scholarly journals Analytical Impedance of Oxygen Transport in the Channel and Gas Diffusion Layer of a PEM Fuel Cell

2021 ◽  
Author(s):  
Andrei Kulikovsky
Keyword(s):  
Fuel Cell ◽  
Diffusion Layer ◽  
Oxygen Transport ◽  
Analytical Formula ◽  
Catalyst Layer ◽  
Gas Diffusion Layer ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Nyquist Plot ◽  
Current Conservation

Abstract An analytical model for impedance of oxygen transport in the gas--diffusion layer (GDL) and cathode channel of a PEM fuel cell was developed. The model is based on transient oxygen mass conservation equations coupled to the proton current conservation equation in the catalyst layer. An analytical formula for the ``GDL+channel'' impedance was derived assuming that the oxygen and proton transport in the cathode catalyst layer (CCL) are fast. In the Nyquist plot, the resulting impedance consisted of two arcs describing oxygen transport in the air channel (low--frequency arc) and in the GDL. The characteristic frequency of GDL arc depends on the CCL thickness: large CCL thickness strongly lowers this frequency. At small CCL thickness, the high--frequency feature on the arc shape forms. This effect is important for identification of peaks in distribution of relaxation times spectra of low--Pt PEMFCs.

Effect of Porosity Gradient in Gas Diffusion Layer on Cell Performance With Thin-Film Agglomerate Model in Cathode Catalyst Layer of a PEM Fuel Cell

2011 ◽  
Author(s):  
Chun-I Lee ◽  
Shiqah-Ping Jung ◽  
Kan-Lin Hsueh ◽  
Chi-Chang Chen ◽  
Wen-Chen Chang
Keyword(s):  
Thin Film ◽  
Fuel Cell ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Water Saturation ◽  
Catalyst Layer ◽  
Gas Diffusion Layer ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Water Flooding

A one-dimensional, steady-state, two-phase, isothermal numerical simulations were performed to investigate the effect on cell performance of a PEM fuel cell under non-uniform porosity of gas diffusion layer. In the simulation, the non-uniform porosity of gas diffusion layer was taken into account to analyze the transport phenomena of water flooding and mass transport in the gas diffusion layer. The porosity of the gas diffusion layer is treated as a linear function. Furthermore, the structure of the catalyst layer is considered to be a cylindrical thin-film agglomerate. Regarding the distribution analysis of liquid water saturation, oxygen concentration and water concentration depend on the porosity of gas diffusion layer. In the simulation, the εCG and εGC represent the porosity of the interfaces between the channel and gas diffusion layer and the gas diffusion layer and the catalyst layer, respectively. The simulation results indicate that when the (εCG, εGC) = (0.8, 0.4), higher liquid water saturation appears in the gas diffusion layer and the catalyst layer. On the contrary, when the (εCG, εGC) = (0.4, 0.4), lower liquid water saturation appears. Once the liquid water produced by the electrochemical reaction and condensate of vapor water may accumulate in the open pores of the gas diffusion layer and reduced the oxygen transport to the catalyst sites. This research attempts to use a thin-film agglomerate model, which analyze the significant transport phenomena of water flooding and mass transport under linear porosity gradient of gas diffusion layer in the cathode of a PEM fuel cell.

scholarly journals A Kernel for Calculating PEM Fuel Cell Distribution of Relaxation Times

2021 ◽  
Vol 9 ◽  
Author(s):  
Andrei Kulikovsky
Keyword(s):  
Fuel Cell ◽  
Oxygen Transport ◽  
Relaxation Times ◽  
Catalyst Layer ◽  
Pem Fuel Cell ◽  
Negative Real Part ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Transport Layer ◽  
Cathode Side

