Effect of Inner Catalyst Layer with PTFE Binder on Performance of High Temperature Polymer Electrolyte Membrane Fuel Cells

Abstract

Herein, gas diffusion electrodes (GDEs) structured with a double catalyst layer were fabricated by introducing an inner catalyst layer containing PTFE. The Pt loading of the inner catalyst layer with Polytetrafluoroethylene (PTFE) was varied over 0.1–0.9 mg·cm-2.The fabricated GDEs were applied to the membrane electrolyte assembly (MEA) as a cathode to evaluate the single cell performance of high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Peak power density improved by 33%, from 266 mW·cm-2 to 355 mW·cm-2 for 0.1 mg·cm-2 of Pt loading of the inner catalyst layer. This substantial enhancement in single cell performance even with a small amount of Pt loading of the inner catalyst layer results from highly hydrophobic catalyst layers leading to improved mass transport. As the Pt loading of the inner catalyst layer increases, the MEA performance in fuel cells improved; however, the performance saturated at Pt loading of 0.5 mg·cm-2 and above.

Overcoming the Electrode Challenges of High-Temperature Proton Exchange Membrane Fuel Cells

“…Innovative approaches have been proposed to improve the triple-phase boundary quality throughout the electrode, from relatively crude approaches (hydrophobicity gradients) to more complex approaches (in situ combination of hydrophobicity and electron/proton conductivity). A gradual increase in the hydrophobic binder content (deposition of a catalyst ink with increasing hydrophobicity) from the MPL to the membrane surface improves the electronic conductivity and acid diffusion while increasing the catalyst utilization and alleviating mass transfer issues [289][290][291][292]. More complex approaches involve (i) depositing hydrophobic NPs on carbon black to locally combine electronic conductivity with hydrophobicity, (ii) functionalizing hydrophobic nanospheres (200 nm PVDF) for interaction with PA and conduction of protons, and (iii) increasing the Pt hydrophobicity using pulse deposition [293][294][295].…”