Chitosan nanohybrid proton exchange membranes based on CNT and exfoliated MoS2 for fuel cell applications

Functionalized carbon nanotubes (CNT) and exfoliated MoS2 nanosheets are employed additives for chitosan (CS) in view to ameliorate the proton transfer along the biopolymer membrane through the formation of additional ion-exchange sites provided as a result of cross-linking the CS chains using citric acid (CA). IR analysis showed that CA acts both as ionic cross-linker and covalent cross-linker as well. Physicochemical characteristics such as water uptake capacity, ion-exchange capacity (IEC), swelling ratio and the ability of the nanohybrid membranes to retain water (self-humidification) are investigated extensively. The conductivity analysis results show that the CS nanohybrid membranes displayed peak proton conductivity of 91.55 mS cm−1 at 100 °C when the dopant concentration is 6 wt%. The CS membrane with 6 wt% of CNT-MoS2 displayed increased selectivity than other nanohybrid membranes at 25 °C (4.14 × 104 S cm−3 s) which almost doubled to 9.19 × 104 S cm−3 s at 40 °C. Furthermore, the additives profoundly improved the mechanical, thermal and oxidation stability of the membranes. Overall, the fabricated CS-CNT-MoS2 nanohybrid membranes exhibited satisfactory property enhancements due to the formation of additional ion-exchange active sites and the presence of reinforcement among the polymer, cross-linker and the additives that make their use in PEMFCs as appealing candidates.