Synthesis of Lead-Free Cs₂AgBiX₆ (X = Cl, Br, I) Double Perovskite Nanoplatelets and Their Application in CO₂ Photocatalytic Reduction

Abstract

Morphology control represents an important strategy for the development of functional nanomaterials and has yet to be achieved in the case of promising lead-free double perovskite materials so far. In this work, high-quality Cs₂AgBiX₆ (X = Cl, Br, I) two-dimensional nanoplatelets were synthesized through a newly developed synthetic procedure. By analyzing the optical, morphological, and structural evolutions of the samples during synthesis, we elucidated that the growth mechanism of lead-free double perovskite nanoplatelets followed a lateral growth process from mono-octahedral-layer (half-unit-cell in thickness) cluster-based nanosheets to multilayer (three to four unit cells in thickness) nanoplatelets. Furthermore, we demonstrated that Cs₂AgBiBr₆ nanoplatelets possess a better performance in photocatalytic CO₂ reduction compared with their nanocube counterpart. Our work demonstrates the first example with two-dimensional morphology of this important class of lead-free perovskite materials, shedding light on the synthetic manipulation and the application integration of such promising materials.