Enhancement on the Quaternized sodium alginate/polyvinyl alcohol membrane performance in the application of passive DEFCs

•The optimum membrane thickness is required to enhance the performance of DEFCs.•The 20 μm has been identified as an optimal thickness of the QSA/PVA membrane.•The highest membrane selectivity has obtained at 13.57×104 S s cm−3.•The maximum power density of passive DEFCs has achieved 11.2 mW cm−2.•QSA/PVA membrane has been sustained for 1000 h of operating condition.