Nb–TiO 2 supported platinum nanocatalyst for oxygen reduction reaction in alkaline solutions

Abstract

Platinum based nanocatalyst at home made Nb–TiO 2 support was synthesized and characterized as the catalyst for oxygen reduction reaction in 0.1 mol dm −3 NaOH, at 25 °C. Nb doped TiO 2 catalyst support, containing 5% of Nb, has been synthesized by modified acid-catalyzed sol–gel procedure in non-aqueous medium. BET and X-ray diffraction (XRD) techniques were applied for characterization of synthesized supporting material. XRD analysis revealed only presence of anatase TiO 2 phase in synthesized support powder. Existence of any peaks belonging to Nb compounds has not been observed, indicating Nb incorporated into the lattice. Nb–TiO 2 supported Pt nanocatalyst synthesized, using borohydride reduction method, was characterized by TEM and HRTEM techniques. Platinum nanoparticles distribution, over Nb doped TiO 2 support, was quite homogenous. Mean particle size of about 4 nm was found with no pronounced particle agglomeration. Electrochemical techniques: cyclic voltammetry and linear sweep voltammetry at rotating disc electrode were applied in order to study kinetics and estimate catalytic activity of this new catalyst for the oxygen reduction reaction in alkaline solution. Two different Tafel slopes were found: one close to −90 mV dec −1 in low current density region and other approximately −200 mV dec −1 in high current density region, which is in good accordance with literature results for oxygen reduction at Pt single crystals, as well as Pt nanocatalysts in alkaline solutions. Similar specific catalytic activity (expressed in term of kinetic current density per real surface area) of Nb(5%)–TiO 2/Pt catalyst for oxygen reduction reaction in comparison with the carbon supported platinum (Vulcan/Pt) nanocatalyst, was found.