Platinum Cubic Nanoframes with Enhanced Catalytic Activity and Durability Toward Oxygen Reduction.

We report the synthesis and electrocatalytic properties of Pt cubic nanoframes with ultrathin ridges less than 2 nm in thickness. The nanoframes were synthesized through site-selected deposition of Pt onto the corner and edge sites of Pd nanocubes, followed by selective removal of the Pd cores via chemical etching. The Br ions chemisorbed on the side faces of a Pd nanocube played a critical role in enabling the siteselected deposition. In addition, the kinetics of deposition and the diffusion of Pt adatoms was optimized by carefully controlling the injection rate of the Pt precursor and the reaction temperature, respectively, to obtain the frame-like structure. When benchmarked against a commercial Pt/C comprised of Pt particles 2-3 nm in size, the Pt frame/C catalyst exhibited not only enhanced mass activity toward oxygen reduction, but also substantially improved catalytic durability. In an accelerated durability test, the Pt frame/C catalyst showed a mass activity more than 6× greater than for the Pt/C reference after 20 000 cycles of repeated potential sweeping. This improvement can be largely attributed to the frame-like structure, which is unique in suppressing both the detachment and aggregation of catalytic particles owing to the significantly enhanced interaction with carbon support.