Impact of Membrane Types and Catalyst Layers Composition on Performance of Polymer Electrolyte Membrane Fuel Cells

Abstract

Performance of a low temperature polymer electrolyte membrane fuel cell (PEMFC) is highly dependent on the kind of catalysts, catalyst supports, ionomer amount on the catalyst layers (CL), membrane types and operating conditions. In this work, we investigated the influence of membrane types and CL compositions on MEA performance. MEA performance increases under all practically relevant load conditions with reduction of the membrane thickness from 50 to 15 μm, however further decrease in membrane thickness from 15 to 10 μm leads to reduction in cell voltage at high current loads. A thick anode CL is found to be beneficial under wet operating conditions assuming more pore space is provided to accommodate liquid water, whereas under dry operating conditions, an intermediate thickness of the anode CL is beneficial. When studying the impact of catalyst layer thickness, too thin a catalyst layer again shows reduced performance due to increased ohmic resistance ruled out the performance of the MEAs which have identical Pt crystallite sizes on the cathode CLs i. e. the thinnest the cathode CL, the highest the voltage were achieved at a defined current load. Adaptation of the operating conditions is highly anticipated to achieve the highest MEA performance.

Numerical Simulation on Impacts of Thickness of Nafion Series Membranes and Relative Humidity on PEMFC Operated at 363 K and 373 K

“…In particular, the molar concentration of H 2 O for Nafion 115 is much smaller than that for the other Nafion membranes. H 2 O flux of PEM as well as the conductivity of the Nafion membrane is promoted when the thickness of the Nafion membrane decreases, particularly below 50 µm [21,47,48], which corresponds to Nafion NRE-212 and Nafion NRE-211 in this study. In addition, the ohmic loss due to proton conductivity of Nafion membrane decreases when the thickness of Nafion membrane [49] decreases.…”

“…The thinner Nafion membrane provides lower ohmic losses, indicating that the proton transfers with a shorter distance to reach the cathode and the H 2 O produced in the cathode catalyst layer reaches the anode faster [49]. In addition, H 2 O flux of Nafion membrane as well as the conductivity of the Nafion membrane is promoted when the thickness of the Nafion membrane decreases, especially below 50 µm [21,47,48], which corresponds to Nafion NRE-212 and Nafion NRE-211 in this study. Therefore, it is revealed that the current density increases when the thickness of Nafion membrane decreases, especially for Nafion NRE-212 and Nafion NRE-211.…”

Effects of Supports BET Surface Areas on Membrane Electrode Assembly Performance at High Current Loads

“…Therefore, the ionomer content in the CL plays a crucial role in optimizing MEA performance by simultaneously minimizing losses caused by mass transport as well as electronic and proton conductivity [47][48][49]. In previous work, we found the optimum ionomer to carbon ratio (I/C) is to be dependent on the Pt content of the catalysts and the BET surface areas of the support materials [6,17,50]. Primarily, we found the optimum I/C ratio to be proportional to the BET surface areas of the support materials [6,17].…”

“…Primarily, we found the optimum I/C ratio to be proportional to the BET surface areas of the support materials [6,17]. Yet, when using the same support material, the optimum ionomer amount was inversely proportional to the catalysts' Pt content [50]. Unfortunately, there are no established tools available to define the optimum I/C ratio purely from the material parameters.…”

“…A thick CL can increase ohmic and reactant transport resistance of the MEA simultaneously; it can also impede the removal of product water. Both can adversely affect MEA performance [50]. We assumed, together with the high ohmic resistance, the low Pt utilization of TKE was likely caused by a rather thick CL compared to the other catalysts since the FIB-SEM images reveal the average CL thickness of TKE, TKV, Pt/CB, Pt/C65, and Pt/GC were 19, 17, 12, 16, and 15 µ m, respectively (see Figure S3).…”