Urchin-like Au/Pd Nanobranches for the Oxygen Reduction Electrocatalysis

Three-dimensional (3D) porous heterogeneous metallic nanomaterials hold remarkable competitiveness in electrocatalytic fields due to their flexible porous structure and the electronic effect between heteroatoms, but challenges in synthesis still remain. Here, we design a facile stepwise reduction method to successfully synthesize urchin-like Au/Pd nanobranches (NBs). In a one-pot synthesis, small Au nanoparticles were initially generated. Later, numerous Pd nanotwigs were epitaxially grown and interlaced on the Au seeds to create unique channels, forming an Au-core/Pd-branches structure eventually. The as-prepared Au/Pd NBs exhibit greatly improved activity and stability for alkaline oxygen reduction reaction (ORR) electrocatalysis compared to the commercial Pt/C, with mass activity (1.4 A mg(-1)) and specific activity (2.4 mA cm(-2)) increased by 8.8 and 8.9 times, respectively. The excellent ORR performances of Au/Pd NBs are mainly attributed to the optimized electronic structure, improved utilization of surface active sites, and accelerated mass and charge transfer, which derives from the strong ligand effect, as well as the abundant porous channels of the Au/Pd NBs structure. The controllable design and synthesis of 3D porous Pd-based nanomaterials sheds light on a gigantic potential for ORR electrocatalysis.