Enhanced performance of high‐temperature proton exchange membrane by introducing 1,2, 4‐triazole‐ functionalized graphene oxide into polybenzimidazole

Abstract

1,2,4-triazole is successfully grafted onto C═C bonds of graphene oxide surface with retained carboxylic acid, hydroxy, and epoxy groups. The structure of the resulting 1,2,4-triazole-doped graphene oxide (NGO) is proved by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy spectra. The polybenzimidazole (PBI)/NGO composite membranes (NGO content:0.5%, 1%, 3%, 5%) were also prepared and subjected to the absorption of various suitable amounts of phosphoric acid (PA). As expected, the composite membranes well maintained their superior mechanical properties (57-69 MPa) containing 2 PA molecules per PBI unit. The morphological characterization using the atomic force microscopy phase images and transmission electron microscopy analysis revealed a micro-phase separation, providing continuous ionic channels and ultimately enhancing the ionic conductivity. As a result, the maximum proton conductivity of 27 mS cm−1 is achieved for PBI/NGO-3 membrane (NGO content: 3%) at 160°C under anhydrous conditions, and the maximum power density of the cell using PBI/NGO-3 membrane is 254 mW cm−2. These composite membranes displayed great potential for high-temperature proton exchange membranes under anhydrous conditions. The scanning electron microscopy images further showed the condensed structures with the suitable quantity of NGO in the composite membranes due to the hydrogen bonding and acid–base interactions between NGO and PBI. This condensed structure improved the mechanical properties, enhanced thermal stability, and increased oxidative stability of the composite membranes. Additionally, the PBI/NGO/PA composite membranes exhibit high thermal decomposition temperature (Td[5%] higher than 284°C) and superior tensile strengths (greater than 55 MPa). Remarkably, the membranes demonstrated exceptional oxidative stability and could maintain less than 15% quantity loss for more than 200 hours in Fenton's reagent (3 wt% H2O2, 4 ppm Fe2+). Novelty statement The manuscript entitled “Enhanced Performance of High-Temperature Proton Exchange Membrane by Introducing 1,2,4-Triazole Functionalized Graphene Oxide into Polybenzimidazole” was written by Haiqiu Zhang In this work, 1,2,4-triazole is successfully grafted onto graphene oxide nanosheets by C═C bonds without damaging other groups, and condensed structure improved the oxidative stability effectively, meanwhile, with the low-acid-loaded quantity and gained higher proton conductivity under anhydrous condition.