Structure and Activity of Carbonyl Cluster-Derived PtFe Nanoparticles as Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

Rationally designing low-content Pt-based cathodic electrodes to effectively avoid the shortcomings of sluggish kinetics reactions in oxygen reduction reactions is still a hot topic. Herein, PtFe carbonyl cluster-derived nanoparticles were synthesized, supported on Vulcan via a wet impregnation method, and modified thermally under hydrogen to change the surface composition and morphology. The prepared electrocatalysts were characterized by electrochemical techniques and by X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to investigate their structure and morphology. The electrochemical experiments indicated that PtFe nanoparticles, thermally treated under H2, showed a high real geometry surface area of 31.57 m2 g-1, almost 2 times higher than that for untreated samples. Remarkably, from Koutecky-Levich analysis and rotating ring disk electrode experiments, the oxygen reduction reaction follows a 4-electron transfer path, and all of the tested electrocatalyst powders showed good stability after 500 voltammetry cycles. The Tafel slope evidenced the better behavior of H2 thermally treated powder because the electronic structure of these clusters has been modified by the treatment, thus probably changing the electronic density of the PtFe nanoparticles, as well as the oxygen affinity for the electrode.