Elemental doping tailoring photocatalytic hydrogen evolution of InP/ZnSeS/ZnS quantum dots

Abstract

Photocatalytic water splitting for hydrogen production has garnered considerable attention as an effective method to alleviate energy shortages. In comparison to cadmium-based quantum dots (QDs) photocatalysts, InP QDs possess a smaller bandgap, larger exciton radius, broader absorption range, and are environmentally friendly. Although InP/ZnS core/shell QDs exhibit immense potential in photocatalysis, they suffer from rapid electron-hole recombination owing to interface defects and lattice mismatch. To address these issues, this study introduces an intermediate ZnSeS shell to reduce defects and tailor QD redox properties through transition metals (manganese and copper) doping. The characterization of QDs was performed from various perspectives, including morphology, element distribution, band structure, and charge transport efficiency. Notably, the photoelectrochemical properties of doped QDs were superior to those of the undoped QDs, while Mn-doped QDs showed inferior catalytic performance compared to the undoped ones. The mechanism of different photoelectrochemical and photocatalytic performances has been studied more intensely. The Mn-doped QDs undergo a process where Mn4+ is converted to Mn2+, consuming electrons in competition with the photocatalytic hydrogen evolution process. Conversely, InP/ZnSeS:Cu/ZnS QDs introduced an additional energy level into the original band structure, capturing some holes and slowing down the electron-hole recombination, thereby providing positive feedback for photocatalytic hydrogen production. Profiting from both the synergies of energy level structure and doping metal state, effective electron-hole separation, and rapid electron transfer to the surface of Cu-doped QDs accomplish the efficient hydrogen generation. The present study offers more possibilities for exploiting the required photocatalytic performance of QD catalysts via elemental doping.