In-situ strategies for melamine-functionalized graphene oxide nanosheets-based nanocomposite proton exchange membranes in wide-temperature range applications.

The traditional preparation of nanocomposite proton exchange membranes (PEM) is hindered by poor organic-inorganic interface compatibility, insufficient proton-conducting sites, easy aggregation of nanoparticles, and difficulty in leveraging nanoscale advantages. In this study, a novel method involving electrochemical anodic oxidation exfoliation was employed to prepare melamine-coated graphene oxide (Me@GO), which was subsequently subjected to in-situ polymerization with poly(2,5-benzimidazole) (ABPBI) to prepare a Me@GO/ABPBI composite proton exchange membrane. Benefiting from the strong hydrogen bonding and large π stacking interactions, melamine (Me) tightly bound to graphene oxide (GO), effectively preventing the secondary aggregation of GO after exfoliation. Moreover, the abundant alkaline functional groups of melamine enhanced the enhancement of phosphoric acid (PA) retention in the Me@GO/ABPBI membranes, thereby increasing the number of proton-conducting sites. The experimental results indicated that the introduction of Me@GO enhanced membrane properties. For Me@GO at a concentration of 1 wt%, the tensile strength of the 1Me@GO/ABPBI composite membrane reached 207 MPa, nearly 2.52 times that of the pure membrane. The proton conductivity of the 1Me@GO/ABPBI composite membrane reached 0.01 S cm across a wide temperature range (40-180 °C), peaking at 0.087 S cm at 180 °C. Additionally, a single-cell incorporating the 1Me@GO/ABPBI composite membrane achieved a peak power density of 0.304 W cm at 160 °C, nearly 1.46 times that of the pure membrane. Benefiting from the well-dispersed and PA-enriched proton channels provided by Me@GO, the Me@GO/ABPBI composite membrane exhibits excellent prospects for wide-temperature range (40-180 °C) applications.