LAUSR

Three‐dimensional (3 D) nanoframes (NFs) with interconnected edges and large surface areas represent a new class of nanostructures with advanced catalytic performance. Herein, we report an efficient chemical strategy for the controlled synthesis of platinum–copper (Pt–Cu) rhombic dodecahedral nanocrystals (RDH NCs) with highly composition‐segregated features. These solid Pt–Cu RDH NCs could be readily transformed into highly open Pt–Cu RDH nanoframes (NFs) with shapes and sizes that were not markedly changed after FeCl3 etching. All of the different Pt–Cu RDH NFs have the same PtCu3 phase but tunable sizes and different channel sizes. These important characteristics of the NFs provide them with much better performance than that observed for commercial Pt/C and Pt–Cu RDH NCs towards both the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR). In particular, PtCu5 RDH NFs with the largest channel size of all the samples investigated exhibited the best activity towards the ORR and MOR and showed much less activity decay after durability tests. This work highlights the importance of precise control of 3 D NF structures in enhancing electrocatalysis electrooxidations.