Oxygen-vacancies-induced enhancement in photocatalystic performance of sea urchin-like Fe${}_3$O${}_4$@ZnO hollow core-shell structures

A novel sea urchin-like Fe${}_3$O${}_4$@ZnO (S-FZ) hollow core-shell photocatalyst is developed, which achieves about fourfold higher photocatalystic degradation efficiency (84.4%) than the waxberry-type Fe${}_3$O${}_4$@ZnO (W-FZ) photocatalyst due to its larger specific surface area. After postannealing at different temperatures under argon atmosphere, the photocatalystic degradation efficiency of S-FZ is effectively improved. When the annealing temperature is 500 °C, the degradation efficiency of S-FZ hollow core-shell structures is further improved to 99%, which is related to the synergistic effect of high density of oxygen vacancies. Such S-FZ catalysts are easily separated with a magnet and reused with only 2% loss in photocatalystic degradation efficiency after five circles. Herein, a practical approach toward high-efficient and recyclable photocatalysts is provided. (© 2021 Wiley‐VCH GmbH)