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 the range of 1.8-2.3 nm and a large electrochemical surface area of >50 m2/g. Their length (30 - 100 nm) and morphology can be tuned by altering the nanostructure synthesis conditions and the Fe amount in the NLs. With increasing Fe content, thinner and longer sheet-enveloped nanowires can be prepared. The side surfaces of Pd-NWs observed by HR-TEM are predominantly Pd (111) facets, 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 surfaces of the nanoleaves, and they demonstrate high reactivity towards electrocatalytic reduction of oxygen in a 0.1 M NaOH electrolyte, i.e., 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 the unique nanoleave structure that provides more Pd (111) facets, a large surface area, and more resistance to Pd oxide formation.
