Incorporating ALD Based Pt Alloy Catalysts into Gas Diffusion Electrodes for Proton Exchange Membrane Fuel Cells

Abstract

Atom layer deposition is a promising method to fabricate gas diffusion electrodes (GDE) with platinum catalysts for high-power-density Proton Exchange Membrane Fuel Cells (PEMFCs). Alloying Pt with transition metals can further improve the intrinsic activity for oxygen reduction reaction due to the ligand and strain effects. Nevertheless, incorporating alloy catalysts into GDE posts more challenges.In this study, we systematically explore and optimize alloy-based catalysts via ALD deposition on gas diffusion layers (GDL). While GDE tolerates 200 oC annealing for alloys that can form under low temperature (e.g.PtxZny) and present high ORR performance, GDE for PtxTiy alloy presents inferior performance after high-temperature annealing.To circumvent this temperature compatibility issue, we successfully developed a modified high-temperature ALD method for PtxTiy alloy by taking advantage of a porous metal felt. With this, ALD-based high temperature annealed PtxTiy series alloy can maintain its atomic structure, and the GDL can keep its high hydrophobicity. Further Membrane Electrode Assembly (MEA) testing results and insights into active site areas and activation energy for different alloys and fabrication methods provide the in-depth elucidation of the relationship between reaction kinetics and GDE structures.