Enhancing hydroxide conductivity of anion exchange membrane via incorporating densely imidazolium functionalized graphene oxide

• Published in: Solid state ionics Vol. 333; pp. 83 - 92
• Main Authors: Mao, Xunli, Li, Zhen, He, Guangwei, Li, Zongyu, Zhao, Jing, Zhang, Yun, Jiang, Zhongyi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2019; Elsevier BV
• Subjects: Anion exchanging; Bisphenol A; Brushes; Composite membrane; Conductivity; Fuel cells; Graphene; Hydroxide conductivity; Ion exchange; Ion exchange capacity; Maximum power density; Membranes; Polymers; Polysulfone resins; Quaternized bisphenol A-type polysulfone; Quaternized graphene oxide; Solid oxide fuel cells; Transport; Ion exchange capacity; Quaternized graphene oxide; Quaternized bisphenol A-type polysulfone; Hydroxide conductivity; Composite membrane
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2019.01.023

This study presents a generic method to increase the hydroxide conductivity of anion exchange membranes by tuning the microphase separation structure. Graphene oxide was functionalized with macromolecular brushes for the first time by a precipitation polymerization method. Densely-functionalized imidazolium groups were aligned in the configuration of macromolecular brushes to act as hydroxide-conductive groups, which endow the functionalized graphene oxide with a high ion exchange capacity value of 3.05 mmol g−1. Polymer-inorganic composite membrane for anion exchange membrane fuel cell was fabricated by incorporating the imidazolium-functionalized graphene oxide into imidazolium-functionalized bisphenol A-type polysulfone. The dense imidazolium groups manipulated the aggregation of conductive groups at the polymer/filler interfaces to induce the well-defined microphase structure of composite membranes, constructing low-resistance channels for ionic transport. The activation energy of hydroxide transport in composite membranes was reduced to 25.17–13.62 kJ mol−1, in comparison with 28.63 kJ mol−1 for control membrane. The hydroxide conductivity of composite membrane was elevated to 22.02 mS cm−1 at 30 °C, which is 2.10 times of that for control membrane. The maximum power density of single fuel cell of 78.7 mW cm−2 at 60 °C was thus achieved. •Quaternized GO with a high IEC value of 3.05 mmol g−1 was prepared.•Quaternized GO is exploited as versatile filler to fabricate composite membrane.•Efficient ionic pathways with the much lowered Ea are built in composite membranes.•The hydroxide conductivity of membranes increases to 2.1 times at 30 °C.