Preparation of ZnFe2O4 nanostructures and highly efficient visible-light-driven hydrogen generation with the assistance of nanoheterostructures

Abstract

ZnFe₂O₄ is a promising visible-light-driven photocatalyst with high energy level CBM for hydrogen generation. However, it could only be synthesized in the bulk form and its photocatalytic activities are limited by the rapid recombination of photo-generated carriers. Here, we report the preparation of a ZnFe₂O₄ nanostructure in ultrathin hollow sphere morphology with a 10 nm thick shell, which could shorten the diffusion distance of photo-generated carriers to minimize their interior recombination. Furthermore, ZnFe₂O₄/ZnO nanoheterostructures, containing 15 nm size heterojunctions, could be synthesized facilely. We have found that this unique structure endows ZnFe₂O₄/ZnO with a large separation of photo-generated carriers. The hydrogen generation rate of ZnFe₂O₄/ZnO nanoheterostructures without co-catalysts is up to 2.15 mmol h⁻¹ g⁻¹ under visible light irradiation (λ > 420 nm), which is 45 times higher than the best yields ever reported for ZnFe₂O₄-based photocatalysts. These research results provide a general and effective route to synthesize other nanoheterostructures for a variety of applications.