Tailoring Ionomer Chemistry for Improved Oxygen Transport in the Cathode Catalyst Layer of Proton Exchange Membrane Fuel Cells

Abstract

Reducing the local oxygen transport resistance in the cathode catalyst layer of the proton exchange membrane fuel cell (PEMFC) is crucial for the improvement of cell performance, particularly for low platinum loading. In this work, we report that the performance of PEMFC can be significantly improved by replacing Nafion with a highly oxygen-permeable perfluoronated ionomer containing dioxole segments on the backbone as both proton conductor and catalyst binder in the cathode catalyst layer, as evidenced by the increased peak power density of 100 mW cm–2. Molecular dynamics simulation results reveal that the synthesized ionomer has higher diffusion coefficient and higher oxygen solubility compared with Nafion. Benefiting from the high oxygen permeability, both the specific activity and mass specific activity of a Pt/C catalyst using the designed ionomer as catalyst binder for the oxygen reduction reaction are three times higher than those of a catalyst using Nafion as catalyst binder. The results demonstrate that the rational design of highly oxygen-permeable ionomers applied in the catalyst layer could be an effective strategy for a high-performance PEMFC with low platinum loading.