Nafion® nanocomposite membranes with enhanced properties at high temperature and low humidity environments

Abstract

Highly proton conductive nanocomposite membranes were synthesized by incorporating modified silica nanoparticles bearing different kinds of acid functionalities into Nafion. The short oligomeric corona, containing either phosphonate or sulfonate functional groups, leads to membranes with non-aggregated, discrete nanoparticles acting synergistically with the polymer.The new membranes exhibit significantly increased proton conductivity in all relative humidities and temperatures, however unprecedented behavior is observed at elevated temperatures (> 80 °C) and/or low relative humidity. Pulse Field Gradient NMR measurements demonstrate that, in contrast to neat Nafion, which shows a precipitous decrease in the self-diffusion of water above 80 °C, the nanocomposite membranes were able to maintain high proton diffusivities pointing to adequate hydration levels for several hours at 130 °C without any external humidification. Furthermore, thermal and dynamic mechanical analysis reveal that the nanocomposite membranes retain their stiffness at much higher temperatures up to 200 o C compared to recast Nafion opening the way for high temperatures applications. The overall high ionic conductivity of the nanocomposite membranes especially above 80 °C coupled with their exceptional water retention capability and mechanical robustness makes them very attractive for potential use in fuel cell applications.

Understanding Surface and Interfacial Chemistry in Functional Nanomaterials via Solid‐State NMR

“…Many SSNMR studies have focused on a number of Nafion‐derived materials, in particular Nafion‐derived nanocomposites with inorganic fillers or other moieties . One advantage of adding an inorganic filler is the enhancement of the water retention and durability of Nafion for fuel cells working at elevated temperatures.…”

Recent Perspectives and Crucial Challenges on Unitized Regenerative Fuel Cell (URFC)

“…Nafion, a widely used PEM for hydrogen fuel cells, provides high proton conductivity and low gas crossover (Antolini 2014). The electrolyte is essentially a conductive polymer membrane that acts as a barrier for the fuel and electrons but a conductor for protons (Boutsika et al 2016). Nafion is expensive and does not work well in high temperature and low humidity.…”

Trifluoromethanesulfonimide-based hygroscopic semi-interpenetrating polymer network for enhanced proton conductivity of nafion-based proton exchange membranes at low humidity

“…[9,10] In the hydrophilic phases, water facilitates the dissociation of acid groups and swelling to form well-connected ionic channels. [11][12][13][14] On the other hand, to realize proton diffusion, water acts as an ion carrier by forming H9O4 + (Eigen cation) or H5O2 + (Zundel cation) (vehicle mechanism) and as a conveyor for rapid delivery of protons by the continuous breaking and forming of hydrogen bonds (Grotthuss mechanism). [15,16] Typically, PEMFCs are expected to operate at high temperatures and low humidities to overcome the problems associated with low electrochemical reaction rates, catalyst poisoning, and complex water management systems.…”