Sulfated titania as additive in Nafion membranes for water electrolysis applications

Hydrogen produced by water splitting is a promising solution for a sustainable economy from renewable energy sources. With this respect, proton exchange membrane (PEM) electrolysis is one of the most suitable technologies, even though low cost, highly active catalysts and durable electrolyte membranes are still needed. Here we demonstrate the successful use of a nano-composite, sulfated titania (S-TiO2)-added Nafion electrolyte coupled with home-made IrRuOx-based anode and commercial Pt cathode in lab-scale water electrolyzers. Superior electrolysis performances were found at 100 °C when comparing the hybrid electrolyte with undoped Nafion. Indeed, current densities of 4 A cm−2 and 3 A cm−2 were found at a terminal voltage of 2 V for the composite and plain membrane, respectively. Ex-situ conductivity measurements, as well as in-operando impedance spectra, were carried out, demonstrating the beneficial effect of the inorganic filler on membrane properties under practical operating conditions. NMR studies (PFG and relaxation time) corroborate the positive role of the nano-additive on the water retention capacity of the membrane, while the dynamic mechanical analysis shows that the hybrid membrane is stiffer and can resist to temperatures higher than undoped Nafion.