Concave Pt-Zn Nanocubes with High-Index Faceted Pt Skin as Highly Efficient Oxygen Reduction Catalyst.

High dosage of expensive Pt to catalyze the sluggish oxygen reduction reaction (ORR) on the cathode severely impedes the commercialization of proton exchange membrane fuel cells. Therefore, it is urgent to cut down the Pt catalyst by efficiently improving the ORR activity while maintaining high durability. Herein, magic concave Pt-Zn nanocubes with high-index faceted Pt skin (Pt 78 Zn 22 ) are proposed for high-efficiency catalysis toward proton exchange membrane fuel cells. These unique structural features endow the Pt-skin Pt 78 Zn 22 /KB with a mass activity of 1.18 mA μg Pt -1 and a specific activity of 3.64 mA cm -2 for the ORR at 0.9 V (vs RHE). Meanwhile, the H 2 -O 2 fuel cell assembled by this catalyst delivers an ultrahigh peak power density of ≈1449 mW cm -2 . Both experiments and theoretical calculations show that the electronic structure of the surface is adjusted, thereby shortening the length of the Pt-Pt bond and reducing the adsorption energy of OH*/O* on the Pt surface. This work demonstrates the synergistic effect of the oxidation-resistant metal Zn and the construction of Pt-rich surface engineering. Also, it guides the future development of catalysts for their practical applications in energy conversion technologies and beyond.