Strong interface contact between NaYF4:Yb,Er and CdS promoting photocatalytic hydrogen evolution of NaYF4:Yb,Er/CdS composites

Abstract

• NaYF 4 :Yb,Er/CdS composite was prepared by growing CdS nanoparticles on the NaYF 4 :Yb,Er nanorods by ion adsorption/precipitation process. • Annealing induced CdS phase transformation and strong interface contact between CdS and NaYF 4 :Yb,Er greatly enhance photocatalytic hydrogen of the composite. To acquire efficient photocatalysts, it is necessary to make effective use of visible light/Near Infrared (NIR) light, which takes up a large percentage of sunlight. Integrating upconversion materials with visible light active photocatalysts has attracted much attention in this regard. The interface contact between upconversion material and photocatalyst has potential influence on the properties and thus the performance of the system. In this work, NaYF 4 :Yb,Er/CdS composites of the upconversion material NaYF 4 :Yb,Er nanorods and CdS nanoparticles were synthesized by ion adsorption/precipitation process and were then annealed in an argon atmosphere at different temperatures to modulate the microstructures. The annealing process endows the crystal transformation of cubic CdS with low crystallinity to hexagonal CdS with high crystallinity and, importantly, good interface contact between NaYF 4 :Yb,Er and CdS. Consequently, the hydrogen evolution activity greatly increases from 171 to 2539 μmol h −1 g −1 under the light irradiation of λ > 400 nm, and from 0 to 19 μmol h −1 g −1 under the light irradiation of λ > 600 nm. This work might provide a useful reference for the rational design of promising photocatalyst involving upconversion materials.