Synthesis and characterization of Pt nanocatalyst on tin oxide based support for oxygen reduction

Abstract

Platinum nanocatalyst on Sb doped tin oxide support has been synthesized and characterized as a catalyst for oxygen reduction reaction in 0.5 mol dm-3 HClO4 solution, at 25°C. Sb doped tin oxide support has been synthesized by sol-gel procedure. Synthesized support was characterized by BET (Brunauer, Emmett, Teller), X-ray diffraction and cyclic voltammetry techniques. Specific surface area of the support determined from nitrogen adsorption/desorption isothermal curves was 42 m2 g-1. Platinum nanocatalyst at modified tin oxide support has been synthesized by borohydride reduction method and characterized by XRD and TEM techniques. Quite homogenous Pt nanoparticles distribution over the support, without pronounced particle agglomeration was observed. Electrochemically active surface area of the catalyst was determined from adsorption/desorption charge of hydrogen atoms, after double layer charge substraction, taking into account the reference value of 210 μC cm-2 for full coverage with adsorbed hydrogen species. The oxygen reduction reaction at Pt/SbSnO2 catalyst has been studied by cyclic voltammetry and linear sweep voltammetry at rotating disc electrode. Two different Tafel slope were observed: one close to 60 mV dec-1 in low current density region, and other close to 120 mV dec-1 at high current densities region, as it was already reported in literature for oxygen reduction at pure polycrystalline Pt, as well as at Pt nanoparticles in acid solutions. The specific activities, expressed in terms of kinetic current densities per electrochemically active surface area at the constant potential, of this new catalyst and Vulcan supported Pt were compared. Pt/SbSnO2 catalyst exhibited similar catalytic activity for oxygen reduction reaction compared to carbon supported one. Better durability of Pt/SbSnO2 catalyst under repetitive cycling up to 1.4 V vs RHE was confirmed, comparing with Pt on carbon support.