Mechanochemical-Aging Synthesis of Bismuth Oxide Nanosheets for Photocatalysis

Mechanochemistry, old chemistry with new perspectives, has provided unprecedented opportunities for us to pursue a greener and more sustainable future, especially in the exploration of solid-state approaches toward the synthesis of functional nanomaterials. Chemical aging is another environmentally benign and low-energy-demand process that could be controlled precisely with solution environments. In this work, we combined these two approaches to design a mechanochemistry-driven and aging-controlled method for synthesizing nonstoichiometric bismuth oxide nanosheets, which demonstrated a great adsorption capacity and photocatalytic degradation performance toward forever chemicals. With thorough monitoring of the crystal structure and morphological and surface composition changes, the strain-to-defect transformations at the molecular-to-crystal level were proposed to be the dominant growth mechanism. The transient strain accumulation and relaxation from applied mechanical forces during grinding lead to defect-rich metallic bismuth bulk rod structures. The following chemical delamination, achieved through capping ligands and oxygen exposure during aging, produces defect-rich, nonstoichiometric Bi₂O_2.33 nanosheet structures. This proof-of-concept synthesis and proposed growth mechanism offer a different perspective toward 2D metal oxide nanosheet design and could help us better design a diverse library of functional nanomaterials through mechanochemistry and chemical aging.