Modification of sulfonated poly (etherether ketone) composite polymer electrolyte membranes with 2D molybdenum disulfide nanosheet-coated carbon nanotubes for direct methanol fuel cell application

Fabrication of novel proton exchange membrane (PEM) is crucial to the development of direct methanol fuel cells (DMFCs). Here, molybdenum disulfide (MoS2) nanosheets were anchored onto carbon nanotubes (CNTs) via a facile in-situ growth method, and then a series of composite PEMs were fabricated via embedding MoS2-coated CNTs (MoS2@CNTs) in the sulfonated polyether ether ketone (SPEEK) matrix. The coating of MoS2 nanosheets improved the dispersibility and compatibility with the polymer matrix and enhanced the mechanical properties of the composite membranes. Owing to the unique one-dimensional structure of CNTs and the hydrophilic MoS2 coating, channel-like ion transport pathways (water channels) could be constructed, which would enhance the ionic conductivity of the composite membrane. It is worth noting that the incorporation of 1 wt% MoS2@CNTs at 80 °C resulted in 1.7-fold proton conductivity relative to pristine SPEEK membrane, and substantially decreased its methanol permeability. As a result, the SPEEK/MoS2-1 composite membrane exhibited excellent fuel cell performance with a high peak power density of 98.5 mW cm−2 at 70 °C, which was 73.7% higher than that of the SPEEK membrane and Nafion-115 membrane. Finally, the durability test further validated the potential of SPEEK/MoS2@CNTs composite membrane to be used as an alternative for Nafion membrane.