Self-Induced Strain in 2D Chalcogenide Nanocrystals with Enhanced Photoelectrochemical Responsivity

Abstract

Strain engineering has become an emerging strategy to tailor the performance of nanocatalysts. However, current strained catalysts overwhelmingly rely on stresses originated at catalyst–support interfaces. Self-standing strained nanostructures are extremely challenging to produce, and thus their impact on catalytic and photocatalytic activities remains largely unknown. Herein, we propose a ligand-based colloidal strategy for the one-step growth of bended metal chalcogenide nanoplates with a built-up strain. This strategy is based on the seeded growth of strained nanostructures from sacrificial seeds which provide a proper lattice mismatch. We demonstrate this strategy for the synthesis of strained orthorhombic SnSe and SnS nanoplates from rock salt SnS seeds. We probe not only the presence of atomic distortions in the periodic lattice but also its coupling with the generation of a large density of selenium vacancies. Geometrical phase analysis evidences the formation of a strain field in self-bended SnSe nanoplates, with a maximum tensile strain up to 12%. Theoretical and experimental results further reveal that the strain-related selenium vacancies strongly affect the electronic structure of SnSe and facilitate the mobility of photogenerated charge carriers, which result in a significantly improved photoelectrochemical activity. The strategy presented here opens a new avenue for precisely tuning semiconductor functionalities via strain engineering.