Dramatic Improvement in Water Retention and Proton Conductivity in Electrically Aligned Functionalized CNT/SPEEK Nanohybrid PEM

TLDR

The authors fabricated electrically aligned functionalized CNT/SPEEK nanohybrid membranes by solution casting, carboxylating and sulfonating CNTs, applying a 500 V cm⁻² electric field during drying, and characterizing them with FTIR, DSC, DMA, UTM, SEM, TEM, and AFM. The nanohybrids exhibit stronger intermolecular interactions, higher ion‑exchange capacity, improved water retention and proton conductivity, lower methanol permeability, with the S‑sCNT‑5 membrane achieving the highest conductivity and methanol‑crossover resistance, making them suitable for fuel cell and battery electrodes.

Abstract

Nanohybrid membranes of electrically aligned functionalized carbon nanotube f CNT with sulfonated poly ether ether ketone (SPEEK) have been successfully prepared by solution casting. Functionalization of CNTs was done through a carboxylation and sulfonation route. Further, a constant electric field (500 V·cm(-2)) has been applied to align CNTs in the same direction during the membrane drying process. All the membranes are characterized chemically, thermally, and mechanically by the means of FTIR, DSC, DMA, UTM, SEM, TEM, and AFM techniques. Intermolecular interactions between the components in hybrid membranes are established by FTIR. Physicochemical measurements were done to analyze membrane stability. Membranes are evaluated for proton conductivity (30-90 °C) and methanol crossover resistance to reveal their potential for direct methanol fuel cell application. Incorporation of f CNT reasonably increases the ion-exchange capacity, water retention, and proton conductivity while it reduces the methanol permeability. The maximum proton conductivity has been found in the S-sCNT-5 nanohybrid PEM with higher methanol crossover resistance. The prepared membranes can be also used for electrode material for fuel cells and batteries.