Advances in hybrid composite membranes engineering for high-performance direct methanol fuel cells by alignment of 2D nanostructures and a dual-layer approach

The inclusion of hydrophilic 2D-nanoparticles in a polymeric matrix demonstrated to be a promising strategy both to improve the proton transport in proton exchange membrane fuel cells (PEMFCs), and to mitigate the methanol crossover in direct methanol fuel cells (DMFCs), acting as physical barriers. Moreover, a higher order's degree in the arrangement of the filler's platelets, e.g. aligned parallel to the membrane surface, may further reduce the detrimental effect of the methanol permeation as a consequence of the greater obstruction and increased tortuosity of the fuel diffusion path. Layered Double Hydroxide (LDH), characterized by a high aspect ratio and hydrophilic functional groups on the surface, was incorporated into Nafion to obtained nanocomposite membranes with appropriate morphology and demonstrating the possibility of mechanical aligning the exfoliated nanoparticles. EIS and PFG-NMR provided indirect evidence of lamellae's alignment at the nanoscale, while Magnetic Resonance Imaging combined with Rheology (Rheo-MRI) has proved to be an effective and elegant method, as well as original for such investigations, to study the organization of nano-lamellae dispersed in a polymeric solution under the shearing. Dual-layer hybrid composite membranes were also designed, optimized and tested in DMFC, showing the outstanding power density of 300 mW cm−2 at 100 °C.