A high-performance PVA proton exchange membranes based on dendritic silica nanoparticles loaded with ionic liquids for direct methanol fuel cells

A novel proton exchange membrane (PEM) has been developed using dendritic mesoporous silica nanoparticles (DMSNs) which are synthesized via a process of self-assembly. Proton ionic liquids (PILs) are loaded into DMSNs' 3D radial pore channels through vacuum impregnation, and IL@DMSN composites with varying weight ratios (1.5–7.5 wt%) are incorporated into crosslinked polyvinyl alcohol (PVA) matrices to form cPVA/IL@DMSN-X nanocomposite films. The design effectively mitigates PIL leaching while leveraging DMSNs' unique structural advantages, namely hierarchical porosity, uniform 57 nm particle size, and high surface area. The optimal formulation (cPVA/IL@DMSN-6) demonstrates exceptional performance, with a reduction in methanol permeability to 4.8 × 10⁻⁷ cm² s⁻¹, and an increase in proton conductivity to 75.4 mS cm⁻¹. It is noteworthy that at relative humidity levels of less than 20 %, the membrane demonstrates a proton conductivity of 25 mS cm⁻¹ and exhibits remarkable thermal stability, with a maximum temperature of 200 °C. A single direct methanol fuel cell (DMFC) based on the prepared membrane exhibits a peak power density of 59.7 mW cm⁻² in pure H₂ operation, and remarkable methanol tolerance with 38.8 mW cm⁻² retained at 10 M methanol feed out. The DMSN incorporation results in a simultaneous enhancement of proton conduction, dimensional stability, and methanol barrier properties, thereby demonstrating significant potential as an alternative PEM for durable DMFC applications.