In Situ and Ex Situ Studies on the Degradation of Pd/C Catalyst for Proton Exchange Membrane Fuel Cells

2014 ◽  
Vol 11 (5) ◽  
Author(s):  
Yongfu Tang ◽  
Shichun Mu ◽  
Shengxue Yu ◽  
Yufeng Zhao ◽  
Hongchao Wang ◽  
...  
Keyword(s):  
Single Cell ◽  
Electrochemical Impedance ◽  
Degradation Mechanism ◽  
Single Cells ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Ex Situ ◽  
Constant Current ◽  
Stress Tests

To investigate the degradation mechanism of the as-prepared Pd/C catalyst, in situ and ex situ accelerated stress tests were carried out via potential cycling. Durability tests of the single cells with Pd/C catalysts were performed through an interval constant current density mode. Electrochemical impedance spectroscopy (EIS) was applied to measure the impedance of the single cell during degradation tests. Results indicate that the degradation of Pd/C catalyst may be attributed to the phase transition of absorbed α-phase PdH to β-phase PdH, the dissolution of Pd metal, and the size increase of Pd nanoparticles. Moreover, the degradation of single cell may be predominantly ascribed to the degradation of catalyst, the deterioration of contact between electronic/ionic conductors, as well as the flooding of gas diffusion channels.

Development of a Reference Electrode for a PEMFC Single Cell Allowing an Evaluation of Plate Potentials

2010 ◽  
Vol 7 (4) ◽  
Author(s):  
Johan Andre ◽  
Nicolas Guillet ◽  
Jean-Pierre Petit ◽  
Laurent Antoni
Keyword(s):  
Fuel Cell ◽  
Single Cell ◽  
Proton Exchange Membrane ◽  
Single Cells ◽  
Electrical Contact ◽  
Reference Electrode ◽  
Proton Exchange ◽  
Ex Situ ◽  
Electrical Contact Resistance ◽  
Hydrogen Electrode

Increasing lifetime and performance is critical for proton exchange membrane fuel cell (PEMFC) using stainless steel plates. A good compromise between passivity and electrical contact resistance of the plate material is required. Measuring the potential of each plate during fuel cell operation is of paramount importance to lead to relevant ex situ tests in order to investigate new materials. From a review on methods used for potential measurements, the present work focused on the realization and use of a dynamic hydrogen electrode (DHE) device as a reference electrode in a PEMFC single cell and its evaluation in terms of accuracy and drift. With classic reference electrodes introduced into the flow field, measurements were shown to be irrelevant because of the impossibility to ensure good and stable ionic conductivity between the reference electrode and the plate when operating the cell. Several examples of DHE found in the literature were reviewed and used to realize a DHE, which showed correct accuracy and stability of its potential under fully humidified conditions. The experimental device was shown to be reliable and easily adaptable for different single cells. It was used to investigate transient phenomena while cycling a cell, but needs some improvement when the cell is operated with unsaturated gases.

scholarly journals High-temperature PEM Fuel Cell Characterization: an Experimental Study Focused on Potential Degradation due to the Polarization Curve

2022 ◽  
Vol 334 ◽  
pp. 04017
Author(s):  
Mathieu Baudy ◽  
Amine Jaafar ◽  
Christophe Turpin ◽  
Sofyane Abbou ◽  
Sylvain Rigal
Keyword(s):  
High Temperature ◽  
Fuel Cell ◽  
Polarization Curve ◽  
Proton Exchange Membrane ◽  
Electrochemical Impedance ◽  
Single Cells ◽  
Active Surface ◽  
Proton Exchange ◽  
Constant Current ◽  
Ohmic Losses

High-Temperature Proton Exchange Membrane Fuel Cell constant current ageing tests highlighted that the characterizations used to monitor the state of health of single cells could be potentially degrading. An experimental campaign to analyze potential degradation due to polarization curves was carried out. More exactly, four methodologies to generate a polarization curve including Electrochemical Impedance Spectroscopies (EIS) were cycled 30 times. The tested single cells were based on a commercial PBI Membrane Electrodes Assembly (MEA) with an active surface of 45 cm2 (BASF Celtec®-P 1100 type). Before the first cycling test and after the last cycling one, complete characterizations, composed by a voltammetry and a polarization curve including EIS, were performed. The results show that one of the MEA has a voltage which increased for one of the four methods to obtain the polarization curve. This growth is linked to a decrease of ohmic losses: in an unexpected way, it could be considered as a way to improve the break-in period. Similarly, the monitoring of CO2 emission (as corrosion has been suspected to be involved at high voltage, i.e. low current density) confirms the potential degradation of the electrodes during the measurement of the polarization curve.

