Electrochemical preparation and characterization of PdPt nanocages with improved electrocatalytic activity toward oxygen reduction reaction

• Pd@Pt nanodendrites are converted to hollow nanocages after potential cycling.
• The nanocages are composed of small PdPt nanoalloys.
• The ORR activity for PdPt hollow structure is higher than that of the Pd@Pt NDs.

Hollow PdPt nanocages were prepared by applying potential cycling treatment on core–shell Pd@Pt nanodendrites in 0.5 M sulfuric acid aqueous solutions, during which Pd core was dissolved and the Pd@Pt structure was transformed to hollow nanocages. The nanocages were comprised of bimetallic PdPt nanoalloys, which was confirmed by high-resolution TEM (HRTEM), scanning TEM-energy dispersive X-ray spectra (STEM-EDX), X-ray diffraction (XRD) and cyclic voltammetry (CV). The PdPt nanocages presented superior catalytic activity toward oxygen reduction reaction in comparison with Pd@Pt nanodendrites and commercial Pt/C catalysts owing to the alloying effect and special morphology. The nanocage morphology was still maintained after long-term durability testing, indicating good structure stability.