Nafion nanocomposite membranes have emerged as a promising replacement to traditional polymer electrolyte membranes for fuel cells and flow batteries due to their ability to minimize crossover of undesired species while still maintaining the high conductivity values for which Nafion is known. Vanadium redox flow batteries have become a popular solution in intermittent energy storage such as wind and solar energy industries, but the lifetime and efficiency of the flow batteries are diminished by vanadium ion crossover. While Nafion nanocomposite membranes have demonstrated reduced vanadium ion crossover, little has been accomplished to understand how the nanoparticles act to reduce crossover. In this study, the surface chemistry of the silica nanoparticles was systematically altered to intelligently tailor their dispersion in the membrane, thereby elucidating how this degree of dispersion ultimately impacts the vanadium ion crossover. Specifically, several types of interactions between silica nanoparticle surface and Nafion were investigated, including electrostatic and covalent interactions within the hydrophilic ionic channels of Nafion and electrostatic interactions with the hydrophobic Teflon backbone. The dispersion state within the membrane was characterized by electron imaging in addition to analyzing the vanadium ion permeability across the nanocomposite membranes via ultraviolet-visible spectroscopy. The bridging support between silica nanoparticle surface and end functional group was also investigated, ranging from a relatively flexible, short saturated chain to a significantly less flexible chain containing aromatic groups. Results from this study indicate that the surface functionalization of the silica nanoparticles plays an important role in controlling the permeation of vanadium ions across these nanocomposite membranes.

Surface functionalization of silica (SiO<sub>2</sub>) nanoparticles in Nafion nanocomposite membranes for vanadium redox flow batteries

255th National Meeting (2018)

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Surface functionalization of silica (SiO2) nanoparticles in Nafion nanocomposite membranes for vanadium redox flow batteries

Surface functionalization of silica (SiO₂) nanoparticles in Nafion nanocomposite membranes for vanadium redox flow batteries