Electrochemical activity towards ORR of mechanically alloyed PdCo supported on Vulcan carbon and carbon nanospheres

A PdCo catalyst with an atomic ratio of 2:1 was synthesized from elemental powders by mechanical alloying. The structural characterization and composition of the catalyst were determined by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Both the electrocatalytic activity of the catalyst for oxygen reduction in acidic media, as well as attempts to support it on Vulcan XC-72 carbon powder and carbon nanospheres were evaluated by cyclic voltammetry, rotating disc electrode and rotating ring-disk electrode techniques. The X-ray diffraction studies indicated that an intermetallic PdCo compound with an average crystallite size of 25 nm was obtained. According to kinetic and thermodynamic parameters, the electrocatalytic activity of the catalyst toward oxygen reduction was determined as PdCo/CNS > PdCo/C with first-order kinetics, a four-electron multielectronic transference pathway, and a negligible amount of hydrogen peroxide produced. Activation energy values of 40 ± 1 kJ mol⁻¹ and 68 ± 1 kJ mol⁻¹ were determined for reactions with PdCo/CNS and PdCo/C, respectively.