共查询到20条相似文献，搜索用时 15 毫秒
1.
In this paper the effect of the addition of carboxymethylcellulose (CMC) to microporous layers (MPLs) formulation is reported and the rheological, morphological and electrical properties of the so‐obtained MPLs are assessed. Two different PTFE/carbon black ratios are considered, with and without CMC in the ink formulation. CMC addition results in a better homogeneity and stability of the inks. Moreover, the presence of CMC leads to a better shear thinning behaviour and to a general increase in viscosity that makes these slurries more appropriate for coating deposition via doctor blade technique. The presence of CMC in MPL formulation also affects the electrochemical performances in terms of I–V curves and impedance spectra. CMC‐containing MPLs show the best performances in terms of generated power at high temperature (80 °C) and low cathodic relative humidity (RH 60 %). Ohmic resistances too, in presence of CMC, are lower than those exhibited by CMC‐free MPLs. 相似文献
2.
The parameter estimation of the proton exchange membrane fuel cell (PEMFC) model is important to accurately present the relationship between voltage versus current. Regarding this problem, the difference between observed voltage and model‐calibrated voltage, which composed of cell reversible voltage, activation voltage drop, ohmic loss, and concentration voltage drop, should be minimized. So far, various optimization algorithms have tackled this problem. However, there is still a way to improve the solution quality using another technique, and in order to fairly compare the solution qualities among the techniques, more information is required which has been so far missed. Thus, this study proposed generalized reduced gradient (GRG) technique which obtained good results. When compared with two variants of harmony search and two variants of particle swarm optimization, GRG could find much better results in terms of mean square error (MSE). Also, this study provided full problem formulation and numerical dataset, which was scattered in literature and not clearly provided in previous literature. Hopefully, this study invites more researchers to replicate this bench‐mark problem of the PEMFC parameter estimation and to tackle it using their own techniques in the future. 相似文献
3.
Impedance spectra of polymer electrolyte membrane (PEM) fuel cells often comprise an “inductive loop” at low frequencies from 1 Hz to 1 mHz additionally to the typically polarization resistances with capacitive behavior between 1 MHz to 1 Hz. To investigate this inductive behavior, systematic variations of operating parameters as humidity, current density and gas compositions are performed. The impedance spectra, including their inductive parts, are deconvoluted by an extended version of the distribution of relaxation times (DRT). Two inductive processes are identified in the DRT and subsequently quantified by fitting the spectra to an extended equivalent circuit model exhibiting negative resistances and constant phase elements. Both inductive processes are depending on relative humidity and current density. The inductive behavior seems to be dominated by the oxygen reduction reaction (ORR) at the cathode, whereas changes in membrane hydration can be excluded as the main cause for the inductive low‐frequency processes. Measurements in symmetrical H2/H2 operating mode prove that the inductive behavior cannot be solely related to the ORR. The ratio of the inductive processes to the ohmic and capacitive loss processes ranges from 15% to 30%. Thus, a considerable cell performance improvement related to the existence of these inductive low‐frequency processes has to be taken into account. 相似文献
4.
In this paper, the Ce1–xSmxO2–x/2 (x = 0.025, 0.05, 0.1, 0.2) samples were synthesized and then mixed with GdBaCo2O5+δ (GBCO) to form GBCO–Ce1–xSmxO2–x/2 composite cathodes. The electrochemical performance of the composite cathodes was investigated by the electrochemical impedance spectroscopy (EIS) as a function of temperature and oxygen partial pressure. The impedance spectra results demonstrated that the introduction of proper Ce1–xSmxO2–x/2 phase remarkably enhanced the electrochemical performance of GBCO cathode and caused a reduction in the total polarization resistance (Rp). Furthermore, as the amount of Ce1–xSmxO2–x/2 in composite cathode was fixed, the variation of Sm content in Ce1–xSmxO2–x/2 also had a significant influence on the electrochemical performance of the GBCO–Ce1–xSmxO2–x/2 cathodes. For example, the Rp of GBCO cathodes containing 10 wt.% Ce1–xSmxO2–x/2 considerably reduced from 0.37 to 0.17 Ω cm2 at 600 °C with the decreasing Sm content x from 0.2 to 0.025. The improvement in performance of the GBCO–Ce1–xSmxO2–x/2 cathodes compared to pure GBCO cathode could be mainly attributed to the catalytic activity of Ce1–xSmxO2–x/2 towards the surface diffusion related processes, which was an elementary step in oxygen reduction reaction at cathode. 相似文献
5.
