organic light-emitting devices with different-thickness top Ag cathodes were fabricated. The tris (8-hydroxyquinoline) aluminium based device with a 23 nm thick Ag cathode shows a maximum efficiency of 11.1 cd A−1 and the brightness of the device can reach 560 cd m−2 at 4 V. The blueshift of the resonant wavelength (RW) in the devices with increasing thickness of the top Ag cathode was observed. The theoretical simulation was described by a model based on the Fabry–Perot microcavity structure. The results indicated that both RW and the efficiency of the devices are Ag thickness dependent.

중저온형 SOFC를 위한 PSCF3737(Pr0.3Sr0.7Co0.3Fe0.7O3) 공기극 물질의 특성 및 최적화께 관한 연구

IT-SOFC(중저온형 고체산화물 연료전지)의 공기극으로 적합한 PSCF3737의 물질 특성을 파악하고 그 특성을 이용하여 낮은 ASR을 갖기 위한 소결 온도 및 두께 최적화에 관한 연구를 수행하였다. 분말 사이즈 및 상형성을 고려할 때 GNP 방법으로 합성된 분말의 하소 온도는 <TEX>$1000^{\circ}C$</TEX>가 적합함을 알 수 있었다. 산소 분압에 따른 ASR 변화 실험을 통하여 PSCF3737의 저항 성분을 전극 자체의 특성과 관련된 중간 주파수 대역(<TEX>${\sim}10^2Hz$</TEX>)과 산소의 확산에 영향 받는 낮은 주파수 대역(<TEX>${\sim}10^{-1}Hz$</TEX>) 2가지로 분류할 수 있었다. 공기극의 특성 실험을 통하여 소결 온도는 <TEX>$1200^{\circ}C$</TEX>가 가장 적합하며 공기극의 두께는 2번 스크린 프린팅 된 <TEX>$27\;{\mu}m$</TEX>가 가장 적합함을 알 수 있었다. 이를 토대로 EIS 측정을 하면 <TEX>$700^{\circ}C$</TEX>에서 <TEX>$0.115\;{\Omega}cm^2$</TEX>의 낮은 ASR값을 얻을 수 있었다. [ <TEX>$PSCF3737(Pr_{0.3}Sr_{0.7}Co_{0.3}Fe_{0.7}O_3)$</TEX> ] is a good candidate cathode material for IT-SOFC(intermediate temperature solid oxide fuel cell) because of high MIEC(mixed ionic electronic conductor) conductivity. In this study, the characteristics of PSCF3737 was investigated and optimizations of sintering temperature and thickness for <TEX>$PSCF3737(Pr_{0.3}Sr_{0.7}Co_{0.3}Fe_{0.7}O_3)$</TEX> was carried out. Impedance responses were divided into two parts by frequency region. Middle frequency part (<TEX>${\sim}10^2\;Hz$</TEX>) was concerned with oxygen reduction reaction on surface and low frequency part (<TEX>${\sim}10^{-1}\;Hz$</TEX>) was related with oxygen diffusion. The reasonable sintering temperature and thickness of cathode were <TEX>$1200^{\circ}C$</TEX> and about <TEX>$27\;{\mu}m$</TEX> with regard to EIS(electrochemical impedance spectroscopy). ASR(areas specific resistance) of optimized cathode is <TEX>$0.115\;{\Omega}\;cm^2$</TEX> at <TEX>$700^{\circ}C$</TEX>.

Novel Design of Microchanneled Tubular Solid Oxide Fuel Cells and Synthesis Using a Multipass Extrusion Process

A novel, microchanneled tubular solid oxide fuel cell was fabricated using a multipass extrusion process, with an outside diameter of 2.7 mm that contained 61 cells. Cell materials used in this work were 8 mol% yttria-stabilized zirconia (8YSZ), La0.8Sr0.2MnO3 (LSM), and NiO–8YSZ (50:50 vol%) as electrolyte, cathode, and anode, respectively. Three stages of heat-treatment processes were applied, at 700°C in N2 condition, at 1000°C in air, and then sintered at 1300°C for 2 h, respectively. The X-ray diffraction analysis confirmed that no reaction phases appeared after sintering. The microstructures of anode and cathode were fairly porous while the electrolyte had a dense microstructure (relative density >96%). The thickness of electrolyte, anode, and cathode were 20, 30, and 40 μm, respectively, and the diameter of the continuous channels was 150 μm.

