Internal Nanocavity Regulation of Embedded Rare Earth Up-Conversion Nanoparticles for H₂O₂ Production Operable at Up to 780 nm

Semiconductor photocatalysts embedded with rare earth upconversion nanoparticles (REUPs) are a promising strategy to improve their photoresponse range, but their photocatalytic performance within the near-infrared (NIR) region is far from satisfactory. Here, a method is reported to improve the photocatalytic activity by adjusting the nanocavity of upconversion nanoparticles inside a semiconductor. Two types of CdS embedded with NaYF₄:Yb,Er photocatalysts with core-shell structure (no cavity) (NYE/CdS) and yolk-shell structure (empty cavity) (NYE@CdS) are synthesized by different methods. Experimental and theoretical analysis indicates that the yolk-shell structure NYE@CdS can enhance the local fluorescence-induced electric field within the hollow cavity, and realize more effective energy transfer from REUPs to CdS. Notably, the H₂O₂ production performance of NYE@CdS reaches 0.33 mmol g^-1 h^-1 under NIR light irradiation (λ > 780 nm), exceeding most of the reported photocatalysts. This research will provide new ideas for the design of high-efficiency photocatalysts for H₂O₂ production.