Synergy effects of hindered phenol and diphosphite antioxidants on promoting alkali resistance of quaternary ammonium functionalized poly(4-vinylbenzyl chloride-styrene) anion exchange membranes

Abstract

The anion exchange membranes (AEMs) possessing a long-term alkaline stability is desired for use as the electrolyte in electrochemical devices. We prepared a series of AEMs with excellent stability and reasonable conductivity as well as acceptable mechanical properties by addition of antioxidants into quaternary ammonium modified poly(4-vinylbenzyl chloride-styrene). It is found that the synergy of hindered phenol and diphosphite antioxidants endowed the AEMs with superior resistance to the attack of both OH– ions and free radicals. The proposed membrane retained about 80% of the original conductivity after soaked in 2 M KOH aqueous solutions at 60 oC for 1300 h. The synergy effect of the dual antioxidants was investigated by Fenton tests and the fluorescence analysis. A peak power density of 526 mW cm−2 was achieved at 60 oC by the membrane-based single fuel cell fueling with humidified H2 and O2 without back pressure.