Mechanism study of functionalized graphene oxide on proton transport of polymer electrolyte membrane

Abstract

In this paper, based on the molecular design perspective, sulfonated poly (aryl ether ketone) sulfone containing carboxyl groups (C-SPAEKS) was synthesized. Next, graphene oxide nanosheets functionalized with 5-amino-1H-tetrazole (5-AT@GO) were prepared by amination reaction. By introducing 5-AT@GO to C-SPAEKS matrix, all proportions of composite membranes were successfully prepared. The 5-AT@GO was characterized and composite membranes were used for testing. The C-SPAEKS/5-AT@GO-1 composite membrane displayed the maximum proton conductivity (163.21 mS cm⁻¹ at 80 °C), which was enhanced by 200.60% compared with the unmodified membrane (81.36 mS cm⁻¹ at 80 °C). Furthermore, the water absorption reached 27.89% at 80 °C, and the swelling rate remained below 20%. The C-SPAEKS/5-AT@GO-1 composite membrane also exhibited good thermal stability, oxidation stability and electrochemical properties. At 80 °C, C-SPAEKS/5-AT@GO-1 composite membrane presented a peak power density of 810.71 mW/cm², and the open circuit voltage (OCV) was 1.0015V. Compared with the pure membrane (0.8973V, 190.72 mW/cm²), the peak power density was 4.25 times higher. After a 65-h durability test, OCV of the membrane showed a loss of 5%, specifically, the date dropped from 0.7429V to 0.7061V. The above results indicate that the 5-amino-1H-tetrazole-functionalized graphene oxide nanosheets successfully improved the overall performance of proton exchange membranes (PEMs).