Highly-Branched Palladium Nanodandelions: Simple, Fast, and Green Fabrication with Superior Oxygen Reduction Property.

Controllable synthesis of highly-branched metallic structures is of great interest and broad significance for their unique properties of superior conductivity, high porosity, low density, etc., that promote the development of high-efficiency electrocatalysts. Herein, a simple, rapid and green method for the synthesis of highly-branched palladium nanodandelions with flexible ultrafine tentacles and bumpy superficial atomic steps is investigated, without the demand of elevated temperature, seed, template, prolonged reaction time and any organically toxic reducing agent from previously reported highly-branched nanostructures. For the first time, N,N'-methylenebisacrylamide (MBAA) serves as the only additive to simultaneously cover the functions of coordinating agent, reducing agent, and structure-directing agent, facilitating the strategy of intramolecular coordination and self-reduction. Derived from their plentiful ultrafine tentacles, porosity due to the highly-branched structure, and abundant surface atom steps, the Pd nanodandelions exhibit a more positive half-wave of 0.863 V (vs. RHE), optimized specific kinetic activity of 3.0 mA cm-2 at 0.9 V, and better cycle stability with a maintenance of 77.8 % after 20000 s for the oxygen reduction reaction (ORR), when compared to commercial Pd black. The architectural design of highly-branched metallic structures, as well as the smart fabrication strategy, may hold great promise for exploring a variety of functional nanomaterials.