Breaking the lattice match of Pd on Au(111) nanowires: manipulating the island and epitaxial growth pathways to boost the oxygen reduction reactivity

Abstract

It remains a grand challenge to control the island growth mode because a conformal growth is theoretically more favorable, in which the lattice mismatch between the overlayer and the substrate is negligible. Herein, we report the first example of “Frank–van der Merwe” mode and “Volmer–Weber” mode of Pd atoms on Boerdijk–Coxeter-type helical Au(111) nanowires. Quantitative analyses suggest that the pH-induced faster kinetic reduction rate (1.2 × 10⁻² s⁻¹) is a crucial factor to switch the Pd-growth mode from the conformal 4-atom-layers to ultrasmall islands. As a proof-of-concept application, the VW Au@Pd HNWs exhibit outstanding ORR activity (E_onset = 1.07 V, E_1/2 = 0.91 V) and stability, outperforming FM Au@Pd NWs, Au(111) NWs, Pd black, and most reported electrocatalysts. Physical characterization systematically elucidated similar components, d-band center locations, and lattice distortions of both the representative structures, giving brand-new insights into the impact of their slightly different surface microstructures. In particular, the segmented oxyphilic–anaerobic interface of the VW Au@Pd HNWs directly balances the adsorbability of the intermediates; meanwhile, the interleaved lattice orientations favor multi-directional electron transmissions to promote ORR kinetics. This finding not only challenges the conventional wisdom of lattice-matched growth but also provides an identical model for the in-depth understanding of the structure–function relationship with a focus on the growth modes.