Monodentate binding of zwitterionic ligands for boosting photocatalytic H2 production of perovskite nanocrystals

Abstract

Perovskite nanocrystals (PNCs) have recently emerged as promising materials for photocatalytic applications. However, weakly bound and long-chain surface ligands on PNCs reduce the colloidal stability, hinder efficient charge transfer, and lower the photocatalytic activity. Herein, we report zwitterionic sulfobetaine (ZSB) ligand-capped CsPbBr3 perovskite nanocrystals (PNCs) for visible-light-driven photocatalytic H2 production. In this system, the ZSB ligands passivate PNC surface defects, thus improving the photoluminescence stability and quantum yield. In particular, the positively charged R4N+ groups of the ZSB ligands preferentially bind to the Br-rich CsPbBr3 PNC surface, leaving unpaired negative SO3− groups in the outermost ligand layer. This unbalanced binding of the ZSB ligands changes the surface potential of the PNCs from positive to negative, inducing a kinetically favorable band alignment at the heterojunction between the PNC and co-catalyst (Pt-deposited TiO2). The heterojunction and electronic structures are stable, even in harsh aqueous environments, resulting in significantly enhanced electron transfer and H2 production rates and greatly improved operational stability. We believe that the use of ZSB ligands for band engineering is highly promising for PNC-based photocatalysis and solar energy conversion systems.