PdNi electrocatalyst for oxygen reduction in acid media

The PdNi nanoparticles dispersed on Nafion solution was used as an ink-type electrode for oxygen reduction reaction (ORR), in acid media. This bimetallic catalyst was synthesized via the metallic reductive precipitations of the chloride precursors with NaBH₄ in tetrahydrofuran (THF) at 25 ^{{ring operator}} C. The characterization of the electrocatalyst using X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed bimetallic nanoparticles having a narrow size ranged 8 - 10 nm with face-centered cubic (fcc) hexagonal structure. Cyclic voltammograms and polarization curves from rotating-disk electrode measurements showed significantly higher activity on PdNi than observed on Pd catalyst, with a mechanism involving four electrons transfer to water formation. The incorporation of Ni, a less electronegative metal to Pd shifts the onset potential for the ORR approximately 110 mV more positive, and at 0.5 mA cm^{- 2} the cathode overpotential is reduced by 260 mV in relation to that obtained on Pd, in a 0.5 M H₂ SO₄ solution at 25 ^{{ring operator}} C.