Surface Trait‐Dependent Photoreduction Products in CsPbBr₃, Embedded Cs₄PbBr₆ Structure

Abstract Perovskite quantum dots exhibit a high carrier photogeneration rate upon light absorption but are hindered by a rapid recombination rate and low stability in polar environments. These critical issues limit their large‐scale applications or require additional surface passivation. The in situ passivation phase formation during Perovskite synthesis can develop a heterostructure of nanocrystals with surface passivation upon polar moieties while enhancing stability and facilitating photoreduction reactions by stabilizing intermediates due to its surface chemistry. In this study, two structures of perovskite quantum dots, CsPbBr ₃ and embedded CsPbBr ₃ in Cs ₄ PbBr ₆ composite structures, are prepared through a flow chemistry route by adjusting operational synthesis parameters. The stability and surface chemistry of two nanostructures are evaluated in a polar atmosphere study for carbon dioxide (CO ₂ )photoreduction, where the absorption edge remains relatively unchanged. The in situ study of Ambient Pressure X‐ray Photoelectron Spectroscopy (APXPS) provides direct evidence of improved CO ₂ adsorption and activation, as well as the alteration of intermediate species, highlighting the critical role of surface characteristics in promoting reduced products in the CsPbBr ₃ ‐Cs ₄ PbBr ₆ embedded structure compared to individual CsPbBr ₃ .