Preparation and characterization of polyvinyl alcohol polyelectrolyte-based membrane-anode assembly for hybrid Fe3+/H2 redox flow microbial fuel cell

The redox Fe3+/H2 flow fuel cell electrolytes are based on thin polymeric membranes that conduct protons (H+ ions). This paper reports the study of polyvinyl alcohol (PVA) based polyelectrolyte membranes (PEM) for application in redox flow fuel cells. The PVA polyelectrolyte membranes (PVA-PEMs) were supported on a gas diffusion electrode (GDE), and cross-linked in situ using glutaraldehyde (GA) in the presence of acidic catalyst, forming a membrane-anode assembly. Multiple coating layers of PVA/GA were applied on the GDE for obtaining different membrane thicknesses. The swelling study indicated that the water uptake of the membranes decreased linearly with the increase in the GA content due to the increase in the cross-link density. The GA content of 11 wt.% showed a maximum gel content of 98.4% and optimum water uptake of 40%. The overall ionic (iron ions and acid) crossover flux through PVA-PEMs was lower than that in the Nafion® 112 ionomer membrane. The two-layer of PVA-PEMs on Nafion postcoated GDE exhibited the maximum power density of 170 mW cm−2 at current density of 472 mA cm−2. In the case of the commercial Selemion HSF ion exchange membrane, the maximum power density was found to be 166 mW cm−2 at current density of 472 mA cm−2. The continuous operation of the redox flow cells with PVA-PEMs exhibited stability with 92% retention in cell voltage after 480 h.