Construction of Reverse Type-II InP/Zn_xCd_1–xS Core/Shell Quantum Dots with Low Interface Strain to Enhance Photocatalytic Hydrogen Evolution

The InP-based quantum dots (QDs) have attracted much attention in the field of photocatalytic H₂ evolution. However, a shell should be used for InP-based photocatalytic systems to passivate the numerous surface defects. Different from the traditional InP-based core/shell QDs with Type-I or Type-II band alignment, herein, the “reverse Type-II” core/shell QDs in which both the conduction and valence bands of shell materials are more negative than those of core materials have been well-designed by regulating the ratio of Cd/Zn of the alloyed Zn_xCd_1–xS shell. The reverse Type-II band alignment would realize the spatial separation of photogenerated carriers. More importantly, the photogenerated holes tend to rest on the shell in the reverse Type-II QDs, which facilitate hole transfer to the surface, the rate-determining step for solar H₂ evolution using QDs. Therefore, the obtained InP/Zn_0.25Cd_0.75S core/shell QDs exhibit superior photocatalytic activity and stability under visible light irradiation. The rate of solar H₂ evolution reaches 376.19 μmol h^–1 mg^–1 at the initial 46 h, with a turnover number of ∼2,157,000 per QD within 70 h irradiation.