Quick synthesis of low-cost NaOH-doped pristine PVA-TEOS composite alkaline membrane electrolyte for power generation from direct sodium borohydride fuel cell at moderate temperature

Abstract

In the present study, laboratory-synthesized low-cost poly(vinyl) alcohol (PVA) membrane doped with silica derived from tetraethyl orthosilicate (TEOS) was prepared for the use in alkaline direct sodium borohydride fuel cell (DSBFC). To make the synthesized membrane alkaline or OH− conducting, NaOH was doped in pristine PVA-TEOS membrane, and the membranes were designated as PVA-TEOS-(0 M), PVA-TEOS-(2 M), PVA-TEOS-(3 M), PVA-TEOS-(4 M), PVA-TEOS-(5 M), PVA-TEOS-(6 M), and PVA-TEOS-(7 M) doped with 0-M, 2-M, 3-M, 4-M, 5-M, 6-M, and 7-M NaOH solutions, respectively. The incorporation of silica in PVA improved the water uptake and NaOH uptake and came up with excellent ionic conductivity in the order of 9.09 ± 0.5 × 10−3 S/cm when doped with 4-M NaOH. The performance of the PVA-TEOS nanocomposite membrane doped with NaOH was further examined in a single DSBFC using varying effective parameters to achieve the highest power density. The electrocatalyst Pt (40 wt.%)/C of varying loading was used for both anode and cathode. The fuel NaBH4 of varying concentrations mixed with 4-M NaOH was used at the anode side, and oxidant pure O2 was used at the cathode side. The PVA-TEOS membrane doped with 4-M NaOH/PVA-TEOS-(4 M) produced maximum power density of 54.91 mW/cm2 at a current density of 128 mA/cm2 when the DSBFC was operated at the room temperature of 25 ℃. The highest power density of 79.87 mW/cm2 at the current density of 166.4 mA/cm2 was obtained at moderate temperature of 55 ℃ for the same membrane electrolyte PVA-TEOS-(4 M). The power density of DSBFC got enhanced 45.46% when cell temperature was increased from 25 to 55 ℃. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.