Large‐Substrate‐Terrace Confined Growth of Arrayed Ultrathin PtSe₂ Ribbons on Step‐Bunched Vicinal Au(001) Facets Toward Electrocatalytic Applications

Ultrathin PtSe 2 ribbons can host spin‐polarized edge states and distinct edge electrocatalytic activity, emerging as a promising candidate for versatile applications in various fields. However, the direct synthesis is still challenging and the growth mechanism is still unclear. Herein, the arrayed growth of ultrathin PtSe 2 ribbons on bunched vicinal Au(001) facets, via a facile chemical vapor deposition (CVD) route is reported. The ultrathin PtSe 2 flakes can transform from traditional irregular shapes to desired ribbon shapes by increasing the height of bunched and unidirectionally oriented Au steps (with step height h step ) is found. This crossover, occurring at h step ≈ 3.0 nm, defines the tailored growth from step‐flow to single‐terrace‐confined modes, as validated by density functional theory calculations of the different system energies. On the millimeter‐scale single‐crystal Au(001) films with aligned steps, the arrayed ultrathin PtSe 2 ribbons with tunable width of ≈20–1000 nm, which are then served as prototype electrocatalysts for hydrogen evolution reaction (HER) is achieved. This work should represent a huge leap in the direct synthesis and the mechanism exploration of arrayed ultrathin transition‐metal dichalcogenides (TMDCs) ribbons, which should stimulate further explorations of the edge‐related physical properties and practical applications.