Highly efficient proton-assisted photocatalytic CO2 reduction over 3-mercaptopropionic acid-capped quantums dots

Abstract

Herein, we demonstrate that 3-mercaptopropionate capping agents on CdS quantum dot surfaces could serve as proton shutters and localize protons near the active sites towards efficient photocatalytic CO₂ reduction. A series of water-soluble 3-mercaptopropionic acid (MPA)-capped CdS quantum dots with different molar ratios of MPA : Cd (denoted as CdS-xA) are successfully synthesized via an aqueous synthesis, promoting the formation of surface Cd atoms as active sites in photocatalytic CO₂ reduction. The enhanced photocatalytic activity of functional CdS quantum dots could be attributed to the cooperative interaction between localized protons and surface Cd atoms, which behave as a Lewis acid and Lewis base, respectively. The representative CdS-1A exhibits the highest CO generation rate of ∼16 μmol h⁻¹ with apparent quantum yield of 4.17% at 420 nm under optimized conditions, which is one of the highest values reported for CdS-based materials. This work aims to understand the important role of protons localized near active sites, which can promote efficient photocatalytic CO₂ to CO reduction.