Polytetrafluoroethylene (PTFE) content in the fuel cell electrode plays an important role on the performance of polymer electrolyte membrane fuel cell (PEMFC) when the cell is tested under low temperature and under ambient pressure. PTFE is added to the PEM fuel cell electrode to improve the mechanical strength and to help in removing the product water formed on the cathode; however, higher PTFE loading increases the resistance and thus decreases the performance of the cell and very low PTFE content has the disadvantage of water flooding in long‐term operation. We have investigated the effect of the PTFE content in the gas diffusion media (carbon paper) and in the microlayer on the performance of PEMFC operating at ambient pressure. The PTFE contents in these two layers have to be finely matched to get the best performance of the cells. The polarisation behaviour, electrochemical surface area and the electrochemical impedance spectra have been analysed. The results are presented in this paper. 相似文献
6.
The impedance characteristics of the ohmic overpotential of the proton exchange membrane (PEM) fuel cells are studied analytically using the process modeling approach. The water transport in the membrane, the cathode catalyst layer, and gas diffusion layer are analyzed. The analytical relation of the impedance of the ohmic loss is determined and is converted to an equivalent circuit. Then, the impedance of a PEM fuel cell is measured experimentally in different current densities, operating temperatures and the anode and cathode relative humidities. The measured impedances are compared with the predicted ones from the analytical model. It is shown that the predicted impedance characteristics are in great agreement with the measured ones in all different operating conditions. 相似文献
7.
P. Leone T. Matencio M. E. Garci Z. R. Domigues A. Lanzini M. Santarelli 《Fuel Cells》2013,13(5):733-742
The work investigates the performance of an anode supported solid oxide fuel cell under relevant conditions at different flow and temperature settings with the aim to identify performance limiting factors through impedance spectroscopy. Impedance spectroscopy is used to deconvolute impedance spectra of an in‐operating SOFC and identify limiting overpotentials. Those measurements are made under a wide range of flow and temperature conditions. In particular, oxidant flow rate is varied yielding fuel cell operation with 20, 40, 60, 80% oxidant utilization; fuel is instead changed in terms of flow and composition: fuel utilization factors in the range of 20–80% are investigated as well as the dilution with nitrogen. The operating temperature is varied in the range between 650 and 800 °C with steps of 50 °C. Results show that charge and mass transport can lead to a performance limitation according to the selected operating range for the investigated cell design. For the investigated anode‐supported design, a major improvement of performance could arise by reducing ohmic resistances (i.e. employing a thin electrolyte) and by an improvement of the anode geometry aiming at enhancing mass transport. In particular, at low temperature and high fuel utilization, fuel oxidation seems to be a relevant performance limiting factor. 相似文献
8.
H. Shirani‐Faradonbeh M. H. Paydar S. Paydar I. Gholaminezhad R. Bazargan‐Lari 《Fuel Cells》2019,19(5):578-586
A novel cathode material of (Nd0.9La0.1)1.6Sr0.4Ni0.75Cu0.25O3.8 (NLSNC4), is synthesized by solid state reaction and is further investigated in combination with samarium doped ceria (SDC) as composite cathodes including 0, 10, 30, 50, and 70 of SDC electrolyte phase. The X‐ray diffraction analysis showed that NLSNC4 was produced in pure phase and was chemically compatible with SDC electrolyte. Electrical conductivities of single phase and composite cathode materials along with their electrochemical performances on SDC electrolytes in symmetric cells were measured by DC four‐probe method and electrochemical impedance spectroscopy (EIS), respectively. Results indicated that the maximum electrical conductivity is 135.56 S cm−1 at 350 °C, measured for single phase NLSNC4, sintered at 1,300 °C. Polarization resistance of pure NLSNC4 cathode was 2.71 Ω cm2 at 800 °C, and NLSNC4‐x wt.% SDC composite cathodes displayed Rp value of 0.35, 0.14, 0.12, and 0.32 Ω cm2 at 800 °C, for x = 10, 30, 50, and 70, respectively. 相似文献
9.
