High Active PdFe-Nanoleave Catalyst for Oxygen Reduction Reaction In Alkaline Media

Abstract: Novel PdFe-nanoleaves (NLs) have been prepared through a wet chemistry-based solution phase reduction synthesis route. High-resolution transmission electron microscopy (HR-TEM) and scanning transmission electron microscopy (S/TEM) coupled with high-spatial-resolution compositional analysis clearly show this newly-developed structure is assembled from Pd-rich nanowires (NWs) surrounded by Fe-rich sheets. The Pd-NWs have a diameter in range of 1.8-2.3 nm and large electrochemical surface area of >50 m²/g. Their length (from 30 to 100 nm) and morphology can be tuned through altering the nanostructure synthesis conditions and Fe amount in the nanoleaves. The side surfaces of Pd-NWs observed by HR-TEM are predominantly Pd (111) facet, while the tips and ends are Pd (110) and Pd (100) facets. By etching away the enveloping Fe-rich sheets using an organic acid, the Pd-rich NWs are exposed on the surface of nanoleaves, and they demonstrated high reactivity towards electrocatalytic reduction of oxygen in a 0.1 M NaOH electrolyte: 3.0× increase in the specific activity and 2.7× increase in the mass activity compared with a commercial Pt/C catalyst (at 0 V vs. Hg/HgO). The electrocatalytic activity enhancement can be attributed to their unique nanoleaves structure, i.e. more Pd (111) facets, large surface area and more resistance to Pd oxide formation.