Ni2+-Directed Anisotropic Growth of PtCu Nested Skeleton Cubes Boosting Electroreduction of Oxygen

Abstract

Structure-controlled Pt-based nanocrystals have the great potential to provide a flexible strategy for improving the catalysis of the oxygen reduction reaction (ORR). Here, a new synthetic approach is developed to tune the 3D structure of Pt-based alloys, and switch a synthetic reaction which produces solid PtCu octahedral stars (OSs) to produce PtCu nested skeleton cubes (NSCs) by simple addition of Ni(acac)2. In particular, Ni2+-guided anisotropic growth is observed to generate the nested skeleton structure in PtCu NSCs. Ni2+, though absent from the nanoalloys, not only endows faster Cu reduction kinetics but also acts as a structure-directing agent. Moreover, it is shown that acetic acid treatment of PtCu NSCs/C exposes Pt-rich surface with a fine-tuned Pt d-band center energy and the reduced Cu leaching, resulting in strikingly high activity and stability. Acid-treated PtCu NSCs/C shows a remarkable ORR mass activity of 5.13 A mgPt–1, about 26 times higher than commercial Pt/C catalyst. This catalyst also exhibits excellent stability with a lower activity decay of 11.5% and the negligible variation in structure after 10 000 cycles.