2162-8769/2013/2(12)/M61/6/$31.00 © The Electrochemical Society Electrocatalytic Activity toward Oxygen Reduction of RuSxNy Catalysts Supported on Different Nanostructured Carbon Carriers

Ruthenium admixed or nanoparticles modified with mixed selenium and nitrogen overlayers (RuSexNy) were fabricated onto different carbon nanostructured supports (that include multiwalled carbon nanotubes, Vulcan and Norit) under analogous experimental conditions. It is apparent from X-ray measurements that both Vulcan and Norit supported RuSexNy crystallites are characterized by the same type of crystallographic phases. Important parameters that influence electrocatalytic activity include the nature of functionalization of carbon support, in addition to its active surface area and morphology that affect distribution and size of active RuSexNy centers. Despite the same loading of ruthenium (40 μg cm−2), diameters of RuSexNy nanoparticles have somewhat differed and ranged from 2 to 6 nm, as it has been evident from transmission electron microscopy measurements. The systems have been evaluated with respect to oxygen reduction reaction in acid (0.5 M H2SO4) medium using rotating ring disk voltammetry and impedance spectroscopy. Having in mind such parameters as the half-wave reduction potential, the electroreduction current density, the heterogenous rate constant, the percent formation of the hydrogen peroxide undesirable intermediate as well as the overall charge transfer resistance appearing during oxygen reduction, the RuSexNy-based system utilizing functionalized Vulcan is characterized by the highest electrocatalytic activity