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

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 8; no. 37; pp. 193 - 1938
• Main Authors: Wang, Jingchun, Qiu, Xiaoyu, Su, Keying, Wang, Siyuan, Li, Jiatian, Tang, Yawen
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 07.10.2020
• Subjects: Electrocatalysts; Epitaxial growth; Gold; Intermediates; Island growth; Lattice matching; Lattice vibration; Nanotechnology; Nanowires; Palladium; Reaction kinetics; Reduction; Structure-function relationships; Substrates
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta05867j

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. The Pd atoms respectively select the "Frank-van der Merwe" and "Volmer-Weber" growth mode on Au(111) nanowires by conducting reduction kinetics.