《Fuel Cells》2018,18(1):96-100
A series of A‐site deficient Gd‐containing Fe‐Co‐based cathodes were synthesized using the glycine‐nitrate process. All the compounds consisted of two phases, i.e., a cubic and orthorhombic phase, as determined by powder X‐ray diffraction (XRD). The thermal expansion coefficient decreased with increasing A‐site deficiency, which could be because cobalt was expelled from the main phases. Likewise, the electrochemical activities of the Gd‐containing Fe‐Co‐based solid oxide fuel cell cathodes toward the reduction of oxygen ware improved by a factor of approximately 3 by making them A‐site deficient. The composition (Gd0.6Sr0.4)0.85Fe0.8Co0.2O3–δ showed the highest activity toward the reduction of oxygen among the five compounds. Electrochemical impedance spectroscopy estimated the area specific resistance as 5.77 Ω cm2 at 600 °C. The electrochemical impedance spectroscopy measurements revealed three arcs for most of the compounds at the three temperatures where the measurements were performed. 相似文献
10.
《Fuel Cells》2017,17(3):367-377
The electrical behavior of a Ni‐YSZ anode of a solid oxid fuel cell (SOFC) cell under H2S has been monitored by impedance spectroscopy combined with in situ Raman spectroscopy and post mortem scanning electron microscopy (SEM) at 500 °C in open circuit potential (OCP) and at 500 mV polarization. In OCP condition, the electrode impedance spectra evolved slowly corresponding quite well to the evolution of Raman signals' intensities. Meanwhile, at 500 mV polarization, the impedance spectra transformed much faster, indicating a quick and severe H2S‐induced poisoning, which is then confirmed by post mortem examinations by SEM with the densification of the bulk anode porous structure with (Ni, S) phase. Based on the experimental data, the elementary steps and location of H2 oxidation are discussed. 相似文献
11.
M. Henke C. Willich C. Westner F. Leucht J. Kallo W. G. Bessler K. A. Friedrich 《Fuel Cells》2013,13(5):773-780
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. 相似文献
12.
The internal resistance of proton exchange membrane fuel cell (PEMFC) system is difficult to measure on‐line due to its variation with time. The traditional electrochemical impedance spectroscopy (EIS) and its variants such as high frequency resistance (HFR) can be used to measure the resistance when the system is in steady state, but they fail in automotive applications where a change in speed or inclination modifications could lead to a sharp fluctuation in demand on power. In order to resolve this problem, a novel algorithm is proposed in this paper to estimate the resistance based on the alternating current (AC) impedance spectroscopy technique by adding an extra term to eliminate the errors caused by voltage variation or when the system is under unsteady state. Numerical simulations show that the proposed algorithm can not only accurately track the variation of the internal resistance, but is also robust against the noises caused by uncertainty and measurements. 相似文献
13.
This paper presents the design and validation of a 2 kW fuel cell test bench for subfreezing studies. The test bench is designed to study the influence of different operational parameters on the cold start of fuel cell. Thus, the effects of ambient temperature, gas and coolant flow rates, current density and fuel cell impedance can be investigated. For cold start experiments, the apparatus is designed to reproduce the environment of a fuel cell in a vehicle parked in a subzero environment. Therefore, the test bench is divided into two parts: the fuel cell, its coolant circuit and main sensors are located in a climatic chamber while the main part of the test bench is at room temperature. The different parts of the test bench are described and validation results are presented. The heat exchange between the fuel cell coolant circuit and the environment is computed using parameters estimation techniques. The power requested to heat the coolant circuit to a given temperature is computed. 相似文献
14.
