Electroreduction of Oxygen on PdPt Alloy Nanocubes in Alkaline and Acidic Media

The electrochemical kinetic behavior of the oxygen reduction reaction (ORR) on PdPt alloy nanocubes of various compositions is investigated in 0.1 M KOH and 0.1 M HClO₄ solutions, adopting the rotating disk electrode (RDE) configuration. The PdPt nanocubes are prepared in the presence of polyvinylpyrrolidone and identified by using transmission electron microscopy (TEM). TEM images reveal that the PdPt alloy nanoparticles have a preferential cubic shape and the average particle size is approximately 8–10 nm. CO-stripping and cyclic voltammetry (CV) experiments are used for electrochemical cleaning and characterization of metal nanoparticles. The CV responses indicate alloy formation. In acidic media, Pd₃₆Pt₆₄ shows the highest specific activity (SA) for the ORR from the alloyed catalysts studied, but this activity is similar to that found with Pt and Pd nanocubes. However, in alkaline solution, the SA value for Pd₇₂Pt₂₈ is about two times higher than that of Pd and Pt nanocubes. The mechanistic pathway of O₂ reduction on PdPt alloy nanocubes is analogous to that of pure Pd and Pt catalysts and the ORR proceeds via a 4-electron pathway in both electrolyte solutions.