Mechanically Robust Nafion-Based Anhydrous Proton Exchange Membranes with High Proton Conductivity and Efficient In Situ Self-Healing Capacities.

Abstract

There is increasing demand for self-healing high-temperature proton exchange membranes (HT-PEMs) with superior mechanical robustness and proton conductivity. In this study, the fabrication of mechanically robust HT-PEMs (denoted as N-IL-PW) is demonstrated by integrating high proton conductivity and the ability to in situ heal fatigue and damage during operation via the complexation of Nafion, phosphotungstic acid (PW) clusters, and ionic liquids (ILs). Originating from the synergistic effect of high-density electrostatic interactions as well as hydrogen bonds in ionic domains and stable crystalline domains, the N-IL-PW membranes are highly resilient and fatigue resistant, and display excellent creep resistance even at 170 °C. Under an anhydrous condition of ≈170 °C, the N-IL-PW membranes have a high proton conductivity of ≈18.86 mS cm^-1. Meanwhile, the hydrogen-powered HT-PEM fuel cells assembled with N-IL-PW membranes exhibit good cell performance under an anhydrous condition of ≈120 °C. More importantly, the reversibility of electrostatic and hydrogen bonding interactions enables the membranes in situ to heal fatigue and mechanical damages under fuel cell operation conditions. Healed membranes can regain their pristine mechanical properties, proton conductivity, hydrogen barrier property, and cell performance. Excellent high-temperature creep resistance, fatigue resistance, and healing capability can work in concert to enhance the reliability of N-IL-PW membranes.