Lattice Mismatch Guided, Confined Growth of Ultrathin PtTe₂ Nanosheets for an Enhanced Oxygen Reduction Reaction.

Abstract

Noble metal dichalcogenides (NTMDs), such as PtTe₂, provide a platform in which noble metal centers are embedded within chalcogen-coordinated lattices, enabling modulation of the electronic structure of Pt while potentially maximizing noble metal utilization in ultrathin architectures. However, the strong interlayer coupling commonly observed in NTMDs makes the preparation of atomically thin structures challenging, limiting access to their coordination-dependent catalytic properties. In this work, a solvothermal strategy is given for the heteroepitaxial vertical growth of ultrathin PtTe₂ nanosheets (NSs) on Te-substituted Cu_1.81S nanorods. Surface anion exchange of Cu_1.81S nanorods generates metastable Cu_6-<i>y</i>Te₄ and Cu₇Te₄ phases with abundant stacking faults, where the Cu_6-<i>y</i>Te₄ domains act as preferential nucleation sites for PtTe₂ epitaxy, leading to vertically aligned NSs with a few-unit-cell thickness. Encouraged by this result, we further attempted the growth of ultrathin PtTe₂ NSs on the peripheral facets of Cu_1.81S nanoplates to fully exploit the catalytically active Pt sites while suppressing the agglomeration of PtTe₂ NSs. Upon thermal treatment, the resulting structures undergo partial phase transformation to PtTe along with the formation of Te vacancies within the PtTe₂ lattice, generating PtTe/Te-vacancy-rich PtTe₂ heterostructures. The combination of ultrathin morphology, defect engineering, and Pt-Te coordination enables efficient exposure and electronic modulation of Pt active centers, resulting in enhanced oxygen reduction activity with a mass activity of 1.22 A mg_Pt^-1 and excellent durability. Overall, this work demonstrates that lattice-mismatch-driven epitaxial growth provides an effective strategy for constructing ultrathin NTMD architectures and for enhancing noble metal utilization through coordination and defect engineering.