E. Effori H. Moussaoui F. Monaco R. K. Sharma J. Debayle Y. Gavet G. Delette G. Si Larbi E. Siebert J. Vulliet L. Dessemond J. Laurencin 《Fuel Cells》2019,19(4):429-444
The reaction mechanism and the impact of microstructure on performances for a porous LSCF‐CGO composite used as O2 electrode in SOCs have been investigated. For this purpose, an integrated approach coupling (i) electrochemical testing, (ii) advanced 3D characterizations, and (iii) modeling was proposed. In this frame, a symmetrical cell was tested in a three‐electrode setup and the microstructure of the LSCF‐CGO working electrode was reconstructed by FIB‐SEM tomography. The experimental polarization curves and the impedance diagrams along with the extracted microstructural parameters were used to validate an in‐house microscale electrochemical model. This model considers two parallel reaction pathways with (i) an oxidation/reduction at TPBls (surface path) and (ii) an oxygen transfer at the gas/LSCF interface (bulk path). It was shown that the LSCF‐CGO electrode reaction mechanism is mostly controlled by the charge transfer at TPBls whatever the polarization. Finally, the impact of electrode composition, porosity and particles size on the cell polarization resistance was investigated by using the electrochemical model in combination with a large dataset of synthetic microstructures generated by a geometrical stochastic model. The effect of each microstructural parameter on the electrode performance was analyzed in order to provide useful guidelines for the cell manufacturing. 相似文献
15.
Different composite materials made of mixed protonic/electronic conductors, SrCe0.9Yb0.1O3–δ (10YbSC) or BaCe0.9Yb0.1O3–δ (10YbBC), and a mixed oxygen‐ion/electronic conductor, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), were investigated for cathode application in intermediate temperature solid oxide fuel cells (IT‐SOFCs) using a high temperature proton conducting BaCe0.8Y0.2O3–δ electrolyte. Only the LSCF/10YbBC composite was found to be chemically stable. Area specific resistance (ASR) measurements were performed in wet air for LSCF/10YbBC cathodes, changing the weight ratio between the phases and the sintering procedure. The best performance was obtained for the composite cathode containing 50 wt.‐% of LSCF and 50 wt.‐% of 10YbBC, sintered at 1,100 °C. Electrochemical impedance spectroscopy (EIS) measurements of the tested cathodes showed two depressed semicircles in the middle and low frequency range, respectively. Performing ASR measurements at different p allowed us to attribute the two semicircles to charge transfer and oxygen diffusion processes, respectively. The microstructure of the LSCF/10YbBC(1:1) composite cathode was optimised changing the ratio of the particle sizes between the two phases. The lowest ASR values (0.14 Ω cm2 at 700 °C) were observed for the LSCF/10YbBC(1:1) composite cathode with different particle size (sub‐micrometer particles for LSCF and nanometer particles for 10YbBC). Fuel cell polarisation curves demonstrated superior performance of the LSCF/10YbBC (1:1) cathode with respect to Pt. 相似文献
16.
《Fuel Cells》2017,17(3):391-401
Electrochemical impedance spectroscopy (EIS) is a very powerful tool to study the behavior of electrochemical systems. According to Ohm's generalized law, the impedance concept is only valid if the linearity condition is met. In the case that the linearity condition is not achieved, the obtained impedance spectra will present distortions which may lead to biased or even erroneous results and conclusions. In this work, an experimental quantification of the effect of nonlinearities on EIS spectra was performed in order to determine the order of magnitude of the effect of the nonlinearity of the system on the obtained spectra of the cathodic electrode of an alkaline electrolyzer. 相似文献
17.