Impedance of all oxygen transport processes in PEM fuel cell has negative real part in some frequency domain. A kernel for calculation of distribution of relaxation times (DRT) of a PEM fuel cell is suggested. The kernel is designed for capturing impedance with negative real part and it stems from the equation for impedance of oxygen transport through the gas-diffusion transport layer (doi:10.1149/2.0911509jes). Using recent analytical solution for the cell impedance, it is shown that DRT calculated with the novel K2 kernel correctly captures the GDL transport peak, whereas the classic DRT based on the RC-circuit (Debye) kernel misses this peak. Using K2 kernel, analysis of DRT spectra of a real PEMFC is performed. The leftmost on the frequency scale DRT peak represents oxygen transport in the channel, and the rightmost peak is due to proton transport in the cathode catalyst layer. The second, third, and fourth peaks exhibit oxygen transport in the GDL, faradaic reactions on the cathode side, and oxygen transport in the catalyst layer, respectively.

Lattice Boltzmann Modeling of Water Cumulation at the Gas Channel-Gas Diffusion Layer Interface in PEM Fuel Cells

2014 ◽  
Author(s):  
Dario Maggiolo ◽  
Andrea Marion ◽  
Massimo Guarnieri
Keyword(s):  
Fuel Cell ◽  
Diffusion Layer ◽  
Lattice Boltzmann ◽  
Gas Diffusion Layer ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Vapor Condensation ◽  
Relative Height ◽  
Gas Channel

Several experiments have proved that water in liquid phase can be present at the anode of a PEM fuel cell due to vapor condensation resulting in mass transport losses. Nevertheless, it is not yet well understood where exactly water tends to cumulate and how the design of the gas channel (GC) and gas diffusion layer (GDL) could be improved to limit water cumulation. In the present work a three-dimensional lattice Boltzmann based model is implemented in order to simulate the water cumulation at the GC-GDL interface at the anode of a PEM fuel cell. The numerical model incorporates the H2-H2O mixture equation of state and spontaneously simulates phase separation phenomena. Different simulations are carried out varying pressure gradient, pore size and relative height of the GDL. Results reveal that, once saturation conditions are reached, water tends to cumulate in two main regions: the upper and side walls of the GC and the GC-GDL interface, resulting in a limitation of the reactant diffusion from the GC to the GDL. Interestingly, the cumulation of liquid water at the interface is found to diminish as the relative height of the GDL increases.

Impact of Microchannel Boundary Conditions on Gas Diffusion Layer Saturation and Transport in Fuel Cells

2008 ◽  
Author(s):  
Kenneth M. Armijo ◽  
Van P. Carey
Keyword(s):  
Boundary Condition ◽  
Fuel Cell ◽  
Boundary Conditions ◽  
Diffusion Layer ◽  
Oxygen Transport ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Two Phase ◽  
Fuel Cell Performance ◽  
Phase Transport

Flooding within a Polymer Electrolyte Membrane (PEM) fuel cell occurs during operation as a result of product water vapor condensing near the surface of the cathode; this can be detrimental to fuel cell performance due to its role in reducing oxygen transport throughout the GDL. Previous Gas Diffusion Layer (GDL) transport models have made use of a zero-saturation boundary condition at the GDL/Oxygen (O2) gas channel (GC) interface. However, the physical correctness of this saturation boundary condition is still unclear. Further investigation of the saturation boundary condition could lead to a more robust model of the GDL saturation distribution and cathodic flooding. This exploration provides a one-dimensional two-phase transport model for saturation as well as liquid water and gaseous oxygen pressure distributions throughout the cathode-side gas diffusion layer (GDL) within a PEM fuel cell. The focus of this investigation is on the impact of non-zero saturation boundary conditions at the GDL / GC interface, and its impact on two-phase transport within the porous medium, with regard to fuel cell performance. Saturation boundary conditions at this location are determined based on GDL interfacial liquid coverage of water droplets that diffuse through the porous medium during operation and block oxygen transport paths. The results of this investigation suggest that non-zero saturation boundary conditions at the GDL/GC interface are evident when analyzing two-phase phenomena, which affect the overall saturation distribution throughout the GDL, and consequent performance of the fuel cell. In addition, GDL membranes with large porosities were found to improve gas and liquid transport by lowering the saturation at the GDL / Cathode interface that would otherwise impede oxygen transport.

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