In-Situ Dual Beam (FIBSEM) Techniques for Probe Pad Deposition and Dielectric Integrity Inspection in 0.2 μm Technology DRAM Single Cells

1999 ◽  
Author(s):  
Gunnar Zimmermann ◽  
Richard Chapman
Keyword(s):  
Electron Beam ◽  
Single Cell ◽  
Single Cells ◽  
Ion Beam ◽  
Gate Oxide ◽  
Ion Milling ◽  
Dual Beam ◽  
Sem Imaging ◽  
Innovative Techniques

Abstract Dual beam FIBSEM systems invite the use of innovative techniques to localize IC fails both electrically and physically. For electrical localization, we present a quick and reliable in-situ FIBSEM technique to deposit probe pads with very low parasitic leakage (Ipara < 4E-11A at 3V). The probe pads were Pt, deposited with ion beam assistance, on top of highly insulating SiOx, deposited with electron beam assistance. The buried plate (n-Band), p-well, wordline and bitline of a failing and a good 0.2 μm technology DRAM single cell were contacted. Both cells shared the same wordline for direct comparison of cell characteristics. Through this technique we electrically isolated the fail to a single cell by detecting leakage between the polysilicon wordline gate and the cell diffusion. For physical localization, we present a completely in-situ FIBSEM technique that combines ion milling, XeF2 staining and SEM imaging. With this technique, the electrically isolated fail was found to be a hole in the gate oxide at the bad cell.

scholarly journals Label-Free and Quantitative Dry Mass Monitoring for Single Cells during In Situ Culture

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1635
Author(s):  
Ya Su ◽  
Rongxin Fu ◽  
Wenli Du ◽  
Han Yang ◽  
Li Ma ◽  
...  
Keyword(s):  
Cell Growth ◽  
Single Cell ◽  
Hela Cells ◽  
Quantitative Measurement ◽  
Single Cells ◽  
Dry Mass ◽  
Quantitative Detection ◽  
Label Free ◽  
Mass Sensitivity

Quantitative measurement of single cells can provide in-depth information about cell morphology and metabolism. However, current live-cell imaging techniques have a lack of quantitative detection ability. Herein, we proposed a label-free and quantitative multichannel wide-field interferometric imaging (MWII) technique with femtogram dry mass sensitivity to monitor single-cell metabolism long-term in situ culture. We demonstrated that MWII could reveal the intrinsic status of cells despite fluctuating culture conditions with 3.48 nm optical path difference sensitivity, 0.97 fg dry mass sensitivity and 2.4% average maximum relative change (maximum change/average) in dry mass. Utilizing the MWII system, different intrinsic cell growth characteristics of dry mass between HeLa cells and Human Cervical Epithelial Cells (HCerEpiC) were studied. The dry mass of HeLa cells consistently increased before the M phase, whereas that of HCerEpiC increased and then decreased. The maximum growth rate of HeLa cells was 11.7% higher than that of HCerEpiC. Furthermore, HeLa cells were treated with Gemcitabine to reveal the relationship between single-cell heterogeneity and chemotherapeutic efficacy. The results show that cells with higher nuclear dry mass and nuclear density standard deviations were more likely to survive the chemotherapy. In conclusion, MWII was presented as a technique for single-cell dry mass quantitative measurement, which had significant potential applications for cell growth dynamics research, cell subtype analysis, cell health characterization, medication guidance and adjuvant drug development.

scholarly journals Scaling up Studies on PEMFC Using a Modified Serpentine Flow Field Incorporating Porous Sponge Inserts to Observe Water Molecules

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 286
Author(s):  
Muthukumar Marappan ◽  
Rengarajan Narayanan ◽  
Karthikeyan Manoharan ◽  
Magesh Kannan Vijayakrishnan ◽  
Karthikeyan Palaniswamy ◽  
...  
Keyword(s):  
Flow Field ◽  
Proton Exchange Membrane ◽  
Electrochemical Impedance ◽  
Scaling Up ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Experimental Investigations ◽  
Serpentine Flow Field ◽  
Exchange Membrane ◽  
Power Densities

