Model-supported characterization of a PEM water electrolysis cell for the effect of compression

Abstract

This paper investigates the influence of the cell compression of a PEM water electrolysis cell. A small single cell is therefore electrochemically analyzed by means of polarization behavior and impedance spectroscopy throughout a range of currents (0.01 A cm −2 to 2.0 A cm −2 ) at two temperatures (60• C and 80• C) and eight compressions (0.77 MPa to 3.45 MPa). Additionally, a computational model is utilized to support the analysis. The main findings are that cell compression has a positive effect on overall cell performance due to decreased contact resistances, but is subject to optimization. In this case, no signs of severe mass transport problems due to crushed transport layers are visible in either polarization curves or impedance plots, even at high currents. However, a Tafel plot analysis revealed more than one slope throughout the current range. The change in the Tafel slope is therefore discussed and connected to the electrochemical reaction or an ohmic contribution from a non-electrode component.

Towards uniformly distributed heat, mass and charge: A flow field design study for high pressure and high current density operation of PEM electrolysis cells

“…For information on the contact losses between the components as a function of compression, the reader is referred to ref. [26].…”

“…From the model, it can be seen that this behavior is caused by a rising cell temperature, which lowers the ohmic resistance and activation losses. Generally speaking, this trend could also be caused by changes in the electrochemistry [44,45,26], however this is not included in the model. Finally, it should be noted that for the applied cell and operating conditions mass transport not a limiting factor.…”

“…This corresponds to a Tafel slope of 48 mV/dec at 333 K, which is slightly higher than the Tafel slope of 45 mV/dec determined from the high frequency resistance corrected Tafel plot analysis in ref. [26] for the same type of cell, compression and temperature. The main difference is due to the fact that the apparent charge transfer coefficient in this work is fitted across four temperatures, whilst in ref.…”

Elucidating the Performance Limitations of Alkaline Electrolyte Membrane Electrolysis: Dominance of Anion Concentration in Membrane Electrode Assembly

“…The inductor (L) in series with the R represents possible inductive parts of cables and other components. The R or high frequency resistance (HFR), which appears as the intercepts of the Nyquist plot with the x‐axis at high frequency (left side of Nyquist plot) represents the total area normalized internal ohmic resistance of the cell, which is expressed as the sum of the contributions from membrane resistance, material resistance of the cell components and contact resistances . CPE1 and CPE2 are related to the double‐layer capacitance for HER at the cathode and OER at the anode side.…”

Cover Feature: Elucidating the Performance Limitations of Alkaline Electrolyte Membrane Electrolysis: Dominance of Anion Concentration in Membrane Electrode Assembly (ChemElectroChem 19/2020)

“…The R or high frequency resistance (HFR), which appears as the intercepts of the Nyquist plot with the x-axis at high frequency (left side of Nyquist plot) represents the total area normalized internal ohmic resistance of the cell, which is expressed as the sum of the contributions from membrane resistance, material resistance of the cell components and contact resistances. [48] CPE1 and CPE2 are related to the double-layer capacitance for HER at the cathode and OER at the anode side. The polarization resistance, R1 and R2, are identified with the overall rate of the HER and OER and incorporates the charge transfer resistances of different step reactions during HER and OER.…”