Sulfonated poly(ether sulfone) based sulfonated molybdenum sulfide composite membranes: proton transport properties and direct methanol fuel cell performance

Abstract

Composite membranes of sulfonated poly(ether sulfone) (sPES) are prepared in combination with sulfonated molybdenum sulfide (s-MoS₂) as an alternative polymer electrolyte for direct methanol fuel cells (DMFC). Hydrothermally prepared MoS₂ is functionalized using 1,3-propanesultone as a sulfonating media and confirmed via FTIR and XPS analysis. The synthesized composite membranes are characterized for their water content, ion exchange capacity (IEC), proton conductivity and thermo-mechanical stabilities. The suitability of composite membranes for DMFC applications is assessed in terms of their methanol cross-over resistance. The composite membranes show better methanol permeation resistance compared to pristine sPES membranes, as s-MoS₂ acts as a barrier for methanol and provides a conduction path for the proton. Composite membrane with 5 wt% of s-MoS₂ shows 91% reduction in methanol crossover and almost four-fold higher electrochemical selectivity compared to a sPES membrane.