Preparation and characterization of a sol-gel derived silica/PVA-Py hybrid anion exchange membranes for alkaline fuel cell application

Ammonium functionalized anion exchange silica precursor (AESP) is synthesized by 3-(2-Aminoethylamino) propyltriethoxysilane and (2, 3-epoxypropyl) trimethylammonium chloride. Then the corresponding series of membranes based on pyridine functionalized polyvinyl alcohol (PVA-Py) with varying AESP content are prepared using sol-gel method. Obtained membranes show ion exchange capacities (IEC) ranging from 0.54 mmol·g −1 to 0.92 mmol·g −1 , but the opposite trend of water uptakes (WU) from 123.97% down to 69.09% because of the formation of organic-inorganic network. The hybrid membranes also exhibit good thermal stability (>140 °C), excellent mechanical properties (25.37 MPa) and high OH − conductivity (9.63 × 10 −2  S·cm −1 , 80 °C). Compared with the commercial Nafion®-117 membrane, the prepared hybrid membrane performs a much lower methanol permeability (7.57 × 10 −8  cm 2 ·s −1 for prepared membrane, 2.00 × 10 −6  cm 2 ·s −1 for Nafion®-117 membrane, 3 M methanol solutions, 30 °C). Only 10.7% decreases in OH − conductivity can be observed in 6 M 80 °C NaOH solutions after 360 h immersions, exhibiting excellent alkaline stability. The highest peak power density of the single cell with 5 M KOH + 3 M methanol fuel is 52.56 mW·cm −2 at 80 °C and 0.2 MPa O 2 .