Pore-filling membrane containing solely zirconium phosphonates with high content through in-situ conversion.

Organic-inorganic composite membranes are used in various applications, especially as proton-conducting electrolyte membranes for proton-exchange membrane fuel cells (PEMFCs). This study proposed a method to fill a flexible porous substrate solely with high amounts of inorganic (approximately 48 wt%) nano-zirconia precursor, surface-modified by acetylacetone (AcAc-Zr). AcAc-Zr can be converted to zirconium phosphate (ZrPi) in situ, and several other zirconium phosphonates, such as zirconium aminotris-methylene-phosphonate (ZrATMP) and zirconium 1-hydroxyethane-1,1-diphosphonate (ZrHEDP). Transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) analysis revealed that the pores were continuously filled with ZrPi, indicating that ZrPi has a percolated structure in the membrane, beneficial for their proton conduction. The proton conductivities of the membranes, including ZrPi, ZrHEDP, and ZrATMP, were sufficiently high, on the order of 1 mS cm−1 at 80 °C and 95% relative humidity. • In situ conversion of the Zr precursor to various derivatives. • High-content zirconium phosphonates (ZrPi, ZrATMP, and ZrHEDP) were solely filled in porous substrates. • Inorganics in the membrane formed continuous pathways for proton conduction. [ABSTRACT FROM AUTHOR]