Platinum scarcity and its high cost have led to the requirement of alternative materials catalysing the oxygen reduction reaction (ORR), which is the main rate‐determining step occurring in electrochemical devices, including metal‐air batteries and fuel cells. We report a study on a sub‐stoichiometric calcium titanate (CaTiO3−δ, CTO) compound used as promoter for the ORR in order to reduce the Pt loading and improve its electrocatalytic activity. Composite catalysts based on Pt/C with different amounts of CTO were prepared and their activity was investigated by rotating disk electrode (RDE). The obtained results proved a higher catalytic activity for the composite electrode, with respect to pure Pt/C, in terms of electrochemically active surface area, oxygen reduction current density, onset potential and stability.
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 nanocomposite, sulfated titania (S-TiO 2)-added Nafion electrolyte coupled with home-made IrRuO xbased 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 inoperando 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.
Nafion composite membranes, containing different amounts of mesoporous sulfated titanium oxide (TiO2-SO4) were prepared by solvent-casting and tested in proton exchange membrane fuel cells (PEMFCs), operating at very low humidification levels. The TiO2-SO4 additive was originally synthesized by a sol-gel method and characterized through x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and ion exchange capacity (IEC). Peculiar properties of the composite membranes, such as the thermal transitions and ion exchange capacity, were investigated and here discussed. When used as an electrolyte in the fuel cell, the composite membrane guaranteed an improvement with respect to bare Nafion systems at 30% relative humidity and 110 °C, exhibiting higher power and current densities.
Manufacturing new electrolytes with high ionic conductivity has been a crucial challenge in the development and large-scale distribution of fuel cell devices. In this work, we present two Nafion composite membranes containing a non-stoichiometric calcium titanate perovskite (CaTiO3−δ) as a filler. These membranes are proposed as a proton exchange electrolyte for Polymer Electrolyte Membrane (PEM) fuel cell devices. More precisely, two different perovskite concentrations of 5 wt% and 10 wt%, with respect to Nafion, are considered. The structural, morphological, and chemical properties of the composite membranes are studied, revealing an inhomogeneous distribution of the filler within the polymer matrix. Direct methanol fuel cell (DMFC) tests, at 110 °C and 2 M methanol concentration, were also performed. It was observed that the membrane containing 5 wt% of the additive allows the highest cell performance in comparison to the other samples, with a maximum power density of about 70 mW cm−2 at 200 mA cm−2. Consequently, the ability of the perovskite structure to support proton carriers is here confirmed, suggesting an interesting strategy to obtain successful materials for electrochemical devices.
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