In a polymer electrolyte membrane fuel cell (PEMFC), slow diffusion in the gas diffusion electrode may induce oxygen depletion when using air at the cathode. This work focuses on the behavior of a single PEMFC built with a Nafion® based MEA and an E-TEK gas diffusion layer and fed at the cathode with nitrogen containing 5, 10 and 20% of oxygen and working at different cell temperatures and relative humidities. The purpose is to apply the experimental impedance technique to cells wherein transport limitations at the cathode are significant. In parallel, a model is proposed to interpret the polarization curves and the impedance diagrams of a single PEMFC. The model accounts for mass transport through the gas diffusion electrode. It allows us to qualitatively analyze the experimental polarization curves and the corresponding impedance spectra and highlights the intra-electrode processes and the influence of the gas diffusion layer. 相似文献
18.
The characteristics of the measured total impedance spectra of polymer electrolyte membrane fuel cells are often not representative of the performance of the cell. This is due in part mainly to two reasons; total impedance measurements are not representative of local phenomena and perturbation of the cell around the steady‐state polarization can result in oscillations of the gas concentrations downstream the flow channels that can affect the trend of the local spectrum. In this study, we overcome these two challenges by measuring the spectra of a segmented cell using local excitation of the segments. With these capabilities, we experimentally investigate the explanation given in works found in literature in regards to the oxygen oscillation in the channel and its effect on the spectra of locally perturbed segments. We further investigate the characteristics of the low frequency arc, measuring for the first time a loop in the spectrum around the transition frequency between the high and low frequency arcs. The characteristics of the spectra are investigated by varying the flow properties with a focus on the effect of air stoichiometry. 相似文献
19.
Investigation of the cathode reaction in solid oxide fuel cells (SOFC) by impedance spectroscopy (IS) measurements using evolutionary‐based programming analysis is demonstrated. In contrast to the conventional analysis methods used for impedance spectroscopy measurements, e.g., equivalent circuits, the impedance spectroscopy genetic programming (ISGP) program seeks for a distribution of relaxation times that has the form of a peak or a sum of several peaks, assuming the Debye kernel. Using this method one finds a functional (parametric) form of the distribution of relaxation times. A symmetric cell configuration of Pt|LSCF|GDC|LSCF|Pt was examined using IS measurements combined with I–V measurements. Different samples at different temperatures and different oxygen partial pressures were examined in order to investigate their influence on the oxygen reduction reaction. The resulting IS data was analyzed using the ISGP program and the resulting peaks constructing the distribution of relaxation times were assigned for the different processes that occur at the cathode side. The activation energies as well as the dependence of the processes on the oxygen partial pressure were also evaluated. 相似文献
20.
M. Zunic L. Chevallier E. Di Bartolomeo A. D'Epifanio S. Licoccia E. Traversa 《Fuel Cells》2011,11(2):165-171
Intermediate temperature solid oxide fuel cells (IT‐SOFCs) were fabricated depositing proton conducting BaCe0.9Y0.1O3–x (BCY10) thick films on cermet substrates made of nickel oxide–yttrium doped barium cerate (NiO–BCY10) using electrophoretic deposition (EPD) technique. The influence of the EPD parameters on the microstructure and electrical properties of BCY10 thick films was investigated. Deposited BCY10 thick films together with green anode substrates were co‐sintered in a single heating treatment at 1,550 °C for 2 h to obtain dense electrolyte and suitably porous anodes. The half‐cells were characterised by field emission scanning electron microscopy (FE‐SEM) and by X‐ray diffraction (XRD) analysis. A composite cathode specifically developed for BCY electrolytes, made of La0.8Sr0.2Co0.8Fe0.2O3(LSCF, mixed oxygen‐ion/electronic conductor) and BaCe0.9Yb0.1O3–δ (10YbBC, mixed protonic/electronic conductor), was used. Fuel cells were prepared by slurry coating the composite cathode on the co‐sintered half‐cells. Fuel cell tests and electrochemical impedance spectroscopy (EIS) were performed in the 550–700 °C temperature range. A maximum power density of 296 mW cm–2 was achieved at 700 °C for electrolyte deposited at 60 V for 1 min. 相似文献