Facile Seed-Mediated Growth of Ultrathin AuCu Shells on Pd Nanocubes and Their Enhanced Nitrophenol Degradation Reactions

Multimetallic core–shell nanocrystals (NCs) with precise control over shell thickness down to few atomic layers have attracted tremendous interest for a variety of catalytic reactions. However, limitations associated with large lattice mismatch, particularly for the metals with a larger lattice mismatch, remained a great challenge in generating multimetallic core–shell NCs. Herein, we demonstrate seed-mediated coreduction of AuCu onto Pd nanocube seeds to obtain Pd@AuCu nL (n = 6,12) core–shell nanocubes with atomic-level control over shell thickness and near-perfect lattice matching of the core–shell interface. Precise control over the shell layer thickness from six to twelve atomic layers could be possible by slow and simultaneous codeposition of the Au and Cu precursors, i.e., AuCl2(OH)2 – and Cu­(OH)2 – ions, by controlling the OH– ion concentration (i.e., pH) in the reaction solution with a low Cu content. Moreover, Pd@AuCu nL core–shell NCs with different shapes such as hexagonal and concave NCs were readily obtained by modulating the reduction kinetics of metal precursors in seeded growth. Importantly, obtained Pd@AuCu6L core–shell nanocubes manifested best catalytic performance for the reduction of 4-nitrophenol (4-NP) by NaBH4. The high catalytic activity of the core–shell nanocubes has been ascribed to the synergetic effect of the Pd core and the AuCu alloy shell. The simple, solution-based approach utilized in this work can be adapted for controlled synthesis of other multimetallic core–shell nanocubes with atomically controlled shell thickness for a variety of heterogeneous catalysis reactions.