Flooding of the cathode flow channel is a major hindrance in achieving maximum performance from Proton Exchange Membrane Fuel Cells (PEMFC) during the scaling up process. Water accumulated between the interface region of Gas Diffusion Layer (GDL) and rib of the cathode flow field can be removed by the use of Porous Sponge Inserts (PSI) on the ribs. In the present work, the experimental investigations are carried out on PEMFC for the various reaction areas, namely 25, 50 and 100 cm2. Stoichiometry value of 2 is maintained for all experiments to avoid variations in power density obtained due to differences in fuel utilization. The experiments include two flow fields, namely Serpentine Flow Field (SFF) and Modified Serpentine with Staggered provisions of 4 mm PSI (4 mm × 2 mm × 2 mm) Flow Field (MSSFF). The peak power densities obtained on MSSFF are 0.420 W/cm2, 0.298 W/cm2 and 0.232 W/cm2 compared to SFF which yields 0.242 W/cm2, 0.213 W/cm2 and 0.171 W/cm2 for reaction areas of 25, 50 and 100 cm2 respectively. Further, the reliability of experimental results is verified for SFF and MSSFF on 25 cm2 PEMFC by using Electrochemical Impedance Spectroscopy (EIS). The use of 4 mm PSI is found to improve the performance of PEMFC through the better water management.

Testing of solid oxide cells at high current densities

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
André Weber
Keyword(s):  
Single Cell ◽  
High Performance ◽  
High Efficiency ◽  
Electrochemical Impedance ◽  
Single Cells ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Current Densities ◽  
Cell Testing ◽  
The Impact

Abstract Solid Oxide Cells (SOCs) have gained an increasing interest as electrochemical energy converters due to their high efficiency, fuel flexibility and ability of reversible fuel cell/electrolysis operation. During the development process as well as in quality assurance tests, the performance of single cells and cell stacks is commonly evaluated by means of current/voltage- (CV-) characteristics. Despite of the fact that the measurement of a CV-characteristic seems to be simple compared to more complex, dynamic methods as electrochemical impedance spectroscopy or current interrupt techniques, the resulting performance strongly depends on the test setup and the chosen operating conditions. In this paper, the impact of different single cell testing environments and operating conditions on the CV-characteristic of high performance cells is discussed. The influence of cell size, contacting and current collection, contact pressure, fuel flow rate and composition on the achievable cell performance is presented and limitations arising from the test bed and testing conditions will be pointed out. As today’s high performance cells are capable of delivering current densities of several ampere per cm2 a special emphasis will be laid on single cell testing in this current range.

scholarly journals AFM and Fluorescence Microscopy of Single Cells with Simultaneous Mechanical Stimulation via Electrically Stretchable Substrates

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4131
Author(s):  
Natalia Becerra ◽  
Barbara Salis ◽  
Mariateresa Tedesco ◽  
Susana Moreno Flores ◽  
Pasquale Vena ◽  
...  
Keyword(s):  
Cell Culture ◽  
Fluorescence Microscopy ◽  
Single Cell ◽  
Spatial Resolution ◽  
Single Cells ◽  
Optical Microscope ◽  
Average Cell ◽  
Atomic Force ◽  
Cell Stretcher

We have developed a novel experimental set-up that simultaneously, (i) applies static and dynamic deformations to adherent cells in culture, (ii) allows the visualization of cells under fluorescence microscopy, and (iii) allows atomic force microscopy nanoindentation measurements of the mechanical properties of the cells. The cell stretcher device relies on a dielectric elastomer film that can be electro-actuated and acts as the cell culture substrate. The shape and position of the electrodes actuating the film can be controlled by design in order to obtain specific deformations across the cell culture chamber. By using optical markers we characterized the strain fields under different electrode configurations and applied potentials. The combined setup, which includes the cell stretcher device, an atomic force microscope, and an inverted optical microscope, can assess in situ and with sub-micron spatial resolution single cell topography and elasticity, as well as ion fluxes, during the application of static deformations. Proof of performance on fibroblasts shows a reproducible increase in the average cell elastic modulus as a response to applied uniaxial stretch of just 4%. Additionally, high resolution topography and elasticity maps on a single fibroblast can be acquired while the cell is deformed, providing evidence of long-term instrumental stability. This study provides a proof-of-concept of a novel platform that allows in situ and real time investigation of single cell mechano-transduction phenomena with sub-cellular spatial resolution.

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