Enhanced electrocatalytic activity of cubic Pd nanoparticles towards the oxygen reduction reaction in acid media

The electrochemical reduction of oxygen on cubic Pd nanoparticles (PdNPs) was studied in acid solution using the rotating disk electrode (RDE) method. The electrocatalytic properties of Pd nanocubes were compared with those of spherical PdNPs and bulk Pd. The morphology of PdNPs was examined by transmission electron microscopy (TEM). For electrochemical experiments, PdNPs were deposited on a gold support and oxidation of pre-adsorbed CO on Pd was employed for cleaning the surface of the nanoparticles. The Pd nanocubes displayed superior electrocatalytic activity towards the oxygen reduction reaction (ORR), exhibiting a threefold increase in the specific activity in comparison with spherical PdNPs and bulk palladium. Four-electron reduction of oxygen to water was observed on the Pd catalysts studied.

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► Pd nanocubes of controlled shape were synthesised and their surface was electrochemically characterised by cyclic voltammetry and CO stripping.
► The specific activity for ORR of cubic PdNPs was three times higher than that of spherical PdNPs and bulk Pd.
► The higher electrocatalytic activity of Pd nanocubes was explained by the predominance of Pd(100) surface sites.