Simple design of PVA-based blend doped with SO<inf>4</inf>(PO<inf>4</inf>)-functionalised TiO<inf>2</inf> as an effective membrane for direct borohydride fuel cells

Abstract

Nanocomposite membranes for low-temperature fuel cells, specifically, direct borohydride fuel cells (DBFCs), are formulated from a ternary polymer blend of poly (vinyl alcohol), poly (vinyl pyrrolidone), and poly (ethylene oxide) with the incorporation of (SO4–TiO2) nanotubes and (PO4–TiO2) as doping agents. The functionalisation of TiO2 is carried out by impregnation-calcination method. Structural and morphological characterisation by FTIR, TEM, SEM, EDX, ICP, and XRD confirmed the successful preparation of the doping materials and their incorporation into the polymer blend. The influence of SO4–TiO2 and PO4–TiO2 doping and their content on the physicochemical properties of the composite membranes is assessed. Water uptake and swelling degree gradually reduced to below 20% with increasing the concentration of TiO2-based doping agent, while the ion exchange capacity raised 3.5 times compared to that of the undoped membrane. The increase of the doping agent content also increased the ionic conductivity, tensile strength and thermal stability of the membrane. DBFC using the composite membrane produced a maximum power density of 75 mW cm−2, close to that using Nafion®117 membrane (81 mW cm−2) but at a significantly lower cost. The promising results obtained in this study pave the way for a simple, green and economic approach for the development of composite membranes for application in DBFCs.