Visible-light driven photocatalytic hydrogen generation by water-soluble all-inorganic core–shell silicon quantum dots

Abstract

The photocatalytic hydrogen (H₂) generation by boron (B) and phosphorus (P) codoped silicon quantum dots (Si QDs) with diameters in the quantum confinement regime is investigated. The codoped Si QDs have an amorphous shell made from B, Si and P. The shell induces negative potential on the surface and makes codoped Si QDs dispersible in water. The hydrophilic shell offers enhanced stability and efficiency in photocatalytic H₂ generation and provides the opportunity to study the size dependence of the H₂ generation rate. A drastic increase of H₂ generation rate with decreasing QD size is observed. Analyses based on the Marcus theory reveal that the upper shift of the lowest unoccupied molecular orbital level of Si QDs by the quantum confinement effect is responsible for the enhanced photocatalytic activity.