Performance enhancement of NaOH doped physically crosslinked alkaline membrane electrolyte by addition of TEOS to PVA solution for direct sodium borohydride fuel cell application

Abstract

In the present study, physically crosslinked polyvinyl alcohol and tetraethyl orthosilicate (PVA-TEOS/PT) composite membrane doped by NaOH was used synthesized to enhance the performance of an alkaline direct sodium borohydride fuel cell (DSBFC) for the first time. The PVA-TEOS (PT) solution was subjected to varying number of freeze-thaw cycle and doped with varying concentration of NaOH for further characterization and performance evaluation in DSBFC. The physical crosslinking increased the amorphous nature of the membrane electrolyte and hence, the ionic conductivity improved significantly. The amount of TEOS in PVA matrix was varied from 5 wt % to 15 wt %. The highest ionic conductivity of 9.67 ± 0.04 × 10−3 S cm−1 was obtained for the membrane freeze-thawed of cycle 7 having 10 wt % of TEOS and dipped in 4 M NaOH solution (PT10 wt%-7Cy-(4 M)). The physically crosslinked NaOH doped PVA-TEOS composites were tested in a single DSBFC using the Pt (40 wt %)/C at anode and cathode both. The fuel NaBH4 mixed with supporting electrolyte NaOH was used at anode and pure oxygen was used as oxidant at cathode. The membrane electrolyte (PT10 wt%-7Cy-(4 M)) with highest conductivity of 9.67 ± 0.04 × 10−3 S cm−1 exhibited highest peak power/maximum power density of 85.19 mW/cm2 at a current density of 184 mA/cm2 at the temperature of 60 °C. The recorded highest power density (85.19 mW/cm2) was capable to run array of LED light (1.2 W) for at least 12 h without any fall in performance. © 2023 Hydrogen Energy Publications LLC