Chemical stability of proton exchange membranes synergistically promoted by organic antioxidant and inorganic radical scavengers

Abstract

The synergistic effects between organic antioxidants with metal ion chelation ability and inorganic radical scavengers were investigated. The different perfluorosulfonic acid (PFSA) composite membranes were prepared by single doping and codoping of alizarin (AZR) and cerium ions. AZR and cerium ion codoping not only significantly enhanced the oxidative stability of the membrane but also lessened both the migration of cerium ions from the membrane and the ionic cross-linkages of cerium ions with sulfonic acid groups. AZR/Ce codoping of the PFSA composite membrane exhibited a maximum power density of 966 mW cm−2 at 75 °C under 80% RH, which was 89.45% of that of the pristine PFSA membrane, whereas only 79.37% remained for cerium ion single doping of the membrane under the same conditions. The AZR/Ce-codoped PFSA composite membrane released much less fluoride than the single-doped PFSA, AZR, or cerium ion composite membranes. The antioxidation effects of AZR/Ce codoping of the PFSA composite membrane were also studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical hydrogen crossover analysis, and cell performance analysis. Notably, the open-circuit voltage (OCV) test indicated that the AZR/Ce-codoped PFSA composite membrane was still viable after 456 h of testing, whereas the other membranes were seriously damaged.