Influence of Anode GDL on PEMFC Ultra-Thin Electrode Water Management at Low Temperatures

Abstract

In this paper, we provide results of new anode gas diffusion layer materials which dramatically improved the performance of ultra-thin electrode polymer electrolyte membrane fuel cells under highly water-condensing operating conditions, realized via optimization of the anode gas diffusion layer backing and microporous layer coatings.

Anode-Design Strategies for Improved Performance of Polymer-Electrolyte Fuel Cells with Ultra-Thin Electrodes

“…In terms of temperature sensitivity ( Figure 1B), the MEA with the MRC C anode GDL is able to maintain a current density above 1 A cm À2 for temperatures down to 50 C, whereas for the MEA with the MRC U105 anode GDL the current drops below 0.5 A cm À2 at 0.5 V for temperatures below 55 C. Therefore, the MEA with MRC C was able to deliver a 4-fold increase in current density at 0.5 V and 50 C compared with that with the MRC U105 anode GDL (i.e., 1 and 0.26 A cm À2 at 50 C for MRC C and MRC U105, respectively). The results presented here are consistent in trend with those reported previously, 19,20 but are quite surprising in terms of magnitude and the fact that one is only changing the anode GDL, which is typically considered less important for overall PEFC performance than the cathode GDL. Figure 2A summarizes the measured polarization curves under the product water balance, temperature series measurements (Table S1, second row) with MEAs containing either the MRC U105 or MRC C based anode GDLs.…”

“…This waviness at the surface no doubt contributes to the lower detachment velocity (and higher contact resistance), since the water droplets emerge from domains that have fewer fibers and thus less pinning. 18,19 The MRC C GDL also had a higher calculated porosity (0.75) compared with that for MRC U105 (0.67), which agrees with the stress-strain data. At all levels of compression, it appears that MRC C has higher porosity by about 0.05 (see Figures S13-S16 and Supplemental Information for a more detailed discussion on porosity).…”

“…It has been shown that the low-temperature performance of NSTF MEAs can be enhanced by changing cell operation or architecture, 19,20 but there is a lack of understanding of the critical properties that are being affected or controlling. For example, substantial gains in MEA maximum power output near room temperature were observed by operating the MEAs with reduced anode reactant pressures, including below atmospheric, but there are questions of practicality and mechanisms including key processes and locations being affected.…”

“…Product water-distribution measurements suggest that the increased performance with reduced anode operating pressure correlates with reduced liquid-water flow rate out of the cathode GDL, likely reducing liquid saturation levels in the cathode electrode and minimizing transport losses. 17,20,21 The anode GDL backing was also found to be highly influential; in experiments conducted with several different anode gas-diffusion layer backings without MPLs, up to a 2-fold variation in the maximum current density was observed at 30 C. 19 Limited experimental results with two anode GDLs with modest performance variation indicated that the anode GDL did not substantially influence the water distribution as was the case with reduced anode operating pressure, 20 indicating that the mechanism of the anode GDL influence on low-temperature response is unclear.…”

Nanostructured Thin Film Electrocatalysts - Current Status and Future Potential

“…More recent reports of oxygen evolution catalysts applied to the NSTF anodes and cathodes for fuel cell, cell reversal tolerance and electrolyzer applications are also starting to appear (29)(30)(31)(32)(33)(34). Finally strategies and approaches to resolve low temperature water management issues characteristic of ultra-thin electrodes have been reported (16,(35)(36)(37). In the following we update various fuel cell performance and durability metrics including new applications for cell reversal tolerant anode catalysts and gas diffusion layers for water management.…”