Full-spectrum-activated Z-scheme photocatalysts based on NaYF4:Yb3+/Er3+, TiO2 and Ag6Si2O7

Abstract

The development of efficient full-spectrum-activated photocatalysts has become a research topic of intense interest in environmental remediation or solar energy conversion applications. Herein, newly Z-scheme UV-vis-NIR-activated photocatalysts consisting of β-NaYF₄:18% Yb³⁺, 2% Er³⁺@TiO₂–Ag₆Si₂O₇ (denoted as NaYF₄@T–ASO) were designed and used as full-spectrum response photocatalysts. For tailoring NaYF₄@T–ASO, the size of in situ deposited ASO nanoparticles on the surface of NaYF₄@T microplates was determined by the pumping rate of the AgNO₃ precursor, which played indirect roles in the photocatalytic activity with different carrier migration distances. Especially, NaYF₄@T–ASO (S10) with the smallest and well distributed ASO nanoparticles showed superior photocatalytic activity than the commercial P25 TiO₂ by 15 fold under the stimulated solar light irradiation. The enhanced photocatalytic performance of NaYF₄@T–ASO could be ascribed to the synergic effect of the upconversion material and the direct Z-scheme heterojunction formed between TiO₂/ASO, where the Z-scheme heterojunction induced efficient separation of photogenerated carriers and highly oxidative species (h⁺ and ˙O₂⁻). Alternative mechanisms of carriers and energy transfer under various light sources have been proposed and discussed in detail.