Poly(2,5-benzimidazole)-Grafted Graphene Oxide as an Effective Proton Conductor for Construction of Nanocomposite Proton Exchange Membrane

Xiang Qiu; Mitsuru Ueda; Huayuan Hu; Yuqian Sui; Xuan Zhang; Lianjun Wang

doi:10.1021/acsami.7b07777

Poly(2,5-benzimidazole)-Grafted Graphene Oxide as an Effective Proton Conductor for Construction of Nanocomposite Proton Exchange Membrane

ACS Appl Mater Interfaces. 2017 Sep 27;9(38):33049-33058. doi: 10.1021/acsami.7b07777. Epub 2017 Sep 13.

Authors

Xiang Qiu¹, Mitsuru Ueda^{1

2}, Huayuan Hu¹, Yuqian Sui¹, Xuan Zhang¹, Lianjun Wang¹

Affiliations

¹ Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science & Technology , 200 Xiaolingwei, Nanjing 210094, Jiangsu Province, China.
² Department of Organic and Polymeric Materials, Tokyo Institute of Technology , 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.

PMID: 28872297
DOI: 10.1021/acsami.7b07777

Abstract

To improve proton conduction properties of conventional sulfonated poly(ether ether ketone) (SPEEK), poly(2,5-benzimidazole)-grafted graphene oxide (ABPBI-GO) was prepared to fabricate nanocomposite membranes, which then were further doped with phosphoric acid (PA). The ABPBI-GO was synthesized through the reaction of 3,4-diaminobenzoic acid with the carboxyl acid groups present on the GO surface. The simultaneous incorporation of ABPBI-GO and PA into SPEEK did not only improve the physicochemical performance of the membranes in terms of thermal stability, water uptake, dimensional stability, proton conductivity, and methanol permeation resistance but also relieve PA leaching from the membranes though acid-base interactions. The resulting composite membranes exhibited enhanced proton conductivities in extended humidity ranges thanks to the hygroscopic character of PA and the increased water uptake. Moreover, the unique self-ionization, self-dehydration, and nonvolatile properties of PA improved the high-temperature proton conductivities (σ) of PA-doped membranes. The PA-doped SPEEK/ABPBI-GO-3.0 delivered a σ of 7.5 mS cm^-1 at 140 °C/0% RH. This value was fourfold higher than that of pristine SPEEK membranes. The PA-doped SPEEK/ABPBI-GO-3.0 based fuel cell membranes delivered power densities of 831.06 and 72.25 mW cm^-2 at 80 °C/95% RH and 120 °C/0% RH, respectively. By contrast, the PA-doped SPEEK membrane generated only 655.63 and 44.58 mW cm^-2 under the same testing conditions.

Keywords: H2/air fuel cell; phosphoric acid doping; poly(2,5-benzimidazole)-grafted graphene oxide; proton exchange membrane; sulfonated poly(ether ether ketone) (SPEEK) nanocomposite membranes.