Microwave-assistant hydrothermal synthesis of SnO2@ZnO hierarchical nanostructures enhanced photocatalytic performance under visible light irradiation

Highlights: • A photocatalyst of SnO₂@ZnO HNSs is prepared via a microwave-assistant hydrothermal method. • Enhanced photodegradation of methylene blue under the visible light irradiation has been observed. • The defect in photocatalyst is the main photocatalytic mechanism under the visible light irradiation. • The superoxide radical is the main photoactive species. - Abstract: In this paper, for the first time, SnO₂@ZnO hierarchical nanostructures (HNSs) were synthesized by a simple two-step microwave-assistant hydrothermal method. Systematical characterization of the SnO₂@ZnO HNSs revealed that the rutile SnO₂ nanowires (NWs) were uniformly and tightly grown on the entire surface of each ZnO nanoflowers (NFs). The photocatalytic performance of the SnO₂@ZnO HNSs showed a remarkably enhanced photocatalytic performance under visible light irradiation (400 nm≤λ ≤ 800 nm). The photoluminescence (PL) spectrum results indicated that the defect related energy level is the main mechanism of the photocatalytic performance under the visible light irradiation. The unique morphology and heterojunction structures in SnO₂@ZnO HNSs were the core enhanced mechanism in photodegradation process. The advantage endowed with the microwave-assistant hydrothermal method can result in the efficient spatial charge separation between ZnO nanorods (NRs) and SnO₂ NWs and reduce the charge recombination along the heterojunction, which makes SnO₂@ZnO HNSs a highly promising for photocatalytic applications.