Interplay between Mechanical, Electrical, and Thermal Relaxations in Nanocomposite Proton Conducting Membranes Based on Nafion and a [(ZrO2)·(Ta2O5)0.119] Core–Shell Nanofiller

Abstract

The thermal, mechanical, and electric properties of hybrid membranes based on Nafion that contain a [(ZrO(2))·(Ta(2)O(5))(0.119)] "core-shell" nanofiller are elucidated. DSC investigations reveal the presence of four endothermic transitions between 50 and 300 °C. The DMA results indicate improved mechanical stability of the hybrid materials. The DSC and DMA results are consistent with our previous suggestion of dynamic R-SO(3)H···[ZrTa] cross-links in the material. These increase the thermal stability of the -SO(3)H groups and the temperature of thermal relaxation events occurring in hydrophobic domains of Nafion. The broadband electrical spectroscopic analysis reveals two electric relaxations associated with the material's interfacial (σ(IP)) and bulk proton conductivities (σ(EP)). The wet [Nafion/(ZrTa)(1.042)] membrane has a conductivity of 7.0 × 10(-2) S cm(-1) at 115 °C, while Nafion has a conductivity of 3.3 × 10(-2) S cm(-1) at the same temperature and humidification conditions. σ(EP) shows VTF behavior, suggesting that the long-range conductivity is closely related to the segmental motion of the Nafion host matrix. Long-range conduction (σ(EP)) occurs when the dynamics of the fluorocarbon matrix induces contact between different delocalization bodies (DB), which results in proton exchange processes between these DBs.