3D-Modelling and Performance Evaluation of Mixed Conducting (MIEC) Cathodes

Mixed electronic/ionic conducting (MIEC) cathode materials are qualified for the application in intermediate-temperature SOFCs. The area specific resistance of MIEC cathodes is likewise determined by chemical composition and microstructure. A three-dimensional finite element method model, which is capable to analyze and predict the performance of MIEC cathodes, was developed. Representations for the actual cathode microstructure are automatically generated according to characteristic measures like cathode thickness, composition, porosity and average particle size. The model calculates the spatial distributions of the oxygen activity, the diffusive oxygen flux in the pores as well as the ionic current density inside the MIEC-cathode and inside the electrolyte material. Based on these values the area specific resistance of the cathode and the penetration depth of the ionic current can be evaluated. This paper will analyze the effect of surface-exchange kO and bulk-diffusion coefficient DO as well as the influence of microstructure properties on the cathode performance.

Variables study for the fast charging lithium ion batteries

Cell components in lithium ion cells have been studied to check their effects to reduce the charge time. Factors including various separator thickness, tab width, LiPF 6 concentration and solvent composition in electrolytes, cathode thickness, anode thickness and cathode active materials were studied. In addition, charge time of lithium ion cells was studied based on the charge voltage of cell. The most important variable in reducing the charge time of lithium ion cells was found to be the thickness of the cathode. The charge time of the lithium ion cells was reduced with thinner cathode. Other variables such as the separator thickness, LiPF 6 concentration and solvent composition in electrolytes, anode thickness and charge voltage of lithium ion cells were also effective in reducing the charge time of the cells, but with fewer impacts.

Constructal flow structure for a single SOFC

This paper presents a model and a structured procedure to optimize the internal structure of a single solid oxide fuel cell (SOFC) so that the power density is maximized. The polarization curve and power density are obtained as functions of temperature, geometry and operating parameters. The internal structure, which accounts for the thickness of the two electrodes and the electrolyte, and the flow channels geometry, has been optimized. The model is developed using a control volume approach, in which, all relevant thermal and electrochemical interactions between adjacent elements are accounted for. The effects of geometry on the compartments temperatures and reactants concentrations in the fuel cell are explored. The optimized internal structure results from optimal balances between the thickness of anode and cathode, L3 and L5, shoulder channel aspect ratio, Lt/Lch, and the total number of fuel and oxidant channels, nch. The optima found are sharp and, therefore, important to be identified in actual SOFC design. The variations of power density in the studied ranges of L3 and L5, Lt/Lch, and nch were of 11, 5 and 5%, respectively, in the three-way optimization process, for the anode-supported single SOFC. Copyright © 2007 John Wiley & Sons, Ltd.

Direct-write fabrication of integrated planar solid oxide fuel cells

Integrated planar solid oxide fuel cell (IP-SOFC) with multilayered structure has been fabricated via direct-writing process named robo-dispensing. Partially stabilized zirconia (PSZ) substrate with sufficient mechanical strength and gas permeability was utilized as a support for SOFC. The 2-cells serially integrated planar SOFC in which each cell is composed of the line-shaped electrode and electrolyte was produced The SOFC component paste materials were dispensed through cylindrical nozzle of 0.21 mm in diameter onto a moving plate that was controlled by robo-dispensing machine. The thicknesses of anode, electrolyte and cathode were 30 μm, 15 μm and 20 μm, respectively. The fabricated IP-SOFC exhibited OCV of 1.82 V and maximum power density of 35 mW.

Detection of Ptz + Ions and Pt Nanoparticles Inside the Membrane of a Used PEMFC

The physical and chemical state of proton exchange membrane fuel cell (PEMFC) electrocatalysts were investigated after of operation under fuel cell relevant conditions (, ) and of rest time under inert atmosphere . Upon aging, pronounced corrosion of the cathode electrocatalyst (carbon-supported platinum nanoparticles: ) was evidenced by field-emission gun scanning electron microscopy (FEG-SEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical techniques. Carbon corrosion was witnessed by the decrease of the cathode thickness and by the presence of nonsupported Pt particles inside the electrode. At the cathode, the corrosion of Pt nanoparticles produces ions which diffuse in the ionomer phase or in solution [ stands for ionic species present in the ionomer phase or in solution]. These ions are highly mobile inside the membrane electrode assembly (MEA) and may cross over from the cathode to the anode through the PEM. The driving force for that is the electro-osmotic drag (if ions combine with anions and carry a negative charge) and the chemical diffusion (concentration gradient of oxidized platinum species). Consequently, ions were detected by ultraviolet (UV) spectroscopy in the PEM. Due to the high mobility of ions, FEG-SEM and HRTEM analysis of the cross sections of MEAs revealed a pronounced change of Pt distribution after operation. Size distributions of both anode and cathode electrocatalysts evidenced an increase of the mean particle size, tailing toward large particle sizes and particle agglomeration. Nonspherical Pt nanoparticles were detected inside the PEM, the size and shape distribution of which strongly depend on the distance from the cathode. We believe ions are reduced chemically inside the membrane by crossing over the PEM and both chemically and electrochemically at the anode/cathode.